Solid cancer risk after treatment of Hodgkin's disease.

We pooled the data from seven studies of second cancer risk after treatment of Hodgkin's disease (HD) and estimated the relative risks (RR) of solid cancers (SC) for the following two treatment groups: (1) radiotherapy, with or without chemotherapy; and (2) chemotherapy alone. For all treatment groups combined, the RR of SC was 2.1 (95% confidence limits: 1.8 to 2.4). In the radiotherapy group, statistically significant RR were found for SC for all anatomic sites (RR: 2.2; 95% confidence limits: 1.9 to 2.6) and for SC of the bones and joints (RR: 20.0), soft tissues (RR: 18.3), non-HD lymphomas (RR: 8.1), melanomas of the skin (RR: 6.7), buccal cavity and pharynx (RR: 4.1), nervous system (RR: 3.6), respiratory system (RR: 2.5), and digestive system (RR: 1.8). In the chemotherapy alone group, none of the RR differed significantly from unity, and the RR for SC of all sites was 1.1 (95% confidence limits: 0.5 to 1.9). The average duration of follow-up for patients with chemotherapy was shorter than the duration of follow-up for patients with radiotherapy. This may explain the general absence of elevated RR after chemotherapy.