Palbociclib plus letrozole as treatment for postmenopausal women with hormone receptor–positive/human epidermal growth factor receptor 2–negative advanced breast cancer for whom letrozole therapy is deemed appropriate: An expanded access study in Australia and India

AIM: Palbociclib was approved in the United States in 2015 to treat estrogen receptor–positive/human epidermal growth factor receptor 2–negative (HER2–) advanced breast cancer (ABC). This study evaluated outcomes and safety in patients treated with palbociclib in Australia and India with hormone receptor–positive (HR+)/HER2– ABC before palbociclib became commercially available. METHODS: Postmenopausal women (≥18 years) with HR+/HER2– ABC who were appropriate candidates for letrozole therapy received palbociclib 125 mg once daily for 21 days followed by 7 days off, and letrozole 2.5 mg once daily (continuous). Safety, tumor response, and patient‐reported outcomes (Australian cohort) were evaluated. RESULTS: In total, 252 patients received palbociclib plus letrozole (Australia, n = 152; India, n = 100). More patients in the Australian versus Indian cohort had received prior chemotherapy (advanced/metastatic setting: 45.9% vs. 32.0%), endocrine therapy (advanced/metastatic setting: 63.2% vs. 54.3%), and advanced/metastatic therapies (61.8% vs. 31.0%). The most frequently reported all‐grade palbociclib‐related treatment‐emergent adverse events were neutropenia (66.7%), fatigue (35.3%), and stomatitis (26.6%); grade 3/4 neutropenia was reported as palbociclib‐related in 62.7% of patients. Febrile neutropenia was reported in six patients (2.4%). Eight patients (3.2%) discontinued because of an adverse event. The objective response rate was 19.4% (95% CI, 14.7%–24.9%) overall and 2.3% in Australian patients with ≥2 lines of prior therapy for metastatic disease. Patient‐reported quality of life scores were maintained throughout the study. CONCLUSIONS: In an expanded access setting in Australia and India, palbociclib plus letrozole was well tolerated in patients with HR+/HER2– ABC, with a safety profile consistent with previous reports.