Frontline Cancer: Vaccines for HPV near guarantee
Dear Scott: “Our son, who is 25, went to the GP yesterday and his doc wasn’t sure about giving the Gardasil I had been bugging him to get. Didn’t you tell me about the benefits of the HPV vaccination?”
The note was from a friend. It was personal, but also a topic of wide public interest and one that remains much discussed among cancer researchers and physicians. That’s why I’m answering my friend here.
Roughly 12 percent of all human cancers worldwide — more than 1 million cases per year — are caused by viral infections (called oncoviruses) and attributed to a relatively small number of pathogens: human papilloma virus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV) and Epstein-Barr virus (EBV). Given the emphasis upon other causal factors of cancer, such as genetic mutations or environmental sources, it’s a statistic that’s not well known nor, I would argue, fully appreciated.
Human viral oncogenesis is complex, and only a small percentage of the infected individuals develop cancer, but that 12 percent translates into more than 500,000 lives lost each year to virus-caused malignancies. Many of those deaths are preventable because effective vaccines already exist for HPV and HBV. Right now. No future discoveries required.
I want to specifically talk about the HPV vaccine. Controversy has constrained its proven effectiveness as a public health tool, but if used as prescribed, the HPV vaccine could essentially eliminate cervical and other HPV-caused cancers. Infection with HPV is very common. It’s estimated that at least 80 million Americans are affected. HPV is actually a group of more than 200 related viruses. There is no cure for HPV, but the infection typically clears on its own without lingering effect.
Forty types of HPV are easily spread through direct sexual contact. They fall into two categories: Low-risk HPVs that do not cause cancer, but can cause skin warts on or around the genitals, anus, mouth or throat. And high-risk HPVs (mostly two strains, type 16 and type 18) that cause approximately 5 percent of all human cancers worldwide. High-risk HPV strains drive the rates of cervical (the leading cause of cancer deaths in women in many developing countries), anal and a dramatically increasing subset of oropharyngeal (the tonsil and parts of the throat and tongue) cancers among men in the United States and other developed countries.
The Food and Drug Administration has approved three vaccines for preventing HPV infection: Gardasil, Garadsil-9 and Cervarix. They have strong safety records and a near-guarantee of dramatically reducing the risk of infection. But they are not widely used. The HPV vaccination rate in the U.S. is just 36 percent for girls and 14 percent for boys (and even lower for Hispanics, blacks and the poor).
The chief reason, it has been argued, relates to the recommended age of vaccination: 11-12 years. Because cancer-causing HPV viruses are transmitted through sexual contact, the idea of vaccinating a young girl or boy as a preventive measure strikes many people (i.e. parents) as premature, unsettling or enabling. My friend and colleague, Howard Bailey, M.D., director of the University of Wisconsin Carbone Cancer Center and a national leader on this topic, believes this attitude costs lives. “We need to shift focus from behavior associated with infection to preventing major cancers,” he says.
There are other factors as well. For example, full vaccination requires three doses, so persistence is required. Safety concerns continue about the vaccine (perhaps part of a larger misplaced mistrust of vaccines in general). And there remains limited public understanding of HPV or HPV-related diseases, especially in men.
The reality is that these vaccines work best if they are given at an early age before exposure to HPV. However, as Howard explained, if this window is missed, the FDA includes indications where the recommendation rises to age 26, to get vaccinated for at least some cancer-causing strains of HPV. Howard recommends every young, unvaccinated adult receive at least the 9-valent HPV vaccine, “which can provide protection against five additional HPV types that cause cancer and are less common than types 16 and 18.” There is the potential for protection against HPV types that a person hasn’t yet been exposed to and if a person hasn’t been exposed to the common HPV types (6, 11, 16 and 18), it can provide protection against them as well.
In a recently published statement paper, the American Society of Clinical Oncology called for a broad, concerted effort by health care professionals and policymakers to increase awareness of the evidence and effectiveness of HPV vaccination. It should be routine. The public health benefit is obvious and indisputable. I completely agree.
Here’s a corollary to consider: Vaccines for HBV have been available for many years and are a routine part of pediatric immunizations in the United States. In the past, countries like Taiwan and Korea suffered endemic HBV infections and high rates of hepatocellular carcinoma (HCC) or liver cancer. In the 1980s, these countries implemented universal infant HBV vaccination policies that have resulted in a dramatic 80 percent decline in HBV infections, cases of hepatitis and, more importantly, reductions in HCC incidence and mortality.
Every day, you can read headlines about research to find new treatments and cures for the many diseases called cancer. Progress is painfully slow and uneven. We’ve been fighting this war for decades. Preventing cancer altogether is a better approach and with cancers caused by HPV, we have the right weapon already at hand. We just need to use it.
— Scott M. Lippman, MD, is director of UC San Diego Moores Cancer Center. His column on medical advances from the front lines of cancer research and care appears in La Jolla Light the fourth Thursday of each month. You can reach Dr. Lippman at email@example.com