Women who are screened for cervical cancer are significantly less likely to develop rare types of the cancer, especially among women who had 2 tests.
In addition to reducing the risk of the most common types of cervical cancer—squamous epithelial cancer and adenocarcinoma—cervical cancer screening also yields benefits for preventing rare types of the disease, especially for those of advanced stage, according to results of a 10-year study.
Compared with having no test in either of their previous 2 recommended screening intervals, women who had 2 tests were more than 75% less likely to develop adenosquamous cell carcinoma (ASC) and more than 65% less likely to have developed other rare types of invasive cervical carcinoma (RICC). The reduction risk was most prominent among women aged 30 to 60 years.
Typically, screening studies have focused on the most common types of cervical cancer, leaving a knowledge gap in understanding the impact of screening on rarer types of the cancer.
“RICC include a group of histological types that are of glandular origin, with overlapping morphology, and the histopathological classification of these types is relatively difficulty,” wrote the researchers. “RICC have also been reported as highly aggressive, with a worse prognosis than squamous cell carcinoma and adenocarcinoma.”
Using the Swedish Cancer Registry, researchers identified 4254 cases of cervical cancer between 2002 and 2011, 338 of which were ASC and other RICC, such as glassy cell carcinoma, clear cell carcinoma, and small cell carcinoma. Each case was compared against 30 age-matched controls.
According to the researchers, women with 2 normal tests had an 84% reduced risk of ASC and a 71% reduced risk of RICC. There was also an observed risk reduction (66%) for women who had 1 normal test, albeit not as significant.
Meanwhile, women with at least 1 abnormal test during any of the 2 intervals had an elevated risk of disease compared with women with no test. However, the researchers noted that the increase was not statistically significant.
“This could be due to the inadequate execution of the management practice after an abnormality,” explained the researchers. “In addition, clinical management of abnormal smears could alter the risk of ASC and RICC after an abnormal smear, and timely assessment through biopsies or treatment (if needed) could be essential for histological types that progress rapidly."
Human papillomavirus (HPV) was identified in 148 of 211 (70%) cases, with HPV18 (37%) being the most common type followed by HPV16 (22%). This high prevalence underscores the importance of HPV vaccination, which has demonstrated that the vaccine prevents the most dangerous types of HPV. However, HPV completion rates continue to lag, suggesting a need for renewed efforts to get patients to complete the 3 doses.
Lei J, Andrae B, Ploner A, et al. Cervical screening and risk of adrenosquamous and rare histological types of invasive cervical carcinoma: population based nested case-study control [published online April 3, 2019]. BMJ. doi: 10.1136/bmj.l1207.