Home / Screening & vaccine topics / Oral cancer / First evidence from a randomised trial that screening reduces oral cancer mortality: the Trivandrum oral cancer screening study (TOCS), Kerala, India


Oral cancer accounted for 274 300 new cases and 145 500 deaths annually in the world around 2002, two-thirds of which occurred in developing countries. Tobacco use in any form and alcohol drinking are major risk factors for oral cancer. Most invasive oral cancers are preceded by precancerous lesions and preclinical early invasive cancers that can be identified by visual inspection of the oral cavity. Oral cancer is thus potentially amenable to primary and secondary prevention. We describe here the findings after 3 rounds of oral screening at 3-year intervals in a cluster randomised controlled trial in Kerala, India.
Study location-Trivandrum, Kerala, India:

Notional map showing Trivandrum, Kerala, India

  • To evaluate the efficacy of screening by visual inspection of the oral cavity in detecting early stages of oral cancer and in reducing mortality
  • To evaluate the cost-effectiveness of intervention

Trivandrum oral cancer screening team

  • 13 clusters randomised to intervention (N=7) and control (N=6) groups
  • 96,517 in the intervention group and 95,356 in the control groups
  • Information on socio demographic factors and habits collected for both intervention and control cohorts
  • Education on the harmful aspects of tobacco/alcohol use for the intervention and control cohorts
  • Between 1996-2004, 3 rounds of oral visual inspection at 3-year intervals provided to eligible individuals (>=35 years) in the intervention group by trained health workers
  • Screen positive cases referred for physician confirmation/ biopsy
  • Precancer cases were advised cessation of habits, medication or surgical excision
  • Oral cancer cases were treated by radiation and/or surgery according to the stage at diagnosis

Intervention and control clusters

Trivandrum study algorithm

Chart for Visual inspection of the oral cavity:
A PDF file is avalaible on the following link: Quick Clinical Reference Chart for Visual Inspection of the Oral Cavity to Detect Precancerous Lesions and Invasive Cancers
Quick clinical reference chart

Criteria for screen positivity:
Presence of one or more of the following lesions:
  • White, red, nodular lesions suggestive of leukoplakia/ erythroplakia
  • Lesions suggestive lichen planus
  • Oral submucous fibrosis
  • Suspicious ulcer/ growth
Referral investigations:
  • Clinical examination by dentist or clinical oncologist
  • Histological examination

Clinical examination by clinical oncologist

Monitoring and Evaluation:
  • Participation in screening
  • Screen (test) positivity
  • Compliance with referral for reference investigators

Patient enumeration and interview

Patient oral examination

Patient medical consultation

Patient oral examination in the field clinic

Patient oral examination

Bidi smoker / cancer in the oral cavity

Trivandrum oral cancer screening centre placard

Intermediate outcomes:
  • Detection rates of precancers and cancer
  • Programme sensitivity
  • Positive predictive value of screening test to detect both precancers and invasive cancer
  • Stage distribution of cancers
  • Survival / case fatality rate

Principal investigators and coordination team

Final outcome:
  • Reduction in mortality from oral cancer
Sources of data:
  • Study database
  • Population based cancer registry
  • Mortality registration offices
  • Death records from churches/mosques
  • Active follow-up by home visits and telephone inquiries

Data entry and statistical team


Distribution of personal habits by sex and groups

Screening history

Stage distribution of incident cases / oral cancer

PYO, oral cancer cases/deaths/incidence/mortality

Study profile of all eligible subjects

Results among persons with tobacco/ alcohol habits

  • Good participation rates for screening (~90%)
  • Moderate compliance to referral (~62%)
  • A significant detection of oral cancer at early stages (stage I & II) by visual inspection (41.5% vs. 23.5%)
  • Significant (34%) reduction in oral cancer mortality among individuals with tobacco/alcohol habits
  • Risk of disease extremely low among persons with no tobacco/alcohol habits
  • Potential to prevent 37,000 oral cancer deaths world-wide
We gratefully acknowledge the Association for International Cancer Research (AICR) for their generous support. We are indebted to the eligible subjects in this project and their families. We thank the Kerala State Health Services for their support. The assistance of the staff of panchayath offices, mortality registers and the Trivandrum population-based cancer registry is gratefully acknowledged.
Kerala landscape

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