Recovery of overall and local lung function loss 18 months after irradiation for malignant lymphoma.

PURPOSE To determine the local and overall pulmonary injury 3 to 18 months after irradiation and to investigate whether the changes in overall lung function can be predicted using the three-dimensional (3-D) dose distribution in combination with dose-effect relations for local injury; and to study the influence of chemotherapy on the injury. PATIENTS AND METHODS Local perfusion (Q), ventilation (V), and tissue density were measured in 25 patients treated for malignant lymphoma, before, 3 to 4 months after, and 18 months after irradiation. Dose-effect relations for local injury, calculated using correlated single-photon emission computed tomographic (SPECT) and computed tomographic (CT) data, were combined with the 3-D dose distribution, to calculate the estimated mean local changes over the complete lung for each patient. The result was correlated with the actual changes in pulmonary function. RESULTS A dose-dependent increase with injury was observed at 3 to 4 months after irradiation, which at 18 months had recovered by approximately 50% to 60%. The estimated mean relative reduction of local Q predicted the change in overall lung function within 10% of the actually observed values in 63% to 73% of patients. Chemotherapy given before radiotherapy enhanced radiation-induced reduction of local Q significantly, with dose-modifying factors of 1.22 and 1.37 at 3 to 4 months and 18 months, respectively. CONCLUSION Partial recovery of radiation-induced reduction of local and overall lung function was observed at 18 months after irradiation. The overall functional outcome of most patients could be well predicted, based on the estimated mean local injury over the complete lung. Chemotherapy given before radiotherapy enhanced the radiation-induced reduction of local Q.