November 11, 2011

HPV Vaccine Greatly Reduces the Incidence of Cervical Cancer

(Ivanhoe Newswire) — The HPV (human papillomavirus) vaccine sufficiently protects against the more serious immediate precursor to invasive cervical cancer (ICC), particularly when given to young adolescent girls before they become sexually active, according to this study. In addition the vaccine partially protects against four other cancer-causing HPV types not targeted by the formulations.

"Provided that organized vaccination programs achieve high coverage in early adolescents before sexual debut, HPV vaccination has the potential to substantially reduce the incidence of cervical cancer, probably allowing modification of screening programs when conducted alongside vaccination strategies", one of the lead authors, Matti Lehtinen from the University of Tampere in Finland, was quoted as saying.

The bivalent vaccine targets HPV types 16 and 18 that are responsible for about 70% of cervical cancers. Most studies of vaccine efficacy have focused on prevention of cervical intraepithelial neoplasia 2 (CIN2) or higher. However, CIN3 is generally believed to be a more reproducible and predictive endpoint than CIN2, and often progresses to ICC.

In 2009, the PApilloma TRIal against Cancer In young Adults (PATRICIA), the largest study of HPV16/18 vaccine efficacy to date, reported that the bivalent vaccine had high efficacy against the precancerous cervical lesions CIN2+.

The study included almost 20 000 healthy women aged 15 years from 14 countries in Asia-Pacific, Europe, Latin America, and North America. Women were randomly assigned to receive the bivalent HPV vaccine or a control (hepatitis A) vaccine, given in three doses at enrolment, 1 month, and 6 months.

Here, the researchers report the final analysis (after 4 years of follow-up) that examined the efficacy of the vaccine against high-grade cervical precancers (CIN3+), the early development of adenocarcinoma (AIS), and 12 other cancer-causing HPV types not targeted by the vaccine.

In young women not already infected with HPV, the vaccine proved over 93% effective against CIN3+ and prevented 100% of AIS regardless of HPV type compared with nearly 46% efficacy against CIN3+ and 77% against AIS in the general population of women. Amongst the previously unexposed young women, the vaccine prevented 100% of HPV16/18-related CIN3+, compared with nearly 46% in the general population regardless of prior exposure to HPV.

"Appropriate effectiveness and implementation studies assessing the combination of vaccination and new screening strategies are warranted," the authors were quoted as saying.

In a second study, the vaccine showed increased cross-protection against other cancer-causing HPV types 31, 33, 45, and 51 in different cohorts representing diverse groups of women.

SOURCE: Lancet Oncology, published online November 8, 2011