Influence of radiation dose rate and lung dose on interstitial pneumonitis after fractionated total body irradiation: acute parotitis may predict interstitial pneumonitis.

This study evaluated patients for the influence of the dose rate and lung dose of fractionated total body irradiation (TBI) in preparation for allogeneic bone marrow transplantation (BMT) on the subsequent development of interstitial pneumonitis (IP). Sixty-six patients at our institute were treated with TBI followed by BMT. All of the patients received a total TBI dose of 12 Gy given in 6 fractions over 3 days and were divided into 3 groups according to the radiation dose rate and lung dose: group A, lung dose of 8 Gy (n = 18); group B, lung dose of 12 Gy at 8 cGy/min (n = 25); and group C, lung dose of 12 Gy at 19 cGy/min (n = 23). The overall survival rate, the cumulative incidence of relapse, and the cumulative incidence of IP were evaluated in relation to various potential indicators of future IP. There were no significant differences in survival and relapse rates between patient group A and combined groups B and C. Clinically significant IP occurred in 13 patients. The cumulative incidence of IP was significantly higher in patients who developed acute parotitis as indicated by either an elevation in the serum amylase level or parotid pain of grade 1 to 2. There was no difference in IP incidence among groups A, B, and C. There was no significant difference in IP incidence between lung dose values of 8 Gy (with lung shielding) and 12 Gy (without lung shielding) and between dose rate values of 8 cGy/min and 19 cGy/ min, at least when TBI was given in 6 fractions. The presence of acute parotitis during or just after TBI may be a predictor of IP.