Eliminating cervical cancer
Currently, the WHO plans for eliminating cervical cancer involve a strategy of vaccinating 90% of girls by the age of 15, screening 70% of women with a high performance test by the age of 35 and again at 45, and treating 90% of women with cervical disease – the so-called “90-70-90” strategy.
Dr. Jit agrees that very high levels of vaccine coverage would eradicate the HPV types causing almost all cases of cervical cancer. The same strategy would also sharply reduce the need for preventive measures in the future.
However, as Dr. Jit argues, 90% female-only coverage will not be sufficient to eliminate HPV 16 transmission, although 90% coverage in both males and females – namely a gender-neutral strategy – might. To show this, Dr. Jit and colleagues used the HPV-ADVISE transmission model in India.
Results from this modeling exercise suggest that 90% coverage of both sexes would bring the prevalence of HPV 16 close to elimination, defined as reducing the prevalence of HPV 16 to below 10 per 100,000 in the population.
In addition, because even at this low level, HPV transmission can be sustained in a small group of sex workers and their clients, achieving 95% coverage of 10-year-old girls who might become female sex workers in the future will likely achieve the goal of HPV 16 elimination, as Dr. Jit suggests.
OPSCC elimination
Elimination of another HPV-related cancer, oropharyngeal squamous cell carcinomas (OPSCCs), is discussed in another paper in the same journal.
HPV-related OPSCCs are mostly associated specifically with HPV 16.
There is currently an epidemic of this cancer among middle-aged men in the Nordic countries of Denmark, Finland, Norway, and Sweden; incidence rates have tripled over the past 30 years, note Tuomas Lehtinen, PhD, FICAN-MID, Tampere, Finland and colleagues.
They propose a two-step action plan – gender-neutral vaccination in adolescent boys and girls, and a screening program for adults born in 1995 or earlier.
The first step is already underway, and the recent implementation of school-based HPV vaccination programs in the Nordic countries is predicted to gradually decrease the incidence of HPV-related OPSCCs, they write.
“Even if HPV vaccination does not cure established infections, it can prevent re-infection/recurrence of associated lesions in 45% to 65% of individuals with anal or cervical intraepithelial neoplasia,” the authors write, “and there is high VE (vaccine efficacy) against oropharyngeal HPV infections as well.”
Furthermore, there is a tenfold relative risk of tonsillar and base of tongue cancers in spouses of women diagnosed with invasive anogenital cancer, researchers also point out. “This underlines the importance of breaking genito-oral transmission chains.”
The screening of adults born in 1995 for HPV-related OPSCC is still at a planning stage.
In a proof-of-concept study for the stepwise prevention of OPSCC, the authors suggest that target birth cohorts first be stratified and then randomized into serological HPV 16 E6 antibody screening or no screening. HPV 16 antibody-positive women and their spouses then could be invited for HPV vaccination followed by 2 HPV DNA tests.
Unscreened women and their spouses would serve as population-based controls. “Even if gender-neutral vaccination results in rapid elimination of HPV circulation, the effects of persistent, [prevalent] HPV infections on the most HPV-associated tonsillar cancer will continue for decades after HPV circulation has stopped,” the authors predict.
The Jit study was funded by the Bill & Melinda Gates Foundation and the National Institute for Health. The Lehtinen study was supported by grants from the Finnish Cancer Society and Tampere Tuberculosis Foundation. Dr. Jit and Dr. Lehtinen have disclosed no relevant financial relationships. Dr. Giuliano serves on the advisory board for Merck, which markets the HPV vaccine Gardasil.
A version of this article first appeared on Medscape.com.