Oct. 19, 2010 – Two human papillomavirus types included in HPV vaccines cause 71% of cervical cancers -- but there are six other cervical cancer-causing HPVs, an international study finds.

Led by Spanish researcher Silvia de Sanjose, MD, the effort analyzed 22,661 tissue samples from 14,249 women from 38 countries in six continents. Researchers looked for any of the 118 known types of HPV.

The samples included 10,575 cases of invasive cervical cancer -- for women, the second most common cancer in the world. HPV is believed to cause nearly all cervical cancers. Although the study detected HPV in only 85% of cervical cancers, de Sanjose and colleagues suggest that various problems (such as DNA degradation in samples) led researchers to miss HPV in the remaining 15% of cases.

There are currently two HPV vaccines: Cervarix from GlaxoSmithKline and Gardasil from Merck. Both protect against HPV types 16 and 18; Gardasil also protects against the genital wart-causing HPV strains 6 and 11.

The new study strongly supports use of these vaccines, as HPV 16 and HPV 18 account for 71% of invasive cervical cancers. HPV 16, HPV 18, and HPV 45 are found in 94% of cervical adenocarcinomas.

HPV types 18 and 45 are found in much younger women with invasive cervical cancer, suggesting that these viruses are particularly deadly. HPV 16 is also linked to cancer in younger women.

In addition to HPV 16, 18, and 45, there are six other HPV types that cause cervical cancer: types 31, 33, 35, 52, and 58.
"This international effort … reinforces the rationale for prevention of cervical cancer through the use of existing vaccines," de Sanjose and colleagues conclude. Their report appears in the Oct. 18 online issue of The Lancet.