High Body Mass Index and Young Age Are not Associated with Post-Mastectomy Pain Syndrome in Breast Cancer Survivors: A Case-Control Study

BACKGROUND Surgery is usually the first treatment for breast cancer which is followed by some complications such as chronic pain. Post mastectomy pain syndrome (PMPS) is a common complication among breast cancer survivors and is considered as a chronic neuropathic pain in the side of surgery which persists more than three months. The exact mechanisms and related risk factors of the chronic pain after breast surgery are unknown. The aim of this study was to investigate the association of body mass index (BMI) and age with PMPS. METHODS In this case-control study, a total of 122 women were assessed; of these, 61 women were diagnosed with PMPS and selected as cases and 61 pain-free patients were selected as controls. The demographic and clinical characteristics of participants were collected through questionnaires and medical record of patients. Logistic regression model was used to determine the association of BMI and age with PMPS, adjusted for demographic and clinical characteristics. RESULTS No significant differences were found in means of weight (68.02±8.80 vs. 68.67±11.82, p=0.726), BMI (26.38±3.28 vs. 27.10±6.03, p=0.410), and age (46.34±11.67 vs. 48.54±12.57, p=0.319) between those with PMPS and those not reporting PMPS. A non-significant slight increase in odds ratio of PMPS was observed in obese category compared to normal weight category [OR=1.152 (95% CI 0.405-3.275), p=0.908], but after adjusting the confounding factors, the risk of pain development was attenuated in obese subjects [OR=0.748 (95% CI 0.228-2.459), p=0.633]. Also, non-significant decrease in odds ratios of PMPS was found in 20-39 y, 40-49 y, and 50-59 y ages categories compared to oldest age category [adjusted OR= 0.781 (95% CI 0.213-2.866), p=0.576; adjusted OR=0.485 (95% CI 0.152- 1.554), p=0.183; adjusted OR=0.735 (95% CI 0.206-2.627), p=0.628; respectively]. CONCLUSION In contrast with some observational studies, present study showed that high BMI and younger age might not be associated with increased risk of PMPS development. Further research is necessary to determine the main risk factors and directionality and causal mechanisms for associations of these risk factors with chronic pain after mastectomy.