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Acute breast edema during 5-fraction ultra-hypofractionated radiotherapy after breast-conserving surgery: A cone-beam
Yanxin Zhang1, Wei Zhang1, Chuheng Chang1
1National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 10021, China.
Background:
With the growing adoption of 5-fraction ultra-hypofractionated radiotherapy (uHFRT) following breast-conserving surgery (BCS), in-treatment breast edema has been increasingly observed. Marked edema may impair target dose coverage and even necessitate radiotherapy interruption. This study aimed to investigate the incidence, evolution and risk factors of this acute adverse event.
Methods:
Patients treated with BCS were enrolled in a prospective phase II trial of uHFRT. Patients received whole-breast irradiation (WBI) at 26 Gy in 5 fractions, with or without simultaneous integrated tumor-bed boost (SIB) of 30 Gy, delivered daily or on alternate days. Cone-beam CT (CBCT) was acquired prior to each fraction. Acute breast edema was defined as outward expansion of the breast contour exceeding 1 mm relative to the planning CT. Clinical and target volume parameters were analyzed to identify risk factors.
Results:
Among 221 patients (224 breasts), edema occurred in 83 breasts (37.1%), with 96.4% developing after the first fraction. The prevalence of edema was 35.7%, 36.6%, 37.1%, and 35.3% at the 2nd to 5th pretreatment CBCT scans, respectively. Edema peaked after the first fraction in 42 swelling breasts (50.6%). Contour expansion was >3-5 mm in 19.6%, >5-8 mm in 7.1%, >8-10 mm in 1.8%, and > 10 mm in 0.9% of all breasts. Multivariate analysis indentified younger age and greater breast thickness as significant factors associated with the occurrence of in-treatment breast edema. Furthermore, breast thickness was positively associated with edema severity.
Conclusions:
The incidence of acute in-treatment breast edema during uHFRT after BCS was 37.1%, with onset immediately after the first fraction in 96.4% of affected cases. Contour expansion >5 mm was observed in 9.8% of the entire cohort. Given the short treatment course and high single-fraction dose, early-onset edema may impair treatment efficacy. Close surveillance and timely intervention are warranted for high-risk patients.
