Long term effect of visual screening on oral cancer incidence and mortality in a randomized trial in Kerala, India
Introduction
Oral cancer (International Classification of Diseases 10th edition codes C00-06) accounted for an estimated 264,000 new cases and 128,000 deaths globally in 2008; of these, 172,000 cases and 97,000 deaths occurred in less developed countries of the world.1 India accounted for a fifth of the global burden at 45,500 cases and 31,100 deaths.1 The high incidence in the Indian sub-continent2 is related to the high prevalence of pan-tobacco chewing in the population, in addition to bidi and cigarette smoking as well as alcohol drinking.[3], [4], [5] Avoiding these risk factors can prevent a large proportion of oral cancers. Whereas 5-year survival exceeds 80% following diagnosis and treatment of early, localized (stages I and II) oral cancer, it drops to less than 20% with advanced clinical stages (III and IV).[6], [7], [8], [9] Although the direct accessibility and visibility of the oral cavity for physical examination greatly facilitates early detection of preclinical invasive oral cancers and potentially malignant disorders (PMDs), a high proportion of oral cancer is still diagnosed in advanced clinical stages in most countries.[6], [7], [8], [9] In 2005, we reported a 34% reduction in oral cancer mortality in high-risk individuals with tobacco chewing or smoking or alcohol drinking habits following three rounds of oral visual screening at 3-year intervals in a cluster-randomized controlled trial, after 9 years of follow-up since its initiation in 1996.10 We now present the results after 15 years of follow-up in this trial and discuss the efficacy of adherence to repeated screening rounds.
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Participants and procedures
The methods of this cluster-randomized trial were described in detail elsewhere.[10], [11], [12] The study protocol was reviewed and approved by the scientific and ethics review committees of the Regional Cancer Centre, Trivandrum, India (RCC) and the International Agency for Research on Cancer, Lyon, France (IARC). In brief, the 13 panchayaths (municipal administrative units), in the Trivandrum District, Kerala, India chosen for the study were randomly assigned to two groups of seven and six
Results
Fig. 1 shows the study profile in terms of eligible subjects, person-years, oral cancer incidence and mortality rates in all individuals; Fig. 2 shows the above in users of tobacco or alcohol or both. The study groups had similar distribution of age, sex, religion, house type, education, occupation, income, pan tobacco chewing, tobacco smoking, and alcohol drinking as detailed elsewhere.10 The total number of eligible individuals, screened individuals, screen-positive individuals, and
Discussion
We have demonstrated a sustained reduction in oral cancer mortality following oral visual screening in high-risk individuals who chewed betel quid with tobacco or smoked or drank alcohol in various forms in the intervention arm after 15 years from the beginning of the study, although the reduction in cumulative mortality was lower than the 34% reduction reported following three rounds of screening after 9 years from the initiation of the study.10 The frequency of oral cancer cases and deaths
Conflict of interest
None declared.
Acknowledgements
The authors gratefully thank the Association for International Cancer Research (AICR), St. Andrews, UK, for their funding support to the study during 1996–2004 and the Imperial Cancer Research Fund for partial funding support during 1996–1998. We are indebted to the eligible subjects in this project and their families for their participation and cooperation. The assistance of the staff of the panchayath offices, mortality registers and the Trivandrum population-based cancer registry and medical
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