Blog | Thursday, October 6, 2011

QD: News Every Day--HPV vaccine may prevent throat cancer, but no trial will happen

Oropharyngeal cancers caused by the human papillomavirus (HPV) are on the rise in the United States since 1984, as changes in sexual habits further the virus' spread. But the focus of the HPV vaccine will remain on preventing genital warts and cervical cancer.

Reuters reported one clinician's opinion that throat cancer linked to HPV will become the dominant cause of the disease, ahead of tobacco use.

To study the issue, researchers determined HPV-positive status among 271 of all 5,755 oropharyngeal cancers collected by the three population-based cancer registries in Hawaii, Iowa and Los Angeles from the Surveillance, Epidemiology, and End Results (SEER) program from 1984 to 2004. Prevalence trends across four calendar periods were estimated by using logistic regression. The study appeared online Oct. 3 in the Journal of Clinical Oncology.

HPV prevalence in oropharyngeal cancers significantly increased over calendar time regardless of HPV detection assay (P trend less than .05). Median survival was significantly longer for HPV-positive than for HPV-negative patients (131 s.v 20 months; log-rank P less than .001; adjusted hazard ratio, 0.31; 95% confidence interval [CI], 0.21 to 0.46). Survival significantly increased across calendar periods for HPV-positive (P=.003) but not for HPV-negative patients (P=.18). Population-level incidence of HPV-positive oropharyngeal cancers increased by 225% (95% CI, 208% to 242%) from 1988 to 2004 (from 0.8 per 100,000 to 2.6 per 100,000), and incidence for HPV-negative cancers declined by 50% (95% CI, 47% to 53%; from 2.0 per 100,000 to 1.0 per 100,000).

Researcher concluded from the trend that the annual number of HPV-positive oropharyngeal cancers will surpass the annual number of cervical cancers by the year 2020. They noted that smoking is declining, while other diseases related to oral sex are rising.

The authors wrote, "The rising burden of HPV-positive OPSCCs [oropharyngeal squamous cell carcinoma] argues for evaluation of the efficacy of vaccination to prevent oral HPV infections, particularly given the unavailability of screening for OPSCCs. The high efficacy of HPV vaccines in preventing extracervical infections among women (e.g., vagina and vulva) and penile and anal infections among men implies that efficacy may be comparable against oral HPV infections. Assuming equivalent efficacy, reevaluation of the cost-effectiveness of male HPV vaccination may also be warranted, given the predominant burden of HPV-positive OPSCCs among men."

An accompanying editorial said, "We are unlikely to get a better picture of the recent history of OPSCC in the United States."

It continued that, "For HPV-positive OPSCC, the combination of increasing incidence, young age at presentation, and substantial long-term survival presents an urgent need for lower-intensity therapy that maintains control of disease while avoiding the significant short- and long-term morbidity of current therapy."

But, the editorial also noted that it's been impractical to enroll enough patients in clinical trials to generate meaningful results, which sets up the next part of the story.

Clinical trials for HPV throat cancer won't happen, reports Bloomberg. The researcher who has been studying this issue said that her line of inquiry was cancelled in 2009, when HPV maker Merck bought Schering-Plough Corp. A company spokesperson told Bloomberg that there are no plans to study its vaccine outside of cervical cancer.

In other words, it's a business decision.

Still, the researchers wrote, "The burden of cancer caused by HPV is going to shift from women to men in this decade. What we believe is happening is that the number of sexual partners and exposure to HPV has risen over that same time period."