In a recent study published in the Canadian Medical Association Journal, researchers modeled the impact of three priority actions of the Canadian Partnership Against Cancer (CPAC) on the time to eliminate cervical cancer in British Columbia (BC), Canada.
Study: Strategies to accelerate the elimination of cervical cancer in British Columbia, Canada: a modelling study. Image Credit: SewCreamStudio/Shutterstock.com
Background
Nine high-risk types of human papillomavirus (HPV) account for over 90% of global cervical cancer cases. Early detection/treatment and HPV vaccination can prevent cervical cancer. While cytological screening of cervical cancer has been successful, the incidence of the cancer has been relatively unchanged since the mid-2000s in Canada.
In Canada, school-based vaccination programs for HPV have been introduced for girls in 2007 and boys in 2013. Given that the first vaccination cohorts have recently reached the screening-eligible age, the current screening-eligible population remains largely non-vaccinated.
Further, HPV testing has more sensitivity than cytological detection. Besides, self-collected vaginal samples could be used for HPV testing, which could improve screening uptake.
The World Health Organization committed to cervical cancer elimination, defined as an annual age-standardized incidence rate (ASIR) < 4 per 100,000 females.
Likewise, the CPAC launched an action plan for eliminating cervical cancer by 2040 and provided strategies and targets in three priority areas – HPV vaccination, HPV-based screening, and follow-up compliance. BC recently introduced a 10-year cancer plan and initiated a transition to HPV screening in 2024.
About the study
In the present study, researchers evaluated how and when BC could achieve cervical cancer elimination after the transition to HPV-based screening.
The OncoSim-Cervical model was used to project outcomes for the BC population under different screening alternatives. Model parameters were modified to reflect BC's screening and vaccination programs and participation levels.
Two reference scenarios were developed; the HPV base case simulated primary HPV testing, while the other represented cytological screening.
The HPV base case involved primary HPV testing every five years for 25–69-year-old individuals with cervix. Model parameters related to the CPAC action plan’s priority areas were identified.
Model scenarios were developed to investigate the effects of increasing 1) the coverage of HPV vaccination, 2) screening recruitment and on-time screening, and 3) follow-up compliance for follow-up HPV testing and colposcopy. The effects of combining the second and third priorities, as well as all three, were also investigated.
Outcomes were simulated between 2023 and 2050. Outcomes included cervical cancer ASIR, projected cervical cancer cases in BC, and elimination year.
Secondary outcomes included precancer treatment and colposcopy volume by year. Besides, sensitivity analyses examined the effects of baseline parameters for vaccination coverage and on-time screening participation.
Findings
BC would not achieve the cervical cancer ASIR < 4 per 100,000 females until 2045 with cytological screening. However, HPV-based screening would eliminate the cancer by 2034, preventing 942 cases compared to cytological screening.
Further, increasing the coverage of vaccination or the proportion of ever-screened individuals would achieve elimination by 2033. Elimination could occur by 2032 if the second or third priority were completed and by 2031 if both were achieved.
However, increasing vaccination, besides achieving the second and third priorities, will have a negligible impact on cervical cancer incidence.
Projected precancer treatment and colposcopy volumes showed substantial increases under HPV-based screening scenarios. Further, a decline in on-time screening participation could delay elimination by three to five years.
Conclusions
The findings indicate that BC would not achieve cervical cancer elimination under the current cytological screening until 2045. However, implementing HPV-based screening would allow for elimination by 2034.
Further, achieving any of the targets in priority areas would accelerate elimination. Increasing on-time screening participation or follow-up compliance would have the most significant impact.
Notably, the HPV base case assumed that current screening participation rates would continue after implementing HPV testing. Nonetheless, HPV testing offers innovative approaches to screening, which could potentially improve participation among never- and under-screened populations.
While increased vaccination had little impact on time to elimination, the benefits of vaccination would emerge beyond the time scale of the model.
Taken together, BC could potentially achieve cervical cancer elimination before 2040. Improving on-time screening participation and follow-up compliance could accelerate the goal.
Screening programs in Canada would require HPV screening implementation in innovative and strategic ways to enhance access to screening, augment timely follow-up and treatment, and decrease disparities across the population.
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