Τρίτη, 19 Απριλίου 2016

TIME TO INCREASE HPV VACCINATION

Human papillomavirus (HPV) vaccines have now been available for 10 years, but despite many medical professional bodies strongly recommending the vaccine, uptake in the United States remains low.
Data from a national survey show that about 36% of girls and 14% of boys have received the full schedule of HPV vaccines needed to provide protection (Vaccine. 2013;31:1673-1679).
Now the American Society of Clinical Oncology (ASCO) has become involved, and in a position statement issued today the organization calls for aggressive efforts to increase uptake of the HPV vaccines to "protect young people from life-threatening cancers."
"With safe and effective vaccines readily available, no young person today should have to face the devastating diagnosis of a preventable cancer like cervical cancer. But unless we rapidly increase vaccination rates for boys and girls, many of them will," ASCO President Julie M. Vose, MD, said in a statement.
"As oncologists, we see the terrible effects of these cancers first hand, and we have to contribute to improving today's alarmingly low vaccination rates," she added.
The new policy statement is published online April 11 in the Journal of Clinical Oncology.
The statement notes that HPV vaccination has been previously recommended by many US medical societies, including the American Cancer Society, the American College of Obstetrics and Gynecology Committee, the American Dental Association, the American Head and Neck Society, the American Nurses Association, the American Pharmacists Association, the Association of Immunization Managers, the Society for Adolescent Medicine, and the Society of Gynecologic Oncology.
In addition, a joint letter was sent out to all physicians urging them to give a strong recommendation from the American Academy of Family Physicians, the American Academy of Pediatrics, the American College of Obstetricians and Gynecologists, the American College of Physicians, the Centers for Disease Control and Prevention, and the Immunization Action Coalition.
Now oncologists are specifically being asked by their professional body, ASCO, to join in with the push toward greater uptake of the HPV vaccines.
"ASCO believes oncologists can play a vital role in increasing the uptake of HPV vaccines," the new policy statement says. "Although most oncologists will not be direct providers of these preventive measures, this does not abrogate us from contributing to this process. Our unassailable role in the mission to lessen the burden of cancer...places us in a position of influence. We should use interactions with our patients, primary care colleagues, and health care systems to raise awareness of HPV-related cancers and the role of vaccination in preventing them."
"Oncology providers have a responsibility to serve as community educators, disseminating evidence-based information to combat misconceptions concerning the safety and effectiveness of the HPV vaccine," it continues
"ASCO encourages oncologists to advocate for and actively promote policy change to increase vaccination uptake," the statement concludes.
Issues With the Statement
However, there are a few issues with the statement, says a prominent researcher in the field of HPV and cervical cancer, Diane Harper MD, professor and chair of the department of Family and Geriatric Medicine, University of Louisville, Kentucky. Dr Harper, who was approached for comment, was involved in early clinical trials with both HPV vaccines (Gardasil, Merck & Co, and Cervarix, GlaxoSmithKline), and has emphasized the need for ongoing screening with Pap tests to prevent cervical cancer.
This is also one of the issues she raises about the ASCO statement, which does not mention screening. "All messages about HPV vaccination must be couched in terms of continued lifetime screening for cervical cancer," Dr Harper told Medscape Medical News.
The ASCO statement highlights the potential that HPV vaccination has for preventing cancer. (Both vaccines protect against HPV types 16 and 18, and Gardasil offers additional protection against several other types). The statement notes that HPV is the cause of nearly all cervical cancer cases and that HPV genotypes 16 and 18 are responsible for 70% of cervical cancers. In the United States, HPV is responsible for 60% of oropharyngeal cancers, 90% of which are caused by HPV 16. HPV is also the cause of 91% of anal cancers, 75% of vaginal cancers, 69% of vulvar cancers, and 63% of penile cancers, again with HPV 16 as the predominant oncogenic genotype.
However, the statement also notes that "because of the long latency and the prolonged preinvasive phase after infection with HPV, many years of follow-up are needed for the ongoing trials to demonstrate a significant reduction in HPV-related cancers."
Therefore, intermediate outcomes are being used as surrogate endpoints, it continues. HPV vaccines have been shown to prevent new cancer-causing HPV genotype-specific infections and resultant diseases, such as grades 2 and 3 cervical intraepithelial neoplasias (CIN), vaginal, vulvar, and anal intraepithelial neoplasias (as precursor lesions to cancer).
There is "almost certainty that cancers caused by oncogenic HPV genotypes will be dramatically reduced," according to the statement.
Dr Harper told Medscape Medical News that the studies conducted to date have shown that "Cervarix has a 93% efficacy against CIN 3 regardless of HPV type; Gardasil has a 47% efficacy against CIN 3 regardless of HPV type, and Gardasil 9 is equivalent to Gardasil in the prevention of CIN 3 disease regardless of HPV type. None of these vaccines can prevent all CIN 3 or potentially all cancers."
"Hence, the most important take home point is that screening is absolutely necessary as a prevention tool for preventing cancer by early detection of disease that when found, is curable," Dr Harper emphasized.
Also, Dr Harper noted that the studies ended at prevention of CIN 2/3 disease as a clinical outcome. CIN 3 on average progresses to cancer in 20% of women within 5 years, and to 40% of women in 30 years. But, she points out, "there are no long-term follow-up studies that show that cancers will be averted."  
"The modeling exercises indicate that we have to wait at least 40 years before we will have a detectable decrease in cervical cancers from vaccination, assuming that at least 70% of the population being surveyed is vaccinated," she added.
In its statement, ASCO cites the success of widespread vaccination against hepatitis B virus in reducing the incidence of liver cirrhosis and liver cancer as "an exemplary health model that supports more widespread HPV vaccination.

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