Effect of sunlight exposure on survival in patients with lymphoma: Results from the prospective Singapore Lymphoma Study.

Abstract

1593 Background: Recently, several studies evaluating the effect of ultraviolet light exposure on the risk of developing lymphoma have yielded conflicting results, in part due to seasonal and latitude variation. Further, most of these studies also lack long term follow up and could not systemically address the influence of sunlight exposure on survival. In this prospective, epidemiological study, we explored the relationship between past sunlight exposure and survival in lymphoma patients in tropical Singapore, where sunlight exposure is constant throughout the year. Methods: Singapore Lymphoma Study was established in 2005. A total of 384 patients with histologically confirmed lymphoma were followed from date of diagnosis through November 2011. Interviewers were trained to conduct in-person interviews to collect detailed information, including every occupational period that lasted at least 1 year and number of hours worked outdoor from 9am to 5pm using a structured questionnaire. Descriptive, multivariate and survival analysis (Kaplan Meier; age, gender, race and education level adjusted) were performed. Results: Among all lymphoma subtypes, the most prevalent was diffuse large B cell lymphoma, 47.7%, followed by Hodgkin lymphoma, 14.6%, follicular lymphoma, 12.2% and T cell lymphoma, 6.5%. 97.1% had black or brown eye color and 49.6% had fair skin. Overall survival of lymphoma and NHL subtype decreased significantly with increasing lifetime occupational hours (ptrend=0.01 and 0.03). Chinese was associated with longer survival with increasing daily sunlight exposure during childhood and adolescent years, whether at school or outdoor leisure (ptrend=0.04) and there were no evidence for non-Chinese (Malays or Indians). Patients with lighter eye color results in shorter survival (HR=2.91, 95% CI: 1.15-7.34, p=0.02). Conclusions: We found leisure sunlight exposure during childhood and adolescent years to be beneficial to the survival of Chinese lymphoma patients and increasing lifetime cumulative occupational exposure is associated with increasing risk of death. This data contributes to the growing research on the effects of sunlight exposure on lymphoma patients.