Skin Cancer after X-Ray Treatment for Scalp Ringworm

Abstract

Some 2,224 children given X-ray therapy for tinea capitis (ringworm of the scalp) have been followed for up to 50 years to determine cancer incidence, along with a control group of 1,380 tinea capitis patients given only topical medications. The study found a relative risk (RR) of 3.6 (95% confidence interval, 2.3-5.9) for basal cell skin cancer (BCC) of the head and neck among irradiated Caucasians (124 irradiated cases and 21 control cases), in response to a scalp dose of about 4.8 Gy. No melanomas of the head and neck have been seen, and only a few squamous cell carcinomas. About 40% of irradiated cases have had multiple BCCs, for a total of 328 BCCs. Although 25% of both the irradiated and control groups are African-American, only 3 skin cancers have been seen among them, all in the irradiated group, indicating the importance of susceptibility to UV radiation as a cofactor. Light complexion, severe sunburning and North European ancestry were predictive of BCC risk in the irradiated group, but chronic sun exposure was not. Children irradiated at young ages had the highest BCC risk. The RR for BCC risk is approximately constant with time since exposure, suggesting that risk will probably last for a lifetime.

The cancer epidemiology of radiation

“…This finding is of particular interest given the 10-fold greater background rate of stomach cancer in Japan, and suggests a multiplicative interaction of risks. In a recent report of a study of skin cancer after irradiation in childhood for ringworm of the scalp, Shore et al (2002) confirmed a strong association between basal cell carcinoma and exposure in childhood. However, unlike the findings of Ron et al (1998) for skin cancer in the LSS, Shore et al (2002) suggested that exposure to UVR was important as a cofactor because of the relatively low level of skin cancer among irradiated black patients.…”

Nonmelanoma skin cancer in relation to ionizing radiation exposure among U.S. radiologic technologists

“…There is very little evidence in the literature of an increased SCC risk associated with radiation at moderate doses 3,12 and the lack of an association with SCC is consistent with the atomic bomb survivor results 11 and those of medically exposed patients. 7,9,12 Risks associated with total number of years worked present some difficulty in interpretation. Note that by adjusting for year first worked, one may be adjusting for part of the effect of duration of work (or exposure) since those who first worked in earlier years would have had more years of employment than more recent workers.…”

“…1 These skin cancers were mostly squamous cell carcinomas (SCCs) and occurred at the site of dermatitis caused by exposure to excessive local doses of ionizing radiation (IR). 2,3 More recent studies of patients irradiated for medical reasons [4][5][6][7][8][9] and Japanese atomic bomb survivors 10,11 have shown an excess risk of skin cancer, particularly basal cell carcinoma (BCC). Medically irradiated patients were mostly exposed to moderately high and fractionated doses of IR early in life.…”

Skin Cancer Incidence among Atomic Bomb Survivors from 1958 to 1996

“…An increased risk of skin cancer associated with exposure to ionizing radiation has been reported in various exposed populations, including the atomic bomb (A-bomb) survivors (1-3), uranium miners (4), radiologists and individuals treated with radiation in childhood for tinea capitis (5,6) and malignant tumors (7,8). The first report among the Abomb survivors in Hiroshima and Nagasaki by the Atomic Bomb Casualty Committee (ABCC) was 26 years after the A-bombs were dropped.…”

“…Age at exposure is one of the most significant modifiers of dose response for skin and many other cancers (1,5,7). The LSS subjects who were exposed in childhood have now reached cancer-prone ages.…”