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

UNLABELLED: 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.