Long term effect of visual screening on oral cancer incidence and mortality in a randomized trial in Kerala, India

Abstract

We studied oral cancer incidence and mortality and the impact of compliance to repeat screening rounds during a 15-year follow-up in a cluster-randomized controlled trial in Trivandrum district, Kerala, India. Healthy individuals aged 35 and above in seven clusters randomized to the intervention arm received four rounds of oral visual inspection by trained health workers at 3-year intervals, and those in six clusters randomized to the control arm received routine care during 1996-2005 and one round of visual screening during 2006-2009. Screen-positive persons were referred for diagnosis and treatment. Oral cancer incidence and mortality were compared between the study arms by intention to treat analysis. Of the 96,517 eligible subjects in the intervention arm, 25,144 (26.1%) had one, 22,382 (23.2%) had two, 22,008 (22.8%) had three and 19,288 (20.0%) had four rounds of screening. Of the 95,356 eligible subjects in the control group 43,992 (46.1%) received one round of screening. Although the 12% reduction in oral cancer mortality in all individuals did not reach statistical significance, there was a 24% reduction in oral cancer mortality (95% CI 3-40%) in users of tobacco and/or alcohol in the intervention arm after 4-rounds of screening; there was 38% reduction in oral cancer incidence (95% CI 8-59%) and 81% reduction in oral cancer mortality (95% CI 69-89%) in tobacco and/or alcohol users adhering to four screening rounds. Sustained reduction in oral cancer mortality during the 15-year follow-up, with larger reductions in those adhering to repeated screening rounds support the introduction of population-based screening programs targeting users of smoking or chewing tobacco or alcohol or both in high-incidence countries.