A comprehensive 10-year study by researchers at the Karolinska Institute has found that rare types of cervical cancer can be effectively prevented with screening.1
Sweden has had a nationwide cervical screening program since the 1960s, with the main aim of discovering and treating lesions that could otherwise become cancerous. While earlier studies have shown that screening reduces the risk of the most common types of cervical cancer, little has been known about the link between screening and the risk of rarer types of cancer.
The Karolinska Institute study investigated all Swedish cases of invasive cervical cancer from 2002 to 2011, identified using the National Swedish Cancer Registry. Of the more than 4,200 cases in the registry, 338 were identified as not belonging to the most common types of cervical cancer (squamous epithelial cancer and adenocarcinoma). For each case, the researchers randomly selected 30 age-matched controls from the Swedish female population, and then calculated the risk of so-called adenosquamous cell carcinoma and other rare types of cervical cancer, in relation to being screened.
The results showed that women who had participated in the screening program on the last two occasions they were invited were less likely to have developed adenosquamous carcinoma (over 75% less likely) and other rare types of cervical cancer (over 65% less likely), than women who had not been screened.
“This shows that rare types of cervical cancer can be effectively prevented through screening,” says coauthor Pär Sparén, Dr. Med. Sc., professor of medical epidemiology and biostatistics at the Karolinska Institute.
The decrease in risk was greater for women who had been screened twice instead of just once. High-risk human papillomavirus (HPV) is the leading cause of cervical cancer and was identified by the study in 70% of the rare tumors in which such typing was possible. The most common type was HPV 18, followed by HPV 16. According to the researchers, this finding suggests that most cases of rare cervical cancer can be prevented by HPV vaccination.
Additionally, the study reported no difference in the effect of screening between women with and without high-risk HPV in their tumors. The researchers also note that continued monitoring of these rare types of cervical cancer is necessary when screening for cervical cancer is performed by HPV testing instead of by primary cytological analysis of cell samples.
For further information, visit the Karolinska Institute.
- Lei J, Andrae B, Ploner A, et al. Cervical screening and risk of adenosquamous and rare histological types of invasive cervical carcinoma: a population-based nested case-control study. BMJ. 2019;365:I1207; doi: 10.1136/bmj.l1207.