For definition of Groups, see Preamble Evaluation.
Supplement 7: (1987) (p. 185)
CAS No.: 80-08-0
Chem. Abstr. Name: Benzenamine, 4,4'-sulfonylbis-
A. Evidence for carcinogenicity to humans (inadequate)
Cases of cancer have been reported in patients treated with dapsone for dermatitis herpetiformis [ref: 1] and leprosy [ref: 2]. Several follow-up studies have been undertaken of patients with leprosy, some of whom were treated with dapsone [ref: 1,3-6]. Increased mortality from cancer, restricted to males (standardized mortality ratio [SMR], 1.5; 95% confidence interval, 1.1-1.9), has been observed only in the most recent of them. The excess was most evident for cancers of the oral cavity and bladder and for lymphoma in males (SMRs, 4.5, 4.0 and 3.0, respectively) and for dapsone users. Possible confounding effects of tobacco and alcohol intake could not be addressed, but there was no substantial increase in mortality from lung cancer [ref: 6].
B. Evidence for carcinogenicity to animals (limited)
Dapsone has been tested by oral administration in mice and rats, by intraperitoneal administration in mice and by prenatal and lifetime oral exposure in mice and rats. In three different studies in rats, high doses of dapsone induced mesenchymal tumours of the spleen in males (and of the peritoneum in two studies). An increased incidence of tumours of the thyroid was found in rats of each sex in one study and in males in a further study. The experiment in mice involving intraperitoneal administration of dapsone could not be evaluated. The other two experiments in mice did not provide evidence of carcinogenicity [ref: 1].
C. Other relevant data
No data were available on the genetic and related effects of dapsone in humans. It was not mutagenic to bacteria [ref: 7].
Dapsone is not classifiable as to its carcinogenicity to humans (Group 3).
For definition of the italicized terms, see Preamble Evaluation.
Also see previous evaluation: Vol. 24 (1980)
1. IARC Monographs, 24, 59-76, 1980
2. Troy, J.L., Grossman, M.E. & Walther, R.R. (1980) Squamous-cell carcinoma arising in a leprous neurotrophic ulcer. Report of a case. J. Dermatol. Surg. Oncol., 6, 659-661
3. Oleinick, A. (1968) Survival among leprosy patients with special consideration of cancer as a cause of death. Int. J. Lepr., 36, 318-327
4. Kolonel, L.N. & Hirohata, T. (1977) Leprosy and cancer: a retrospective cohort study in Hawaii. J. natl Cancer Inst., 58, 1577-1581
5. Tokudome, S., Kono, S., Ikeda, M., Kuratsune, M. & Kumamaru, S. (1981) Cancer and other causes of death among leprosy patients. J. natl Cancer Inst., 67, 285-289
6. Brinton, L.A., Hoover, R., Jacobson, R.R. & Fraumeni, J.F., Jr (1984) Cancer mortality among patients with Hansen's disease. J. natl Cancer Inst., 72, 109-114
7. IARC Monographs, Suppl. 6, 210-211, 1987