Abstract: Background and purpose: Upper limb lymphedema, which is a kind of treatment-related toxicity commonly seen in breast cancer patients, significantly affects the quality of life in this population. The aim of this study was to observe the onset of upper limb lymphedema in breast cancer patients treated with postmastectomy radiation therapy (PMRT), and to analyze the correlation between lymphedema and the outcome of axillary lymph node surgery (number of positive lymph nodes, total number of dissected lymph nodes and the ratio of the two, also called positive lymph node ratio), and the influence of age, body mass index and other treatment-related factors on lymphedema. Methods: In this study, 202 breast cancer patients treated with PMRT in Shanghai Huangpu District Central Hospital from Jan. 2015 to Dec. 2015 were prospectively collected. The onset of upper limb lymphedema in these patients from the beginning of radiation therapy to the 12th month after radiotherapy was observed by using upper limb circumference measurement. Results: One hundred and ninety-seven patients accomplished the follow-up and among them, 38 were diagnosed with upper limb lymphedema (19.3%). In univariate analysis, number of positive lymph nodes (P<0.001), total number of dissected lymph nodes (P<0.001) and positive lymph node ratio (P=0.002) between patients with and without lymphedema were significantly different, while age, body mass index and other treatment-related factors were not significantly different. In multivariate analysis, an increase in total number of dissected lymph nodes was the only independent risk factor for lymphedema in patients treated with PMRT (P <0.001). Conclusion: The onset of upper limb lymphedema in breast cancer patients treated with PMRT had correlation with the outcome of axillary lymph node surgery. An increase in total number of dissected lymph nodes was the independent risk factor for lymphedema. For patients with larger total number of dissected lymph nodes, we should take its risk for lymphedema into full consideration in the decision of postoperative treatment for breast cancer patients.

Key words: Breast cancer, Postmastectomy radiation therapy, Upper limb lymphedema, The outcome of axillary lymph node surgery