Efficacy and safety of palbociclib and ribociclib in patients with estrogen and/or progesterone receptor positive, HER2 receptor negative metastatic breast cancer in routine clinical practice

Abstract

Background There is scant data from India on efficacy and safety of palbociclib and ribociclib in routine clinical practice. Methods This retrospective, observational, single institution study included patients with estrogen and/or progesterone receptor positive and human epidermal growth factor receptor 2 (HER2) negative metastatic breast cancers, who received palbociclib or ribociclib with any partner endocrine therapy in any line of treatment between January 2016 and June 2019. Data were analyzed for progression-free survival (PFS), overall survival (OS) and toxicity. Results The study included 101 female patients with median age of 57 (IQR 48–62) years, of whom 80 (79.2%) were postmenopausal, 79 (78.2%) received palbociclib or ribociclib in second- or later-line treatment, 59 (58.4%) received fulvestrant and 41 (40.6%) received an aromatase inhibitor. In first-line treatment, at a median follow-up of 21.7 (0.5–41.9) months, median PFS and OS were 21.1 (95%CI 16.36-not estimable) months and not reached, respectively. In second- or later-line setting, at a median follow-up of 17.2 (0.5–43.7) months, median PFS and OS were 5.98 (95%CI 4.96–7.89) months and 20.2 (95%CI 14.1-not estimable) months, respectively. Grade 3–4 neutropenia and febrile neutropenia were seen in 45 (45.0%) and 9 (9.0%) patients, respectively while dose reduction was required in 32 (31.7%) patients. In multivariable Cox regression analysis, first-line setting (HR 0.49, 95%CI 0.25–0.97, p = 0.043) and ECOG performance status 1 (HR 0.43, 95%CI 0.20–0.91, p = 0.028) were significantly associated with PFS while only ECOG PS 1 was significantly associated (HR 0.04, 95%CI 0.008–0.206, p = 0.000) with OS. Conclusion Palbociclib and ribociclib, when used in routine clinical practice in first or subsequent lines of treatment, resulted in efficacy and toxicity outcomes in concordance with those expected from pivotal trials.

Efficacy of cyclin-dependent kinase 4/6 inhibitors in patients with metastatic hormone positive breast cancer: a single institutional study from India

“…Only 27 (19%) patients were premenopausal at the time of presentation, which was similar to the IRIS study [8]. Ductal carcinoma was the most common histology in our study, similar to that reported by Rath et al [9]. Bone-only metastases were seen in 32 (23%) patients.…”

“…The median OS of our study population was 29.7 months, more than 27.1 months reported by Rath et al [9]. In the same study, the median OS in the first-line setting was not reached, while it was 39.9 months in our study [9]. These two differences can be attributed because the overall study population differed in both studies.…”

“…The median PFS of the overall population was 16.1 months which was much more than that reported by Rath et al [9] where it was 7.7 months. This gross difference can be attributed by the fact that there were heavily pretreated patients in the study by Rath et al [9] compared to our research. However, when used in the first liner, the median PFS with CDK4/6 inhibitors was comparable in both studies and was around 20 months.…”

“…In comparison, other studies have reported 17%-20% [6,10]. The median PFS of the overall population was 16.1 months which was much more than that reported by Rath et al [9] where it was 7.7 months. This gross difference can be attributed by the fact that there were heavily pretreated patients in the study by Rath et al [9] compared to our research.…”

“…It requires further validation in other real-world studies. In another real-world study, prior treatment and performance score were found to be prognostic factors, and we have found prior treatment is a poor prognostic factor [9].…”