Impact of Vitamin D on the Clinical Outcome of Gastro-Entero-Pancreatic Neuroendocrine Neoplasms: Report on a Series from a Single Institute.

Background/aims: Vitamin D deficiency is hypothesized to represent a risk factor in several neoplasms. The aim of this study was to determine whether serum 25-hydroxyvitamin D (25-OHvitD) deficiency represents a risk factor for neuroendocrine neoplasms (NENs) and can be associated with overall survival (OS) and progression-free survival (PFS).

Methods: From 2010 to 2015, 138 patients with gastro- entero-pancreatic NENs (61 females; median age, 63 years) were included in the study. Serum 25-OHvitD levels, which were measured at baseline, were defined as deficient if ≤20 ng/mL. In such cases, 25-OHvitD supplementation was administered to the patients. The possible associations between 25-OHvitD levels and disease grading, staging, overall OS, and PFS were considered. Furthermore, the possible association between 25-OHvitD supplementation and PFS or OS was evaluated by Cox proportional hazards regression.

Results: Median 25-OHvitD levels were 12.9 ng/mL (range 2-32); in detail, 94 patients (68%) had ≤20 ng/mL, with 46 cases (33%) having ≤10 ng/mL. An inverse correlation was observed between 25-OHvitD levels and OS (p = 0.03, rs = -0.18) and PFS (p = 0.01, rs = -0.22). At Cox proportional hazards regression, mortality was not related to 25-OHvitD levels; however, there was an association between 25-OHvitD supplementation and OS (p < 0.002).

Conclusions: Vitamin D deficiency is highly prevalent among NEN patients. 25-OHvitD supplementation potentially plays an important role in the correction of 25-OHvitD values, and has an influence on the clinical outcome. However, further studies are needed to confirm this observation.