바로가기  >

Abstract
Purpose: Spontaneous rib fracture (SRF) is a common late complication in treated breast cancer patients. This study evaluated the incidence and risk factors of ipsilateral SRF after radiotherapy (RT) in breast cancer patients. In addition, we identified dosimetric parameters that were significantly associated with ipsilateral SRF.

Methods: We retrospectively reviewed 2204 patients with breast cancer who underwent RT between 2014 and 2016, and were followed up with bone scans. We evaluated clinical risk factors for ipsilateral SRF. Dose-volume histogram analysis was also performed for patients (n = 538) whose dosimetric data were available. All ipsilateral ribs were manually delineated, and dosimetric parameters of the ribs were converted into the equivalent dose in 2 Gy fractions (EQD2).

Results: Most of the patients with SRF (87.3%) were asymptomatic, and the remaining symptomatic patients complained of mild tenderness or chest wall discomfort; these symptoms all resolved within 6 months without any treatment. Ipsilateral SRF occurred in 14.5% of patients 3 years after RT. The median time to develop ipsilateral SRF was 15 months. In dosimetric analysis, near-maximum rib dose (D2cc) best predicted ipsilateral SRF. The cut-off value of D2cc was EQD2 52 Gy, as determined by receiver operating characteristic analysis. In multivariate analysis including dosimetric variables, D2cc EQD2 ≥ 52 Gy was the only significant risk factor for ipsilateral SRF.

Conclusion: Our data demonstrated that near-maximum rib dose was the best dosimetric parameter to predict ipsilateral SRF in RT-treated breast cancer patients. In addition, our results suggest that patients who received RT with exceeding rib dose cut-off value and had ipsilateral SRF on bone scan be recommended routine follow-up without additional imaging tests.

Affiliations

Dowook Kim 1, Kyubo Kim 2, Jae Sik Kim 1 3, Seonghee Kang 4 5, Jong Min Park 1 4 5, Kyung Hwan Shin 6 7 8
1Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea (Republic of).
2Department of Radiation Oncology, Ewha Womans University College of Medicine, Seoul, Korea (Republic of).
3Department of Radiation Oncology, Kyung Hee University Hospital at Gangdong, Seoul, Korea (Republic of).
4Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea (Republic of).
5Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea (Republic of).
6Department of Radiation Oncology, Seoul National University College of Medicine, Seoul, Korea (Republic of). radiat@snu.ac.kr.
7Department of Radiation Oncology, Seoul National University Hospital, Seoul, Korea (Republic of). radiat@snu.ac.kr.
8Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea (Republic of). radiat@snu.ac.kr.