International Agency for Research on Cancer (IARC) - Summaries & Evaluations
VOL.: 21 (1979) (p. 431)
5. Summary of Data Reported and Evaluation
(N.B. - This section should be read in conjunction with the General Remarks on Sex Hormones and with
the General Conclusions on Sex Hormones.)
5.1 Experimental data
Megestrol acetate alone or with ethinyloestradiol was tested in mice,
rats and dogs by oral administration and in rats by subcutaneous
administration. It produced mammary tumours in dogs when tested alone
and in mice when tested in combination with ethinyloestradiol.
Experiments in which it was tested in rats in combination with
ethinyloestradiol were negative or inadequate.
5.2 Human data
No case reports or epidemiological studies on megestrol acetate alone
were available to the Working Group. Epidemiological studies on steroid
hormones used in oestrogen-progestin oral contraceptive preparations have been summarized
in the section, 'Oestrogens and Progestins in Relation to Human Cancer'.
There is limited evidence for the carcinogenicity of megestrol acetate
in dogs. In humans, oral contraceptives containing oestrogens in
combination with progestins have been related causally to an increased
incidence of benign liver adenomas and a decreased incidence of benign
For definition of the italicized terms, see Preamble Evaluation.
Subsequent evaluation: Suppl. 7 (1987) (Progestins;
combined oral contraceptives)
Last updated: 7 April 1998