Importance Obesity is a cancer risk factor, and bariatric surgery in patients with obesity is associated with reduced cancer risk. However, evidence of an association among obesity, bariatric surgery, and skin cancer, including melanoma, is limited.

Objective To investigate the association of bariatric surgery with skin cancer (squamous cell carcinoma and melanoma) and melanoma incidence.

Design, Setting, and Participants This nonrandomized controlled trial, the Swedish Obese Subjects (SOS) study, is ongoing at 25 surgical departments and 480 primary health care centers in Sweden and was designed to examine outcomes after bariatric surgery. The study included 2007 patients with obesity who underwent bariatric surgery and 2040 contemporaneously matched controls who received conventional obesity treatment. Patients were enrolled between September 1, 1987, and January 31, 2001. Data analysis was performed from June 29, 2018, to November 22, 2018.

Interventions Patients in the surgery group underwent gastric bypass (n = 266), banding (n = 376), or vertical banded gastroplasty (n = 1365). The control group (n = 2040) received the customary treatment for obesity at their primary health care centers.

Main Outcomes and Measures The SOS study was cross-linked to the Swedish National Cancer Registry, the Cause of Death Registry, and the Registry of the Total Population for data on cancer incidence, death, and emigration.

Results The study included 4047 participants (mean [SD] age, 47.9 [6.1] years; 2867 [70.8%] female). Information on cancer events was available for 4042 patients. The study found that bariatric surgery was associated with a markedly reduced risk of melanoma (adjusted subhazard ratio, 0.43; 95% CI, 0.21-0.87; P = .02; median follow-up, 18.1 years) and risk of skin cancer in general (adjusted subhazard ratio, 0.59; 95% CI, 0.35-0.99; P = .047). The skin cancer risk reduction was not associated with baseline body mass index or weight; insulin, glucose, lipid, and creatinine levels; diabetes; blood pressure; alcohol intake; or smoking.

Conclusions and Relevance The results of this study suggest that bariatric surgery in individuals with obesity is associated with a reduced risk of skin cancer, including melanoma.

Trial Registration ClinicalTrials.gov identifier: NCT01479452

肥胖是癌症的重要危险因素，肥胖患者的减肥手术与降低癌症风险有关。但是，肥胖，减肥手术和皮肤癌（包括黑色素瘤）之间存在关联的证据有限。

目的 探讨减肥手术与皮肤癌（鳞状细胞癌和黑色素瘤）及黑色素瘤发生率的关系。

设计，环境和参与者 这项瑞典瑞典肥胖受试者（SOS）研究是一项非随机对照试验，目前正在瑞典的25个外科部门和480个初级卫生保健中心进行，旨在检查减肥手术后的结局。该研究包括2007年接受减肥手术的肥胖患者和2040名同时接受常规肥胖治疗的对照患者。在1987年9月1日至2001年1月31日之间招募了患者。从2018年6月29日至2018年11月22日进行数据分析。

干预 手术组的患者进行了胃旁路手术（n = 266），束带术（n = 376）或垂直束带胃成形术（n = 1365）。对照组（n = 2040）在其初级保健中心接受了肥胖的常规治疗。

主要结果和措施 SOS研究与瑞典国家癌症登记处，死亡原因登记处和总人口登记处进行了交叉链接，以获取有关癌症发生率，死亡和移民的数据。

结果 该研究包括4047名参与者（平均[SD]年龄，47.9 [6.1]岁； 2867 [70.8％]名女性）。有4042名患者可获得有关癌症事件的信息。该研究发现，减肥手术与黑素瘤的风险显着降低（调整后的亚危险比为0.43； 95％CI为0.21-0.87；P  = .02；中位随访时间为18.1年）和皮肤癌的总体风险有关。 （调整后的亚危险比为0.59； 95％CI为0.35-0.99；P  = .047）。皮肤癌风险的降低与基线体重指数或体重无关。胰岛素，葡萄糖，脂质和肌酐水平；糖尿病; 血压; 酒精摄入量；或吸烟。

结论与相关性 这项研究的结果表明，肥胖者的减肥手术与包括黑色素瘤在内的皮肤癌风险降低有关。

试验注册 ClinicalTrials.gov标识符：NCT01479452