Research has shown that there is a link between prostate cancer and low vitamin D levels. They have found that men with prostate cancer tend to have lower levels of vitamin D. This relationship is still being researched.
These findings are suggesting vitamin D slows the tumor cells life cycle and prevents growth by promoting cellular differentiation and reducing tumor blood vessel formation.

https://www.harvardprostateknowledge.org/low-vitamin-d-tied-aggressive-pr…
https://www.health.harvard.edu/mens-health/can-vitamin-d-levels-signal-ag…