Radiation Induced Pneumonitis after Whole Breast Radiation: A Cross-Sectional Study

Abstract

A series of studies concluded that whole breast irradiation plus breast conserving surgery is as efficient as mastectomy. Meanwhile, quality of life and adverse events should be paid more attention to. Radiation induce pneumonitis (RIP), as a common adverse event after thoracic radiotherapy, is seldom evaluated. Therefore, to investigate the incidence rate, characteristics, high risk time, treatment and prognosis, we designed this cross-sectional study. We searched cases of patients treated at our institution, between January 1st 2018 and December 31th 2018. Inclusion criteria included: pathologically confirmed breast cancer and received breast conserving surgery as the first treatment; patients received postoperative whole breast irradiation; intensity modulated radiotherapy or volumetric modulated arc therapy is delivered; available CT scan within one year from the accomplishment of radiotherapy, patients received IMRT/VMAT with dose of 43.5 Gy(2.9 Gy per fraction). Exclusion criteria included history of thoracic radiation history, male breast cancer and patients who received partial breast irradiation. RIP was evaluated by a senior radiation oncologist and a senior radiologist according to CTCAE4.0 Totally, 472 patients fulfilled the eligibility criteria. The median age of the whole group was 57 years old. The median PTV volume was 640.84cm3. Chemotherapy was delivered to 320 patients (67.8%). RIP was observed in 77.8% patients, including 0.2% with grade 3, 1.1% with grade 2 and 76.5% with grade 1. One hundred and eighty-seven patients had CT scan at the time of 1-3 months after radiation and 38.0% of them had diagnosis of RIP (G1: 38.0%, G2/3:0%). Two hundred and thirty-seven patients received CT scan at the time of 3-6months after radiation and 80.2% of them were with diagnosis of RIP (G1 78.1%, G2:1.7%, G3 0.4%). Three hundred and twelve patients had CT scan at the time of 6-12 months after radiation and 77.1% of them were diagnosed as RIP (G1 76.9%, G2:0.3%, G3:0.0%). The mean lung dose of affected side of the patients who had RIP was higher than that who did not [9.21Gy (2.03-16.13 Gy) vs 8.38 Gy (2.81-15.4 Gy), P = 0.003]. The same result was recorded in the value of affected lung V20 [17.92% (7.00%-32.64%) vs.15.41% (4.00-28.00%)]. Patients with Grade 1 RIP received no special care and no progression of RIP is observed. Patients with Grade 2 RIP were on antibiotic treatment. For the only one patient with Grade 3 RIP, glucocorticoid was delivered. All the Grade 2/3 RIP were cured at the last follow up. Grade 1 RIP after whole breast radiation were very common and most of them occurred at the time of 3-6 months after radiotherapy and often clears without treatment. Grade≥ 2 RIP is rare but always has favorable prognosis after systemic treatment. The affected side lung dose including mean lung dose and V20 is associated with the RIP.