e13028 Background: CDK4/6 inhibitors (CDKi), in combination with endocrine therapy (ET), has become the standard of care in the treatment of hormone positive (HR+)/ HER2 neu negative metastatic breast cancer (MBC) patients. We evaluated clinical outcomes and toxicity in MBC patients, who have received ET with two CDKi, namely palbociclib and ribociclib. Methods: This is an ambispective, single institutional analysis of de-novo HR+ MBC patients treated with CDKi (palbociclib 125 mg and ribociclib 600 mg once a day for 21 days /28 days cycle) from November 2016- October 2020 at AIIMS, New Delhi, India. The primary endpoint was progression-free survival (PFS) and the secondary endpoint was response rate and toxicity. A total of 157 female patients were recruited in this study however the response and toxicity data were available in 120 cases. All premenopausal women received ovarian suppression or ovarian ablation. Results: A total of 120 patients were included in this study with a median age of 57 years (35-75) and 93 (77.5%) cases were postmenopausal. Twenty-three (19.1%) patients had a bone-only disease, 49 (40.9%) had bone and visceral disease and 48 (40%) had only visceral disease. In this study 91 (75.9%) patients received palbociclib and 29 (24.2%) received ribociclib. The median PFS was 18 months (4-36). Twenty four (20%) patients achieved a complete response, 69 (57.5%) patients attained partial response, 18(15%) patients had stable disease and 9 (7.5%) had disease progression. Grade 3–4 neutropenia, thrombocytopenia, and anaemia were observed in 18(15%), 8 (6.7%), and 4 (3.3%) cases respectively. None of the patients developed febrile neutropenia. Cutaneous, renal, hepatic, and gastrointestinal toxicity was observed in 1,1,3,4 cases respectively. Prolonged QTc was observed in one case. Grade 3 fatigue was observed in 7 cases. Dose interruption/delay (mean dose delay of 7 days), dose modification, and drug discontinuation were observed in 24 (20%), 12 (10%), and 10 (8.3%) of cases respectively. Conclusions: This is one of the largest real-world Indian data on CDK4/6 inhibitors on upfront HR+ MBC. Side effects are less than published literature with similar efficacy. Neutropenia was the most common side effect which was managed by brief dose interruption.
Genomic Characterization of de novo Metastatic Breast Cancer