To evaluate the prevalence and risk factors of arm lymphedema in patients with breast cancer.

Between 2006 and 2017, we investigated patients with breast cancer after breast surgery who received adjuvant radiotherapy at the breast or chest wall, and/or adjuvant radiotherapy at regional lymph nodes, and standard systemic chemotherapy depending on disease stage and risk factors. We assessed arm lymphedema using arm circumference measurement differences on the treated side compared with the opposite arm (≥2 cm measurements at any one position). Associations between arm lymphedema and potential risk factors were identified using statistical analysis.

In 308 patients, arm lymphedema prevalence was 6·2%. Patients having ≥20 lymph nodes removed (hazard ratio (HR) = 3·29; 95% confidence interval (CI): 1·12–8·87), undergoing regional lymph node irradiation (HR = 1·81; 95% CI: 1·09–13·28), and no arm and shoulder exercises after treatment (HR = 3·16; 95% CI: 1·89–5·26) had a higher risk of arm lymphedema.

Arm lymphedema is a serious breast cancer complication and is a preventable morbidity. Planning arm and shoulder exercises in line with adjuvant treatments and increasing clinical awareness of early indications could help lower the risk of occurrence.