Although radiation-induced bronchiolitis obliterans organizing pneumonia (BOOP) is a possible side effect of radiation therapy in women with breast cancer, a study from the Department of Radiation Oncology at the University of Tsukuba in Japan found that the risk is quite low but is more prevalent in older women. “Radiation-induced Bronchiolitis Obliterans Organizing Pneumonia (BOOP) Syndrome in Breast Cancer Patients is Associated With Age,” which was published in the journal Radiation Onocology, studied over 1,000 breast cancer patients treated with radiation therapy to determine the risk for BOOP.
“Radiation-induced bronchiolitis obliterans organizing pneumonia (BOOP) syndrome is a rarely observed phenomenon characterized by infiltration of the lungs outside of the radiation field, differentiating it from radiation pneumonitis (RP),” explained the authors of the study. They identified that little is known about the definitive risk factors for developing BOOP following radiation therapy after breast conserving surgery (BCS) and post-mastectomy radiation therapy (PMRT), motivating the need for their study.
On average, older patients were more likely to be affected by BOOP than younger patients. However, out of the 1,176 patients studied, only 16 patients (1.4%) were diagnosed with BOOP. Twelve were BCS patients, and four were PMRT patients.
In light of other risk factors, irradiated lung volume at 20 Gy and type of treatment (BCS or PMRT) were not associated with a greater risk for RT-BOOP. In addition to age, smoking status was also significantly associated with RT-BOOP.
It was important to determine the risk factors for RT-BOOP, as many women are treated with radiation therapy to manage their breast cancer. Postoperative irradiation has been shown to reduce locoregional recurrence, helping to improve the prognosis of breast cancer over the years. Since the risk for RT-BOOP is so low, patients are likely better served by receiving radiation therapy than going without for fear of RT-BOOP. However, when a patient is affected by RT-BOOP, the outcome can be a diminished quality of life.
Since older age (greater than 52 years old) was predictive of RT-BOOP, the authors conclude, “The older age is the most important factor for the prediction of RT-BOOP syndrome in breast cancer patients who receive radiation therapy. We should pay attention to old breast cancer patients treated with postoperative RT to have the early diagnose of RT-BOOP syndrome.”