Obesity is an independent risk factor for cancer development following diagnosis of dermatomyositis.

Patients with dermatomyositis (DM) are at an increased risk of cancer development, especially around the time of diagnosis of DM. Obesity is also a risk factor in the general population for cancer development. This study aimed to assess the association between cancer in DM patients with and without obesity as defined by ICD code and BMI data. In this analysis of patients with DM, logistic regression modeling of the odds of cancer outcome was performed for patients with DM and obesity compared to those without obesity, adjusted for age and sex. A total of 12,722 patients with DM were identified, of whom 6,055 had available BMI data. DM patients who were coded obese at any point had significantly higher odds 1.98 (95 % Confidence interval (CI) 1.70, 2.30) of a subsequent cancer diagnosis. This association was also found in the subgroup analysis with available BMI where patients with obesity (BMI ≥30 kg/m) had an increased odds of cancer 1.23 (1.02, 1.49) when compared to patients with BMI <30 kg/m with DM. In time to event analysis any obesity code was associated with a 16 % increased hazard of cancer (adjusted hazard ratio 1.16 [95 % CI 1.02, 1.31]). Overall, the most frequent type of cancer was breast cancer, however patients with DM and obesity had higher frequencies of lymphoma, colorectal, melanoma, uterine, renal cancers compared to patients with DM without obesity.