Sun exposure has been linked to increased survival from melanoma and now new research suggests that this is due, at least in part, to sunlight-related tumors being inherently less aggressive than those not tied to sun exposure.
The effects of sun exposure on cancer, however, may not be limited to cutaneous malignancies. In another study, also reported in the Journal of the National Cancer Institute for February 2, researchers shows that high UV radiation exposure is associated with a reduced risk of non-Hodgkin lymphoma (NHL). “Our findings provide the strongest evidence to date that the better prognosis of (sunlight-related) melanomas is not simply due to earlier detection of these types,” Dr. Marianne Berwick, lead author of the first study, told Reuters Health. Dr. Berwick, a researcher from the University of New Mexico in Albuquerque, noted that “further studies are needed to determine how sun exposure might reduce melanoma aggressiveness,” but said that the effect could be mediated through vitamin D or involve an enhancement of DNA repair capacity.The findings stem from a study of 528 melanoma patients who were entered in the Connecticut Tumor Registry.Sunburn, high intermittent sun exposure, self-reported skin awareness, and solar elastosis, a histologic marker of sun damaged-skin, were all linked to increased survival from melanoma. Conversely, melanoma thickness, mitoses, ulceration, and head and neck location were associated with decreased survival.On multivariate analysis, skin awareness was a strong, independent predictor of increased survival, consistent with the belief that earlier detection leads to better outcomes. However, solar elastosis, which does not relate to detection, was found to be an even stronger predictor of increased survival. Dr. Berwick emphasized that these findings have no bearing on current recommendations that “avoiding sun exposure reduces the risk of melanoma.” Moreover, she added that they also do not suggest that exposing melanomas to sunlight, ex post facto, will improve survival.In the second study, Dr. Karin Elkstrom Smedby, from the Karolinska Institutet in Stockholm, and colleagues investigated UV radiation exposure as a possible cause for increasing rates of malignant lymphoma in recent decades. Instead, the researchers found that high UV radiation exposure, as measured by frequent sunbathing and sunburns, cut the risk of NHL by up to 40% depending on the level of exposure.The study involved 3740 patients with malignant lymphomas and 3187 population controls. High UV radiation exposure also seemed to protect again Hodgkin’s lymphoma but the association was weaker than with NHL. The authors found that a history of skin cancer doubled the risk of both types of lymphoma. Given the other findings, this association is “unlikely to be mediated by UV exposure,” they add. (Source: J Natl Cancer Inst 2005;97:195-209: Reuters Health: Anthony J. Brown, MD: Oncolink: February 2005.)