Childhood cancer survivors at risk for cervical cancer urged to get HPV vaccine

    Melissa Hudson

    The human papillomavirus (HPV) vaccine is recommended to protect against cervical cancer, but St. Jude researchers suspect even high-risk childhood cancer survivors need encouragement to get immunized.

    Survivors at high risk for cervical cancer later in life include adolescents and young women whose treatment included hematopoietic stem cell transplants.

    In the October 7 online edition of Cancer, St. Jude investigators reported that the transplants are linked to a 13-fold increased risk of cervical cancer. The therapy involves extreme, sometimes prolonged, immune suppression. Other survivors reported to be at elevated risk include those who had Hodgkin lymphoma and females who received pelvic irradiation.

    For other survivors, HPV vulnerability is linked to socio-economic factors, such as income and education, or to treatment side effects, such as inattention and hyperactivity, which are associated with risky behaviors, researchers reported.

    Melissa Hudson, MD, Oncology, said anecdotal evidence suggests even these high-risk survivors are failing to take advantage of vaccine protection. Hudson is St. Jude Cancer Survivorship Division director and co-leader of the Cancer Prevention and Control Program. She is also senior author of the Cancer report.

    “Many families are missing an opportunity for primary cancer prevention and for markedly decreasing their daughters’ risk of cervical cancer,” she said. “I tell parents this is a very prevalent virus. Why take a chance?”

    The study comes about three years after Gardasil became the first vaccine approved by the U.S. Food and Drug Administration (FDA) to protect against HPV infection in women. HPV causes cervical and other cancers. In October, the FDA expanded Gardasil approval to include protection against genital warts in boys and young men. The agency also approved a second vaccine, Cervarix, to protect against cervical cancer in girls and young women.

    James Klosky, PhD, Behavioral Medicine, said researchers decided to focus on HPV vaccination among cancer survivors because the revised Children’s Oncology Group (COG) survivor treatment guidelines released last fall recommend it for all eligible survivors. COG is the world’s largest cooperative childhood cancer research organization. Klosky is first author of the Cancer paper.

    Gardasil protects against four strains of HPV blamed for 70 percent of cervical cancers and 90 percent of genital warts. In clinical trials, the vaccine was 98 percent effective at protecting against those strains. But to be protected, girls must be vaccinated before they are exposed to the virus, which is transmitted through sexual contact and has been linked to vaginal, penile and several other cancers. The vaccine is approved for use in females ages 9 to 26. A federal immunization advisory panel recommends beginning that three-shot series at age 11 or 12.

    Although federal health officials set a goal of having 90 percent of eligible persons vaccinated by 2010, HPV immunization rates are lagging. Current national estimates are that no more than 25 percent of adolescents and young women have started the process. Currently, information about the percentage of female cancer survivors who are vaccinated is lacking.

    St. Jude investigators are planning additional research to answer that question and to track vaccine effectiveness and immune response in survivors. They also want to identify barriers to vaccination and develop strategies to address them.

    The Cancer report includes one piece of advice for getting more survivors protected: Get physicians involved. “Physician recommendation of HPV vaccine within the oncology setting may maximize the likelihood of HPV vaccination,” the researchers wrote.

    Hudson said the HPV vaccine is safe and effective. She said reports suggest factors likely impacting vaccination rates range from the vaccine’s cost to exaggerated accounts of vaccine side effects to parental ambivalence about a vaccine to protect against a sexually transmitted infection.

    Cervical cancer typically strikes women in middle age, and childhood cancer survivors are just beginning to reach that milestone in greater numbers. But Klosky said anecdotal reports suggest younger survivors are experiencing higher than expected rates of gynecological complications related to HPV. They include abnormal Pap tests, cervical dysplasia and other precancerous changes of cervical cells.

    Klosky said among the other survivors at greater risk of HPV-related complications are women who fail to get recommended screening Pap tests. A 2004 study of Childhood Cancer Survivor Study participants found women who survived childhood cancer were significantly less likely than their healthy siblings to have undergone Pap tests in the previous three years.

    Other St. Jude authors of this paper are Sheri Spunt, MD, Oncology; Mary Randolph, PhD, Behavioral Medicine; and Daniel Green, MD, Epidemiology and Cancer Control.

    The study was funded in part by the National Institutes of Health and ALSAC.

    December 2009