Cervical cancer and human papillomavirus: epidemiological evidence and perspectives for prevention.

Cervical cancer is a major public health problem, as it is the second most common cancer in women world-wide after breast cancer. About 80% of the half a million cases estimated to occur annually in the world, occur in developing countries. The epidemiological evidence linking human papillomavirus (HPV) to cervical cancer is reviewed. It is concluded that over 90% of cervical cancers can be attributed to certain HPV types. HPV 16 accounts for the highest proportion (50%) followed by HPV 18 (12%), HPV 45 (8%) and HPV 31 (5%). The association with these HPV types are very strong and consistent with odds ratios over 15 in all case-control studies in high- and low-risk countries for cervical cancer. However, HPV is not a sufficient cause of this malignancy; certain cofactors are necessary for a proportion of HPV persistent infections to eventually progress to cancer. These include host factors such as histocompatibility types and immunological response, hormonal influences and infections with other sexually transmitted agents such as Chlamydia trachomatis. In addition, results from our studies carried out in Spain and Colombia support the hypothesis that male carriers of HPV play an important role in the development of cervical cancer in their wives. The recognition of the central role of HPV in cervical cancer has far-reaching implications for the primary and secondary prevention of this malignancy. Prophylactic and therapeutic HPV vaccines are now under development and HPV typing is being integrated into screening programmes in pilot studies in a few developed countries. In developing countries, well conducted conventional screening programmes remain the best approach for the control of cervical cancer until a safe and efficient HPV vaccine can be used in the general population.