Low baseline vitamin D levels correlate with adverse pathological features and clinical outcomes among patients with breast cancer.

Abstract

552 Background: Serum vitamin D levels have been linked to breast cancer development; however, the impact on breast cancer features and outcomes remains unclear. The present study aimed at investigating the prognostic value of baseline vitamin D level among non-metastatic breast cancer patients. Methods: In this study; we prospectively assessed female patients presenting to our department with non-metastatic breast cancer during the period from October 2018 to December 2019 for their baseline serum vitamin D levels measured by ELISA test before starting systemic therapy, in addition to other clinicopathological factors. Low Vit-D was defined as Vit-D level less than 30 ng /l. Chi-square test (Fisher’s exact test) was used to examine the relation between qualitative variables. Survival analysis was done using Kaplan-Meier method and comparison between two survival curves was done using log-rank test. Multivariate analysis was done using Cox-regression hazard model for the significant factors affecting survival on univariate analysis. Results: We enrolled 221 patients with non-metastatic breast cancer as they matched our eligibility criteria. Median age at diagnosis was (50.7± 10.9). About two thirds of the patients (64.7%) were post menopause. Median vitamin D level was (23.1 ng/l) with a range of (4-62.46 ng/liter). Around half of the patients (56.5%) had vitamin D level lower than 30 ng/liter, with higher numbers of low vitamin D levels among HER2 positive and triple negative (TNBC) patients compared to hormonal receptor positive (HR+ve) patients (P=<0.001). There was a significant negative correlation between vitamin D levels and tumor size, lymph node positivity and stage at diagnosis (the lower the vitamin D level, the larger the tumor size, and the higher the number of positive lymph nodes and the stage; r= -0.414, r= -0.586, r= -0.674; respectively; p<0.001). On follow up, the number of local recurrences, bone metastases and liver metastases were significantly higher among the low vitamin D level group, however; there was no significant difference between the two groups in terms of development of brain and lung metastases. Disease free survival (DFS) and overall survival (OS) was significantly worse among the low vitamin D level group (p<0.001). Conclusions: Low serum vitamin D in breast cancer patients negatively correlates with tumor size, lymph node positivity and stage at diagnosis. It is linked to HER-2 positive and TNBC, and is significantly associated with worse DFS and OS.