[Hormonal contraceptives--an ongoing matter of research. Statement on the paper of C. Giersig: Progestin and breast cancer. The missing pieces of a puzzle].

Since their first marketing, hormonal contraceptives have been used by millions of women, often over many years. There is no consolidated knowledge on late effects of hormonal contraceptives, especially on tumour proliferation. Following a critical review on the available evidence (accompanying paper of C. Giersig) on this issue, further clinical and epidemiological research is deemed necessary in order to elucidate a hypothesised causal relationship between hormonal contraceptives use and breast cancer.