Session Item

We aimed to estimate the cumulative incidence of lymphedema in patients with breast cancer who received postoperative radiotherapy (RT). We compared hypofractionated and conventional RT for lymphedema development and identified novel prognostic factors affecting lymphedema in these patients.

A total of 590 patients with ductal carcinoma in situ or invasive carcinoma of the unilateral breast were retrospectively reviewed. The median follow-up duration after RT was 5.4 years (range, 1.0–6.3 years). All patients underwent breast surgery and postoperative RT with or without systemic treatment in 2015. Hypofractionated RT with a median fraction size of 2.7 Gy was administered to 405 (68.6%) patients.

A total of 109 (18.5%) patients experienced lymphedema during follow-up. The cumulative incidence of lymphedema at 1, 2, 3, and 5 years was 10.5%, 14.8%, 17.0%, and 18.2%, respectively. There was no difference in the incidence of lymphedema between patients with hypofractionated or conventional RT (3-year cumulative incidence, 18.3% vs. 14.0%, p=0.220). Multivariate analysis showed that high body mass index (hazard ratio [HR] 1.066, 95% confidence interval [CI] 1.020–1.115, p=0.005), left-sided breast cancer (HR 1.498, 95% CI 1.007–2.229, p=0.046), a large number of dissected lymph nodes (HR 1.041, 95% CI 1.008–1.075, p=0.015), and taxane-based chemotherapy ( neoadjuvant, HR 3.792, 95% CI 1.590–9.048, p=0.003; and adjuvant, HR 2.572, 95% CI 1.097–6.033, p=0.030) were significantly associated with increased lymphedema risks. For patients not receiving adjuvant chemotherapy, a prolonged interval between surgery and RT decreased the likelihood of lymphedema (HR 0.579, 95% CI 0.355–0.925, p=0.023).

We did not find any relationship between lymphedema and the scheme of RT. However, a shorter interval from surgery to RT when adjuvant chemotherapy was not performed may affect lymphedema development. Although further validation is required, left-sided breast cancer was associated with a higher risk of lymphedema than right-sided breast cancer in this study.