Pneumonitis and fibrosis after breast cancer radiotherapy: occurrence and treatment-related predictors

Radiation pneumonitis (RP) and radiation fibrosis (RF) are common side effects after breast cancer (BC) radiotherapy (RT). However, there is a great variation in the frequency of RP and RF. This study presents the occurrence of- and the treatment-related predictors for RP and RF. Further, physician- and patient-reported pulmonary symptoms during the first year after postoperative RT for BC are demonstrated. From 2007 to 2008, 250 BC patients referred for postoperative RT were included in a prospective cohort study and followed during the first year after RT. High-resolution computed tomography of the lungs and symptom registration were performed before RT and 3, 6, and 12 months after RT. Patient-reported symptoms were registered by standard quality of life questionnaires. Logistic regression analyses were applied to estimate treatment-related predictors for radiological RP (rRP), clinical RP (cRP), radiological RF (rRF), and clinical RF (cRF). The occurrence of rRP and cRP at three months was 78% and 19%, while 12 months after RT rRF and cRF was 89% and 16%, respectively; all reported as grade 1. In multivariable analyses, mastectomy predicted cRP at three months (OR = 2.48, <i>p</i> = .03) and cRF at six months, ipsilateral lung volume receiving 20 Gray or more (V20), V30, and mean lung dose (MLD) predicted rRP at six months (OR = 1.06, <i>p</i> = .0003; OR = 1.10, <i>p</i> = .001; and OR = 1.03, <i>p</i> = .01, respectively). Endocrine treatment predicted cRF at 12 months (OR = 2.48, <i>p</i> = .02). Physicians reported significant more dyspnea at 3 months (<i>p</i> = .003) and patients reported ‘a little dyspnea’ more at 3 and 12 months compared to baseline (<i>p</i> = .007). RP and RF are prevalent in the first year after BC radiation. Mastectomy predicted cRP at three months. V20, V30, D25, and MLD predicted rRP at 6 months, and endocrine treatment predicted cRF at 12 months. Patients and physicians reported dyspnea differently.