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Background: Bidirectional crosstalk between HER2 and estrogen receptor (ER) pathways may influence outcomes and the efficacy of endocrine therapy (ET). Low HER2 expression levels (HER2-low) have emerged as a predictive biomarker in patients with breast cancer (BC)., Methods: PALLAS is an open, international, phase 3 study evaluating the addition of palbociclib for 2 years to adjuvant ET in patients with stage II-III ER-positive/HER2-negative BC. To assess the impact of HER2 expression on patient outcomes in the phase III PALLAS trial, we analyzed (1) the association between rate of HER2-low with demographic and clinicopathological parameters, (2) the prognostic value of HER2-low status on invasive disease-free survival (iDFS), distant relapse-free survival (DRFS), and overall survival (OS) and (3) HER2 expression's value as a predictive biomarker of response to palbociclib. HER2-low was defined as HER2 immunohistochemistry (IHC) 1 + or IHC 2 + with negative in situ hybridization (ISH). All pathologic evaluation was performed locally. Prognostic and predictive power of HER2 were assessed with Cox models., Results: From the original PALLAS intention-to-treat population (N = 5753), 5304 patients (92.2%) were included in this analysis. Among these, 2254 patients (42.5%) were classified as having HER2 IHC 0 (HER2-0), and 3050 (57.5%) as having HER2-low disease (1838 with IHC 1 + and 1212 with IHC 2 +). Median follow-up was 59.8 months. HER2-low prevalence varied significantly across 21 participating countries (range 16.7% to 75.6%; p < 0.001) and was more frequent in patients enrolled in North America (63.1%) than in Europe (53.4%) or other regions (53.4%) (p < 0.001). HER2 status was not significantly associated with iDFS in a multivariable Cox model (hazard ratio 0.93, 95% confidence interval 0.81 - 1.06). No significant interaction was observed between treatment arm and HER2 status for iDFS (p = 0.43). Similar results were obtained for DRFS and OS., Conclusions: In this large, prospective, global patient cohort, no differences were observed in clinical parameters, prognosis, or differential benefit from palbociclib between HER2-0 and HER2-low tumors. Significant geographic variability was observed in the prevalence of HER2-low status, suggesting a high degree of variation in pathologic assessment of HER2 expression without impact on outcomes., (© 2024. The Author(s).)

Purpose: The Clinical Treatment Score post-5 years (CTS5) is an easy-to-use tool estimating the late distant recurrence (LDR) risk in patients with hormone receptor-positive breast cancer after 5 years of endocrine therapy (ET). Apart from evaluating the prognostic value and calibration accuracy of CTS5, the aim of this study is to clarify if this score is able to identify patients at higher risk for LDR who will benefit from extended ET., Methods: Prognostic power, calibration, and predictive value of the CTS5 was tested in patients of the prospective ABCSG-06 and -06a trials (n = 1254 and 860 patients, respectively). Time to LDR was analyzed with Cox regression models., Results: Higher rates of LDR in the years five to ten were observed in high- and intermediate-risk patients compared to low-risk patients (HR 4.02, 95%CI 2.26-7.15, p < 0.001 and HR 1.93, 95%CI 1.05-3.56, p = 0.035). An increasing continuous CTS5 was associated with increasing LDR risk (HR 2.23, 95% CI 1.74-2.85, p < 0.001). Miscalibration of CTS5 in high-risk patients could be observed. Although not reaching significance, high-risk patients benefitted the most from prolonged ET with an absolute reduction of the estimated 5-year LDR of - 6.1% (95%CI - 14.4 to 2.3)., Conclusion: The CTS5 is a reliable prognostic tool that is well calibrated in the lower and intermediate risk groups with a substantial difference of expected versus observed LDR rates in high-risk patients. While a numerical trend in favoring prolonged ET for patients with a higher CTS5 was found, a significantly predictive value for the score could not be confirmed., Clinical Trial Registration: ABCSG-06 trial (NCT00309491), ABCSG-06A7 1033AU/0001 (NCT00300508)., (© 2024. The Author(s).)

Competing Interests: Conflict of Interest: Michael Gnant reports personal fees/travel support from Amgen, AstraZeneca, Daiichi Sankyo, Eli Lilly, Menarini-Stemline, MSD, Novartis, Pierre Fabre, Sandoz, Veracyte; an immediate family member is employed by Sandoz. No other potential conflicts of interest relevant to this article was reported.

Purpose: BMI affects breast cancer risk and prognosis. In contrast to cytotoxic chemotherapy, CDK4/6 inhibitors are given at a fixed dose, irrespective of BMI or weight. This preplanned analysis of the global randomized PALLAS trial investigates the impact of BMI on the side-effect profile, treatment adherence, and efficacy of palbociclib., Methods: Patients were categorized at baseline according to WHO BMI categories. Neutropenia rates were assessed with univariable and multivariable logistic regression. Time to early discontinuation of palbociclib was analyzed with Fine and Gray competing risk models. Unstratified Cox models were used to investigate the association between BMI category and time to invasive disease-free survival (iDFS). 95% CIs were derived., Results: Of 5,698 patients included in this analysis, 68 (1.2%) were underweight, 2,082 (36.5%) normal weight, 1,818 (31.9%) overweight, and 1,730 (30.4%) obese at baseline. In the palbociclib arm, higher BMI was associated with a significant decrease in neutropenia (unadjusted odds ratio for 1-unit change, 0.93; 95% CI, 0.91 to 0.94; adjusted for age, race ethnicity, region, chemotherapy use, and Eastern Cooperative Oncology Group at baseline, 0.93; 95% CI, 0.92 to 0.95). This translated into a significant decrease in treatment discontinuation rate with higher BMI (adjusted hazard ratio [HR] for 10-unit change, 0.75; 95% CI, 0.67 to 0.83). There was no significant improvement in iDFS with the addition of palbociclib to ET in any weight category (normal weight HR, 0.84; 95% CI, 0.63 to 1.12; overweight HR, 1.10; 95% CI, 0.82 to 1.49; and obese HR, 0.95; 95% CI, 0.69 to 1.30) in this analysis early in follow-up (31 months)., Conclusion: This preplanned analysis of the PALLAS trial demonstrates a significant impact of BMI on side effects, dose reductions, early treatment discontinuation, and relative dose intensity. Additional long-term follow-up will further evaluate whether BMI ultimately affects outcome.

Background: The widespread adoption of adjuvant bisphosphonate therapy for postmenopausal early breast cancer (EBC) patients was based on results of the Early Breast Cancer Trialist Group (EBCTCG) meta-analysis. Despite multiple regimens evaluated, there was no signal of varying efficacy with type, dose/dose intensity of bisphosphonate administration. We evaluated the effect of early treatment cessation using long-term outcome data from the ABCSG-12 trial., Patients and Methods: ABCSG-12 randomized 1803 hormone-receptor positive EBC patients on ovarian suppression between 1999 and 2006 to receive 4 mg zoledronic acid 6-monthly or not (and tamoxifen or anastrozole, 2:2 factorial design). In the current study, we evaluated whether the number of zoledronate infusions had an impact on breast cancer-specific outcomes. We hypothesized that amongst patients who received at least one zoledronate infusion, the number of infusions had no effect on outcomes. Time-to-event endpoints were analysed with Cox models and Kaplan Meier curves starting from a 3-year landmark. BMD analysis was restricted to patients who participated in the BMD sub-study., Results: 725 patients who received at least one zoledronate infusion were included in the time-to-event analysis. There was no statistically significant difference in disease-free or overall survival in the patients who received ≤6 zoledronate infusions (n = 170) compared to those who received ≥7 zoledronate infusions (n = 555)., Conclusions: Comparable to efforts to de-escalate treatment duration in metastatic bone disease, there was no evidence to indicate that a reduced number of zoledronate infusions is associated with reduced adjuvant efficacy. Further studies to define optimal regimens of adjuvant bone-targeted therapies are required., Competing Interests: Conflict of interest statement The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2022. Published by Elsevier Ltd. All rights reserved.)

Purpose: The PALLAS study investigated whether the addition of palbociclib, an oral CDK4/6 inhibitor, to adjuvant endocrine therapy (ET) improves invasive disease-free survival (iDFS) in early hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) breast cancer. In this analysis, we evaluated palbociclib exposure and discontinuation in PALLAS., Methods: Patients with stage II-III HR+, HER2- disease were randomly assigned to 2 years of palbociclib with adjuvant ET versus ET alone. The primary objective was to compare iDFS between arms. Continuous monitoring of toxicity, dose modifications, and early discontinuation was performed. Association of baseline covariates with time to palbociclib reduction and discontinuation was analyzed with multivariable competing risk models. Landmark and inverse probability weighted per-protocol analyses were performed to assess the impact of drug persistence and exposure on iDFS., Results: Of the 5,743 patient analysis population (2,840 initiating palbociclib), 1,199 (42.2%) stopped palbociclib before 2 years, the majority (772, 27.2%) for adverse effects, most commonly neutropenia and fatigue. Discontinuation of ET did not differ between arms. Discontinuations for non-protocol-defined reasons were greater in the first 3 months of palbociclib, and in the first calendar year of accrual, and declined over time. No significant relationship was seen between longer palbociclib duration or ≥ 70% exposure intensity and improved iDFS. In the weighted per-protocol analysis, no improvement in iDFS was observed in patients receiving palbociclib versus not (hazard ratio 0.89; 95% CI, 0.72 to 1.11)., Conclusion: Despite observed rates of discontinuation in PALLAS, analyses suggest that the lack of significant iDFS difference between arms was not directly related to inadequate palbociclib exposure. However, the discontinuation rate illustrates the challenge of introducing novel adjuvant treatments, and the need for interventions to improve persistence with oral cancer therapies., Competing Interests: Erica L. MayerConsulting or Advisory Role: Lilly, Novartis, AstraZeneca, Gilead SciencesResearch Funding: Pfizer (Inst) Christian FeslResearch Funding: Pfizer (Inst) Dominik HlauschekResearch Funding: Pfizer (Inst) Laura Garcia-EstevezConsulting or Advisory Role: Daiichi Sankyo/Astra Zeneca, Palex, Seattle GeneticsResearch Funding: Roche/Genentech (Inst) Nicholas ZdenkowskiHonoraria: Roche, Pfizer, EisaiConsulting or Advisory Role: Lilly, AstraZeneca, EisaiResearch Funding: Roche (Inst), Pfizer (Inst)Travel, Accommodations, Expenses: Roche, Amgen, Novartis Kathy D. MillerThis author is the Senior Deputy Editor of Journal of Clinical Oncology. Journal policy recused the author from having any role in the peer review of this manuscript.Consulting or Advisory Role: Merck, Genentech/Roche, Athenex, AstraZeneca, Bristol Myers Squibb/CelgeneResearch Funding: Taiho Pharmaceutical (Inst), Novartis (Inst), Seattle Genetics (Inst), Pfizer (Inst), Astex Pharmaceuticals (Inst), British Biotech (Inst), CytomX Therapeutics (Inst), Alphamab (Inst) Marija BalicConsulting or Advisory Role: Amgen, AstraZeneca, Daiichi Sankyo/Astra Zeneca, Lilly, MSD, Novartis, Pierre Fabre, Pfizer, Roche, SamsungSpeakers' Bureau: Amgen, AstraZeneca, Daiichi Sankyo/Astra Zeneca, Lilly, Novartis, Pierre Fabre, Pfizer, Roche, Seattle GeneticsResearch Funding: Lilly (Inst), Novartis (Inst), Pfizer (Inst)Travel, Accommodations, Expenses: MSD Ingrid A. MayerConsulting or Advisory Role: Novartis, AstraZeneca, Lilly, Genentech, GlaxoSmithKline, Immunomedics, Macrogenics, Pfizer, AbbVie, Seattle Genetics, Puma Biotechnology, Cyclacel, Blueprint Medicines, SanofiResearch Funding: Novartis (Inst), Pfizer (Inst), Genentech (Inst) David CameronConsulting or Advisory Role: Lilly (Inst), Novartis (Inst), Novartis (Inst), Research Triangle Institute RTI Health Solutions (Inst), Daiichi Sankyo (Inst), Prima BioMed (Inst), Merck Sharp & Dohme (Inst), Zymeworks (Inst), Eisai (Inst), Puma Biotechnology (Inst), Pfizer (Inst), Oncolytics (Inst), Roche (Inst), Roche (Inst), Samsung Bioepis (Inst), Seattle Genetics (Inst), Synthon (Inst), Clarity Pharmaceuticals (Inst), Bexon/Zymeworks (Inst), Sanofi (Inst)Research Funding: Roche (Inst), Novartis (Inst), AstraZeneca (Inst) Eric P. WinerHonoraria: Genentech/Roche, Genomic HealthConsulting or Advisory Role: Leap Therapeutics, Seattle Genetics, Jounce Therapeutics, GlaxoSmithKline, Carrick Therapeutics, Lilly, G1 Therapeutics, Syros Pharmaceuticals, Genentech/Roche, Gilead Sciences, Zymeworks, AthenexResearch Funding: Genentech (Inst)Other Relationship: InfiniteMD José Juan Ponce LorenzoHonoraria: Seattle Genetics, Novartis, Pfizer, AstraZeneca/Daiichi Sankyo, Lilly, RocheConsulting or Advisory Role: Seattle Genetics, Novartis, AstraZeneca/Daiichi Sankyo, Roche Tufia C. HaddadResearch Funding: Takeda (Inst) Hiroji IwataHonoraria: Chugai Pharma, AstraZeneca, Eisai, Pfizer, Daiichi Sankyo, Lilly Japan, Kyowa Hakko Kirin, Taiho PharmaceuticalConsulting or Advisory Role: Chugai Pharma, Daiichi Sankyo, Pfizer, AstraZeneca, Lilly Japan, Kyowa Hakko Kirin, NovartisResearch Funding: MSD (Inst), AstraZeneca (Inst), Kyowa Hakko Kirin (Inst), Daiichi Sankyo (Inst), Chugai Pharma (Inst), Nihonkayaku (Inst), Lilly Japan (Inst), Novartis (Inst), Bayer (Inst), Pfizer (Inst), Boehringer Ingelheim (Inst), Sanofi (Inst) Matthew GoetzConsulting or Advisory Role: Lilly, bioTheranostics, Genomic Health, Novartis, Eisai, Sermonix Pharmaceuticals, Context Therapeutics, Pfizer, BiovicaResearch Funding: Lilly (Inst), Pfizer (Inst), Sermonix Pharmaceuticals (Inst)Patents, Royalties, Other Intellectual Property: Methods and Materials for Assessing Chemotherapy Responsiveness and Treating Cancer, Methods and Materials for Using Butyrylcholinesterases to Treat Cancer, Development of Human Tumor Xenografts from Women with Breast Cancer Treated with Neoadjuvant Chemotherapy (Inst)Travel, Accommodations, Expenses: Lilly Fatima CardosoConsulting or Advisory Role: Roche, Novartis, Pfizer, AstraZeneca, Teva, Astellas Pharma, Merus, Celgene, Eisai, Daiichi Sankyo, Genentech, Merck Sharp & Dohme, Sanofi, Pierre Fabre, Macrogenics, Amgen, GE Healthcare, GlaxoSmithKline, Mylan, Mundipharma, Seattle Genetics, Samsung Bioepis, Medscape, Prime OncologyTravel, Accommodations, Expenses: Pfizer, Roche, AstraZeneca Tiffany A. TrainaConsulting or Advisory Role: Genentech/Roche, Pfizer, AstraZeneca, Merck, Puma Biotechnology, Athenex, Daiichi Sankyo, Ionis Pharmaceuticals, Seattle Genetics, Eisai, Exact Sciences, Foundation Medicine, Ayala Pharmaceuticals, Gilead Sciences, Blueprint Medicines, Ellipses Pharma, Fuji Pharma, ITeos Therapeutics, AgendiaResearch Funding: Eisai (Inst), Pfizer (Inst), Novartis (Inst), Innocrin Pharma (Inst), AstraZeneca (Inst), Astellas Pharma (Inst), Immunomedics (Inst), Genentech/Roche (Inst), Daiichi Sankyo (Inst), Carrick Pharm (Inst), Ayala Pharmaceuticals (Inst) Urs BreitensteinConsulting or Advisory Role: AstraZeneca (Inst), Elie Lilly (Inst), Novartis (Inst), Pierre Fabre (Inst), Roche (Inst) Kerstin AckerlResearch Funding: Pfizer (Inst) Otto Metzger FilhoHonoraria: Grupo Oncoclinicas, RocheResearch Funding: Susan G. Komen for the Cure (Inst), Pfizer (Inst), Roche/Genentech (Inst), Eisai (Inst), Cascadian Therapeutics (Inst), AbbVie (Inst)Travel, Accommodations, Expenses: Grupo Oncoclinicas Karin ZehetnerResearch Funding: Pfizer (Inst) Kadine SolomonEmployment: Alliance Foundation TrialsStock and Other Ownership Interests: Pfizer, Merck, Moderna Therapeutics Sarra El-AbedEmployment: Astellas Pharma (I), argenx (I)Research Funding: Novartis (Inst), Roche/Genentech (Inst), Pfizer (Inst) Kathy Puyana TheallEmployment: Pfizer (I)Stock and Other Ownership Interests: Pfizer (I)Honoraria: PfizerTravel, Accommodations, Expenses: Pfizer Dongrui Ray LuEmployment: PfizerStock and Other Ownership Interests: Pfizer Amylou DueckPatents, Royalties, Other Intellectual Property: Royalties from licensing fees for a patient symptom questionnaire (MPN-SAF) Michael GnantEmployment: Sandoz (I)Honoraria: Amgen, Novartis, AstraZeneca, LillyConsulting or Advisory Role: Daiichi-Sankyo, Veracyte, Tolmar, LifeBrain, Lilly Angela DeMicheleResearch Funding: Pfizer (Inst), Genentech (Inst), Calithera Biosciences (Inst), Novartis (Inst)No other potential conflicts of interest were reported.

Purpose: To validate the clinical performance of the OncoMasTR Risk Score in the biomarker cohort of Austrian Breast and Colorectal Cancer Study Group (ABCSG) Trial 8., Experimental Design: We evaluated the OncoMasTR test in 1,200 formalin-fixed, paraffin-embedded (FFPE) surgical specimens from postmenopausal women with estrogen receptor (ER)-positive, human epidermal growth factor receptor 2 (HER2)-negative primary breast cancer with 0 to 3 involved lymph nodes in the prospective, randomized ABCSG Trial 8. Time to distant recurrence (DR) was analyzed by Cox models., Results: The OncoMasTR Risk Score categorized 850 of 1,087 (78.2%) evaluable patients as "low risk". At 10 years, the DR rate for patients in the low-risk group was 5.8% versus 21.1% for patients in the high-risk group ( P < 0.0001, absolute risk reduction 15.3%). The OncoMasTR Risk Score was highly prognostic for prediction of DR in years 0 to 10 in all patients [HR 1.91, 95% confidence interval (CI) 1.62-2.26, P < 0.0001; C-index 0.73], in patients that were node negative (HR 1.79, 95% CI, 1.43-2.24, P < 0.0001; C-index 0.72), and in patients with 1 to 3 involved lymph nodes (HR 1.93, 95% CI, 1.44-2.58, P < 0.0001; C-index 0.71). The OncoMasTR Risk Score provided significant additional prognostic information beyond clinical parameters, Ki67, Nottingham Prognostic Index, and Clinical Treatment Score., Conclusions: OncoMasTR Risk Score is highly prognostic for DR in postmenopausal women with ER-positive, HER2-negative primary breast cancer with 0 to 3 involved lymph nodes. In combination with prior validation studies, this fully independent validation in ABCSG Trial 8 provides level 1B evidence for the prognostic capability of the OncoMasTR Risk Score., (©2021 American Association for Cancer Research.)

Background: Endocrine therapy-based neoadjuvant treatment for luminal breast cancer allows efficient testing of new combinations before surgery. The activation of the phosphatidylinositol-3-kinase (PI3K) pathway is a known mechanism of resistance to endocrine therapy. Taselisib is an oral, selective PI3K inhibitor with enhanced activity against PIK3CA-mutant cancer cells. The LORELEI trial tested whether taselisib in combination with letrozole would result in an increased proportion of objective responses and pathological complete responses., Methods: In this multicentre, randomised, double-blind, parallel-cohort, placebo-controlled phase 2, study, we enrolled postmenopausal women (aged ≥18 years) with histologically confirmed, oestrogen receptor (ER)-positive, HER2-negative, stage I-III, operable breast cancer, from 85 hospitals in 22 countries worldwide. To be eligible, patients had have an Eastern Cooperative Oncology Group (ECOG) performance status 0-1, adequate organ function, and had to have evaluable tumour tissue for PIK3CA genotyping. Patients were randomly assigned (1:1) by means of a permuted block algorithm (block size of four) via an interactive voice or web-based response system, to receive letrozole (2·5 mg/day orally, continuously) with either 4 mg of oral taselisib or placebo (on a 5 days-on, 2 days-off schedule) for 16 weeks, followed by surgery. Randomisation was stratified by tumour size and nodal status. Site staff, patients, and the sponsor were masked to treatment assignment. Coprimary endpoints were the proportion of patients who achieved an objective response by centrally assessed breast MRI and a locally assessed pathological complete response in the breast and axilla (ypT0/Tis, ypN0) at surgery in all randomly assigned patients and in patients with PIK3CA-mutant tumours. Analyses were done in the intention-to-treat population. This trial is registered with ClinicalTrials.gov, number NCT02273973, and is closed to accrual., Findings: Between Nov 12, 2014, and Aug 12, 2016, 334 participants were enrolled and randomly assigned to receive letrozole and placebo (n=168) or letrozole and taselisib (n=166). Median follow-up was 4·9 months (IQR 4·7-5·1). The study met one of its primary endpoints: the addition of taselisib to letrozole was associated with a higher proportion of patients achieving an objective response in all randomly assigned patients (66 [39%] of 168 patients in the placebo group vs 83 [50%] of 166 in the taselisib group; odds ratio [OR] 1·55, 95% CI 1·00-2·38; p=0·049) and in the PIK3CA-mutant subset (30 [38%] of 79 vs 41 [56%] of 73; OR 2·03, 95% CI 1·06-3·88; p=0·033). No significant differences were observed in pathological complete response between the two groups, either in the overall population (three [2%] of 166 in the taselisib group vs one [1%] of 168 in the placebo group; OR 3·07 [95% CI 0·32-29·85], p=0·37) or in the PIK3CA-mutant cohort (one patient [1%) vs none [0%]; OR not estimable, p=0·48). The most common grade 3-4 adverse events in the taselisib group were gastrointestinal (13 [8%] of 167 patients), infections (eight [5%]), and skin-subcutaneous tissue disorders (eight [5%]). In the placebo group, four (2%) of 167 patients had grade 3 or worse vascular disorders, two (1%) had gastrointestinal disorders, and two (1%) patients had grade 3 or worse infections and infestations. There was no grade 4 hyperglycaemia and grade 3 cases were asymptomatic. Serious adverse events were more common in the taselisib group (eight [5%] patients with infections and seven [4%] with gastrointestinal effects) than in the placebo group (one [1%] patient each with grade 3 postoperative wound and haematoma infection, grade 4 hypertensive encephalopathy, grade 3 acute cardiac failure, and grade 3 breast pain). One death occurred in the taselisib group, which was not considered to be treatment-related., Interpretation: The increase in the proportion of patients who achieved an objective response from the addition of taselisib to endocrine therapy in a neoadjuvant setting is consistent with the clinical benefit observed in hormone receptor-positive, HER2-negative, metastatic breast cancer., Funding: Genentech and F Hoffmann-La Roche., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Purpose: Prognostic molecular assays may aid in treatment decisions for women with estrogen receptor (ER)-positive, HER2-negative breast cancer. The prognostic value of a 12-gene expression assay (EndoPredict) was reevaluated in the combined ABCSG-6/8 cohorts with longer clinical follow-up., Experimental Design: EndoPredict (EP; molecular score, EPclin score) was evaluated in women with ER-positive, HER2-negative node-positive and node-negative breast cancer who received 5 years of endocrine therapy only (median follow-up, 9.6 years; N = 1,702). Distant recurrence-free rate (DRFR; 95% confidence interval) was assessed 10 and 15 years after diagnosis., Results: Overall, 62.6% of patients had low-risk EPclin scores with significantly improved DRFR relative to high-risk patients (HR, 4.77; 95% CI, 3.37-6.67; P < 0.0001). Ten-year DRFR (0-10 years) was improved among patients with low-risk versus high-risk EPclin scores in the full cohort [95.5% (94.1%-97.0%) vs. 80.3% (76.9%-83.9%)] as well as for patients with node-negative disease [95.5% (94.0%-97.1%) vs. 87.0% (82.6%-91.7%)] or with 1 to 3 positive nodes [95.6% (92.2%-99.1%) vs. 80.9% (75.9%-86.1%)]. The molecular and EPclin scores were significant predictors of DRFR after adjusting for clinical variables, regardless of nodal status. Similar results were observed for late recurrence (5-15 years; HR, 4.52; 95% CI, 2.65-7.72; P < 0.0001). The EPclin score significantly added prognostic information to a late metastasis nomogram (CTS5 score; P < 0.001)., Conclusions: This study demonstrates that EPclin can identify patients at low risk for early or late recurrence who may safely forgo adjuvant chemotherapy or extended endocrine therapy, respectively, regardless of nodal status., (©2019 American Association for Cancer Research.)

Purpose: EndoPredict (EPclin) is a prognostic test validated to inform decisions on adjuvant chemotherapy to endocrine therapy alone for patients with oestrogen receptor-positive, HER2-negative breast cancer. Here, we determine the performance of EPclin for estimating 10-year distant recurrence-free interval (DRFI) rates for those who received adjuvant endocrine therapy (ET) alone compared to those with chemotherapy plus endocrine therapy (ET + C)., Methods: A total of 3746 women were included in this joint analysis. 2630 patients received 5 years of ET alone (ABCSG-6/8, TransATAC) and 1116 patients received ET + C (GEICAM 2003-02/9906). The primary objective was to evaluate the ability of EPclin to provide an estimate of the 10-year DR rate as a continuous function of EPclin separately for ET alone and ET + C. Cox proportional hazard models were used for these analyses., Results: EPclin was highly prognostic for DR in women who received ET alone (HR 2.79 (2.49-3.13), P < 0.0001) as well as in those who received ET + C (HR 2.27 (1.99-2.59), P < 0.0001). Women who received ET + C had significantly smaller increases in 10-year DR rates with the increasing EPclin score than those receiving ET alone (EPclin = 5; 12% ET + C vs. 20% ET alone). We observed a significant positive interaction between EPclin and treatment groups (P- interaction  = 0.022)., Conclusions: In this comparative non-randomised analysis, the rate of increase in DR with EPclin score was significantly reduced in women who received ET + C versus ET alone. Our indirect comparisons suggest that a high EPclin score can predict chemotherapy benefit in women with ER-positive, HER2-negative disease.