Serious side effects are obviously of concern to those who take medications. For this reason, drug side effects overall are usually well documented through clinical trials and toxicity studies. Long-term side effects such as cancer, however, are much more difficult to evaluate and remain mostly unknown.
Epidemiologic evaluation, nevertheless, has been able to establish associations, even evidence of carcinogenicity, and the use of certain drugs. These associations have influenced clinical and public health practice and have provided insights into the mechanisms of carcinogenesis.
Drugs that have been associated with cancer in humans include:
- Radioactive drugs – potential malignancies include acute leukemia, nasal sinus carcinoma, osteosarcoma, angiosarcoma of the liver
- Chlornaphazine – after high dose treatment for Hodgkin’s disease and polycythemia Vera and was found to cause bladder cancer, it was withdrawn from use in 1964
- Arsenic – when taken internally, inorganic arsenics can induce skin cancer
- Methoxypsoralen – can increase the risk of squamous cell carcinoma of the skin when used with ultraviolet light to treat psoriasis
- Phenacetin – can induce renal pelvis carcinoma and possibly bladder cancer
- Alkylating agents – drugs in this class, such as melphalan, chlorambucil, and cyclophosphamide, may induce cancer in part by breaking chromosomes. Several malignancies are suspected, including bladder (cyclophosphamide) and acute nonlymphocytic leukemia
- Immunosuppressive agents – have been associated with lymphoma, soft-tissue sarcoma, skin cancer, and possibly with melanoma, lung adenocarcinoma, and cancer in the liver and gall bladder
- Androgenic-anabolic steroids – methyltestosterone and oxymetholone derivatives have been linked to hepatocellular carcinoma. More recently, possible links to hepatic angiosarcomas have been reported
- Estrogen containing drugs – despite laboratory evidence of cancer, large numbers of healthy women continue to use high doses for long periods of time. Between four and six million Americans [mothers (directly), daughters and sons (in utero)] have been exposed to diethylstilbestrol (DES) during pregnancy. As many as 50 percent of menopausal women in one are of the U.S. were given estrogen containing drugs over ten years. Approximately 80 million women throughout the world use oral contraceptives. Prenatal estrogen containing drugs (DES) have been linked to vaginal adenocarcinoma. Postnatal estrogen containing drugs (DES, oral contraceptive drugs, conjugated estrogens) have been associated with endometrial carcinoma, benign liver tumors, and possibly breast, cervical and ovarian cancers, and choriocarcinoma and melanoma.