Radiation-induced cancers of the pharynx and larynx: a study of five clinical cases.

Radiation-induced cancer, a rare clinical entity, is often difficult to diagnose and manage. This study reports a series of five cases of radiocarcinogenesis of the pharynx and/or larynx that developed after external radiotherapy. The primary lesion was diagnosed at a mean age of 50 years (+/-12.9) and the radiation-induced cancer at a mean age of 59 years (+/-13.1), giving a latent period of 9 years (+/-3.7). Analysis of gammagraphic records indicated that four of the patients had developed a secondary tumour in the penumbra of irradiation fields. In these zones, the delivered dose was between 20 and 80% of the prescribed dose, corresponding to an estimated cumulative mean dose of 14.1-56.3 Gy. These results are compared with data in the literature to determine the diagnostic criteria for radiation-induced cancer, possible predisposition (genetic or acquired) and the dose effect.