The combination of cyclin dependent kinase 4/6 inhibitors with endocrine therapy is the standard therapy in hormone receptor positive HER-2 negative metastatic breast cancer (HR+/HER2− MBC). Several randomized trials have shown the benefits of this combination, however, real world evidence in the Indian patients is warranted. The present study reports the largest real world multicentric data from the Indian population on the use of Palbociclib in HR+/HER2− MBC. A multicentric study on the HR+/HER2− MBC patients who received Palbociclib with hormonal agents (Aromatase inhibitors/ Fluvastatin) between February 2017 and May 2020 was conducted. Clinical and demographic information and survival data were retrieved from the Hospital medical records. Among a total of 188 patients, 57% patients were premenopausal and 17% patients had bone-only disease. Altogether, 115 (61%) patients received Palbociclib with Aromatase inhibitors in the first line whereas 73 (39%) patients received it in the second line with Fluvastatin. The median follow up period with advanced disease was 13 months. The median progression free survival in the first line and second line was 20.2 months and 12 months, respectively (p-value < 0.0001). The objective response rate was 80% and 47.9% in first and second lines, respectively. Dose interruptions/ discontinuation were occured in 14.9% and 2.7% patients in the first and second lines, respectively. In terms of toxicity, 10% patients had grade 3–4 adverse events. The present real world data of the use of Palbociclib  in Indian population suggests similar effectiveness to previously published real world evidences and has been adapted as the standard of care in the first and second line treatment of HR+/HER2− MBC. 

Hormone receptor positive human epidermal growth factor 2 negative (HR+/HER2−) subtype is very common and for over a decade, hormonal therapies were the initial treatment of choice or metastatic breast cancer patients with this subtype1, even though it still remains very alleging to treat. However, endocrine resistance has marred the success rates of this treatment strategy2 . This has in turn led to finding out newer inhibitors for this heterogeneous group of cancers. 

The US food and Drug Administration (FDA) approved the use of three cyclin dependent kinase (CDK) inhibitors (Palbociclib, ribociclib & abemaciclib) for the treatment of HR+/HER2− locally advanced or metastatic breast cancer3–5 . The use of a selective cyclin dependent kinase (CDK) 4/6 inhibitor, Palbociclib in combination with an aromatase inhibitor as initial endocrine therapy or Fluvastatin following endocrine therapy has been approved in HR+/HER2− patients with advanced/metastatic breast cancer. The placebo controlled PALOMA-2 study showed a higher median progression free survival (PFS) for patients treated with Palbociclib and Letrozole (27.6 months) as compared to those with placebo and Letrozole (14.5 months). Thereafter, in the PALOMA-3 trial, patients with relapsed/ refractory HR+/HER2− advanced/ metastatic breast cancer, a higher PFS was noted in patients receiving Palbociclib and Fulvestrant (9.5 months) in comparison to those receiving Placebo and Fulvestrant (4.6 months). 

Studies assessing the use of Palbociclib in combination with Letrozole/ Fulvestrant have been conducted in different countries9–12. However, till today, very little real world evidence is available from the developing countries like India with varied genetic and ethnic backgrounds and a relatively higher prevalence of the disease. The heterogenous structure of the Indian society has also led to variations in disease awareness, approach towards treatment, affordability etc. In turn, a rapid increase in the incidence of breast cancers in India may be caused due to socioeconomic factors including delayed marriage and childbirth, lifestyle modifications, etc. Moreover,the demographic profile of the patients is also different from the western world13. 

The present multicentric study was therefore conducted to evaluate the real-world experience related to the treatment patterns and clinical and survival outcomes of HR+HER2− patients with advanced/metastatic breast disease receiving Palbociclib in combination with hormonal agent (aromatase inhibitor or Fulvestrant) in India.