Ahmet ORUÇ, Bilgeşah KILIÇTAŞ, Melek KARAKURT ERYILMAZ, Murat ARAZ, Mehmet ARTAÇ
Journal of Oncological Sciences - 2026;12(2):282-289
Objective: CDK4/6 inhibitors are the standard of care for metastatic hormone receptor (HR)-positive and human epidermal growth factor receptor 2 (HER2)-negative breast cancer. Markers for predicting prognosis and survival during follow-up of these patients are not yet available. Therefore, this study aimed to examine the effect of changes in prognostic nutritional index (PNI) and systemic immune-inflammation index (SII) on survival in patients treated with CDK4/6 inhibitors plus letrozole. Material and Methods: This was a retrospective study of 88 patients. Both PNI and SII values were calculated just before, at 3 months, and at 6 months. Changes at 0-3 months and 0-6 months were divided into two groups: increasing and decreasing. Changes in progression-free survival (PFS) between these two groups were analyzed. Results: PFS was 28.2 months [95% confidence interval (CI): 23.6-32.89] in the PNI-increasing group and 23.3 months (95% CI: 15.55-31.21) in the PNI-decreasing group at the 3rd month of treatment (p=0.048). At 6 months, PFS was 29.1 months (95% CI: 24.2-33.9) in the PNI increasing group and 23.2 months (95% CI: 15.9-30.6) in the PNI decreasing group. In the group with decreased SII at 3 months, PFS was almost 7 months longer than in the group with increased SII. At month 6, PFS was 27.7 months (95% CI: 23.4-32.1) in the SII-decreasing group and 14.8 months (95% CI: 10.5-19.1) in the SII-increasing group (p=0.017). In multivariate Cox regression analysis, only a reduction in SII between 0-6 months was a negative independent risk factor for PFS, hazard ratio 0.24 (95% CI: 0.06-0.87), p=0.031. Conclusion: A decrease in PNI during follow-up is associated with poor survival in metastatic HR-positive and HER2 negative patients receiving letrozole in combination with a CDK4/6 inhibitor, whereas a decrease in SII may be a prognostic indicator in these patients.
