Cancer incidence after nasopharyngeal radium irradiation

Abstract

Background: From 1940 until 1970, nasopharyngeal radium irradiation was used to treat children and military personnel suffering from Eustachian tube failure attributable to local lymphoid hyperplasia.

Methods: We studied cancer incidence in a cohort of 4339 Dutch patients treated with nasopharyngeal radium irradiation, mostly in childhood, and 4104 frequency-matched nonexposed subjects. Average doses to the nasopharynx, pituitary gland, brain, and thyroid gland were 275, 10.9, 1.8, and 1.5 cGy, respectively. We assessed cancer incidence from cancer registry linkage (1989-1996), self-report including medical verification (1945-1988), and death certificates (1945-1996).

Results: During 18-50 years of follow-up, four thyroid malignancies (standardized incidence ratio [SIR] = 2.8; 95% confidence interval [CI] = 0.8-7.2) and five malignant brain tumors (SIR = 1.3; CI = 0.4-3.1) were observed. Increased risks were observed for malignancies of lymphoproliferative and hematopoietic origin (SIR = 1.9; CI = 1.2-2.8) and breast cancer (SIR = 1.5; CI = 1.1-2.1). Strong dose-response trends could not be demonstrated for any cancer outcome, although relative risk estimates were elevated in the highest-dose category for head and neck cancer and breast cancer.

Conclusions: These data provide little evidence for a high excess risk of cancer associated with nasopharyngeal radium irradiation treatment as applied in the Netherlands. Inconsistent findings across studies and public concern warrant the continuing follow-up of available cohorts.