Dose-volumetric parameters of acute esophageal toxicity in patients with lung cancer treated with three-dimensional conformal radiotherapy

Purpose: To retrospectively evaluate which dose-volumetric parameters are associated with the risk of < Grade 3 acute esophageal toxicity (AET) in lung cancer patients treated with three-dimensional conformal radiotherapy (3D-CRT). Methods and Materials: One hundred twenty-four lung cancer patients treated curatively with 3D-CRT were retrospectively analyzed. All patients received conventionally fractionated radiotherapy (RT) with median dose of 60 Gy (range, 54-66 Gy) delivered in 30 fractions (range, 27-33 fractions). Thirty-one patients underwent curative surgery before RT. Ninety-two patients received chemotherapy (induction, 18; concurrent ± induction, 74). Acute esophageal toxicity was scored by Radiation Therapy Oncology Group criteria. The parameters analyzed included sex; age; Karnofsky performance score; weight loss; surgery; concurrent chemotherapy; the percentages of organ volume receiving <20 Gy (V20), <30 Gy (V30), <40 Gy (V40), <50 Gy (V50), <55 Gy (V55), < 58 Gy (V58), <60 Gy (V60), and <63 Gy (V63); the percent and absolute length of the esophagus irradiated; the maximum and mean dose to the esophagus; and normal tissue complication probability. Results: Of the 124 patients, 15 patients (12.1%) had Grade 3 AET, and 1 (0.8%) patient had Grade 4 AET. There was no fatal Grade 5 AET. In univariate and multivariate logistic regression analyses, concurrent chemotherapy and V60 were significantly associated with the development of severe (< Grade 3) AET (p < 0.05). Severe AET was observed in 15 of 74 patients (20.3%) who received concurrent chemotherapy, and in 1 of 50 patients (2.0%) who did not (p = 0.002). Severe AET was observed in 5 of 87 patients (5.7%) with V60 ≤ 30% and in 11 of 37 patients (29.7%) with V60 > 30% (p < 0.001). Among 50 patients who did not receive concurrent chemotherapy, severe AET was observed in 0 of 43 patients (0%) with V60 ≤ 30% and in 1 of 7 patients (14.2%) with V60 > 30% (p = 0.140). Among 74 patients who received concurrent chemotherapy, severe AET was observed in 5 of 44 patients (11.4%) with V60 ≤ 30% and in 10 of 30 patients (33.3%) with V60 > 30% (p = 0.037). Conclusions: Concurrent chemotherapy and V60 were associated with the development of severe AET < Grade 3. For patients being treated with concurrent chemotherapy, V60 is considered to be a useful parameter predicting the risk of severe AET after conventionally fractionated 3D-CRT for lung cancer.