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Introduction The effect of neoadjuvant systemic therapies (NST) on technical aspects of operation for resectable stage III melanoma is unknown. Prospective capture of the estimated and actual degree of difficulty of therapeutic lymphadenectomy at presentation and after NST may inform the relative merits of NST versus surgery followed by adjuvant therapy. Methods We designed surgeon survey tools to capture key impressions at baseline prior to NST and postoperatively. We conducted a sub-study within a multi-institutional clinical trial for high-risk operable stage III melanoma (NeoACTIVATE, NCT03554083) which enrolls clinically node-positive patients to 12 weeks of combinatorial NST determined by BRAF status. Survey data were analyzed. Results Surveys were completed for 24 of 25 patients (96%). Affected nodal basins were cervical (3, 13%) axillary (9, 38%), inguinal ± pelvic (14, 58%); 2 (8%) involved ≥ 2 basins. Baseline estimates included largest affected node size (median/range 4/1.4-11 cm), number of involved nodes (median/range 3/1-10) and tumor fixation (present in 12, 50%). At operation, actual degree of difficulty increased from the baseline estimate in 4 (17%) and decreased in 6 (25%). Surgery was less difficult, average, or more difficult versus usual operation in 4, 9, and 11 cases (17%, 38%, 46%), respectively. Conclusions Although many operations were judged to be more difficult than the usual therapeutic lymphadenectomy, operation following NST was more often perceived as easier than more difficult versus baseline impression. Engaging surgical oncologists to perform similar structured assessments across clinical trials will permit cross-study analysis of the effect of NSTs on the technical conduct of lymphadenectomy.

For patients with stage III melanoma with occult lymph node metastasis, the use of adjuvant therapy is increasing, and completion lymph node dissection (CLND) is decreasing. We sought to evaluate the use of modern adjuvant therapy and outcomes for patients with stage III melanoma who did not undergo CLND. Patients with a positive SLNB from 2015 to 2020 who did not undergo CLND were evaluated retrospectively. Nodal recurrence, recurrence-free survival (RFS), distant metastasis-free survival (DMFS), and melanoma-specific survival were evaluated. Among 90 patients, 56 (62%) received adjuvant therapy and 34 (38%) underwent observation alone. Patients who received adjuvant therapy were younger (mean age: 53 vs. 65, p

Patients with resected stage III melanoma have a heterogeneous prognosis with an especially high risk of relapse for patients with stage IIIB, IIIC and IIID according to the 2018 classification inThe aim of this article is to review the mechanisms of action, pharmacokinetics and safety data of pembrolizumab in resected stage III melanoma and to compare its safety profile to other immune checkpoint inhibitors for the same indication.Pembrolizumab as adjuvant therapy of resected stage III melanoma showed an acceptable safety profile, which is comparable to that in advanced melanoma. However, it caused one death. There is uncertainty about its benefits in AJCC-8 stage IIIA melanoma patients. Additionally, caution is required since OS and long-term safety data are not available yet.

Background The role of surveillance imaging in high-risk stage III melanoma patients after complete surgical resection remains controversial, and with the advent of adjuvant therapy, it may also be expanded. Therefore, we evaluated two fluorine-18 fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) protocols in two cohorts. Methods Cohort 1 (n = 35) focused on surveillance in asymptomatic patients (before approval and reimbursement of adjuvant therapy) and was assigned to 5x FDG-PET/CT's after surgery: one every 6 months for 2 years, with one final scan after 3 years. Cohort 2 (n = 42) was assigned to one screening FDG-PET/CT, which took place in between surgery and the start of adjuvant treatment. Results In cohort 1 (median follow-up: 33 months), 12 patients (34.3%) developed recurrence detected by FDG-PET/CT, of which 7 (20.0%) were detected with the first scan. Sensitivity and specificity were 92.3% and 100%, respectively. In cohort 2, recurrence was suspected on nine scans (21.4%) and four (9.5%) were true positive. The number of scans needed to find one asymptomatic recurrence were 8.8 and 10.5 in cohort 1 and 2, respectively. Conclusions FDG-PET/CT is a valuable imaging tool to detect recurrence in stage III melanoma, even shortly after surgery. A surveillance FDG-PET/CT protocol after surgery or a screening PET/CT before adjuvant therapy should be considered.

PURPOSE Three new therapies have been approved recently for the adjuvant treatment of stage III melanoma, substantially reducing the risk of tumor recurrences. This study evaluates 3 independent data sets to clarify the survival probabilities of patients with stage III melanoma. PATIENTS AND METHODS The Central Malignant Melanoma Registry (CMMR) evaluated 1,553 patients with a primary diagnosis of stage III melanoma from 2000 to 2012. Studies from the European Organisation for Research and Treatment of Cancer (EORTC), of 573 patients in the observation arm of the 18991 study and 445 patients in the placebo arm of the 18071 study, were evaluated as reference cohorts. The survival outcomes were compared with the published American Joint Committee on Cancer version 8 (AJCCv8) stage III survival data. RESULTS For the CMMR stage III cohort versus the AJCCv8 cohort, the melanoma-specific survival (MSS) rates at 5 years were 67% versus 77%, and at 10 years were 56% versus 69%, respectively. For stage IIIA, the MSS rates at 5 years were 80% versus 93%, and at 10 years were 71% versus 88%; for stage IIIB, the MSS rates at 5 years were 75% versus 83%, and at 10 years were 61% versus 77%. The MSS rates of the EORTC studies either overlapped with or were lower than, the CMMR data. CONCLUSION The MSS rates in the CMMR and EORTC cohorts over the entire stage III are less favorable than those published in AJCCv8. This is particularly true for substages IIIA and IIIB.

PURPOSE Improved understanding of the incidence, risk factors, and timing of CNS metastasis is needed to inform surveillance strategies for patients with melanoma. PATIENTS AND METHODS Clinical data were extracted from the databases of 2 major melanoma centers in the United States and Australia for 1,918 patients with American Joint Committee on Cancer (AJCC) 8th edition stage III melanoma, diagnosed from 1998-2014, who had (negative) baseline CNS imaging within 4 months of diagnosis. The cumulative incidence of CNS metastasis was calculated in the presence of the competing risk of death, from stage III presentation and at benchmark time points 1, 2, and 5 years postdiagnosis. RESULTS At a median follow-up of 70.2 months, distant recurrence occurred in 711 patients (37.1%). The first site of distant metastasis was CNS only for 3.9% of patients, CNS and extracranial (EC) for 1.8%, and EC only for 31.4%. Overall, 16.7% of patients were diagnosed with CNS metastasis during follow-up. The cumulative incidence of CNS metastasis was 3.6% (95% CI, 2.9% to 4.6%) at 1 year, 9.6% (95% CI, 8.3% to 11.0%) at 2 years, and 15.8% (95% CI, 14.1% to 17.6%) at 5 years. The risk of CNS metastasis was significantly influenced by patient sex, age, AJCC stage, primary tumor site, and primary tumor mitotic rate in multivariable and conditional analyses. High primary tumor mitotic rate was significantly associated with increased risk of CNS metastasis at diagnosis and all subsequent time points examined. CONCLUSION Similar rates of CNS metastasis were observed in 2 large, geographically distinct cohorts of patients with stage III melanoma. The results highlight the importance of primary tumor mitotic rate. Furthermore, they provide a framework for developing evidence-based surveillance strategies and evaluating the impact of contemporary adjuvant therapies on the risk of CNS metastasis development.

PURPOSE We conducted the phase III double-blind European Organisation for Research and Treatment of Cancer (EORTC) 1325/KEYNOTE-054 trial to evaluate pembrolizumab versus placebo in patients with resected high-risk stage III melanoma. On the basis of 351 recurrence-free survival (RFS) events at a 1.25-year median follow-up, pembrolizumab prolonged RFS (hazard ratio [HR], 0.57; P < .0001) compared with placebo. This led to the approval of pembrolizumab adjuvant treatment by the European Medicines Agency and US Food and Drug Administration. Here, we report an updated RFS analysis at the 3.05-year median follow-up. PATIENTS AND METHODS A total of 1,019 patients with complete lymph node dissection of American Joint Committee on Cancer Staging Manual (seventh edition; AJCC-7), stage IIIA (at least one lymph node metastasis > 1 mm), IIIB, or IIIC (without in-transit metastasis) cutaneous melanoma were randomly assigned to receive pembrolizumab at a flat dose of 200 mg (n = 514) or placebo (n = 505) every 3 weeks for 1 year or until disease recurrence or unacceptable toxicity. The two coprimary end points were RFS in the overall population and in those with programmed death-ligand 1 (PD-L1)–positive tumors. RESULTS Pembrolizumab (190 RFS events) compared with placebo (283 RFS events) resulted in prolonged RFS in the overall population (3-year RFS rate, 63.7% v 44.1% for pembrolizumab v placebo, respectively; HR, 0.56; 95% CI, 0.47 to 0.68) and in the PD-L1–positive tumor subgroup (HR, 0.57; 99% CI, 0.43 to 0.74). The impact of pembrolizumab on RFS was similar in subgroups, in particular according to AJCC-7 and AJCC-8 staging, and BRAF mutation status (HR, 0.51 [99% CI, 0.36 to 0.73] v 0.66 [99% CI, 0.46 to 0.95] for V600E/K v wild type). CONCLUSION In resected high-risk stage III melanoma, pembrolizumab adjuvant therapy provided a sustained and clinically meaningful improvement in RFS at 3-year median follow-up. This improvement was consistent across subgroups.

This pilot study explored the value of localized index node removal after neoadjuvant immunotherapy in patients with stage III melanoma, for use as a response indicator to guide the extent of completion lymph node dissection. Promising technology.

Aim: To estimate incidence of stage III melanoma using the American Joint Committee on Cancer (AJCC) staging, 7th and 8th edition. Patients & methods: The SEER US cancer registry was analyzed (2010–2014). AJCC7 stages were recorded in the data; AJCC8 stages were inferred. Results: Of 106,195 melanoma patients, 7669 and 7342 had stage III melanoma by AJCC7 and AJCC8, respectively (95% overlap). Nearly 30% of patients with AJCC7 stage III melanoma were reclassified in a higher stage III group by AJCC8 versus 7% in lower stage group. Regardless of the AJCC edition, incidence of stage III melanoma has increased from 2010 to 2014 both overall and within each stage III group. Conclusion: Providing appropriate management to this growing population of high-risk patients is a priority.

Last decade brought new achievements in the melanoma research, which resulted in an important changes in the clinical management of stage III melanoma. The article summarizes recent updates with particular focus on practical aspects. Results from surgical studies, Multicenter Selective Lymphadenectomy Trial II (MSLT-II) and German Dermatologic Cooperative Oncology Group (DeCOG-SLT) proved that surgical dogmatic approach that all sentinel node melanoma metastasis warrants completion lymphadenectomy is no longer valid; omission of completion lymphadenectomy in large proportion of sentinel node positive melanoma patients has no negative impact on survival rates. Moreover oncological trials (COMBI-AD, EORTC 1325/KEYNOTE-054 and CheckMate 238) showed that in stage III melanoma patients' chances of recurrence-free survival can be improved by 10-20% by modern immunotherapy and/or molecular targeted therapy. These findings led to fall of another dogma in oncology: lack of effective adjuvant therapy for stage III melanoma at acceptable toxicity. At the end of the day in 2021 modern multidisciplinary approach incorporating newest findings offer stage III melanoma patients less surgical complications of better tailored surgery and longer survival in result of efficient adjuvant therapy.

Immunotherapy with immune checkpoint inhibition has dramatically changed the treatment of melanoma. Immune checkpoint inhibitors targeting cytotoxic T-lymphocyte-associated protein 4 and programmed cell death protein 1 are approved for the treatment of advanced melanoma alone and in combination. In addition, these agents are approved for use in high-risk resected stage III melanoma in the adjuvant setting. Clinical trials testing the combination of immune checkpoint inhibition with other therapies and novel immunotherapies continue. This article reviews the current literature on approved uses of immune checkpoint inhibition in melanoma and discusses ongoing trials and future directions.

Background It is not known whether there is a survival benefit associated with more frequent surveillance imaging in patients with resected American Joint Committee on Cancer stage III melanoma. Objective The aim of this study was to investigate distant disease-free survival (DDFS), melanoma-specific survival (MSS), post distant recurrence MSS (dMSS), and overall survival for patients with resected stage III melanoma undergoing regular computed tomography (CT) or positron emission tomography (PET)/CT surveillance imaging at different intervals. Patients and Methods A closely followed longitudinal cohort of patients with resected stage IIIA–D disease treated at a tertiary referral center underwent 3- to 4-monthly, 6-monthly, or 12-monthly surveillance imaging between 2000 and 2017. Survival outcomes were estimated using the Kaplan–Meier method, and log-rank tests assessed the significance of survival differences between imaging frequency groups. Results Of 473 patients (IIIA, 19%; IIIB, 31%; IIIC, 49%; IIID, 1%) 30% underwent 3- to 4-monthly imaging, 10% underwent 6-monthly imaging, and 60% underwent 12-monthly imaging. After a median follow-up of 6.2 years, distant recurrence was recorded in 252 patients (53%), with 40% detected by surveillance CT or PET/CT, 43% detected clinically, and 17% with another imaging modality. Median DDFS was 5.1 years (95% confidence interval 3.9–6.6). Among 139 IIIC patients who developed distant disease, the median dMSS was 4.4 months shorter in those who underwent 3- to 4-monthly imaging than those who underwent 12-monthly imaging. Conclusion Selecting patients at higher risk of distant recurrence for more frequent surveillance imaging yields a higher proportion of imaging-detected distant recurrences but is not associated with improved survival. A randomized comparison of low versus high frequency imaging is needed.

Background The previous OpACIN and OpACIN-neo studies investigating neoadjuvant IPI plus NIVO have demonstrated high pathologic response rates (74–78%) and favorable long-term outcomes for patients (pts) with a pathological response; at 36 and 18 months follow up only 1/71 (1.4%) responders has relapsed. In contrast, pathological non-responders have a poor prognosis; 15/23 (65.2%) have relapsed so far. This emphasizes the need for baseline biomarkers predictive of non-response and new neoadjuvant treatment combinations for these pts. In our previous studies, baseline IFN-γ signature high pts were more likely to respond to IPI plus NIVO. The DONIMI study tests the combination of NIVO ± IPI combined with a class 1 histone deacetylase inhibitor, domatinostat (DOM), according to the pts IFN-γ signature. We have developed a neoadjuvant IFN-γ signature, based on the signature previously described by Ayers et al., that will be used for the first time to classify pts in this prospective trial. Trial design This two-center investigator-initiated phase 1b study aims to assess the safety and feasibility of neoadjuvant NIVO ± DOM ± IPI in 45 stage III melanoma pts with macroscopic de-novo or recurrent disease. IFN-γ signature high pts (n=20) will be randomized (stratified by center) to Arm A (2 cycles NIVO 240 mg q3wk) or Arm B (2 cycles NIVO 240 mg q3wk + DOM 200 mg twice daily (BID), d1-14, q3wk). IFN-γ signature low pts (n=25) will be randomized to Arm C (2 cycles NIVO 240 mg q3wk + DOM 200 mg BID, d1-14, q3wk) or Arm D (2 cycles NIVO 240 mg q3wk + IPI 80 mg q3wk + DOM 200 mg once daily (OD), d1-14, q3wk). Based on safety data of the first 5 pts in arm D, the remaining pts will be treated with either a higher dosing scheme (200 mg BID, d1-14, q3wks), a lower dosing scheme (100 mg OD, d1-14, q3wks) or the same dosing scheme (200 mg OD, d1-14, q3wks). The primary endpoint is safety and feasibility. A treatment arm will be declared as not feasible if 2/5 or 3/10 patients cannot adhere to the planned time of surgery (week 6 ± 1week) due to treatment-related adverse events. Biopsies (week 0, 3), blood samples (week 0, 3, 6, 12) and feces (week 0, 3, 6) will be collected for translational research. To date, 7 patients have been enrolled. Clinical trial information NCT04133948 Disclosure Information I.L.M. Reijers: None. E.A. Rozeman: None. P. Dimitriadis: None. O. Krijgsman: C. Other Research Support (supplies, equipment, receipt of drugs or other in-kind support); Modest; BMS. L.J.W. Bosch: None. S. Cornelissen: None. J. Bouwman: None. J.M. Versluis: None. D. Rao: None. B. van de Wiel: None. A.J. Spillane: None. R.A. Scolyer: F. Consultant/Advisory Board; Modest; MSD, Neracare, Myriad, Novartis. A.M. Menzies: F. Consultant/Advisory Board; Modest; BMS, MSD Oncology, Novartis, Pierre Fabre, Roche. A.C.J. van Akkooi: B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Modest; Amgen, BMS, Novartis. F. Consultant/Advisory Board; Modest; Amgen, BMS, Novartis, MSD, Merck, Merck-Pfizer, 4SC. G.V. Long: F. Consultant/Advisory Board; Modest; Aduro, Amgen, BMS, Mass-Array, Pierre-Fabre, Novartis, Merck MSD, Roche. C.U. Blank: B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Modest; BMS, Novartis, Nanostring. F. Consultant/Advisory Board; Modest; BMS, MSD, Roche, Novartis, GSK, AZ, Pfizer, Lilly, Genmab, Pierre Fabre.

Tremendous progress has been made in treating patients with metastatic melanoma over the past decade. In that timeframe, the FDA has approved 12 novel treatments for patients with advanced unresectable melanoma, comprising both kinase-targeted therapies and immune checkpoint inhibitors (ICI), and five treatments for adjuvant (postoperative) use in patients with high-risk resectable stage III melanoma. It is not known whether outcomes can be further improved by administering kinase inhibitors or ICI in the neoadjuvant (presurgical) setting in patients with high-risk resectable melanomas. Noting research community interest in exploring the neoadjuvant approach for treating melanoma and recognizing that early harmonization of methodologies may expedite the development of therapeutics in this space, the FDA and Melanoma Research Alliance convened a public workshop on November 6, 2019, in National Harbor, Maryland, to discuss key issues. The workshop consisted of 23 faculty and included more than 250 live participants. Topics discussed included opportunities for advancing novel endpoints for regulatory purposes as well as translational research, clinical trial design considerations, and strategies for optimizing patient selection while mitigating risk.

Background With the approval of adjuvant therapy for stage III melanoma, accurate staging is more important than ever. Sentinel node biopsy (SNB) is an accurate staging tool, yet the presence of capsular nevi (CN) can lead to a false-positive diagnosis. Patients and methods Retrospective analysis of the American Joint Committee on Cancer 7th edition stage IIIA melanoma patients who were treated at our institute between 2000 and 2015. SNB slides were reviewed for this study by an expert melanoma pathologist. Results Of 159 eligible patients, 14 originally diagnosed with metastatic melanoma merely had CN (8.8%). Another two merely had melanophages (1.3%). Thus, 10.1% of SNs were considered false positive after revision. In 12 patients, the SN tumor burden was originally reported as larger than 1 mm but turned out to be less than 1 mm. Four patients originally reported as SN tumor burden less than 1 mm before revision turned out to have larger than 1 mm. These patients might have been over- or undertreated in the current era of adjuvant therapy for stage III melanoma. Conclusions Distinguishing metastatic melanoma from benign CN and melanophages can be a diagnostic challenge. We plead for an expert pathologists' review, especially when using the SNB + results to determine treatment consequences.

BACKGROUND In the previously reported primary analysis of this phase 3 trial, 12 months of adjuvant dabrafenib plus trametinib resulted in significantly longer relapse-free survival than placebo in patients with resected stage III melanoma with BRAF V600E or V600K mutations. To confirm the stability of the relapse-free survival benefit, longer-term data were needed. METHODS We randomly assigned 870 patients who had resected stage III melanoma with BRAF V600E or V600K mutations to receive 12 months of oral dabrafenib (at a dose of 150 mg twice daily) plus trametinib (2 mg once daily) or two matched placebos. The primary end point was relapse-free survival. Here, we report 5-year results for relapse-free survival and survival without distant metastasis as the site of the first relapse. Overall survival was not analyzed, since the required number of events to trigger the final overall survival analysis had not been reached. RESULTS The minimum duration of follow-up was 59 months (median patient follow-up, 60 months for dabrafenib plus trametinib and 58 months for placebo). At 5 years, the percentage of patients who were alive without relapse was 52% (95% confidence interval [CI], 48 to 58) with dabrafenib plus trametinib and 36% (95% CI, 32 to 41) with placebo (hazard ratio for relapse or death, 0.51; 95% CI, 0.42 to 0.61). The percentage of patients who were alive without distant metastasis was 65% (95% CI, 61 to 71) with dabrafenib plus trametinib and 54% (95% CI, 49 to 60) with placebo (hazard ratio for distant metastasis or death, 0.55; 95% CI, 0.44 to 0.70). No clinically meaningful between-group difference in the incidence or severity of serious adverse events was reported during the follow-up period. CONCLUSIONS In the 5-year follow-up of a phase 3 trial involving patients who had resected stage III melanoma with BRAF V600E or V600K mutations, 12 months of adjuvant therapy with dabrafenib plus trametinib resulted in a longer duration of survival without relapse or distant metastasis than placebo with no apparent long-term toxic effects. (Funded by GlaxoSmithKline and Novartis; COMBI-AD ClinicalTrials.gov number, NCT01682083; EudraCT number, 2012-001266-15.).

International audience; Background: Adoptive tumor-infiltrating lymphocytes (TIL) therapy and interleukin-2 (IL-2) have been investigated in melanoma.Aim: To confirm previously observed preventive effects of TIL + IL2 in a subgroup of patients with relapsing metastatic stage III melanoma.Methodology: Open-label, randomized two-group, multicenter five-year trial in adult stage III melanoma patients with only one invaded lymph node after complete resection. Patients received TIL + IL2 or abstention. TIL + IL2 was administered within 8 weeks after lymph node resection and 4 weeks after. Disease-free survival was assessed every 2 months up to month 18, every 3 months up to month 36 and every 4 months up to 5 years. A once-a-year follow-up was scheduled beyond the five-year follow-up. Safety was assessed throughout the trial.Results: Overall, 49 patients accounted for the modified intent-to-treat and 47 for the PP. Slightly more male than female patients participated; mean age was 57.7 ± 11.4 years in the TIL + IL2 group and 53.5 ± 13.0 years in the abstention group. After 5 years of follow-up, 11/26 patients in the TIL + IL2 group and 13/23 in the abstention group had relapsed. There was no statistical difference between the groups (HR: 0.63 CI 95% [0.28-1.41], p = 0.258), nine patients in the TIL + IL2 and 11 in the abstention group died with no significant difference between the two groups (HR: 0.65 CI95% [0.27 - 1.59], p = 0.34). Safety was good.Conclusion: We did not confirm results of a previous trial. However, ulceration of the primary melanoma may be considered predictive of the efficacy of TIL in melanoma in adjuvant setting, in a manner similar to interferon α.

The aim of this study was to assess the prognostic importance of lymph node ratio (LNR) in stage III melanoma after complete lymph nodal dissections. From European Organization for Research and Treatment of Cancer randomized trials 18871, 18952, and 18991, 2358 patients had full information on positive and examined lymph nodes (LNs) and were included. Cox proportional hazards models stratified by trial were used to assess the prognostic impact of LNR adjusted for confounders on melanoma-specific survival. Optimal cutoff values for LNR were calculated for each LN dissection site (axillary, inguinal, and neck). LNR (≥ vs.35%: hazard ratio=1.44, 95% confidence interval: 1.23-1.69) and number of positive LNs appeared to be of independent strong prognostic importance. Dissection sites impacted the optimal LNR cutoff: 35% for axillary, 40% for inguinal, and 50% for neck dissections. Combining these into one 'high versus low LNR' resulted in a highly significant multivariately adjusted hazard ratio of 1.48 (95% confidence interval: 1.26-1.74). In subgroup analyses, LNR was only significant in advanced disease (American Joint Committee on Cancer stage N2b, N3; IIIC). LNR was most significant for inguinal dissections, followed by axillary dissections, but seemed less useful in neck dissections. LNR is an independent significant prognostic factor in stage III melanoma patients. Our study showed higher than previously reported cutoffs that differed per dissection site. However, because of conflicting results compared with other studies and apparent limited prognostic impact confined to subgroups, the practical use of LNR seems limited.

Melanoma is a form of skin cancer that is frequently diagnosed at early stages. In most cases, surgical resection is curative. In case of thicker melanomas (> pT1b) without clinical or instrumental evidence of metastasis, a sentinel lymph node biopsy is recommended for staging purposes. If the lymph nodes are the only site of disease (macroscopic or microscopic> 1mm), configuring stage III, the international guidelines recommend the use of adjuvant therapy with checkpoint inhibitors (nivolumab or pembrolizumab) or targeted therapies (dabrafenib plus trametinib). These drugs have shown a significant increase in recurrence-free survival, although some doubts and open questions remain. Specifically, none of the available treatments has shown a clear benefit in the overall survival rates, the advantages they give in stage IIIA are not well known, and finally there are still no prospective clinical studies identifying the best approach to continue the therapeutic process in case of relapse. Furthermore, there are new opportunities opening up with the upcoming results of the neoadjuvant trials that could revolutionize the treatment of clinically evident stage III melanoma.

Purpose: There is a need for sensitive, reproducible biomarkers for patients with stage III melanoma to guide clinical decision making. Circulating tumor cells (CTCs) can be detected in patients with melanoma; however, there are limited data regarding their significance in stage III disease. The aim of this study was to determine whether CTCs are associated with early relapse in stage III melanoma. Experimental Design: We prospectively assessed CTCs at first presentation in clinic (baseline) for 243 patients with stage III melanoma. CTCs were measured using the CellSearch System. Relapse-free survival (RFS) was compared between patients with one or more baseline CTC versus those with no CTCs. Log-rank test and Cox regression analysis were applied to establish associations of CTCs with RFS. Results: At least one baseline CTC was identified in 90 of 243 (37%) patients. Forty-five (19%), 67 (28%), 118 (49%), and 13 (5%) patients were stage IIIA, IIIB, IIIC, or IIID, respectively. CTC detection was not associated with substage, or primary tumor characteristics. Multivariable analysis demonstrated that the detection of ≥1 baseline CTC was significantly associated with decreased 6-month RFS [log-rank, P < 0.0001; HR, 3.62, 95% confidence interval (CI), 1.78–7.36; P < 0.0001] and 54-month RFS (log-rank, P = 0.01; HR, 1.69; 95% CI, 1.13–2.54; P = 0.01). Conclusions: ≥1 CTC was independently associated with melanoma relapse, suggesting that CTC assessment may be useful to identify patients at risk for relapse who could derive benefit from adjuvant therapy.

Even though both the involvement of regional lymph nodes and the number of metastatic lymph nodes are regarded as major determinants of survival in cutaneous melanoma, the extent of node dissection has been analyzed as an independent prognostic indicator in only a few studies. This study aims to determine how the extent of lymph node excision (EN) might predict the disease relapse and survival in melanoma.A total of 317 patients with stage III melanoma were included in the study and reviewed retrospectively. The patients were divided into 2 groups based on the number of the excised lymph nodes: EN1 for fewer than 10 and EN2 for 10 or more lymph nodes removed.The median number of positive nodes was 1 (range, 1-32). The largest group was N1 (52.4%), which was followed by N2 (29.6%) and N3 (18%). The median number of EN was 13 (range, 1-73). The patients were allocated to EN1 and EN2 as follows: 31.9% and 68.1%, respectively. The rates of EN2 patients were 62.2%, 72.2%, and 78.2% in N1, N2, and N3, respectively. For all patients, the estimated 5- and 10-year relapse-free survival rates were 41% and 39%, respectively; and the estimated 5- and 10-year overall survival rates were 51% and 42%, respectively. Extension of lymph node excision was found to be not prognostic for relapse and survival (P = 0.55 and P = 0.88, respectively).Extension of lymph node excision has no impact on relapse and survival of stage III cutaneous melanomas.

Objectives: Pathological stage III melanoma patients have variable clinical presentation and outcome when divided by substages, and the number of metastatic lymph nodes is the most significant inde...

Aims: To evaluate the cost-effectiveness of adjuvant pembrolizumab relative to observation alone following complete resection of high-risk stage III melanoma with lymph node involvement, from a US ...

International audience; Improved knowledge of sentinel node procedures coupled with the results of adjuvant clinical trials in stage III melanoma have prompted the French Cutaneous Oncology Group to propose new guidelines for the management of stage III melanoma. These guidelines comply with the principles of the evidence-based medicine.

9582 Background: In the COMBI-AD trial (NCT01682083), 12 mo of adjuvant D+T led to significant improvement of RFS vs PBO (hazard ratio [HR], 0.47; P < .001) in pts with resected BRAF V600–mutant stage III melanoma; 3- and 4-year RFS rates were 59% and 54%, respectively. Previous results demonstrated consistent treatment benefit across baseline disease stage according to AJCC edition 7 or 8. Here, we further explored the association between baseline disease characteristics and RFS to identify pt subgroups likely to benefit from adjuvant treatment. Methods: Randomized pts with completely resected BRAF V600E/K–mutant stage III melanoma received 12 mo of adjuvant D (150 mg BID) + T (2 mg QD) or PBO. Within each subgroup, predictive value was explored using Kaplan-Meier analysis, and HRs were calculated using a Pike estimator. Results: Minimum follow-up was 40 mo for 870 enrolled pts (D+T, 438; PBO, 432). Kaplan-Meier analysis demonstrated treatment benefit across all subgroups analyzed. Assessment of RFS by extent of primary tumor (T stage) showed consistent benefit favoring D+T vs PBO (HR [95% CI]; T1, 0.42 [0.25-0.70]; T2, 0.51 [0.34-0.76]; T3, 0.55 [0.39-0.77]; T4, 0.42 [0.29-0.60]). HRs by nodal burden (N stage) also showed consistent treatment benefit (N1, 0.52 [95% CI, 0.37-0.72]; N2, 0.38 [95% CI, 0.28-0.53]; N3, 0.58 [95% CI, 0.41-0.83]). Substantial treatment benefit was observed in pts with baseline in-transit metastases (HR, 0.45 [95% CI, 0.24-0.82]) and those with no in-transit metastases detected at baseline (HR, 0.49 [95% CI, 0.40-0.60]). When RFS was assessed according to melanoma presentation, treatment benefit favoring D+T vs PBO was observed in pts with superficial spreading melanoma (HR, 0.48 [95% CI, 0.35-0.66]) and those with nodular melanoma (HR, 0.53 [95% CI, 0.37-0.75]). Conclusions: These results confirm earlier findings showing that treatment benefit with adjuvant D+T vs PBO is independent of baseline factors. Clinical trial information: NCT01682083.

Objective: To determine the efficacy of pembrolizumab relative to other treatments used in stage III melanoma by conducting a systematic literature review (SLR) and network meta-analysis (NMA). Methods: A SLR was conducted to identify randomized clinical trials (RCTs) evaluating approved adjuvant treatments including interferon-containing regimens, BRAF-inhibitors, and PD-L1 inhibitors in stage III melanoma patients. Relative treatment effects for recurrence-free survival (RFS) were synthesized with Bayesian NMA models that allowed for hazard ratios (HRs) to vary over time. Results: Included studies formed a connected network of evidence composed of eight trials. In high-risk stage III patients, the HR for pembrolizumab vs observation decreased significantly over time with the superiority of pembrolizumab over observation becoming statistically meaningful before 3 months. By 9 months, the HR for pembrolizumab vs observation was statistically significantly lower than the HR for most other treatments vs observation, with the exception of ipilimumab and biochemotherapy due to overlapping 95% credible intervals. In BRAF + patients, pembrolizumab was statistically significantly better than observation after 3 months. The HR for both BRAF-inhibitors vs observation increased significantly over time and pembrolizumab was statistically superior to both BRAF-inhibitors after 15 months. Conclusions: Pembrolizumab results in statistically significantly improved RFS compared to all competing regimens after 9 months, except ipilimumab and biochemotherapy, for the adjuvant treatment of stage III melanoma. However, point estimate HRs vs observation for pembrolizumab are much lower than those for ipilimumab. In BRAF + patients, the advantage of pembrolizumab versus competing interventions increases over time with respect to RFS.

International audience; Les résultats des études sur le ganglion sentinelle et des essais de thérapies ciblées ou d’immunothérapie en situation adjuvante dans le mélanome ont rendu indispensable une actualisation des recommandations de prise en charge des mélanomes de stade III. À la demande du Groupe de cancérologie cutanée de la Société française de dermatologie, une actualisation a donc été réalisée en utilisant les méthodes classiques d’analyse de la littérature selon les principes de la médecine fondée sur les preuves.

e18758 Background: There are now numerous effective adjuvant immunotherapy options for surgically resected stage III melanoma including novel checkpoint inhibitors and targeted therapies. Current guidelines recommend that the decision to treat stage III melanoma with adjuvant immunotherapy should be individualized and based upon disease burden, patient goals and anticipated therapy tolerance. We sought to assess the contribution of patient, tumor and facility factors on the implementation of immunotherapy in patients with surgically resected stage III melanoma. Methods: Using the National Cancer Database (NCDB), patients from 2012-2017 that underwent excision and were found to have a positive sentinel node were identified. A multivariable mixed effects logistic regression model with a random intercept for site was used to determine the effect of patient, tumor, and facility variables on the probability of immunotherapy. Reference Effect Measures (REM) were used to estimate the variation in immunotherapy use due to unmeasured facility factors (contextual effects) after adjusting for measured patient, tumor, and facility variables. Results: From 2012 to 2017, the percent of patients with stage III melanoma treated with adjuvant immunotherapy increased from 23.7% to 38.5% (p < 0.05). Overall, younger patients and patients with private insurance were more likely to receive immunotherapy. Tumor factors associated with increased use of adjuvant immunotherapy included increasing depth, mitotic rate ³1, ulceration, lymphovascular invasion (LVI), and undergoing a completion lymph node dissection (CLND). Additionally, treatment at a facility with a surgical volume

e21570 Background: Advancements in systemic therapy have reduced recurrence, and the adoption of nodal surveillance in place of dissection has reduced morbidity for patients with Stage III melanoma. The objective of this study was to describe the timing and pattern of recurrence in stage III melanoma patients and evaluate the impact of adjuvant treatment and nodal surveillance. Methods: A multicenter retrospective chart review of patients with pathologically confirmed Stage III cutaneous melanoma seen at either the Juravinski Cancer Centre or Walker Family Cancer Centre in Ontario, Canada from January 1, 2017 to December 31, 2019. Results: There were 137 patients with Stage III melanoma: 18% IIIA, 22% IIIB, 52% IIIC, and 8% Stage IIID as per the 8th American Joint Committee on Cancer (AJCC) 2018 staging system. 103 (75%) patients had sentinel lymph node biopsy (SLNB) only as part of initial surgical therapy, 6 (4%) had SLNB with completion dissection, and 25 (18%) had upfront radical nodal dissection. 67 (49%) patients received adjuvant therapy, of which 50 (74%) had immunotherapy, 17 (25%) received BRAF-targeted therapy, and 1 (1%) had interferon. 54 (39%) patients developed recurrent disease, with a median time to recurrence of 8.5 months (IQR: 4.3-14.9). The recurrence rates were 63% in patients who did not have adjuvant treatment and 37% in those who had adjuvant therapy, with a median time-to-recurrence of 7.5 and 9.0 months respectively. There were 30 (56%) loco-regional recurrences and 24 (44%) distant recurrences. Of the patients with loco-regional recurrence, 26 (87%) had SLNB only compared to 4 (13%) who had upfront or completion dissection. 12 (24%) patients recurred while on adjuvant treatment (7 distant recurrences and 5 loco-regional recurrences), and 8 (13%) patients recurred following completion of adjuvant treatment (5 distant recurrences and 3 loco-regional recurrences). Recurrences were detected by patients, clinicians, CT and nodal US surveillance in 43%, 20%, 28% and 9% of cases, respectively. The majority of loco-regional recurrence was detected clinically (67%) rather than by radiologic surveillance (33%). Of the 30 loco-regional recurrences, 24 underwent surgical resection of the recurrence, 4 had subsequent systemic therapy without surgery, 1 had intra-tumoral injections and 1 had no treatment. Conclusions: Recurrences in Stage III melanoma occur early, often within a year, with higher rates of loco-regional rather than distant disease. Recurrence rates were lower in those who received adjuvant therapy, but the majority of recurrences were detected by patients or clinicians, including loco-regional recurrences in patients who had SLNB only despite surveillance nodal US.

9579 Background: Recently, trials have shown the benefit of adjuvant aPD-1 therapy in macroscopic stage III melanoma patients. This treatment has been incorporated in daily clinical practice, however, a substantial part of patients still does not benefit from this therapy, as they develop recurrences. The aim of this study is to evaluate the results of adjuvant aPD-1 therapy and the potency of the IFNγ signature as a prognostic or predictive marker, as it has proven to be predictive of response in neoadjuvant trials. Methods: Patients participating in an ongoing biobank study and naïve for systemic therapy were included, between 10-2017 and 06-2020, after complete resection of macroscopic stage III melanoma. Approval and reimbursement of adjuvant therapy in the Netherlands started in 12-2018, resulting in 2 cohorts of similar high risk patients: prior to availability of adjuvant aPD-1 (cohort A) and thereafter (cohort B). Data cut-off for clinical data was January 1st 2021. Transcriptome sequencing was performed on samples of stage III melanoma by CeGaT GmbH, IFNγ signature was determined on these data with the median as cut-off. Clinical data were compared between cohort A and B as intention-to-treat population, including patients with a recurrence before adjuvant therapy start (n=10). Results: In total, 99 patients were included: 50 in cohort A and 49 in cohort B. Majority of included patients had thick primary melanomas (Breslow >2mm in 59.6%) and stage IIIC/IIID disease (83.3%) according to AJCC 8th edition. At a median follow-up of 20.6 months (95% confidence interval [CI] 16.6-24.7), median recurrence-free survival (RFS) was 6.1 months (95%CI 3.9-8.4) versus 22.8 months (95%CI 8.7-36.9), significantly in favor of cohort B (p=0.011). Median overall survival (OS) was not reached in both patient groups, but was overall significantly different (p=0.040), favoring cohort B. RNA sequencing was performed in 25 patients who received adjuvant therapy and in 24 who did not, excluding patients with an early recurrence (

9577 Background: The management of patients with resected stage III melanoma has changed in recent years, and real-world data on recurrence patterns and adjuvant therapy responses are scarce. This study assessed adjuvant treatment patterns and outcomes in patients with advanced melanoma by BRAF status and relapse location. Methods: Patients diagnosed with stage III advanced melanoma between January 2011 and February 2020 in the nationwide Flatiron Health electronic health record–derived deidentified database were included if they were ≥18 years, received approved first-line (1L) adjuvant therapy after January 2018 with checkpoint inhibitors (CPIs; eg, nivolumab, pembrolizumab) or targeted therapies (TTs; eg, dabrafenib/trametinib), had 6 months’ follow-up and had ≥1 visit after starting adjuvant therapy (Cohort 1). Patients from Cohort 1 were included in Cohort 2 if they had a recurrence following initiation of adjuvant therapy, and those from Cohort 2 were included in Cohort 3 if they had a distant recurrence and available documented BRAF status at any time. Time to next systemic treatment (TTNT), overall survival (OS) and relapse free survival (RFS) were estimated using Kaplan-Meier (KM) methods from adjuvant therapy start (Cohort 1), first recurrence date (Cohort 2) or first distant recurrence date (Cohort 3). Results: Cohort 1 included 447 patients receiving 1L adjuvant therapy; Cohort 2 included patients after first distant (n = 47) or local (n = 35) relapse; Cohort 3 included distant-recurrent patients with tumors that were BRAF wild type (WT) (n = 22) or BRAF mutant (n = 23). The majority of patients were aged < 65 years. Across cohorts, relative use of TTs vs CPIs was similar: Cohort 1 (4.5% vs 96%), Cohort 2 (2.4% vs 98%) and Cohort 3 (2.2% vs 98%). Nivolumab was the most frequent treatment used across cohorts (84%-88%). In Cohort 1, 1- and 2-year KM probabilities for OS, RFS and TTNT were 93.5%/83.8%, 83.2%/70.6% and 84.0%/62.4%, respectively. In Cohort 2, for patients with local recurrence, 6- and 12-month OS probabilities were 93.4% and 78.8%, respectively, which were substantially higher than those for patients with distant recurrence (64.5% and 46.9%). In Cohort 3, for patients with documented BRAF mutations, 6- and 12-month OS rates from disease recurrence were 79.1% and 49.4%, respectively, which were greater than for those with BRAF-WT tumors (54.1% and 46.3%). Conclusions: Early RFS and OS outcomes for patients with surgically resected Stage III melanoma appear comparable to those reported in randomized clinical studies. The majority of patients with advanced melanoma, including patients who experienced recurrence, initiated treatment with CPIs. OS rates were numerically greater for Cohort 3 patients with BRAF-mutant tumors. Outcomes for patients with distant recurrence after adjuvant therapy remain unfavorable and represent a continued unmet medical need.

9502 Background: Neoadjuvant therapy (NT) for pts with clinical stage III melanoma remains an active area of research interest. Recent NT trial data demonstrates that achieving a pathologic complete response (pCR) correlates with improved relapse-free (RFS) and overall survival (OS). Checkpoint inhibitor (CPI) NT with either high or low dose ipilimumab and nivolumab regimens produces a high pCR rate of 30-45% but with grade 3-4 toxicity rate of 20-90%. In metastatic melanoma (MM), the combination of nivo with rela (anti Lymphocyte Activation Gene-3 antibody) has demonstrated a favorable toxicity profile and responses in both CPI-naïve and refractory MM. We hypothesized that NT with nivo + rela will safely achieve high pCR rates and provide insights into mechanisms of response and resistance to this regimen. Methods: We conducted a multi-institutional, investigator-initiated single arm study (NCT02519322) enrolling pts with clinical stage III or oligometastatic stage IV melanoma with RECIST 1.1 measurable, surgically-resectable disease. Pts were enrolled at 2 sites and received nivo 480mg IV with rela 160mg IV on wks 1 and 5. Radiographic response (RECIST 1.1) was assessed after completion of NT; surgery was conducted at wk 9 and specimens were assessed for pathologic response per established criteria. Pts received up to 10 additional doses of nivo and rela after surgery, with scans every 3 mo to assess for recurrence. The primary study objective was determination of pCR rate. Secondary objectives included safety, radiographic response by RECIST 1.1, event-free survival (EFS), RFS, and OS analyses. Blood and tissue were collected at baseline, at day 15, day 28, and at surgery for correlative analyses. Results: A total of 30 pts (19 males, median age 60) were enrolled with clinical stage IIIB/IIIC/IIID/IV (M1a) in 18/8/2/2 pts, respectively. 29 pts underwent surgery; 1 pt developed distant metastatic disease while on NT. pCR rate was 59% and near pCR ( < 10% viable tumor) was 7% for a major pathologic response (MPR, pCR + near pCR) of 66%. 7% of pts achieved a pPR (10-50% viable tumor) and 27% pNR (≥50% viable tumor). RECIST ORR was 57%. With a median follow up of 16.2 mos, the 1 -year EFS was 90%, RFS was 93%, and OS was 95%. 1-year RFS for MPR was 100% compared to 80% for non-MPR pts (p = 0.016). There were no treatment related gr 3/4 AEs that arose during NT; 26% of pts had a gr 3/4 AE that began during adjuvant treatment. Conclusions: Neoadjuvant and adjuvant treatment with nivo and rela achieved high pCR and MPR rates with a favorable toxicity profile in the neoadjuvant and adjuvant settings. Pts with MPR had improved outcomes compared to non-MPR pts. Translational studies to discern mechanisms of response and resistance to this combination are underway. Clinical trial information: NCT02519322.

e21569 Background: Neoadjuvant immunotherapy with nivolumab 3mg/kg and ipilimumab 1mg/kg for two cycles(N3+I1) or anti-PD1 for 3-8 weeks for clinical stage III melanoma have shown rates of pCR/near-pCR about 60% or 30%, respectively. The prognosis of this group seems to be excellent so far. On the other hand, patients classified as pathological non-response have a worse outcome and early identification of this group may allow us to tailor treatment before surgery. Methods: We conducted a retrospective analysis of patients with clinical stage III melanoma treated with neoadjuvant immune checkpoint blockade who did baseline and pre-operative FDG-PET/CT. The total number of FGD avid lesions and the percentual difference between the maximum SUV per lesion was calculated. The pathological results were correlated to FGD-PET/CT findings. Results: Between January 2019 and January 2021, nine patients with clinical stage III melanoma were identified. Six patients received Nivolumab 3m/kg and Ipilimumab 1mg/kg for two cycles and 3 received anti-PD1 for 60 days. Baseline FDG-PET/CT showed just one avid lesion in 7 patients, 2 avid lesions in one patient and 3 avid lesions in one patient. All known lesions identified by CT scan were also captured by FGD-PET/CT. After the neoadjuvant treatment, 4 patients achieved pCR/near-pCR. All of them were treated with N3+I1. Two of them had metabolic complete response (including the one with 3 PET- avid lesions) and 2 had reduction on FDG concentration (-31% and – 76%). Three patients had absence of response: 100% of viable tumor cells (VTC), all of them with increase in FDG concentration (+12% to + 307%) and appearance of a new lesion in one case. Two out of them were treated with anti-PD1. One patient had partial response (40% of VTC). Interestingly, this patient developed sarcoidosis-like reaction with increase of SUV in the index lesion (+68%) and appearance of mediastinal lymph-nodes. One patient, who had two lesions, presented a mixed response: complete response in one and 90% of VTC in the other. FDG-PET/CT was able to detect both responses (metabolic complete response and increase of FGD concentration of 17%, respectively). Conclusions: Reduction in FGD-PET/CT concentration with no appearance of new lesion(s) is associated with significant pathological response. An increase of SUV or appearance of new lesion(s) should be carefully interpreted.

9551 Background: Recent data suggest that patients with stage III melanoma are at high enough risk for developing CNS metastases to consider routine surveillance neuroimaging (Journal of Clinical Oncology; PMID: 31990608). Given that a subset of stage II patients have a worse prognosis than stage III patients, we investigated the risk of developing brain metastases in stage II disease and compared it to the risk in stage III disease. Methods: We studied a cohort of prospectively enrolled melanoma patients who had protocol driven follow-up at New York University (NYU) Langone Health. We investigated both the incidence and time to development of CNS metastases, and explored whether the frequency of CNS metastases as a first isolated site of distant disease varies among the different stages. Results: The study cohort included a total of 1,102 patients (stage II: n = 619 with median follow-up 56.5 months; stage III: n = 483 with median follow-up 40.9 months). 85/619 (14%) stage II and 91/483 (19%) stage III patients developed CNS metastases (p = 0.03). The estimated 5-year cumulative incidence was 9% in stage IIA, 14% in stage IIB, and 29% in stage IIC patients (p = 0.0001). It was 10% in stage IIIA, 32% in stage IIIB, 23% in stage IIIC, and 49% in stage IIID (p = 0.0001). The CNS was the site of first metastasis for 32/154 (21%) stage II patients who developed distant disease compared to 28/214 (13%) stage III patients (p = 0.06). Conclusions: A subset of stage II patients are at an elevated risk for developing CNS metastases within 5 years of their initial diagnosis, which is comparable to that seen in stage III patients. The frequency of the CNS as a first site of metastasis in stage II melanoma suggests a propensity for brain tropism that cannot only be explained by a generalized pro-metastatic phenotype. Surveillance strategies that incorporate serial neuroimaging should be considered for these individuals.

9500 Background: The phase 3 double-blind EORTC 1325/KEYNOTE-054 trial evaluated pembrolizumab (pembro) vs placebo in stage III cutaneous melanoma patients (pts) with complete resection of lymph nodes. Pembro improved RFS (hazard ratio [HR] 0.57) and DMFS (HR 0.60) (Eggermont, NEJM 2018, TLO 2021). In the pembro group, the incidence of immune related AE (irAE) grade 1-5 was 37%, and of grade 3-5 was 7%. We present the safety profile, response rate and PFS for the subset of pts who had a recurrence and crossed over or were rechallenged with pembrolizumab, within protocol. Methods: Pts were randomized to receive iv. pembro 200 mg (N=514) or placebo (N=505) every 3 weeks for a total of 18 doses (~1 year). Upon recurrence with no brain metastases, pts with an ECOG PS 0-2 were eligible to enter part 2 of the study, i.e. to receive pembro 200 mg iv. every 3 weeks for a maximum of 2 years, for crossover (those who received placebo) or rechallenge (those who recurred ≥6 months after completing one year of pembro therapy). Treatment was stopped in case of disease progression (RECIST 1.1) or unacceptable toxicity. Results: At the clinical cut-off (16-Oct-2020), 298 (59%) pts had a disease recurrence in the placebo group; 155 pts participated in the crossover part 2 of the trial. A total of 297 (58%) pts completed the 1-yr pembro adjuvant treatment, of whom 47 had a recurrence ≥6 mths from the stop of treatment and 20 entered in the rechallenge part of the trial. Among 175 pts who started pembro in Part 2, 160 discontinued due to completion of therapy (N=24), disease progression (N=88), toxicity (N=20), investigator's decision (N=21), or other reason (N=7); 15 pts were still on-treatment. Results for the 2 groups are provided in the table. The median number of doses was 12 and 5.5, respectively (resp), and the median follow-up was 41 and 19 mts, resp. Among the 175 pts, 51 (29%) had a grade 1-4 irAE (by group: 47 [30%] and 4 [20%] resp) and 11 (6%) a grade 3-4 irAE. Conclusions: Pembrolizumab treatment after crossover yielded a 39% ORR in evaluable pts and an overall 3-yr PFS of ̃32%, but after rechallenge the efficacy was lower. Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., Kenilworth, NJ, USA The median PFS (95% CI) from start of Part 2 was 14 (5-27) and 8 (5-15) mts for stage III-resected and III/IV various, resp. Among the 80 stage IV crossover pts with evaluable disease, 31 (39%) had an objective response: 14 (18%) CR, 17 (21%) PR. The 2-yr PFS rate from response was 69% (95% CI 48-83%). For these 80 pts, the median PFS was 6.1 mts and the 3-yr PFS rate was 31% (95% CI 21-41%). Among 9 stage IV rechallenged pts with an evaluable disease, 1 (11%) reached CR, 3 had SD and 5 PD. Clinical trial information: NCT02362594. [Table: see text]