Burstein, H.J.

Abstract Background The PALLAS trial investigated the addition of palbociclib to standard adjuvant endocrine therapy reduces breast cancer recurrence. This pre-specified analysis was conducted to determine whether adjuvant palbociclib benefited patients diagnosed with lower risk stage IIA disease compared to those with higher stage disease. Methods PALLAS was an international, multicenter, randomized, open-label, phase III trial, representing a public-private partnership between Pfizer, the Austrian Breast Cancer Study Group and, the U.S. ALLIANCE Foundation. Patients diagnosed with stage II-III, hormone-receptor-positive, HER2/neu negative breast cancer who were within 12 months of diagnosis, and had completed all definitive therapy aside from endocrine therapy, which was started within 6 months prior to study entry. All patients were required to submit a formalin-fixed paraffin-embedded (FFPE) tumor block. Patients were randomly assigned 1:1 to receive standard adjuvant endocrine therapy (of physicians’ choice) for at least 5 years with or without 2 years of Palbociclib, administered orally at a starting dose of 125 mg daily, given for 21 days followed by a 7-day break. Results A total of 5,796 patients with HR+/HER2- early breast cancer (including 1,010 with stage IIA) were enrolled. Median follow-up was 50 months for stage IIA patients and 43.1 months overall. In the stage IIA cohort, four-year iDFS in the palbociclib arm was 92.9% versus 92.1% for ET alone (HR 0.75, 95%CI 0.48–1.19, p = 0.23). There was no differential benefit by histologic grade, chemotherapy receipt, age, or anatomic/clinical risk. Additionally, no benefit to palbociclib was seen in this cohort in invasive breast cancer-free survival (iBCFS), locoregional relapse-free survival (LRFS), distant relapse-free survival (DRFS), or overall survival (OS). For the stage IIB/III patients, 4-year iDFS was 85.3% for palbociclib + ET versus 83.6% for ET alone (HR 0.91, 95% CI 0.77–1.07, p = 0.24). Conclusions and Relevance: While there were substantial differences in outcome for stage IIA versus IIB/III patients at 4 years of follow-up, the addition of 2 years of palbociclib did not improve outcomes for patients, regardless of stage. Trial Registration: The study was registered on Clinicaltrials.gov on July 31, 2015, and was assigned the clinical trial number (NCT02513394).

Abstract Background: As the development and use of oral anticancer agents increases, it is critical to understand patient adherence to both standard and investigational agents. The open label, phase 3 multicenter PALLAS trial investigates whether adding 2 years of the CDK4/6 inhibitor palbociclib (P) to adjuvant endocrine therapy (ET) improves invasive disease-free survival (iDFS) over adjuvant ET alone in patients (pts) with HR- positive, HR2-negative, stage II-III breast cancer. Pts were randomly assigned to either Palbociclib (125 mg/day, 3 weeks on, 1 week off, in a 28-day cycle) plus ongoing provider/patient-choice adjuvant ET (P+ET) versus ET alone. We examined patient-reported adherence to ET +/- P during the first two years of study treatment. Methods: Adherence outcomes were measured in English-speaking pts in the U.S., UK, Ireland and Australia, Spanish-speaking pts in Spain and Mexico, and German-speaking pts in Germany and Austria. Adherence measures included drug diaries completed at each cycle, pill counts (for P only) collected at each study visit, and the Morisky Medication Adherence Scale-4 item and the McHorney Adherence Estimator questionnaires completed at cycles 2, 3, 6, 12, 18, and 24 (22 months). Mean adherence for each cycle was defined as the average proportion of prescribed pills taken (via drug diary) across all patients who initiated that cycle. Persistence was defined as the duration of drug initiation to treatment cessation (via drug diary). Generalized estimating equations were used to model the “most adherent” pts on the Morisky (score = 5 vs score <5) and “low risk” for adherence problems on the McHorney (score=0 vs score >0) to compare the average difference between arms over time for ET, adjusting for baseline demographic and clinical variables. Results: 81% (N=4688) of PALLAS pts were included in this analysis. Median persistence to ET was 23.6 months in P + ET (n=2169), 23.7 months in ET alone (2136) and 20.4 months for P (n=2194). The number of pts who initiated each cycle for ET declined over time and was similar between arms; the decline was more marked for P (Table 1). Mean adherence range as measured by drug diary was 98.2-99.3% for ET in P+ET and 98.0 - 99.4% in ET alone; and for P, ranged from 93.4 - 98.8%. The adherence and persistence results were nearly identical whether measured by drug diary or pill count for P. The observed percent “most adherent” for P measured by the Morisky scale ranged from 71.9% - 79.6% and the percent “low risk” for adherence problems measured by the McHorney scale, 64.0% - 73.4%. The percent of pts “most adherent” and “low risk” for adherence problems to ET was higher, on average over time, in the P+ET group compared to ET alone (75% vs 68%, p<0.01; 75% vs 72%, p=.05, respectively). Conclusions: Self-reported mean adherence for both P + ET and ET alone was strikingly high for pts who remained on therapy; persistence was also high with ET during the 2-year treatment period. Current analyses suggest that nonadherence to either P or ET was likely not a major contributor to the iDFS results seen in the overall PALLAS trial. These results illustrate the importance of measuring and monitoring patient adherence to oral study agents. Support: AFT, Pfizer; ClinicalTrials.gov (NCT02513394) and EudraCT (2014-005181-30). https://acknowledgments.alliancefound.org Table 1.Adherence and persistence in PALLAS over the 24 month treatment periodPalbocicilb + ETETPalbociclibETETTreatment cycleMean Adherence (SD)N*Mean Adherence (SD)NMean Adherence (SD)N193.4 (13.8)229098.7 (6.1)230999.0 (5.2)2343294.7 (13.3)218198.8 (6.4)220398.4 (7.1)2206397.4 (10.1)211298.7 (7.3)214298.8 (6.3)2168497.6 (10.2)203598.6 (7.8)211099.0 (5.7)2154597.6 (11.1)197598.3 (7.9)209398.1 (8.3)2148698.1 (8.7)189998.7 (6.6)203798.5 (8.2)2116798.1 (9.3)185599.0 (6.3)201298.6 (7.3)2102898.0 (9.1)181098.2 (8.2)199798.1 (8.2)2092998.4 (7.4)173399.0 (6.4)196298.8 (6.8)20511098.3 (8.6)171499.2 (4.9)194699.0 (5.5)20381198.3 (8.0)169198.5 (7.3)193798.2 (8.2)20311298.7 (6.2)161299.1 (5.3)191098.7 (7.5)19861398.5 (7.7)159698.9 (6.4)189398.8 (7.1)19691497.9 (9.3)157698.4 (7.3)188298.0 (9.1)19611598.5 (6.9)151499.2 (4.6)185499.0 (6.0)19281698.2 (8.7)148699.1 (4.6)183599.1 (5.7)19131798.1 (9.8)147998.3 (7.8)182698.5 (6.4)19031898.7 (6.8)141699.3 (4.1)176899.2 (5.3)18601998.7 (7.3)140899.3 (3.8)175699.4 (3.1)18482098.4 (8.9)139798.9 (5.3)174298.7 (5.8)18382198.5 (7.5)130199.0 (6.1)167698.8 (7.1)17842297.8 (9.7)124698.8 (6.2)164799.2 (5.7)17692398.1 (8.8)118098.2 (8.5)161998.4 (8.0)17552498.8 (7.2)108699.0 (6.3)146898.9 (7.1)16192598.8 (6.7)99699.2 (5.2)143298.8 (7.1)15892697.9 (11.2)84599.1 (5.7)140998.6 (8.8)1578ET=Endocrine therapy * Number of pts who initiated the treatment cycle. Citation Format: Eileen Shinn, David Zahrieh, Angela DeMichele, Nick Zdenkowski, Julie Lemieux, Jun Mao, Vesna Bjelic-Radisic, Michelle Naughton, Georg Pfeiler, Karen Gelmon, Ingrid Mayer, Daniel Egle, Gabriele Zoppoli, Tiffany Traina, Miguel Martin Jiménez, Silvia Antolin Novoa, Tufia Haddad, Arlene Chan, Alistair Edward Ring, Antonio Wolff, Jose JuanPonce Lorenzo, Dhanusha Sabanathan, Hal Burstein, Zbigniew Ireneusz Nowecki, Gunda Pristauz-Telsnigg, Adam Brufsky, Meritxell Bellet-Ezquerra, Theodoros Foukakis, Yelena Novik, Gabor Rubovszky, Karoline Muehlbacher, Otto Metzger, Theodora Goulioti, Ernest Law, Ann Partridge, Lisa Carey, Alex Zoroufy, Dominik Hlauschek, Christian Fesl, Erica Mayer, Michael Gnant. Adherence with adjuvant endocrine therapy with or without Palbociclib in the PALLAS trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P4-12-01.

Abstract Background Advances in the multidisciplinary care of hormone-receptor positive (HR+) early breast cancer (eBC) have markedly improved clinical outcomes: however, disease recurrence may still occur, particularly in patients (pts) with moderate or high-risk cancers at the time of diagnosis. The use of CDK4/6 inhibitors (CDK4/6i) combined with endocrine therapy (ET) is a standard of care for advanced breast cancer, supporting the rationale to study CDK4/6i in the eBC setting. Here we present the final protocol-planned analyses of the global phase III PALLAS trial investigating whether the addition of the CDK4/6i palbociclib (P) to adjuvant ET improves outcomes over ET alone for HR+/HER2- eBC. Methods PALLAS (PALbociclib CoLlaborative Adjuvant Study, NCT02513394) is a randomized phase III open-label trial in which pts with stage II-III HR+/HER2- eBC were randomized to receive either 2 years of P with adjuvant ET (P+ET) or ET alone. The primary endpoint is invasive disease-free survival (iDFS); secondary endpoints include distant recurrence-free survival (DRFS), locoregional recurrence-free survival (LRRFS), overall survival (OS), and safety. Mandatory biospecimen collection has supported the creation of an expansive translational science program, and long-term follow-up is planned. Revised sample size calculations required recruitment of 5600 pts in order to detect a 25% iDFS improvement in patients receiving P+ET with 85% power; this final protocol-planned analysis was planned after 469 iDFS events. Results From September 1, 2015 to November 30, 2018, 5,761 pts (median age 52 years, range 22-90) were randomized in 406 centers in 21 countries worldwide. 1,014 (17.6%) had stage IIA disease (capped) and 4,728 (82.1%) stages IIB/III. 4,754 (82.5%) had received prior (neo)adjuvant chemotherapy. After a protocol-planned 2nd interim analysis in May 2020 crossed the futility threshold, 349 P+ET pts still on active treatment stopped P and were transferred to follow-up. At the time of final analysis cutoff date (November 20, 2020), after a median follow-up of 31 months and 516 events recorded, iDFS was similar between the two arms, with 3-year iDFS of 89.3% (95% CI: 87.8-90.6%) for Palbo+ET, and 89.4% (88.0-90.7%) for ET alone (hazard ratio 0.96, 95% CI: 0.81-1.14). There was no statistically significant difference in secondary outcome endpoints. Subgroup analyses revealed no significant interactions between treatment effect and other factors (including risk category). The safety profile of P was as expected, with grade 3 or 4 neutropenia the most common side effect (safety population: 1759/2841 [61.9%] vs 11/2902 [0.4%]). Overall 42% of pts. discontinued P prior to the planned 2-year duration, 28.2% of Palbo+ET pts discontinued therapy due to adverse events, without an observed impact on survival outcomes. Conclusions Now with the full number of events, this analysis of the PALLAS trial shows that the addition of 2 years of P to ongoing adjuvant ET did not improve survival endpoints for pts with stage II-III HR+/HER2- eBC. Whether P is beneficial in the adjuvant setting for certain sub-groups of pts will be further evaluated with longer-term follow-up and by the ongoing translational science program. Support: ABCSG; AFT; Pfizer; ClinicalTrials.gov Identifier: NCT02513394; https://www.abcsg.org; https://acknowledgments.alliancefound.org Citation Format: Michael Gnant, Amylou C Dueck, Sophie Frantal, Miguel Martin, Hal Burstein, Richard Greil, Peter Fox, Antonio C Wolff, Arlene Chan, Eric Winer, Christian Singer, Kathy Miller, Marco Colleoni, Michelle Naughton, Gabor Rubovszky, Judith Bliss, Ingrid A Mayer, Guenther G Steger, Zbigniew Nowecki, Olwen Hahn, Norman Wolmark, Hope Rugo, Georg Pfeiler, Hannes Fohler, Otto Metzger, Céline Schurmans, Kathy P Theall, Dongrui R Lu, Kathleen Tenner, Christian Fesl, Angela DeMichele*, Erica L Mayer, *shared last authorship. Adjuvant palbociclib in HR+/HER2- early breast cancer: Final results from 5,760 patients in the randomized phase III PALLAS trial [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr GS1-07.

PURPOSE Palbociclib is a cyclin-dependent kinase 4 and 6 inhibitor approved for advanced breast cancer. In the adjuvant setting, the potential value of adding palbociclib to endocrine therapy for hormone receptor–positive breast cancer has not been confirmed. PATIENTS AND METHODS In the prospective, randomized, phase III PALLAS trial, patients with hormone receptor–positive, human epidermal growth factor receptor 2–negative early breast cancer were randomly assigned to receive 2 years of palbociclib (125 mg orally once daily, days 1-21 of a 28-day cycle) with adjuvant endocrine therapy or adjuvant endocrine therapy alone (for at least 5 years). The primary end point of the study was invasive disease-free survival (iDFS); secondary end points were invasive breast cancer–free survival, distant recurrence-free survival, locoregional cancer-free survival, and overall survival. RESULTS Among 5,796 patients enrolled at 406 centers in 21 countries worldwide over 3 years, 5,761 were included in the intention-to-treat population. At the final protocol-defined analysis, at a median follow-up of 31 months, iDFS events occurred in 253 of 2,884 (8.8%) patients who received palbociclib plus endocrine therapy and in 263 of 2,877 (9.1%) patients who received endocrine therapy alone, with similar results between the two treatment groups (iDFS at 4 years: 84.2% v 84.5%; hazard ratio, 0.96; CI, 0.81 to 1.14; P = .65). No significant differences were observed for secondary time-to-event end points, and subgroup analyses did not show any differences by subgroup. There were no new safety signals for palbociclib in this trial. CONCLUSION At this final analysis of the PALLAS trial, the addition of adjuvant palbociclib to standard endocrine therapy did not improve outcomes over endocrine therapy alone in patients with early hormone receptor–positive breast cancer.