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.

No abstract

Medical conditions related to hormonal abnormalities were investigated in a case-control study of breast cancer among women who attended a screening centre. Information was obtained by telephone interview regarding physician-diagnosed medical conditions such as thyroid or liver diseases, diabetes, and hypertension, as well as hirsutism, acne, galactorrhoea, and reproductive, menstrual, and gynaecological factors. Results are presented for 354 cases and 747 controls. Women with fertility problems who never succeeded in becoming pregnant were at significantly increased breast cancer risk (adjusted odds ratio [OR] = 3.5; 95% confidence interval [CI]:1.1-10.9). An elevated cancer risk was also associated with having excess body hair (OR = 1.5; 95% CI:1.0-2.3), or having excess body hair in addition to persistent adult acne (OR = 6.8; 95% CI:1.7-27.1). Recurrent amenorrhea (OR = 3.5; 95% CI:1.1-11.5), and a treated hyperthyroid condition (OR = 2.2; 95% CI:1.1-4.4) were significantly associated with risk. A non-significant elevation of risk was present for endometrial hyperplasia (OR = 1.8; 95% CI: 0.8-4.0). There was a suggestion of an association between a history of galactorrhoea and breast cancer risk (OR = 2.0; 95% CI:0.8-4.9) among premenopausal women. No associations were found with other medical or gynaecological factors. The possibility that some of these findings are due to chance cannot be excluded because of the problem of multiple comparisons.

A cohort of 2,657 infants in Rochester, New York, who were given x-ray treatment for a purported enlarged thymus gland, along with 4,833 siblings, have been followed by mail surveys through about 1986, which represents an average of 37 years of follow-up, to determine their incidence of thyroid cancer. Estimated thyroid doses ranged from 0.03 to > 10 Gy, with 62% receiving > 0.5 Gy. There were 37 pathologically diagnosed thyroid cancers in the irradiated group and five in the sibling controls. The dose-response relation was essentially linear, with no evidence of an additional dose-squared component. The estimated relative risk at 1 Gy was 10 (90% confidence interval 5-23). Thyroid cancer rates were elevated even at low doses; i.e., a dose-response analysis over the range of 0-0.3 Gy showed a significant positive slope. The risk ratio was declining over time but was still highly elevated to at least 45 years after irradiation. An examination of potential risk factors showed that older age at first childbirth was significantly associated with thyroid cancer risk. An evaluation of interactions between possible risk factors and radiation suggested that Jewish subjects and women with older ages at menarche or at first childbirth were at greater risk for radiogenic thyroid cancer.