Background. The correlation between treatment-related factors and lung toxicity has not been sufficiently evaluated in salvage radiotherapy. Methods. Twenty-one patients with recurrent non-small- cell lung cancer (NSCLC) after lobectomy received salvage radiotherapy to a total dose of 46-60 Gy. The effects of radiotherapy parameters on the development of radiation pneumonitis (RP) were examined using dose-volume histograms. Results. Grade 1 RP was observed in 4, grade 2 in 2, and grade 3 in 1 patient. Patients who developed RP had a significantly higher value in V dose (V13, V20) parameters and mean lung dose (MLD) than those who did not develop RP. Concerning G2 or higher RP, 3 patients who developed ≥G2 RP had a significantly higher value in V20, V13, and MLD than the remaining patients with P values of 0.01, 0.015, and 0.016, respectively. The mean V20, V13, and MLD in these 3 patients were 27%, 29.3%, and 14.8 Gy, respectively, whereas the mean V20, V13, and MLD in the remaining 18 patients were 15.8%, 18.3%, and 8.8 Gy, respectively. Three of 6 patients with a V20 ≥20% developed ≥G2 RP whereas this did not occur in the remaining patients (P = 0.015). Similarly, 3 of 6 patients with a V13 ≥23% developed ≥G2 RP whereas this did not occur in the remaining patients (P = 0.015). Conclusions. These data suggest that a somewhat lower V dose value or MLD, as compared with the setting of definitive radiotherapy, could be a surrogate for RP in patients undergoing salvage radiotherapy for recurrent NSCLC.
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