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Abstract: The CanSat Competition is an international event held annually that is focused around design/build/fly engineering. In this year’s mission, the team must design and build a CanSat which will be launched 700m high using a high-powered model rocket and then perform a controlled descent while transmitting data from its onboard sensors to a ground station computer. Initially, the CanSat descends under a parachute at 15 m/s. The first payload is released at 500m and the second payload will be released at 400m. The payloads are designed to function like maple seeds; upon deployment, they will auto-rotate and descend at a rate of 20 m/s. The CanSat must be equipped with sensors to monitor environmental conditions (temperature, pressure, GPS position, altitude) and system performance (orientation, battery voltage). It must be capable of transmitting telemetry in real-time to a ground station computer, which the team must also design and build.

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Purpose:We assessed plasma circulating tumor DNA (ctDNA) level as a prognostic marker for progression-free survival (PFS) following first-line metastatic colorectal cancer (mCRC) therapy.Experimental Design:The Sequencing Triplet With Avastin and Maintenance (STEAM) was a randomized, phase II trial investigating efficacy of bevacizumab (BEV) plus 5-fluorouracil/leucovorin/oxaliplatin (FOLFOX) and 5-fluorouracil/leucovorin/irinotecan (FOLFIRI), administered concurrently or sequentially, versus FOLFOX-BEV in first-line mCRC. Evaluation of biomarkers associated with treatment outcomes was an exploratory endpoint. Patients in the biomarker-evaluable population (BEP) had 1 tissue sample, 1 pre-induction plasma sample, and 1 post-induction plasma sample collected ≤60 days of induction from last drug date.Results:Among the 280 patients enrolled in STEAM, 183 had sequenced and evaluable tumor tissue, 118 had matched pre-induction plasma, and 54 (BEP) had ctDNA-evaluable sequencing data for pre- and post-induction plasma. The most common somatic variants in tumor tissue and pre-induction plasma were TP53, APC, and KRAS. Patients with lower-than-median versus higher-than-median post-induction mean allele fraction (mAF) levels had longer median PFS (17.7 vs. 7.5 months, HR, 0.33; 95% confidence interval, 0.17–0.63). Higher levels of post-induction mAF and post-induction mean mutant molecules per milliliter (mMMPM), and changes in ctDNA (stratified by a 10-fold or 100-fold reduction in mAF between pre- and post-induction plasma), were associated with shorter PFS. Post-induction mAF and mMMPM generally correlated with each other (ρ = 0.987, P < 0.0001).Conclusions:ctDNA quantification in post-induction plasma may serve as a prognostic biomarker for mCRC post-treatment outcomes.

PURPOSE Effective therapies are needed for the treatment of patients with human epidermal growth factor receptor-2 (HER2)-positive metastatic breast cancer (MBC) with brain metastases. A trastuzumab radioisotope has been shown to localize in brain metastases of patients with HER2-positive MBC, and intracranial xenograft models have demonstrated a dose-dependent response to trastuzumab. METHODS In the phase II PATRICIA study (ClinicalTrials.gov identifier: NCT02536339 ), patients with HER2-positive MBC with CNS metastases and CNS progression despite prior radiotherapy received pertuzumab plus high-dose trastuzumab (6 mg/kg weekly) until CNS or systemic disease progression or unacceptable toxicity. The primary end point was confirmed objective response rate (ORR) in the CNS per Response Assessment in Neuro-Oncology Brain Metastases criteria. Secondary end points included duration of response, clinical benefit rate (complete response plus partial response plus stable disease ≥ 4 or ≥ 6 months) in the CNS, and safety. RESULTS Thirty-nine patients were treated for a median (range) of 4.5 (0.3-37.3) months at clinical cutoff. Thirty-seven patients discontinued treatment, most commonly because of CNS progression (n = 27); two remained on treatment. CNS ORR was 11% (95% CI, 3 to 25), with four partial responses (median duration of response, 4.6 months). Clinical benefit rate at 4 months and 6 months was 68% and 51%, respectively. Two patients permanently discontinued study treatment because of adverse events (left ventricular dysfunction [treatment-related] and seizure, both grade 3). No grade 5 adverse events were reported. No new safety signals emerged with either agent. CONCLUSION Although the CNS ORR was modest, 68% of patients experienced clinical benefit, and two patients had ongoing stable intracranial and extracranial disease for > 2 years. High-dose trastuzumab for HER2-positive CNS metastases may warrant further study.

Background LCMC3 (NCT02927301), an open-label, single-arm Phase 2 study to investigate neoadjuvant (neoadj) and adj atezo (anti-PD-L1) in patients (pts) with early-stage non-small cell lung cancer (NSCLC), met its primary endpoint with a 20% major pathological response (MPR) rate after neoadj atezo. Here we report efficacy and safety from the adj phase. Methods Eligible pts aged ≥18 y had resectable stage IB-IIIA or select IIIB NSCLC and ECOG PS of 0 or 1. Pts received neoadj atezo 1200 mg IV for ≤2 cycles (Days 1 and 22) followed by surgery (Day 40±10). Pts deemed to have clinical benefit were offered the option to receive adj atezo every 3 weeks for up to 12 months. The primary endpoint was MPR rate (≤10% viable tumor cells at surgery) in pts without EGFR/ALK mutations. Exploratory endpoints included DFS and OS. Safety was assessed during the adj phase. Results Data cutoff was Oct 21, 2022. The primary efficacy population (PEP) was 137 pts without EGFR/ALK alterations who had surgery and MPR assessment. In the PEP, 53 pts (39%) received adj atezo and 84 (61%) did not. The 3-y DFS rate was 83% with adj atezo vs 64% without (HR, 0.43; 95% CI: 0.21, 0.90; P=0.025). 3-y OS and results by MPR status are provided in the table. In the adj atezo safety population (n=57), treatment-related (TR) AEs after adj atezo occurred in 55 pts (97%; Gr 3/4, 40%), including 11 TRAEs (19%; Gr 3/4, 16%) leading to discontinuation of adj atezo. No Gr 5 TRAEs were seen in the adj phase. Multivariate analysis also showed a trend toward better DFS for pts receiving adj atezo vs those with no adj atezo (HR, 0.52; 95% CI: 0.22, 1.21; P=0.126). Conclusions This exploratory analysis revealed that LCMC3 pts with resectable stage IB-IIIA or select IIIB NSCLC who received adj atezo had improved DFS and showed a trend toward improved OS vs pts who did not receive adj atezo. Furthermore, the non-MPR subgroup had the same trend toward improved DFS and OS with adj atezo vs pts who did not receive adj atezo. Adj atezo was well tolerated, with no new safety concerns. Table Adj atezoa n=53 No adj atezob n=84 Tx patterns Adj atezo + adj chemo, n (%) 17 (32) 0 Adj atezo, n (%) 36 (68) 0 Adj chemo, n (%) 0 36 (43) None, n (%) 0 48 (57) Tx cycles Adj atezo, n, median (range) 53, 16 (1-18) 0 Adj chemo, n, median (range) 16, 3 (0-4.2) 35, 3 (0-4.1) HR (95% CI) P PEP (N=137) 3-y DFS, % 83 64 0.43 (0.21, 0.90) 0.025 3-y OS, % 89 77 0.48 (0.19, 1.21) 0.118 MPR (n=29) n=22 n=7 3-y DFS, % 86 86 0.93 (0.10, 8.92) 0.948 Non-MPR (n=108) n=31 n=77 3-y DFS, % 80 62 0.48 (0.20, 1.12) 0.088 3-y OS, % 87 75 0.49 (0.17, 1.46) 0.202 Multivariable Cox regression (n=114)c MPR vs non-MPR 0.37 (0.11, 1.31) 0.125 Adj atezo vs no adj atezo 0.52 (0.22, 1.21) 0.126 Adj chemo vs no adj chemo 0.57 (0.27, 1.19) 0.133 Stage I/II vs III 0.71 (0.35, 1.43) 0.338 PD-L1 tumor proportion score ≥1% vs Citation Format: David Paul Carbone, Saiama N. Waqar, Jamie E. Chaft, Mark G. Kris, Bruce E. Johnson, Jay M. Lee, Ignacio I. Wistuba, David Kwiatkowski, Paul Bunn, Katja Schulze, Ann Johnson, Evelise Brandao, Mark Awad, Karen L. Reckamp, Anne C. Chiang, Alan Nicholas, Valerie Rusch. Efficacy and safety of adjuvant (adj) atezolizumab (atezo) from the Phase 2 LCMC3 study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT215.

Multimodality treatment for resectable non-small cell lung cancer has long remained at a therapeutic plateau. Immune checkpoint inhibitors are highly effective in advanced non-small cell lung cancer and promising preoperatively in small clinical trials for resectable non-small cell lung cancer. This large multicenter trial tested the safety and efficacy of neoadjuvant atezolizumab and surgery.Patients with stage IB to select IIIB resectable non-small cell lung cancer and Eastern Cooperative Oncology Group performance status 0/1 were eligible. Patients received atezolizumab 1200 mg intravenously every 3 weeks for 2 cycles or less followed by resection. The primary end point was major pathological response in patients without EGFR/ALK+ alterations. Pre- and post-treatment computed tomography, positron emission tomography, pulmonary function tests, and biospecimens were obtained. Adverse events were recorded by Common Terminology Criteria for Adverse Events v.4.0.From April 2017 to February 2020, 181 patients were entered in the study. Baseline characteristics were mean age, 65.1 years; female, 93 of 181 (51%); nonsquamous histology, 112 of 181 (62%); and clinical stages IIB to IIIB, 147 of 181 (81%). In patients without EGFR/ALK alterations who underwent surgery, the major pathological response rate was 20% (29/143; 95% confidence interval, 14-28) and the pathological complete response rate was 6% (8/143; 95% confidence interval, 2-11). There were no grade 4/5 treatment-related adverse events preoperatively. Of 159 patients (87.8%) undergoing surgery, 145 (91%) had pathologic complete resection. There were 5 (3%) intraoperative complications, no intraoperative deaths, and 2 postoperative deaths within 90 days, 1 treatment related. Median disease-free and overall survival have not been reached.Neoadjuvant atezolizumab in resectable stage IB to IIIB non-small cell lung cancer was well tolerated, yielded a 20% major pathological response rate, and allowed safe, complete surgical resection. These results strongly support the further development of immune checkpoint inhibitors as preoperative therapy in locally advanced non-small cell lung cancer.

In an ongoing, open-label, single-arm phase II study ( NCT02927301 ), 181 patients with untreated, resectable, stage IB-IIIB non-small cell lung cancer received two doses of neoadjuvant atezolizumab monotherapy. The primary end point was major pathological response (MPR; ≤10% viable malignant cells) in resected tumors without EGFR or ALK alterations. Of the 143 patients in the primary end point analysis, the MPR was 20% (95% confidence interval, 14-28%). With a minimum duration of follow-up of 3 years, the 3-year survival rate of 80% was encouraging. The most common adverse events during the neoadjuvant phase were fatigue (39%, 71 of 181) and procedural pain (29%, 53 of 181), along with expected immune-related toxicities; there were no unexpected safety signals. In exploratory analyses, MPR was predicted using the pre-treatment peripheral blood immunophenotype based on 14 immune cell subsets. Immune cell subsets predictive of MPR in the peripheral blood were also identified in the tumor microenvironment and were associated with MPR. This study of neoadjuvant atezolizumab in a large cohort of patients with resectable non-small cell lung cancer was safe and met its primary end point of MPR ≥ 15%. Data from this single-arm, non-randomized trial suggest that profiles of innate immune cells in pre-treatment peripheral blood may predict pathological response after neoadjuvant atezolizumab, but additional studies are needed to determine whether these profiles can inform patient selection and new therapeutic approaches.

Purpose:We assessed plasma circulating tumor DNA (ctDNA) level as a prognostic marker for progression-free survival (PFS) following first-line metastatic colorectal cancer (mCRC) therapy.Experimental Design:The Sequencing Triplet With Avastin and Maintenance (STEAM) was a randomized, phase II trial investigating efficacy of bevacizumab (BEV) plus 5-fluorouracil/leucovorin/oxaliplatin (FOLFOX) and 5-fluorouracil/leucovorin/irinotecan (FOLFIRI), administered concurrently or sequentially, versus FOLFOX-BEV in first-line mCRC. Evaluation of biomarkers associated with treatment outcomes was an exploratory endpoint. Patients in the biomarker-evaluable population (BEP) had 1 tissue sample, 1 pre-induction plasma sample, and 1 post-induction plasma sample collected ≤60 days of induction from last drug date.Results:Among the 280 patients enrolled in STEAM, 183 had sequenced and evaluable tumor tissue, 118 had matched pre-induction plasma, and 54 (BEP) had ctDNA-evaluable sequencing data for pre- and post-induction plasma. The most common somatic variants in tumor tissue and pre-induction plasma were TP53, APC, and KRAS. Patients with lower-than-median versus higher-than-median post-induction mean allele fraction (mAF) levels had longer median PFS (17.7 vs. 7.5 months, HR, 0.33; 95% confidence interval, 0.17–0.63). Higher levels of post-induction mAF and post-induction mean mutant molecules per milliliter (mMMPM), and changes in ctDNA (stratified by a 10-fold or 100-fold reduction in mAF between pre- and post-induction plasma), were associated with shorter PFS. Post-induction mAF and mMMPM generally correlated with each other (ρ = 0.987, P < 0.0001).Conclusions:ctDNA quantification in post-induction plasma may serve as a prognostic biomarker for mCRC post-treatment outcomes.

Background: There is an unmet need for evidence-based systemic therapies for pts with HER2-positive MBC and progressive brain metastases. Despite assumptions that monoclonal antibodies do not cross the blood-brain barrier, molecular imaging in pts shows localization of 89Zr-trastuzumab to brain metastases. Furthermore, preclinical data support dose-dependent activity of H in intracranial tumor models. The PATRICIA study (NCT02536339) evaluated safety and efficacy of P plus high-dose H in pts with HER2-positive MBC with CNS metastases and CNS progression after RT. Herein, we present results from the primary efficacy analysis of PATRICIA. Methods: PATRICIA was a US-based, phase II, open-label, single arm study. Eligible pts had measurable (≥10 mm) CNS disease that had progressed after CNS-directed RT, in the setting of stable extracranial disease. CNS-directed RT included whole-brain RT (WBRT) or stereotactic radiosurgery (SRS) and must have been completed ≥60 days before study entry. Pts received P (840 mg loading dose, then 420 mg every 3 weeks) and high-dose H (6 mg/kg weekly), which continued until progression (CNS or systemic) or unacceptable toxicity. Pts could continue their existing systemic anti-cancer therapy during the study, with the exception of trastuzumab emtansine (T-DM1) or lapatinib. Switch of other anti-cancer therapy was not permitted during the study. Restaging evaluations including brain MRI were completed every 2 cycles. The primary efficacy endpoint was confirmed objective response rate (ORR) in the CNS per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) criteria. Secondary endpoints included duration of response (DOR), clinical benefit rate (CBR) in the CNS, and safety. Samples were collected for exploratory pharmacokinetic analyses on Day 1 of weeks 1, 4, 10, and 16. Results: From 15 Dec 2015 to 18 May 2017, 40 pts were enrolled across 16 sites. Median age was 48 (range 34–69) years, with 33% and 67% of pts having an Eastern Cooperative Oncology Group Performance Status score of 0 or 1, respectively. 41% of pts had received prior WBRT only, 28% had received prior SRS only, and 31% had received both. At the data cut off (1 May 2019), of 39 treated pts, 2 remained on study treatment and 37 discontinued treatment, most commonly due to CNS progression (n=27). Median treatment duration was 4.5 (range 0.3–37.3) months. Four pts in the efficacy population (N=37) experienced a confirmed partial response (Table), leading to an ORR of 11% (95% confidence interval [CI], 3–25%). Response durations were 3.2, 3.3, 4.6, and 5.6 months (median DOR 4.6 months). The CBR (complete response + partial response + stable disease [SD] of ≥4 or ≥6 months) was 68% (SD ≥4 months) and 51% (SD ≥6 months). Results from exploratory pharmacokinetic analyses confirmed greater H exposure with the high-dose schedule. The adverse event profile was similar to that previously reported for P and H, with no new safety signals. One pt discontinued treatment due to an adverse event (grade 3 left ventricular dysfunction, considered related to study treatment). No Grade 5 adverse events were reported. Conclusions: The CNS ORR of 11%, ≥6-month CBR of 51%, and lack of any new safety signals suggest that P plus high-dose H may have clinical utility in some pts with HER2-positive MBC with progressive CNS metastases. Table. Efficacy within the CNS per RANO-BM criteriaEfficacy population (N=37)n (%)95% CIORR*4 (11)3, 25CBR (CR + PR + stable disease [SD] ≥4 months)25 (68)50, 82CBR (CR + PR + SD ≥6 months)19 (51)34, 68Confirmed best response (SD ≥4 months)CR0—PR4 (11)—SD ≥4 months21 (57)—Pts without clinical benefit12 (32)—Confirmed best response (SD ≥6 months)CR0—PR4 (11)—SD ≥6 months15 (41)—Pts without clinical benefit18 (49)—*Confirmed complete response (CR) or confirmed partial response (PR). Citation Format: Nancy U Lin, Priya Kumthekar, Solmaz Sahebjam, Nuhad Ibrahim, Anita Fung, Anna Cheng, Alan Nicholas, Bei Wang, Mark Pegram. Pertuzumab (P) plus high-dose trastuzumab (H) for the treatment of central nervous system (CNS) progression after radiotherapy (RT) in patients (pts) with HER2-positive metastatic breast cancer (MBC): Primary efficacy analysis results from the phase II PATRICIA study [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P1-18-03.

Background: PD-L1 expression evaluated by immunohistochemistry (IHC) is a well-established predictor of anti-PD-L1/PD-1 cancer immunotherapy (CIT). The Phase II LCMC3 (NCT02927301) study evaluated pre-operative treatment (tx) with atezolizumab (anti-PD-L1) in pts with untreated early stage resectable NSCLC, achieving a 20% major pathologic response (MPR) rate (primary efficacy pts, n=143). A digital PD-L1 scoring method was developed to assess PD-L1 expression as a potential predictive marker for MPR in squamous and non-squamous tumor samples from LCMC3. Methods: Manual scoring was used to determine PD-L1 status on pre-tx biopsy samples using the tumor proportion score (TPS) with a positive threshold of TPS≥50 (22C3). Binary results were correlated with MPR and stratified by squamous/non-squamous histology. A digital pathology workflow for automated PD-L1 scoring was developed to yield a precise continuous PD-L1 TPS. Deep convolutional neural networks trained using pathologist annotations were used to detect individual cells within the tumor and tumor microenvironment and quantify their PD-L1 expression. These cell type predictions were used to compute a digital PD-L1 TPS. LCMC3 pts with available digital and manual PD-L1 scores were then used to assess the role of PD-L1 expression in predicting MPR. Results: PD-L1 scores were available for pre-tx biopsies from 108 pts. No significant difference in scores was seen between histological subtypes. At cutoff (Oct 15, 2021), TPS≥50 was seen in 41 (non-squamous, n=26 [39%]; squamous, n=15 [36%]) of 108 pts and was associated with MPR in non-squamous (odds ratio [OR], 28.6; P Conclusions: These findings support using digitally assessed PD-L1 IHC as a centralized and standardized scoring system and suggest that tumor histological subtype could be an important factor in the utility of PD-L1 as a predictive biomarker for neoadjuvant CIT in early stage NSCLC. Citation Format: John Abel, Christopher Rivard, Filip Kos, Guillaume Chhor, Yi Liu, Jennifer Giltnane, Sara Hoffman, Murray Resnick, Cyrus Hedvat, Amaro Taylor-Weiner, Farah Khalil, Alan Nicholas, Gregory A. Fishbein, Lynette M. Sholl, Natasha Rekhtman, Stephanie Hennek, Ilan Wapinski, Ann Johnson, Michael Montalto, Katja Schulze, Bruce E. Johnson, David P. Carbone, Konstantin Shilo, Andrew H. Beck, Sanja Dacic, William D. Travis, Ignacio Wistuba. AI-powered and manual assessment of PD-L1 are comparable in predicting response to neoadjuvant atezolizumab in patients (pts) with resectable non-squamous, non-small cell lung cancer (NSCLC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT112.

2519 Background: Resistance to immune checkpoint blockade (ICB) can manifest as disease progression either at the initiation of treatment (primary resistance) or after some initial response (acquired resistance). To better understand the mechanisms underlying acquired resistance, the imCORE Network is conducting a study (NCT03333655) to examine changes in tumor biology from pre-treatment to disease progression across cancer types. Methods: Eligible patients included those experiencing clinical benefit on ICB (defined as objective response or stable disease longer than 6 months) and had evaluable tissue samples from both pre-treatment and within 30 days of progression. Samples were subjected to whole exome sequencing (WES), RNA sequencing (RNA-Seq), and immunohistochemistry (IHC). Whole blood samples or adjacent normal tissue were used as a reference for tumor variant calling. Results: As of December 3rd, 2021, 24 enrolled patients have complete sample pairs. Of those, melanoma, bladder, and lung were most common (n = 7, 6 and 5 pairs, respectively), but our cohort also included patients with breast cancer, squamous head & neck, and renal cell carcinoma. IHC data unexpectedly showed a modest, but consistent increase in tumor infiltrating CD8+ T cells at progression. In addition, IHC evidence of a decrease in MHC-I proteins (HLA-A and B2M) suggest that in 5 out of 24 cases, key proteins needed for antigen presentation are lost. Global differential gene expression analysis showed that immune gene expression was significantly increased at progression, including numerous chemokines and significant enrichment in gene sets responsible for antigen presentation machinery. Protein-altering mutations at progression appeared in B2M in one patient, and CXCL9 in another. However, in most cases it is unclear what genetic alterations are responsible. We do not observe evidence of consistent IFNγ and Jak/stat signaling loss or antigen presentation loss. Conclusions: While ICB resistance is thought to be associated with a lack of immune response within the TME, we found that acquired resistance is usually associated with either maintenance or an increase in immune infiltration. Multiple alterations that are unique to individual patients also continue to emerge. Our data shows ICB resistance is multifactorial and associated with dynamic changes to markers amid immune activation and inhibition. Clinical trial information: NCT03333655.

Effective therapies are needed for the treatment of patients with HER2-positive MBC who develop brain metastases. In the open-label, phase II PATRICIA study (NCT02536339), 40 patients with HER2-positive MBC with CNS metastases and CNS progression post-radiotherapy (median age 48 years [range, 34–69]; prior CNS treatment [whole brain radiotherapy 71%, stereotactic radiosurgery 59%, both 31%]) were enrolled to receive pertuzumab plus high-dose trastuzumab (6-mg/kg weekly) until CNS or systemic disease progression or unacceptable toxicity. Following a median (range) treatment duration of 4.5 (0.3–37.3) months, the CNS-confirmed objective response rate per Response Assessment in Neuro-Oncology Brain Metastases criteria (primary endpoint) was 11% (95% confidence interval: 3.03, 25.42), and the clinical benefit rate at 4 months was 68%, indicating sustained clinical stability. Patient-reported outcomes (PROs) were evaluated using the MD Anderson Symptom Inventory-Brain Tumor (MDASI-BT), which includes sub-scales for symptom severity (average of 13 core symptom and 9 brain-tumor specific items) and symptom interference (average of 6 interference-with-life items representing overall symptom distress). Among 36 patients included in the PRO analyses, mean (standard deviation [SD]) symptom severity scores at baseline and weeks 12 and 28 were 1.65 (1.62), 2.24 (2.14), and 1.94 (2.55), respectively. Mean (SD) symptom interference scores at baseline and weeks 12 and 28 were 2.51 (2.63), 2.81 (3.39), and 1.76 (2.43), respectively. Mean (SD) changes in symptom severity and interferences scores from baseline to week 12 were 0.34 (1.54) and 0.33 (3.08), respectively. On average, patients who did not achieve stable disease or better in the CNS following treatment had worsened symptom severity and symptom interference scores over 12 weeks, while those with stable disease or better in the CNS exhibited stable or improving scores. Pertuzumab plus high-dose trastuzumab provided clinical benefit to the majority (68%) of patients in PATRICIA, without a decrement in quality of life.

Statement of the Problem: Recent historians have argued that the term “frontier” and the related concepts of frontier societies or zones (as used by scholars of medieval Spain in particular and the Middle Ages in general) are all amorphous and ill-defined concepts, lacking predictive value because of their conflicting usages by different historians. Is it possible to create a solid foundation for the term “frontier” so that it can be utilized in historical discourse? Do any of the elements of the frontier hypothesis as it was originally conceived hold up when applied to contemporary medieval notions of the frontier? Methodology or Procedures: This thesis utilizes three law codes from medieval Spain: the Code of Cuenca, which is the municipal charter granted to the town of Cuenca after it was conquered from the Muslims in the 12 century by the King of Castile; the combined Fueros (the Spanish term for municipal charters) of the towns of Borja and Zaragoza in the Kingdom of Aragon, produced around 1150; and Las Siete Partidas (The Seven Laws) which were codified around the mid-13 century to apply to the entirety of Castile. This study analyzes the Code of Cuenca and the Fueros de Borja y Zaragoza for their descriptions of the boundaries of their respective communities in order to find a contemporary vision of the frontier, and then compares them to each other to establish the fundamental similarity of the frontier experience between kingdoms. Finally, it compares both Charters to Las Siete Partidas in order to establish their influence on that code and to track the changes in the concept of the frontier over the course of the Reconquista. Findings: The pre-existing concept of the frontier in medieval Spain, la frontera, provides a stable theoretical basis for the use of the term “frontier” in analyzing medieval Spain because it is grounded in the local perceptions of the term rather than outside theoretical constructs that were originally intended to describe the American frontier. The characteristics of the Spanish frontier are visible within the law codes and town charters of the various kingdoms of Spain, and these sources are representative of the broader mindset because they were based on both the views of the powerful kings and the deeply rooted Visigothic customs kept by the peasants and local lords. The original conception of the frontier held (in part) that it shaped culture away from European norms, and this particular proviso of the original theory applies to Castile in that those previous Visigothic customs were reified by the granting of town charters and were thus made resistant to later pressure to conform to European norms. Specifically, the concept of partible inheritance, inherited from the Visigoths, remained the norm in Spanish law in direct contrast to the prevailing notions of primogeniture and/or maleonly inheritance in most of the rest of Europe.

Background: Based on the Ph III IMbrave150 trial, atezo + bev has been approved globally and is the standard of care for pts with unresectable HCC who have not received prior systemic therapy. With an additional 12 mo of follow-up from the primary analysis (median, 15.6 mo), atezo + bev showed consistent clinically meaningful treatment benefit and safety (Finn ASCO GI 2021). Here, we report results of updated analyses considering high-risk factors. Methods: Pts were randomized 2:1 to receive atezo 1200 mg IV q3w + bev 15 mg/kg IV q3w or sor 400 mg PO BID until loss of clinical benefit or unacceptable toxicity. High-risk pts were defined as those who had tumor invasion of the main trunk of the portal vein and/or the portal vein branch contralateral to the primarily involved lobe (Vp4), and/or bile duct invasion and/or tumor occupancy of ≥ 50% of liver. Results: In the ITT population, 64 (19%) pts randomized to atezo + bev and 37 (22%) pts randomized to sor were defined as high risk. 10 pts had bile duct invasion, 73 had Vp4 portal vein invasion and 31 had liver tumor occupancy of ≥ 50%. 9 pts in the atezo + bev arm and 4 pts in the sor arm had 2 high-risk factors. OS, PFS and ORR all favored atezo + bev over sor, in both non-high-risk and high-risk patients. See table for efficacy results. In safety-evaluable pts, Grade 3/4 treatment-related AEs (TRAEs) occurred in 122 (45%) of 269 non-high-risk and 21 (35%) of 60 high-risk atezo + bev pts. Grade 5 TRAEs occurred in 5 (2%) non-high-risk and 1 (2%) high-risk atezo + bev pt. Conclusions: Efficacy benefit was seen with atezo + bev vs sor regardless of the presence of high-risk features. HRs remained similar despite the numerical differences in median OS between non-high-risk and high-risk pts. Further, the overall safety data in the atezo + bev arm were comparable between non-high-risk and high-risk pts and in line with the known safety profile of each drug. Non-High RiskHigh RiskITTAtezo + BevSorAtezo + BevSorAtezo + BevSorEvaluable for OS/PFS, n2721286437336165Median OS (95% CI), mo22.8 (19.1, 24.9)15.7 (13.2, 19.0)7.6 (6.6, 12.8)5.5 (4.1, 6.7)19.2 (17.0, 23.7)13.4 (11.4, 16.9)HR (95% CI)0.68 (0.51, 0.91)0.62 (0.39, 1.00)0.66 (0.52, 0.85)Median PFS (95% CI), moa7.2 (6.5, 9.6)4.4 (4.0, 5.8)5.4 (4.0, 6.9)2.8 (2.5, 5.3)6.9 (5.7, 8.6)4.3 (4.0, 5.6)HR (95% CI)0.61 (0.48, 0.78)0.74 (0.47, 1.17)0.65 (0.53, 0.81)Evaluable for ORR, n2631246335326159Confirmed ORR, n (%)a,b81 (31)13 (10)16 (25)5 (14)97 (30)18 (11)Complete response, n (%)a20 (8)05 (8)1 (3)25 (8)1 (1)Median DOR (95% CI), moa,c19.0 (14.6, NE)12.6 (4.9, 17.0)16.3 (13.5, NE)16.5 (3.9, NE)18.1 (14.6, NE)14.9 (4.9, 17.0)NCT03434379.Clinical cutoff date: Aug 31, 2020.DOR, duration of response; HR, hazard ratio; IRF, independent review facility; NE, not estimable; ORR, objective response rate; OS, overall survival; PFS, progression-free survival.aAssessed by an IRF per RECIST 1.1.bORR IRF RECIST 1.1-evaluable population was based on patients who presented with measurable disease at baseline.cDOR analysis was based on all confirmed responders. Citation Format: Richard S. Finn, Shukui Qin, Masafumi Ikeda, Peter R. Galle, Michel Ducreux, Tae-You Kim, Masatoshi Kudo, Ho Yeong Lim, Valeriy Breder, Philippe Merle, Ahmed Kaseb, Daneng Li, Yin-Hsun Feng, Wendy Verret, Alan Nicholas, Lindong Li, Ning Ma, Andrew X. Zhu, Ann-Lii Cheng. IMbrave150: Updated efficacy and safety by risk status in patients (pts) receiving atezolizumab (atezo) + bevacizumab (bev) vs sorafenib (sor) as first-line treatment for unresectable hepatocellular carcinoma (HCC) [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT009.

4073 Background: Atezo + bev has been approved in >60 countries for pts with unresectable HCC who have not received prior systemic therapy, based on IMbrave150 (NCT03434379; Finn RS NEJM 2020). Due to their poor prognosis and the hemodynamic changes from increased portal vein pressure, pts with main portal vein tumor thrombus are often excluded from pivotal HCC trials. Here, we report exploratory efficacy and safety results of pts with Vp4 (presence of a tumor thrombus in the main trunk and/or contralateral portal vein) using updated IMbrave150 data (Finn RS ASCO GI 2021). Methods: Pts were randomized 2:1 to atezo 1200 mg IV q3w + bev 15 mg/kg IV q3w or sor 400 mg bid until unacceptable toxicity or loss of clinical benefit per investigator. IMbrave150 enrolled 501 systemic treatment (tx)–naive unresectable HCC pts, ≥1 measurable untreated lesion (RECIST 1.1), Child-Pugh class A liver function and ECOG PS 0/1, including 73 (15%) Vp4 pts. This post hoc exploratory analysis was conducted with a median follow-up of 15.6 mo in ITT pts. Results: Of the Vp4 pts, 48 received atezo + bev and 25 received sor. Median OS (mOS) was 7.6 vs 5.5 mo (HR, 0.62; 95% CI: 0.34, 1.11) and median PFS (mPFS) per independent review facility (IRF)–assessed RECIST 1.1 was 5.4 vs 2.8 mo (HR, 0.62; 95% CI: 0.35, 1.09) with atezo + bev and sor, respectively. ORR per IRF RECIST 1.1 was 23% (11/47) with atezo + bev (2 [4%] pts had CR) vs 13% (3/23) with sor (1 [4%] pt had CR). All-grade variceal bleeding was higher with atezo + bev in Vp4 (13.6%) vs rest of ITT pts (2.5%). See table for further efficacy and safety data. Conclusions: The benefits of atezo + bev over sor in Vp4 pts are consistent with those in ITT pts across all efficacy endpoints, despite the expected disease-intrinsic increase in variceal bleeding in Vp4 vs rest of ITT pts. The overall positive benefit-risk profile supports the use of atezo + bev in pts with Vp4. Clinical trial information: NCT03434379. [Table: see text]

4071 Background: Based on IMbrave150 (NCT03434379) results, atezo + bev has been approved in > 60 countries for pts with unresectable HCC who have not received prior systemic therapy (Finn RS, NEJM 2020). OS and objective response rate (ORR) improvements with atezo + bev vs sor were maintained with an additional 12 mo of follow up since primary analysis. Updated median OS was 19.2 mo with atezo + bev vs 13.4 mo with sor (stratified HR, 0.66; 95% CI: 0.52, 0.85). Updated ORR was 30% with atezo + bev vs 11% with sor by independently-assessed (IRF) RECIST 1.1 (Finn RS, ASCO GI 2021). Here, we report an exploratory analysis examining the association of response by RECIST 1.1 with OS and independent predictors of survival. Methods: Pts in this Ph III study were systemic treatment–naive with unresectable HCC, ≥1 measurable untreated lesion (RECIST 1.1), Child-Pugh class A liver function and ECOG PS 0/1. Pts were randomized 2:1 to atezo 1200 mg IV q3w + bev 15 mg/kg IV q3w or sor 400 mg bid until unacceptable toxicity or loss of clinical benefit per investigator. ORR was determined by IRF RECIST 1.1. Kaplan-Meier analyses of OS by response status were conducted without landmark and with 4- and 6-mo landmarks. Multivariate analysis was conducted using Cox modeling with time-dependent covariate (responder [yes/no]) with backwards elimination. These analyses only included pts treated with atezo + bev. Results: IMbrave150 enrolled 501 pts, including 336 treated with atezo + bev. Median follow-up was 15.6 mo. OS was longer in pts with confirmed response per RECIST 1.1 (responders, CR + PR) vs non-responders by Kaplan-Meier analyses without landmark and with 4- and 6-mo landmarks (Table). By multivariate analysis, in addition to responder (yes/no), 5 of the 10 initially included predictors of OS remained in the final Cox model ( P< 0.10): ECOG PS (0/1), geographic region (Asia excluding Japan/rest of the world), etiology (hepatitis B/hepatitis C/non-viral), macrovascular invasion and/or extrahepatic spread (yes/no), and baseline alpha-fetoprotein ( < 400 ng/mL/≥400 ng/mL). Conclusions: Atezo + bev is the new standard of care for pts with previously untreated, unresectable HCC. Here we showed that in IMbrave150 pts treated with atezo + bev, response by RECIST 1.1 was associated with OS, suggesting that confirmed response is an independent predictor of OS in these pts. Clinical trial information: NCT03434379. [Table: see text]

106 Background: PathR is an efficacy endpoint in Phase II and III neoadjuvant trials and is proposed as a surrogate for disease-free survival (DFS) and overall survival. Machine learning (ML)–based, automated approaches standardize quantification of areas of tumor bed and residual viable tumor. Here we show that automation may provide a scalable alternative to or complementary tool for manual assessment. Methods: We determined inter-reader variability for PathR among pathologists in the LCMC3 (NCT02927301) study and developed an AI-powered digital PathR assessment tool in line with manual consensus recommendations. Study cases were reviewed for PathR by a local site pathologist and 3 central expert pathologists (n = 127). When determined manually, major PathR (MPR) was defined as ≤10% viable tumor averaged per case. ML models were trained and validated by the PathAI research platform using digitized H&E-stained tumor sections. The digital PathR model predicted percent viable tumor for each case as the sum of the cancer epithelium area from each slide divided by the sum of tumor bed area for each slide. DFS (clinical cutoff: Oct 23, 2020) was reported for patients with manual and digital PathR assessment (n = 135). For digital MPR, we used a prevalence-matched cutoff that maintained the same proportion of patients as manual MPR. Results: Inter-reader agreement among 1 local and 3 central pathologists for manual PathR was good (n = 127; ICC = 0.87; 95% CI: 0.84-0.90). Agreement was 91% (κ = 0.82) on manual MPR and 98% (κ = 0.88) on pathologic complete response (pCR). 6 patients had unanimous pCR. Digital and manual PathR were strongly correlated (n = 135, Pearson r = 0.78) and digital PathR demonstrated an outstanding predictability for manual MPR (AUROC = 0.975). The range was 0%-60% for digital PathR and 0%-100% for manual PathR with a regression line slope < 1.0 (m = 0.303) indicating systematic differences between the methods, consistent with digital PathR using a high-resolution segmentation of cancer epithelium from stroma across each slide. Longer DFS was observed for MPR yes vs no with both digital and manual assessment (Table). Conclusions: This analysis showed good inter-reader agreement for manual and strong correlation of AI-powered digital and manual PathR. Comparable DFS rates for manual MPR and digital MPR are encouraging in the preliminary data. These data support further studies of digital PathR as a standardized and scalable tool to determine PathR. Clinical trial information: NCT02927301. [Table: see text]

The contributions of domain-general abilities and domain-specific knowledge to subsequent mathematics achievement were longitudinally assessed (n = 167) through 8th grade. First grade intelligence and working memory and prior grade reading achievement indexed domain-general effects and domain-specific effects were indexed by prior grade mathematics achievement and mathematical cognition measures of prior grade number knowledge, addition skills, and fraction knowledge. Use of functional data analysis enabled grade-by-grade estimation of overall domain-general and domain-specific effects on subsequent mathematics achievement, the relative importance of individual domain-general and domain-specific variables on this achievement, and linear and non-linear across-grade estimates of these effects. The overall importance of domain-general abilities for subsequent achievement was stable across grades, with working memory emerging as the most important domain-general ability in later grades. The importance of prior mathematical competencies on subsequent mathematics achievement increased across grades, with number knowledge and arithmetic skills critical in all grades and fraction knowledge in later grades. Overall, domain-general abilities were more important than domain-specific knowledge for mathematics learning in early grades but general abilities and domain-specific knowledge were equally important in later grades.

BACKGROUND. First‐line treatment for metastatic colorectal cancer (mCRC) typically entails a biologic such as bevacizumab (BEV) with 5‐fluorouracil/leucovorin/oxaliplatin (FOLFOX) or 5‐fluorouracil/leucovorin/irinotecan (FOLFIRI). STEAM (NCT01765582) assessed the efficacy of BEV plus FOLFOX/FOLFIRI (FOLFOXIRI), administered concurrently (cFOLFOXIRI‐BEV) or sequentially (sFOLFOXIRI‐BEV, FOLFOX‐BEV alternating with FOLFIRI‐BEV), versus FOLFOX‐BEV for mCRC. PATIENTS AND METHODS. Patients with previously untreated mCRC (n = 280) were randomized 1:1:1 to cFOLFOXIRI‐BEV, sFOLFOXIRI‐BEV, or FOLFOX‐BEV and treated with 4–6‐month induction followed by maintenance. Coprimary objectives were overall response rate (ORR; first‐line cFOLFOXIRI‐BEV vs. FOLFOX‐BEV) and progression‐free survival (PFS; pooled first‐line cFOLFOXIRI‐BEV and sFOLFOXIRI‐BEV vs. FOLFOX‐BEV). Secondary/exploratory objectives included overall survival (OS), liver resection rates, biomarker analyses, and safety. RESULTS. ORR was 72.0%, 72.8%, and 62.1% and median PFS was 11.9, 11.4, and 9.5 months with cFOLFOXIRI‐BEV, sFOLFOXIRI‐BEV, and FOLFOX‐BEV, respectively. OS was similar between arms. ORR between cFOLFOXIRI‐BEV and FOLFOX‐BEV did not significantly differ (p = .132); thus, the primary ORR endpoint was not met. cFOLFOXIRI‐BEV and sFOLFOXIRI‐BEV numerically improved ORR and PFS, regardless of RAS status. Median PFS was higher with pooled concurrent and sequential FOLFOXIRI‐BEV versus FOLFOX‐BEV (11.7 vs. 9.5 months; hazard ratio, 0.7; 90% confidence interval, 0.5–0.9; p < .01). Liver resection rates were 17.2% (cFOLFOXIRI‐BEV), 9.8% (sFOLFOXIRI‐BEV), and 8.4% (FOLFOX‐BEV). Grade ≥ 3 treatment‐emergent adverse events (TEAEs) were observed in 91.2% (cFOLFOXIRI‐BEV), 86.7% (sFOLFOXIRI‐BEV), and 85.6% (FOLFOX‐BEV) of patients, with no increase in serious chemotherapy‐associated TEAEs. CONCLUSION. cFOLFOXIRI‐BEV and sFOLFOXIRI‐BEV were well tolerated with numerically improved ORR, PFS, and liver resection rates versus FOLFOX‐BEV, supporting triplet chemotherapy plus BEV as a first‐line treatment option for mCRC. IMPLICATIONS FOR PRACTICE. The combination of first‐line FOLFIRI with FOLFOX and bevacizumab (concurrent FOLFOXIRI‐BEV) improves clinical outcomes in patients with metastatic colorectal cancer (mCRC) relative to FOLFIRI‐BEV or FOLFOX‐BEV, but it is thought to be associated with increased toxicity. Alternating treatment of FOLFOX and FOLFIRI (sequential FOLFOXIRI‐BEV) could improve tolerability. In the phase II STEAM trial, which is the largest study of FOLFOXIRI‐BEV in patients in the U.S., it was found that both concurrent and sequential FOLFOXIRI‐BEV are active and well tolerated in patients with previously untreated mCRC, supporting the use of these regimens as potential first‐line treatment options for this population.

8503 Background: Small pilot studies (e.g., N Engl J Med. 2018;378:1976) have shown that preoperative immune checkpoint inhibitor therapy may be of benefit in early-stage NSCLC. This large multicenter trial assesses the benefit of neoadjuvant treatment with atezolizumab (atezo; NCT02927301). Methods: Patients (pts) with stages IB to selected IIIB resectable NSCLC receive 2 cycles of atezo 1200 mg (days 1, 22) then undergo resection (day 40 ± 10). Primary tumor +/- node biopsies and blood samples are obtained before atezo and at surgery for biomarker studies. The primary endpoint is major pathological response (MPR), defined as ≤ 10% viable tumor cells in the resection specimen. Secondary endpoints include safety and correlation of response with PD-L1 expression, tumor mutation burden (TMB) and gene expression signatures. Results: For this interim efficacy analysis (5 Sep 2018 data cut), we report on the first 101 of 180 planned pts: 47 males, median age, 64 y; all ECOG PS 0-1; 23 current and 68 former smokers; 66 non-squamous NSCLC; clinical stages IB/IIA/IIB/IIIA/IIIB n = 11/16/28/39/7. There were 2 treatment-unrelated Gr 5 AEs (cardiac death post surgical resection; death due to disease progression), 29 Gr 3-4 AEs (6 [6%] treatment related). 90 pts had surgery. Excluding 8 pts who had driver mutations (7 EGFR, 1 ALK, no MPR), MPR rate was 15/82 (18%, 95% CI 11%-28%), 4 pts had pathological complete response (pCR). By RECIST, 6/82 pts had PR, 72 had SD and 4 had PD. Two of 26 (8%) PD-L1− (TC0 and IC0, clone SP142) and 10 of 35 (29%) PD-L1+ had MPR ( P= 0.055). Five of 44 (11%) TPS < 50 (PD-L1 clone 22C3) and 7 of 20 (35%) TPS > 50 had MPR ( P= 0.040). Exome sequencing data was available for 47/101 pts. Median TMB was 10.4 (range, 1.5-46.5) mutations per Mb and was not different in those with MPR compared with those without MPR. Further analysis of TMB, mutation signatures, and gene expression profiling is ongoing. Conclusions: Atezo in the neoadjuvant setting was well tolerated, and pCR and MPR rates are encouraging in this large multicenter trial. Efficacy interim analysis passed its futility boundary, and study enrollment continues. Safety, efficacy results and ongoing correlative analyses will be presented. Clinical trial information: NCT02927301.

3545Background: STEAM (clinical trial NCT01765582) assessed efficacy and safety of concurrent and sequential FOLFOXIRI-bevacizumab (BEV) vs FOLFOX-BEV for first-line treatment of mCRC. The AVENIO c...

8541Background: Platinum-based chemotherapy, before or after surgery, provides only a 5% benefit in 5yr. OS in locally advanced NSCLC. A recent pilot study (JCO 2017 35:15suppl, 8508) showed that p...

e15118 Background: STEAM (NCT01765582) evaluated the efficacy and safety of concurrent (c) and sequential (s) FOLFOXIRI-bevacizumab (BEV) versus FOLFOX-BEV for first-line treatment of mCRC. Methods: The AVENIO ctDNA Expanded Kit (Research Use Only) was used to identify somatic mutations in 77 cancer-related genes by next-generation sequencing (NGS) in both pre- and post-induction plasma samples (n = 118 for both groups) from STEAM. Demographics for patient tested were similar to the overall cohort. The mutant allele fraction (mAF) represents the mutation frequency in ctDNA for single nucleotide variants (SNVs) and indels detected per patient. Results: Overall, patients with a pre-induction mAF below the median had longer PFS compared to patients with mAF above the median (13.4 vs 9.5 mo, HR 0.49, p = 0.002). A similar trend was seen for overall survival (OS). Within the below median mAF group, longer PFS was observed in patients treated with cFOLFOXIRI-BEV versus FOLFOX-BEV (25.2 vs 9.5 mo, HR 0.34, p = 0.020). In contrast, no differences in PFS were observed in the treatment arms in the above median mAF group. Patients with a post-induction mAF below the median had longer PFS compared to patients with mAF above the median (15.3 vs 8.1 mo, HR 0.51, p = 0.0064). Correlations of post-induction genomic changes with outcomes, according to treatment groups, will also be presented. Conclusions: The level of pre- and post-induction mAF appears to correlate with PFS in STEAM overall. Furthermore, a lower median pre-induction mAF suggests PFS benefit for cFOLFOXIRI-BEV versus FOLFOX-BEV. Thus, plasma analysis of mAF via the AVENIO ctDNA Expanded Kit may identify patients who benefit from specific treatment in mCRC. These results are hypothesis generating and require further clinical validation. Clinical trial information: NCT01765582.

2074 Background: There is currently no clear standard of care to address the management of recurring/multiple intracranial metastases post RT in HER2-positive MBC. The ongoing PATRICIA study (NCT02536339) is evaluating the safety and efficacy of P in combination with high-dose h for patients with HER2-positive MBC with CNS metastases who have CNS progression following RT. Reported herein are results from the protocol-specified interim analysis of PATRICIA. Methods: All eligible patients must have measurable (≥10 mm) CNS progression post RT, and stable non-CNS disease. Patients receive P (840-mg loading dose, then 420 mg every 3 weeks) and high-dose h (6 mg/kg weekly). The primary efficacy endpoint is objective response rate (ORR) in the CNS per Response Assessment in Neuro-Oncology Brain Metastases (RANO-BM) criteria. The interim analysis was planned after 15 patients were enrolled and had ≥2 left ventricular ejection fraction (LVEF) measurements, 2 cycles of study drugs, and 2 response measurements. The study would proceed to full enrollment (n=40) if objective response or stable disease in the CNS was observed in ≥1 of 15 patients and

11510 Background: STEAM (NCT01765582) assessed the efficacy and safety of concurrent (c) and sequential (s) FOLFOXIRI-bevacizumab (BEV) vs FOLFOX-BEV for first-line treatment of mCRC. Methods: The AVENIO ctDNA Expanded Kit (Research Use Only) was used to assess somatic mutations in 77 cancer-related genes by NGS in tissue, and both pre- and post-induction plasma samples (n = 182, 150 and 118 respectively) from STEAM. Four mutation classes including single-nucleotide variants (SNVs), indels, copy number amplifications (CNAs) and fusions were identified. SNVs and indels were called in tissue and plasma at allele frequencies of 5% and 0.25% respectively. Results: Overall concordance of mutations in pre-induction plasma with tissue was 83%. Concordance for the seven most mutated genes ranged from 91.5%-100%. In pts with matched samples (n = 118), RAS WT pts showed significantly longer progression-free survival (PFS) in both cFOLFOXIRI-BEV (A) and sFOLFOXIRI-BEV (B) arms versus FOLFOX-BEV (C), using genotyping of either tissue or plasma. This was not seen in RAS MUT pts. In contrast, TP53 WT showed no significant treatment differences while TP53 MUT showed longer PFS for cFOLFOXIRI-BEV versus FOLFOX-BEV. A list of mutation frequencies for all samples, as well as hierarchical clustering analysis of tissue mutations will be presented. Conclusions: The AVENIO ctDNA Expanded Kit identified mutations in 77 cancer-related genes, in both plasma and tissue, with high overall concordance. Compared to FOLFOX-BEV, longer PFS was observed for c- or s- FOLFOXIRI-BEV in RAS WT pts and for cFOLFOXIRI-BEV in TP53 MUT pts, irrespective of sample type. These results are hypothesis generating and require further clinical validation. Clinical trial information: NCT01765582. [Table: see text]

657 Background: STEAM (NCT01765582) assessed efficacy and safety of 1L cFOLFOXIRI-BV and sFOLFOXIRI-BV vs FOLFOX-BV. Updated efficacy, safety, and exploratory biomarker data are reported. Methods: 280 tx-naive pts with mCRC were randomized 1:1:1 to BV-containing (5 mg/kg q2w) arms (cFOLFOXIRI, sFOLFOXIRI [alternating FOLFOX and FOLFIRI every 4 weeks {q4w}], or FOLFOX) in a 4–6 month (mo) induction phase, followed by maintenance. Primary objectives include progression-free survival (PFS). Secondary objectives include overall survival (OS). Tumor-relevant biomarker evaluations were exploratory. Results: Median PFS significantly improved and median OS showed a positive trend with cFOLFOXIRI-BV vs FOLFOX-BV. PFS significantly improved with cFOLFOXFIRI-BV vs FOLFOX-BV in BRAF wild type (WT); there was a positive trend in RAS WT and mutant (MUT) pts; no tx difference observed in BRAF MUT pts. In the safety pop., (n = 271), 88% had Grade ≥ 3 tx emergent AEs: 91% cFOLFOXIRI-BV; 87% sFOLFOXIRI-BV; 86% FOLFOX-BV. Conclusions: Improved PFS and a positive trend in OS were observed for cFOLFOXIRI-BV vs FOLFOX-BV. A positive PFS trend was seen in RAS WT and MUT pts, with significantly improved PFS in BRAF WT. The small number of BRAF MUT pts precluded estimation of tx effects. AEs for all 3 txs were consistent with previous reports. Clinical trial information: NCT01765582. [Table: see text]

99 Background: Targeting PD-L1/PD-1 to activate anti-tumor immunity is associated with improved response and survival compared to chemo in NSCLC pts. We present a preliminary analysis of the clinical efficacy, safety and peripheral blood (PB) immunophenotyping from an ongoing multicenter atezolizumab (atezo) neoadjuvant immunotherapy study in resectable NSCLC. Methods: Pts received 2 cycles of atezo, 1200mg, days 1, 22 before resection. Tumor biopsies and PB were obtained pre-atezo & pre-surgery. The biomarker evaluable population (BEP) included pts with paired PB analyzed within 72 hrs by 10-color flow cytometry (IMMUNOME) and major pathological response (MPR) assessment (defined as ≤ 10% residual tumor). The primary endpoint was MPR. Secondary endpoints included safety, MPR by PD-L1, OS, and DFS. Immunophenotypic analyses were correlated with treatment, MPR and PD-L1 expression. Results: 116 patients have been enrolled as of October 31, 2018 and here we report on 54 of 180 planned pts with follow-up through surgery. 15 pts had Gr 3-4 AEs (3 treatment related), one Gr 5 AE (sudden death) was unrelated. By RECIST there were 3 PR, 49 SD, and 2 PD. 50/54 pts underwent the planned surgery, 47 pts had MPR assessment: 4 pts discontinued study preop (2 radiographic PD, 2 other reasons); 3 were unresectable. Excluding 5 pts with EGFR or ALK mutations, MPR rate was 10/45 (22%, 95% CI 11-37%). Baseline PD-L1 status was evaluable in 44/54 pts; BEP included 31 pts, 23 had tissue PD-L1 status: 16 PD-L1+. We observed significant increases in natural killer (NK) cells, CD8+ T-cells, Th1-response related dendritic cells (DC), and decreases in B-cells after atezo. Non-MPR pts showed significant increases in late activated NK cells, monocytic myeloid cells and Th2 and Th17-response–related DCs. PD-L1+ pts showed significant decreases of senescent T cells, monocytic myeloid cells, and increases of Th1-response–related DCs. We analyzed 22/54 tumor pairs, PD-L1+ cells increased in most pts after atezo treatment. Conclusions: Neoadjuvant atezo was well tolerated and the MPR rate is encouraging. Preliminary immunophenotyping data showed significant changes in PB with immunotherapy. Clinical trial information: NCT02927301.