June 25, 2015 — Between 2008 and 2012, there were declines in the incidence of adenocarcinoma in situ, or CIN2+, among U.S. women ages 18 to 20 and ages 21 to 29, which could be related to the introduction of the human papillomavirus vaccine and new cervical screening guidelines, according to a new study published in CANCER, MedPage Today reports (Jackson, MedPage Today, 6/23).
CIN, or cervical intraepithelial neoplasia, refers to abnormal cervical cells that can become cancerous if left untreated. It is graded on a scale of one to three based on the severity of cell abnormality and how much of the cervix has been affected (National Cancer Institute).
According to MedPage Today, the American Cancer Society and the American Society for Colposcopy and Cervical Pathology in 2012 released guidelines recommending that women under age 21 not receive Pap tests and that women ages 21 to 30 receive Pap tests once every three years.
The HPV-IMPACT Project conducted the study. According to MedPage Today, the project is a partnership between CDC and five sites in the Emerging Infections Program Network that was created in 2008 to track how the HPV vaccination affects the incidence of CIN2+.
From 2008 to 2012, the HPV-IMPACT Project received data on 9,119 CIN2+ cases among women ages 18 to 39. The cases were from sites in California, Connecticut, New York and Oregon. The researchers calculated the CIN2+ rate by age group for each site. They also used administrative and survey data to assess annual cervical screening data from three of the sites: California, New York and Oregon.
The researchers found that CIN2+ incidence rates among women ages 18 to 20 decreased across all four sites. According to the study, the incidence rate decreased from 94 to five per 100,000 women in California; from 450 to 57 per 100,000 women in Connecticut; from 299 to 43 per 100,000 women in New York; and from 202 to 37 per 100,000 women in Oregon.
Meanwhile, for women ages 21 to 29, the researchers found that the CIN2+ incidence rate decreased from 762 to 589 per 100,000 women in Connecticut and from 770 to 465 per 100,000 women in New York. The rates did not change among women ages 30 to 39.
Further, the researchers found that screening rates also fell between 2008 and 2012. The largest decrease was among women ages 18 to 20, while women ages 21 to 29 and ages 30 to 39 reported lesser declines (MedPage Today, 6/23).
The researchers said, "The declines in CIN2+ detection in young women were likely due to reduced screening but could also reflect the impact of [HPV] vaccination" (Hariri et al., CANCER, 6/22).
Specifically, the researchers said the decline among the youngest cohort of women was "likely due to widescale implementation of [the] new guidelines," but they noted that "the larger decreases in CIN2+ incidence with respect to declines in screening suggest the possible impact of the [HPV] vaccine on reducing the true burden of CIN2+ in this age group."
However, in an accompanying editorial, the University of Toronto's Harinder Brar and Allan Covens wrote that some factors mean that it is difficult "to draw any meaningful conclusions about how much of the decrease in CIN2+ can be attributed to vaccination alone." Such factors include the lack of a central screening and cancer vaccine registry, an inability to determine the vaccination rate and heterogeneity among the vaccinated group.
According to the editorial and the study authors, standardization of the cervical cancer screening guidelines and an uptick in the number of women vaccinated against HPV will help make the HPV vaccination's effect more apparent (MedPage Today, 6/23).