Abstract B58: Sunlight exposure and overall survival in melanoma, colon cancer, and non-Hodgkin's lymphoma
Authors: Hampras Shalaka S. , Sondak Vernon K. , Shibata David , Dalia Samir M. , Rollison Dana E. 
Published: May 2019

Background: Sunlight exposure is a major source of vitamin D, which is thought to inhibit tumor growth as well as enhance the efficacy of chemotherapy. Accumulating evidence suggests sunlight exposure is associated with prognosis of several cancers through vitamin D related or other unknown biological pathways. We hypothesized that, due to variation in Vitamin D receptors as well as potential variation in underlying biological mechanisms across different tissues, the protective effect of sunlight exposure on overall survival may vary across cancer types.

Methods: A retrospective cohort study was conducted at Moffitt Cancer Center, Florida, to evaluate sunlight related factors in association with overall survival of three different cancers. Cases included patients with pathologically confirmed primary colon cancer (n=380), primary non-Hodgkin's lymphoma (NHL) (n=311) and primary melanoma (n=1364), who were treated at Moffitt Cancer Center from 2007 through 2012. At their first visit to Moffitt, patients completed an electronic questionnaire including information on demographics, past medical history, current symptoms, and a variety of lifestyle risk factors that can impact prognosis of cancer. Questions related to sunlight exposure included history of blistering sunburn, history of sunbed, sunlamp or tanning bed use, frequency of sunburns and other risk factors for skin cancer. Data on vital status were obtained from Moffitt's cancer registry. Cox proportional hazards ratios were estimated to determine the association of sun exposure related factors with overall survival, adjusting for confounders. Analyses were further stratified by stage at diagnosis.

Results: History of blistering sunburns was associated with 52% significantly improved overall survival among NHL cases (HR=0.48, 95% CI=0.23-0.97), after adjusting for age and stage at diagnosis. While no association was observed between history of sunburns and survival of NHL cases with early stage at diagnosis, 63% improved overall survival was observed among cases with advanced stage disease (HR=0.37, 95% CI=0.17-0.84). Although not significant, history of sunbed use was associated with 50% (HR=0.50, 95% CI=0.07-3.69) improved overall survival among NHL cases. No significant associations were observed between history of sunburn or history of sunbed use and survival of colon cancer and melanoma.

Conclusion: Sunlight exposure may be an important predictor of overall survival in NHL but not in colon cancer and melanoma and may be related to protective effect of increased Vitamin D levels. The protective effect of sunlight exposure may differ by stage at diagnosis in patients with NHL. Additional research should be conducted to further investigate biological pathways, with a focus on Vitamin D, which may explain these findings.

Citation Format: Shalaka S. Hampras, Vernon K. Sondak, David Shibata, Samir M. Dalia, Dana E. Rollison. Sunlight exposure and overall survival in melanoma, colon cancer, and non-Hodgkin's lymphoma. [abstract]. In: Proceedings of the Twelfth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2013 Oct 27-30; National Harbor, MD. Philadelphia (PA): AACR; Can Prev Res 2013;6(11 Suppl): Abstract nr B58.