Screening and vaccines lead to a decrease in cervical cancer

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Screening and vaccination have led to a decrease in cervical cancer, although other cancers caused by the human papillomavirus (HPV) for which there are no clear guidelines for routine screening are increasing, according to research by the American Society of Clinical Oncology ( ASCO) annual meeting in June.

“Without standardized screening, HPV-related cancers such as oropharyngeal cancers and anal-rectal cancers will increase,” said Dr. Cheng-I Liao from Kaohsiung Veterans General Hospital in Taiwan, who presented the study results on May 14th, pre-admission. “To reduce these trends and achieve success comparable to what we see in cervical cancer, we need to develop effective screening strategies and determine the effectiveness of the vaccine in these patient populations.”

HPV is one of the most common sexually transmitted infections, and most people acquire some of the 150+ known types of the virus soon after becoming sexually active. HPV triggers abnormal cell growth that leads to genital and anal warts, precancerous cell changes and, if undetected and left untreated, cancers of the cervix, anus, vulva, vagina, penis, mouth and throat (oropharyngeal cancer) can lead.

Cervical cancer deaths fell dramatically after the introduction of routine Pap smear screening in the 1950s, which allows abnormal cell changes to be detected before they progress to invasive cancer. Nowadays, women are advised to have a Pap smear (cytology test) with or without an HPV test every three years. Screening is not routinely recommended for oral cancer or anal cancer, although some experts recommend anal screening for people at high risk, such as: B. Men who have sex with men (especially those living with HIV).

HPV vaccines can prevent these cancers, but only about half of teenagers are fully vaccinated, according to the Centers for Disease Control and Prevention (CDC). The Gardasil 9 vaccine, approved in December 2014, protects against the two main cancer-causing HPV types (16 and 18), five other high-risk types (31, 33, 45, 52 and 58) and two other genital-causing types and anal warts (6 and 11) . The original Gardasil vaccine, which was protected against four types (6, 11, 16, and 18), was approved for young women in 2006 and for young men in 2011.

The vaccine is most effective when given to adolescents before they become sexually active. The CDC recommends Gardasil 9 for girls and boys as well as girls aged 11 or 12 years with catch-up vaccination for people up to 26 years of age. The Food and Drug Administration approved the vaccine for women and men up to 45 years of age. The CDC advises people between the ages of 27 and 45 to discuss with their health care providers whether they could still benefit from it.

Trends in HPV-related cancers

Liao and colleagues examined trends in HPV-related cancers in the US and analyzed data for more than 657,000 people with such malignancies (60% women and 40% men) from the US cancer statistics program between 2001 and 2017. Overall, the incidence The number HPV-related cancers rose 2.4% per year during this period – 0.8% in women and 2.7% in men.

However, cervical cancer decreased by 1.0% annually. The decline was even greater in women aged 20 to 24 years (4.6% per year) than in older women who were adolescents before the widespread HPV vaccination. However, oral, anal-rectal and vulvar cancers in women increased by 1.3% annually, mainly due to anal cancer. Cervical cancer accounted for 52% of all HPV-related cancers in women during this period. However, as anal cancer increases, cervical cancer is expected to exceed cervical cancer in women of any age group above 50 by 2025.

“It is likely that the significant decrease in cervical cancer incidence is due to clear guidelines for screening cervical cancer and also reflects the promotion and acceptance of vaccination, especially among younger women,” Liao said.

In men, HPV-related cancers increased 2.4% per year, including a 2.7% increase in oral cancer and a 1.7% increase in anal cancer. The increase in oral cancer was greatest in men over 65. Oral cancer accounted for 81% of HPV-related cancers in men – an incidence almost five times higher than that in women.

“The decline in cervical cancer is welcome news and may reflect an intense effort to screen and vaccinate people at risk,” said Dr. med. Lori J. Pierce, President of ASCO, in a press release. “This study clearly shows that we still have a lot of work to do to reverse the rising incidence rates of other HPV-related cancers.”

HPV infection rates

Another recent study showed that vaccination dramatically reduced the prevalence of HPV infection in women, which is expected to reduce future cases of HPV-related cancer.

Hannah Rosenblum, MD, of the CDC’s Epidemic Intelligence Service, and colleagues analyzed nationally representative data from the National Health and Nutrition Examination Survey from 2003 to 2018.

The researchers found that the prevalence of the four HPV types covered by the original Gardasil vaccine, which was mainly used through 2015, decreased by 88% in teenagers ages 14-19, from 11.5% in the time before vaccination (2003 to 2006). in the last period (2015 to 2018) to only 1.1%. In young women aged 20 to 24, the prevalence decreased by 88% from 18.5% to 3.3%.

In addition, the results suggest that vaccination confers indirect “herd effects” on unvaccinated young women. In sexually experienced women who received at least one dose of vaccine, the prevalence of the four types of HPV decreased by 97% in the 14- to 19-year-old age group and by 86% in the 20- to 24-year-old age group. But even in non-vaccinated women, the rates fell by 87% and 65%, respectively.

The researchers also saw a 65% decrease in the prevalence of the additional five types of HPV covered by the Gardasil 9 vaccine in teenagers ages 14-19, but no significant change in the older group. The prevalence of other types of HPV that were not covered by either vaccine also decreased in the younger group, but not in the older group. The authors suggested that this could be due to a decrease in sexual activity reported by the younger but not the older group.

“These data show an increasing impact of HPV vaccination in the US,” the study authors wrote. “The HPV vaccination is an important prevention tool against HPV infections, anogenital warts, and HPV-related precancerous and cancerous diseases.”

Click here to read the abstract of the ASCO study.
Click here to read the CDC study.
Click here to learn more about cervical, anal and oral cancers.




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