Erin Roesch, MD
The role of adjuvant olaparib was investigated in the phase 3 OlympiA trial , which included 1,836 patients with high-risk HER2-negative gBRCAm early breast cancer who received local treatment and adjuvant or neoadjuvant chemotherapy. One year of adjuvant olaparib was associated with a significant improvement in invasive disease-free survival (hazard ratio [HR] 0.58, P < .001) and distant disease-free survival (HR 0.57, P < .001). The 3-year invasive disease-free survival (iDFS) was 85.9% in the olaparib group and 77.1% in the placebo group (absolute benefit of 8.8%), and 3-year distant disease-free survival (dDFS) was 87.5% and 80.4%, respectively (difference of 7.1%). These results are considered practice changing and lead to questions regarding the expansion of germline testing in early stage breast cancer. Furthermore, PARP inhibitors have shown exciting results in the neoadjuvant setting. Among 61 patients with gBRCAm HER2-negative early breast cancer, neoadjuvant talazoparib produced a pathologic complete response (pCR) in 49.2%, and there may be a subgroup of patients for whom this approach is relevant.
The presence of residual disease after neoadjuvant chemotherapy has prognostic implications and can help tailor adjuvant treatment recommendations. The CREATE-X trial has established the role of adjuvant capecitabine for patients with triple-negative breast cancer with residual disease after pre-operative chemotherapy. The phase 3 EA1131 trial randomized 415 patients with stage II-III triple-negative breast cancer and residual disease post-neoadjuvant chemotherapy to platinum agent or capecitabine. There was no significant difference in 3-year iDFS (42% for platinum vs 49% for capecitabine; HR 1.06, 95% CI 0.62-1.81), and higher hematologic toxicity and dose reductions in the platinum arm. These data support the continued use of capecitabine in this population, and the high event rate highlights the need for more effective therapies in this setting.
The majority of patients with HR+/HER2- MBC will receive a CDK 4/6 inhibitor at some point during their treatment course. In an updated analysis of the phase 3 MONALEESA-3 trial which included postmenopausal patients with HR+HER2- MBC, with median follow-up of 56.3 months, ribociclib plus fulvestrant continued to show an overall survival (OS) benefit of greater than 1 year compared with fulvestrant alone (median OS 53.7 months vs 41.5 months in the ribociclib vs placebo arm, respectively; HR 0.726, 95% CI 0.59-0.90). Additionally, extended follow-up of the PALOMA-3 trial demonstrated OS benefit with palbociclib plus fulvestrant compared to fulvestrant alone in patients with HR+/HER2- MBC; at median follow-up of 73.3 months, median OS was 34.8 months in the palbociclib arm vs 28.0 months in the placebo arm (HR 0.81, P = .0221). Sequencing of other targeted therapies (such as PI3K inhibitors), predictors of CDK 4/6 inhibitor response in different intrinsic subtypes, and the role of CDK 4/6 inhibitor use beyond progression are areas where further research is warranted.
References:
Robson M, Im SA, Senkus E, et al. Olaparib for Metastatic Breast Cancer in Patients with a Germline BRCA Mutation. N Engl J Med. 2017;377(6):523-533.
Litton JK, Beck JT, Jones JM, et al. Neoadjuvant talazoparib in patients with germline BRCA1/2 (gBRCA1/2) mutation-positive, early HER2-negative breast cancer (BC): Results of a phase 2 study. J Clin Oncol 39, 2021 (suppl 15; abstr 505).
Symmans WF, Wei C, Gould R, et al. Long-Term Prognostic Risk After Neoadjuvant Chemotherapy Associated With Residual Cancer Burden and Breast Cancer Subtype. J Clin Oncol. 2017;35:1049-1060.
Masuda N, Lee SJ, Ohtani S, et al. Adjuvant Capecitabine for Breast Cancer after Preoperative Chemotherapy. N Engl J Med. 2017;376:2147-2159.
Cristofanilli M, Rugo H, Im SA, et al. Overall survival (OS) with palbociclib (PAL) + fulvestrant (FUL) in women with hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2–) advanced breast cancer (ABC): Updated analyses from PALOMA-3. J Clin Oncol. 2021; 39:15_suppl, 1000-1000.