. Carcinoma of the cervix is a sexually-transmitted disease due to infection with specific oncogenic types of the HPV. Yet not all infected women develop cancer. It has been posited that injectable progestogen-only contraceptives (IPCs) and/or combined estrogen-progestogen oral contraceptives (COCs) may act as cofactors, together with HPV, in the aetiology of cervical cancer. There is also some evidence to suggest that IPCs may reduce the risk. South Africa is an ideal country to test these hypotheses, because exposure to IPCs and COCs is common, as is invasive cervical cancer; screening is uncommon and biases associated with screening will be minimized. A four-year case-control study will be conducted in Cape Town, Africa, in which 500 cases of invasive cervical cancer (stages Ib-IVb) and 1500 controls admitted to the two main tertiary care hospitals will be enrolled. After giving written, informed consent, the controls will undergo Pap smears, and the cervical scrapings will also be tested for HPV infection. An estimated 500 controls, testing positive for HPV, will be compared with the cases for IPC and COC use. HPV-positive and negative controls will also be compared. Sera and white cells obtained from consenting cases and controls will be stored at -70 degrees C for the testing of future hypotheses. The study is designed to determine whether IPCs and COCs increase (or decrease) cervical cancer risk. An important source of confounding, sexual activity, will be controlled by confining the analysis to HPV-positive women. Independently of cervical cancer risk, the study is intended to determine whether IPCs and COCs predispose to HPV infection. The stored sera and white cells are intended to be available for future analysis related to the study hypotheses, and other hypotheses.
