Extended field radiation therapy in Hodgkin's disease: analysis of failures

A retrospective analysis of 116 primary cases of stage I, II and III-A Hodgkin's disease demonstrated 27 failures, fourteen confirmed by biopsy. Twenty of the 27 (74%) were in lymph node areas only and seven had extranodal extensions. The most frequent site of failure was the hilar nodes and contiguous lung. The majority of failures (78%) occurred within 30 months of treatment and the cause of failure determined in 23 (85%), sixteen of which were due to technical errors of irradiation. Analysis of the dosimetry in the mediastinal, hilar nodes and contiguous lung failures revealed three factors which may have contributed to a low dose. These factors are: 1) the equivalent square, 2) off-axis beam diminution, and 3) the anteroposterior dose profile. Combined radiation therapy and chemotherapy was more effective than either modality alone in the treatment of these failures.