The objectives of EuroDeucaTam Project are to evaluate the potential carcinogenic risks linked to several treatment modalities for breast cancer. In particular, the study will quantify any increases in selected second cancers following breast cancer. For the period 1996-1998, the study will concentrate on cancers of the endometrium, ovary and liver following breast cancer. It will determine the etiological role of all reproductive variables, other variables known to be associated with risk of breast cancer and of the other tumour under study, and of primordial interest will be the assessment of the effect of the various treatment modalities of breast cancer (surgery, radiotherapy, chemotherapy and hormonotherapy). The main exposure under study will be tamoxifen, with a detailed evaluation of the effects on risk of daily dose, duration of treatment and the interaction with other treatments radiotherapy, chemotherapy, and castration with evaluation of its effects according to method used (radiotherapy versus surgery).
The methodology used will be that of case-control studies. The cases will be women developing the second cancer of interest after having had breast cancer. Breast cancer diagnosis should have been made after the introduction of tamoxifen in the country concerned (1976). The source of cases on referents will be population-based cancer registries (to avoid biased ascertainment of cases and referents). The two diagnoses (breast cancer and second cancer) will have been recorded by the participating cancer registries. There will be four controls for every case. These will be women diagnosed with breast cancer at the same time and in the same registry as the case. They will be matched for age (+ 2 years) and date of breast cancer diagnosis (+ 2 years) with the case. They will have survived at least until the date of diagnosis of the case, and for controls of endometrial cases, not having at that date undergone a hysterectomy, and for controls of ovarian cancers, not having at that date undergone an ovariectomy. The source of information on exposure will be the cancer registry files and the clinical records with no personal interview of the women themselves.
This study will provide useful information on the long-term safety of breast cancer treatment. In addition, tamoxifen, a synthetic antioestrogen which has been widely used for the treatment of breast cancer and has been shown to be effective in reducing overall mortality as well as mortality from breast cancer and the occurrence of contralateral breast cancer is being proposed for the prevention of breast cancer among healthy women considered to be at high risk of developing breast cancer. Preventive trials are now underway both in the USA and in Europe. Nevertheless, concerns have been raised with regard to the side effects of tamoxifen and in particular the carcinogenicity of this product. This study will help to answer these concerns.