Prognostic Nutritional Index (PNI) as a Useful Prognostic Indicator in Patients With HR + HER-2 Negative Metastatic Breast Cancer Treated With CDK 4/6 Inhibitor + Endocrine Therapy
Authors: Keskinkilic Merve , Semiz Huseyin Salih , Oztop Ilhan , Yavuzsen Tugba , Polat Gul , Arayici Mehmet Emin 
Published: September 2022

Abstract
Background: The combination of endocrine therapy and CDK 4/6 inhibitors in the treatment of hormone receptor positive, HER-2 negative metastatic breast cancer resulted in significant increases in survival.In general, the presence of malnutrition in cancer patients is a condition that negatively affects the success of treatment. For this reason, it is important to evaluate the nutritional status of cancer patients and to give appropriate nutritional support. One of the most widely used nutritional assessment methods in the literature is the Prognostic Nutritional Index (PNI). In this study, it was aimed to evaluate the effect of PNI on treatment response and prognosis in patients with HR+ HER-2- metastatic breast cancer who received CDK 4/6 inhibitor together with endocrine therapy.
Materials and Methods: Patients with HR+ HER-2- metastatic breast cancer who received CDK 4/6 inhibitor together with endocrine therapy were evaluated retrospectively. In all patients, PNI values were recorded on the day of initiation of treatment and at the 3rd month after treatment. The Prognostic Nutritional Index was calculated as follows: serum albumin (gr/dl) + (total lymphocyte count (109/L) X 5). The optimal cutoff value for the pre-treatment PNI score was 49 as a result of the ROC analysis, and the patients were divided into two groups as low PNI group (<49.0) and high PNI group (> 49.0).
Results: A total of 106 patients with HR+ HER-2- metastatic breast cancer who received CDK 4/6 inhibitor therapy together with endocrine therapy were evaluated. While 47 (44.3%) of the patients were receiving AI + CDK 4/6 inhibitor treatment; 59 (55.7%) were taking fulvestrant + CDK 4/6 inhibitor. According to the pre-treatment PNI score, 40 (37.7%) of the patients in the whole group were in the low PNI group and 66 (62.3%) were in the high PNI group. When the effect of PNI on treatment response in the whole group was analyzed, it was found that a numerically higher response was obtained, although not statistically significant, in the group with high pre-treatment PNI compared to the group with low PNI (ORR: 61.1% vs 53.8%, respectively; p=0.301). Similarly, when the effect of PNI on PFS and OS in the whole group was analyzed, it was observed that the group with high pre-treatment PNI had a numerically higher, but not statistically significant, advantage of PFS and OS compared to the low group (mean PFS is 22.56 ± 1.28 vs 19.52 ± 1.30, p=0.757, respectively; and mean OS is 27.43 ± 0.61 vs 20.55 ± 1.17, p=0.055, respectively). It was determined that numerically similar response and survival advantages continued in both endocrine therapy subgroups.
Conclusion: The results we obtained from this study suggest that PNI may have a potentially predictive and prognostic role in patients with HR+ HER-2- metastatic breast cancer treated with CDK 4/6 inhibitor together with endocrine therapy. To the best of our knowledge, this is the first study in the literature to date with CDK 4/6 inhibitors. We think that evaluating the nutritional status before treatment and providing appropriate nutritional support in patients receiving these treatments may increase the success of the treatment.