There are a lot of published data that showed association between vitD deficiency and many disorders e.g. diabetes, metabolic syndrome, CVD, cancer,...
The majority of studies found a protective relationship between sufficient vitamin D status and lower risk of cancer. The evidence suggests that efforts to improve vitamin D status, for example by vitamin D supplementation, could reduce cancer incidence and mortality at low cost, with few or no adverse effects.
Article The Role of Vitamin D in Cancer Prevention