Status of HPV-Related Cancers and Vaccination Trends
Status of HPV-Related Cancers and Vaccination Trends
Today we discuss cancers associated with the human papillomavirus (HPV) and HPV vaccination methods. The “Annual Report to the Nation on the Status of Cancer,” published in the Journal of the National Cancer Institute, shows that although cancer rates overall are on the decline, cancers associated with HPV are rising and there still appears to be a low vaccination coverage among teenagers for HPV. We are joined today by one of the authors of this study, Edgar Simard, PhD, MPH, senior epidemiologist of surveillance research, who studies the impact of prevention and screening on cancer incidence at the American Cancer Society.
—Interviewed by Anna Azvolinsky, PhD
Cancer Network: Can you tell us about the type of data that was used in this report for the analysis and conclusions?
Dr. Simard: The “Annual Report to the Nation on the Status of Cancer” is published every year by a group of leading cancer surveillance scientists through a collaboration of the American Cancer Society, the Centers for Disease Control and Prevention (CDC), the National Cancer Institute, and the North American Association of Central Cancer Registries. We focus on two main outcomes in the report. The first is the cancer death rates, and those are assessed by evaluating information reported on death certificates to every state health department that are then aggregated by the CDC. We then analyze the aggregated data to evaluate trends over time and cancer death rates. The second data source that we use for the main body of the annual report is population-based cancer registry data, used to assess incidence rates; that’s new cases of cancer that occur that are then aggregated at the national level to look at trends and cancer incidence rates over time.
Cancer Network: What were the broad conclusions from this study?
Dr. Simard: The broad conclusions were that the overall cancer death rate has continued to decline. This has been noted since the early 1990s. This decline was noted among both men and women and of every racial and ethnic group, and for all of the major cancer sites. These are lung, breast, colorectal, and prostate cancers. During the most recent 10-year time period for which we have available data, from 2000 to 2009, death rates increased among men and women for cancers of the liver, pancreas, melanoma of the skin among men, and for cancer of the uterine corpus among women.
Cancer Network: Let’s focus on the HPV findings. Can you briefly describe how one becomes infected with HPV and the cancers that are associated with this virus?
Dr. Simard: HPV infection is quite common. HPV is passed through genital contact most often through vaginal and anal sex, and it may also be passed from one person to another during oral sex and through genital-to-genital contact. It should also be known that HPV can be passed from one partner to another even when someone has no signs or symptoms of HPV infection. So while many people are infected with HPV at some point in their lives, most people clear the infection and therefore have no risk of developing cancer due to the infection later in life. The risk of cancer really comes for those people who have what is called a persistent HPV infection, which means their immune system is unable to clear the infection and they are infected for decades. That increases their risk for getting a number of different cancers that we describe in the report.
Cancer Network: What are some of the cancers that one can get through chronic HPV infection?
Dr. Simard: The most common cancer that people get from HPV infection is one that is really well known, and that is cervical cancer. The vast majority of cervical cancers are due to HPV infection among women. Persistent HPV infection also causes many anal, vaginal, vulvar, as well as oropharyngeal cancers.
Cancer Network: What were the specific takeaways for HPV-related cancers and were any of the results surprising?
Dr. Simard: For the HPV-related cancers, we looked at incidence rates during the most recent 10-year time period, so again, from 2000 to 2009. We found that incidence rates of HPV-associated oropharyngeal cancer increased among white men and women, and also that rates of anal cancer increased among white and black men and women. We also found that rates of vulvar cancer increased among white and black women, and this is in contrast to rates of cervical cancer that have continued to decline among virtually all women. The increases that we noticed for most of these cancers, by race and ethnicity, as well as by sex, have really been noted by a number of previous studies, so they weren’t necessarily surprising. But why the rates of, for instance, oropharyngeal cancers are increasing among white men and women only and not black men and women, or people of other races and ethnicities, is not known. Some of the differences by race and ethnicity in terms of isolated increases in oropharyngeal and anal cancers are still somewhat of an unknown.
Cancer Network: There are now several HPV vaccines that have been approved for several years. The vaccines can protect against several of the strains of HPV that are known to cause cancer. The vaccines were first approved for girls between the ages of 9 and 26, and then in boys for the same age. What are the major recommendations for both girls and boys for HPV vaccination, and what types of outcomes and cancers does the vaccine protect against?
Dr. Simard: The HPV vaccines are given as three shots to protect against HPV infection and HPV-related diseases. Two vaccines, Cervarix, which is the bivalent vaccine that protects against HPV types 16 and 18, and Gardasil, which is the quadrivalent vaccine that protects against HPV types 16 and 18, which are associated with most HPV-related cancers, as well as HPV types 6 and 11, which are associated with the occurrence of anal and genital warts, have both been approved to protect against cervical cancers in women. Gardasil also protects against genital warts, and as I mentioned, it has been shown to protect against cancers of the anus, vagina, and vulva. Both vaccines are available for females, and Gardasil is available for males. In terms of the current recommendations by the Centers for Disease Control and Prevention and the advisory committee on immunization practices, both preteen girls and boys are recommended to receive the vaccine at ages 11 or 12. The HPV vaccines are recommended for all teen girls and women up to age 26 who did not get all three doses of the vaccine when they were younger, and for all teen boys and men through age 21 who did not get all three doses of the vaccine when they were younger. It is also recommended for gay and bisexual men or any men who have sex with men, as well as men with compromised immune systems, including HIV infection, through age 26.
Cancer Network: While HPV infection can have side effects for women, is it true that men and boys do not generally have any symptoms of HPV infection?
Dr. Simard: I wouldn’t say that they don’t have any symptoms. You asked about vaccination side effects?
Cancer Network: Not side effects of the vaccine, but actual HPV infection symptoms. Women can have symptoms, but do boys and men also develop symptoms of actual HPV infection?
Dr. Simard: They certainly can, especially when you think of the occurrence of anal and genital warts. That would be one instance where a symptom is physical to the naked eye. The other point I wanted to mention, since you asked about the outcomes that the vaccines protect against—the randomized clinical trials that have been conducted to evaluate the efficacy of the vaccines for various outcomes followed men and women from when they were vaccinated to look at whether they were protected against the occurrence of preneoplastic or precancerous lesions. For instance, looking at cervical cancer, both vaccines show protection for women in terms of reducing the incidence of precancerous lesions of the cervix. But women and men were not followed for the occurrence of invasive cancer because that type of trial would take too long to conduct. We know that in terms of the indication for each vaccine, they protect against the occurrence of the precancerous lesions for which they are indicated.
Cancer Network: Your study mentions that while the goal is to vaccinate approximately 80% of girls aged 13 to 17 in the United States, the actual percentage of girls who received all three shots of either of these vaccines, at least in 2010, was only 32%. Do we know some of the reasons why these numbers are well below the goal?
Dr. Simard: Yes, we used a different data source to look at the trends in vaccination coverage between 2008 and 2010, and that was the national immunization survey for teens, or NIS-TEEN, which is our telephone survey conducted by the CDC that is representative of the entire US teen population. We did find an increase in coverage between 2008 and 2010, and as you know, about 32% of girls aged 13 to 17 in 2010 had received three doses of the vaccine, but that is really well below the 80% goal that we have set for the Healthy People 2020 target. The reasons for why the vaccine uptake is low are really multifaceted. The survey data we analyzed didn’t really delve into why the coverage levels were low, but we do have knowledge from other studies as to what those reasons may be. Really, the most important reason in terms of our assessment of the literature is really provider recommendation. What I mean by that is that the most important determinant of whether a child will receive the HPV vaccine is whether or not their physician or healthcare provider recommended it to them and their parents, in terms of having the parent accept the vaccine. There are other things as well that may play a role. For instance, health insurance status and issues around cost of the vaccine, as well as parental knowledge and acceptance of the vaccine. There may also be a role for school mandates as well.
Cancer Network: Hopefully, the vaccination of boys against HPV will continue to rise. You mentioned primary care providers as being instrumental to this. Are there strategies to bring about awareness to get more boys and girls vaccinated, both from the parent and child side and the physician side?
Dr. Simard: There are a number of campaigns in terms of getting information out there for parents and physicians. Really the CDC takes the lead in disseminating that type of information, but the American Cancer Society also is involved in some of these activities. The main message, I think, for everyone, whether it be a parent or a healthcare provider, is the fact that the HPV vaccine is an anticancer vaccine. We are lucky to have a vaccine that protects against these different cancers, and we definitely encourage following the vaccine recommendations to increase uptake among boys and girls. The point is that later in the future with these vaccinated cohorts of boys and girls, we will hopefully see decreases in the incidences and death rates of HPV-related cancers in decades to come.
Cancer Network: Do you think that the school mandate for vaccination is useful and may happen in the short term?
Dr. Simard: I think that is really questionable because there are other, maybe political and infrastructural issues with regards to a school mandate. Really, what we found in our critical review of the knowledge out there, is that provider recommendation is probably the most important determinant.
Cancer Network: Thank you so much for joining us today, Dr. Simard.
Dr. Simard: Thank you!