New research presented at the European Congress on Obesity in Vienna, Austria (23-26 May), shows that obesity (bariatric) surgery is associated with a 61% fall in the risk of developing malignant melanoma skin cancer, and a 42% drop in the risk of skin cancer in general. The study is by Magdalena Taube and colleagues from University of Gothenburg, Sweden.
Melanoma is a deadly skin cancer, the incidence of which has increased steadily in many countries of the world, especially high-income countries. For example, in the UK, cases have more than doubled since the 1990s, and it is the fifth most common cancer in men and women, with over 15,000 cases each year and more than 2,000 deaths.*
Obesity is an established risk factor for cancer and some studies indicate that intentional weight loss sometimes reduces the risk. However, evidence for a link between obesity, weight loss, and malignant melanoma is limited. In this study, the authors used data from the matched Swedish Obese Subjects (SOS) study - a prospective controlled intervention trial examining bariatric surgery outcomes - to analyse the impact of weight loss on melanoma incidence.
The surgery group consists of 2007 subjects who chose surgical treatment, and the control group consists of 2040 individuals matched for 18 variables (including sex, age, anthropometric measurements, cardiovascular risk factors, psychosocial variables, and personality traits). To analyse malignant melanoma incidence, statistical tests were used to compare time to first melanoma cancer diagnosis between the surgery and control groups. In additional analyses, risk ratios between the surgery and control groups were compared.
The authors found that bariatric surgery markedly reduced the risk of melanoma. Over a median follow-up time of 18 years, they observed a 61% reduced risk of malignant melanoma and a 42% reduced risk of skin cancer in general compared to controls given usual obesity care.
The authors conclude: "In this long?term study, bariatric surgery reduced the risk of malignant melanoma. This finding supports the idea that obesity is a melanoma risk factor, and indicates that weight loss in individuals with obesity can reduce the risk of a deadly form of cancer that has increased steadily in many countries over several decades."