Could macrocytosis predict survival In advanced breast cancer patients that were treated with CDK 4–6 inhibitors?

Introduction

Cyclin Dependent Kinase (CDK) 4–6 inhibitors are the recommended first-line treatment option for hormone-positive metastatic breast cancer (MBC). They show their effects by causing cell cycle arrest in G1-S phase. Neutropenia is the most common haematological side effect. In the literature, data on the association between CDK 4–6 inhibitors and macrocytosis are limited. We aimed to investigate the effect of macrocytosis on survival.

Methods

We retrospectively analysed 133 patients with de novo hormone positive MBC using CDK 4–6 inhibitors in first line treatment. Mean Corpuscular Volume (MCV) > 100 was considered macrocytosis and patients were divided into two groups; MCV<100 and MCV >100. The association of macrocytosis with clinicopathological features, Progression Free Survival (PFS) and Overall Survival (OS) were evaluated.

Results

42 patients were receiving palbociclib and 81 patients were receiving ribociclib. Median OS was determined as 33 months and median PFS was determined as 22 months. Macrocytosis ever rate was 45.8 % during follow-up. Macrocytosis was observed in 4.2 % of the patients in the first month, 16.7 % in the third month, 41.6 % in the sixth month and 42.2 % in the twelfth month. ER receptor level, ki-67, macrocytosis at 6–12 months and macrocytosis-ever which were found to affect OS as a result of univariate Cox regression analysis, were evaluated with multivariate Cox regression models and it was observed that they had significant effect on PFS and OS.

Conclusion

Macrocytosis may be a useful biomarker for the prediction of PFS and OS in MBC patients receiving CDK 4–6 inhibitors.