Routine Cervical Cancer Screening Reduces Risk of Stage I/II+ Disease, But More Awareness Needed

Rebecca Landy, PhD

Routine cervical screening, conducted every 3 years, was found to reduce the incidence of stage I and stage II+ cervical cancers by 48% and 83%, respectively, according to results of a trial published in the International Journal of Cancer.

However, no additional benefits were reported with more frequent screening. Additionally, results showed that 38% of cervical cancer cases and 61% of matched-control cases underwent screening within a 3-year period.

In the case-control study, which utilized records from population-based registries in the New Mexico Tumor Registry, investigators obtained records from women who were diagnosed with cervical cancer and obtained 5 controls per case from the New Mexico HPV Pap Registry and were matched to cases by sex, age, and place of residence.

Next, researchers estimated the odds ratio of localized (stage I) and nonlocalized (stage II+) cervical cancer associated with attending screening in the 3 years prior to case‐diagnosis compared with women not screened in 5 years.

Moreover, women who were screened 3 years prior to their diagnosis had an 83% lower risk of nonlocalized cancer (odds ratio [OR], 0.17; 95% CI, 0.12-0.24) and a 48% lower risk of localized cancer (OR, 0.52; 95% CI, 0.38-0.72) compared with women who were not screened 5 years prior to their diagnosis.

Women also remained at low risk of nonlocalized cervical cancer for 3.5 to 5 years after a negative screening compared with women who had no negative screening in the 5 years prior to diagnosis.

“While we have shown that cervical screening in New Mexico is effective at preventing cervical cancer, only 61% of controls aged 25 to 64 years had attended cervical screening in a 3-year period,” first author Rebecca Landy, PhD, National Cancer Institute, and coinvestigators wrote. “Therefore, initiatives, which increase screening coverage are likely the best investment for improving the prevention of cervical cancer, especially among women from birth cohorts which did not benefit from HPV vaccination prior to sexual initiation.”

In the case-control study, 876 women were diagnosed with cervical cancer between January 1, 2006 and December 31, 2016. Seventy percent of cases were squamous histology, 19% had adenocarcinoma, 2% had adenosquamous histology, and 8% of cases were of other morphologies.

Moreover, 646 women were diagnosed from January 2009 to December 2016 with ≥3 years of potential screening history recorded. Of those women, 2.3% were <25 years of age, 16.1% were between 25 and 34 years, 25.1% were between 35 and 44 years, 22.8% were between 45 and 54 years, 18.0% were between ages 55 and 64, and 15.8% were ≥65 years of age.

Data were collected on all cervical cancer diagnoses in the New Mexico Tumor Registry, and researchers were given information on the month and year of birth, diagnosis, morphology, and stage at diagnosis. The control group was selected from The New Mexico HPV Pap Registry with 5 women selected per case; women selected matched the date of birth and residence at diagnosis with the New Mexico Tumor Registry. Those within the control group also had to be alive without a recorded hysterectomy or diagnosis of cervical cancer at the date of the case’s diagnosis, in order to be eligible.

Women with ≥5 years of screening history and were between 25 and 64 years old with a negative screening remained at risk of localized (OR, 0.20; 95% CI, 0.14-0.28) and nonlocalized cancer (OR, 0.11; 95% CI, 0.07-0.17) for ≥3.5 years compared with those who had no negative screening in the last 5 years.

Women who were screened frequently, which was considered 2 screenings within a minimum of 10 months apart and >30 months between, were at a lower risk of nonlocalized (OR, 0.10; 95% CI, 0.05-0.19) and localized cancer (OR, 0.43; 95% CI, 0.28-0.65) compared with women who did not attend screening within a 5-year period.

Those who underwent screening within 5 years, but did not meet the criteria for frequent screening, also experienced a reduced risk of nonlocalized (OR, 0.26; 95% CI, 0.18-0.37) and localized cancer (OR, 0.58; 95% CI, 0.40-0.82) compared with women who did not get screened within 5 years. However, these women who were screened but not at a frequent schedule also had a greater risk of nonlocalized cancer compared with those who were screened frequently (OR, 2.54; 95% CI, 1.33-4.84).

“In conclusion, our study demonstrates that routine screening at a population level has had a beneficial effect in preventing cervical cancer,” Landy and coinvestigators wrote. “However, only 61% of controls in our study had attended screening in a 3-year period. Thus, increasing screening coverage will have the greatest impact in achieving further reductions in cervical cancer rates.”

Landy R, Sasieni PD, Mathews C, et al. Impact of screening on cervical cancer incidence: a population-based case—control study in the United States [published online ahead of print December 13, 2019]. Int J Cancer. doi: 10.1002/ijc.32826