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Impact of Treatment Related Neutropenia on Response to Palbociclib in Metastatic Hormone Positive, her2neu Negative Breast Cancer

Year: 2026

Type: article

Abstract: Cyclin-dependent kinases (CDK4/6) inhibitors play an important role in the management of metastatic hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) breast cancer. They act by inhibiting the proteins CDK4 and CDK6, which are implicated in the advancement of the cell cycle and unchecked cell proliferation- the primary causes of the development of cancer. The blocking of these proteins can slow or stop the growth of cancer cells. Palbociclib is a highly active substance in the management of hormone positive, her2neu negative metastatic breast cancer [1]. METHODS: A retrospective study was conducted at King Fahad Hospital (Al Jaber Oncology Centre). Sixty-four metastatic, hormone-positive, HER2neu-negative breast cancer cases who received. Palbociclib were included in the study and followed up for a median time of 30 months. RESULTS: Our study indicated that 58 patients were treated with Palbociclib combined with letrozole (90.6%), whereas 6 patients (9.4%) were treated with Palbociclib along with fulvestrant. Neutropenia induced by Palbociclib occurred in 87.5% of cases, whereas 12.5% of cases did not experience neutropenia (8 cases). Regarding neutropenia, our study showed that 32.1% of the participants experienced grade I neutropenia, while 58.9% had grades II, and 8.9% had grade III neutropenia. A dose reduction of Palbociclib was implemented in 19 cases (29.7%) throughout the entire treatment duration. With the adjustment of the dose of Palbociclib, there was no statistically significant difference between the different doses. The 30-month PFS rate was 75% with the dose of 100 mg, 90.9% with 75 mg, and 97.2% with the dose of 125 mg. Median PFS was not reached. A total of 5 deaths were noted in the entire study group. There was no statistically significant difference in overall survival based on neutropenia grades. CONCLUSION: Neutropenia induced by palbociclib and subsequent dose reduction did not impact the disease outcome.

Source: Asian Pacific Journal of Cancer Prevention

DOI: 10.31557/apjcp.2026.27.2.769