D Nadayil’s research while affiliated with Indian Council of Medical Research and other places

A Population-Based Cancer Registry (PBCR) was set up in Sikkim (a state in the North Eastern India) in 2003. We examined incidence rates by ethnic groups from 2003-2008. Age-adjusted incidence rates (AARs) per 100,000 person-years were calculated by direct method using the world standard population, and analysed by ethnic group (Bhutia, Rai and other). There were a total of 1148 male and 1063 female cases of cancer between 2003 and 2008 on the Sikkim PBCR. The overall AARs were 89.4 and 99.4 per 100,000 person-years in males and females, respectively. Incidence rates were highest amongst the Bhutia group (AAR=172.4 and 147.4 per 100,000 person-years in males and females, respectively), and the largest difference in rates were observed for stomach cancers with AARs being 12.6 and 4.7 times higher in the Bhutia group compared with other ethnic groups in males and females, respectively. These observations call for further epidemiological investigations and the introduction of screening programmes.

It is an article published in CRAB, Vol 16(3), 2011.

Recently, NCRP (ICMR), Bangalore, has published a report on Time Trends in Cancer Incidence Rates. The report also provided projected numbers of cancer cases at the India country level for selected leadingsites. In the present paper, an attempt has been made to project cancer cases for India by sex, years and cancer groups. The incidence data generated by population-based cancer registries (PBCRs) at Bangalore, Barshi, Bhopal, Chennai, Delhi and Mumbai for the years 2001-2005 formed the sources of data. In addition, the latest incidence data of North Eastern Registries for the year 2005-06 were utilized. The crude incidence rate (CR) was considered suitable for assessing the future load of cancer cases in the country. The Linear Regression method (IARC 1991) was used to assess the time trend and the projection of rates for the periods 2010-2020. For whichever sites where trends were not found to be significant, their latest rates were taken into consideration and assumed to remain same for the period 2010-2020. The total cancer cases are likely to go up from 979,786 cases in the year 2010 to 1,148,757 cases in the year 2020. The tobacco-related cancers for males are estimated to go up from 190,244 in the year 2010 to 225,241 in the year 2020. Similarly, the female cases will go up from 75,289 in year 2010 to 93,563 in the year 2020. For the year 2010, the number of cancer cases related to digestive system, for both males and females, are estimated to be 107,030 and 86,606 respectively. For, head and neck cancers, the estimates are 122,643 and 53,148 cases, respectively. and for the lymphoid and hematopoietic system (LHS), for the year 2010, are 62,648 for males and 41,591 for females. Gynecological-related cancers are estimated to go up from 153,850 in 2010 to 182,602 in 2020. Among males and females, cancer of breast alone is expected to cross the figure of 100,000 by the year 2020.

The present paper examines the problem of small numbers (<20 cases) associated with many sites of cancers in Indian cancer registries. The cancer incidence data of 14 Population Based Cancer Registries for the periods of 2001-03 and 2004-05 were utilized for the analysis. Nine out of 14 registries had more than 50% of their sites being associated with small numbers while seven registries had 50% of their sites having as low as 5 cases. Sites associated with small numbers showed a lot of variation and significant differences in their incidence rates within two years duration which are not feasible. The percentage age distribution was also found to vary with different periods. The paper has effectively shown the effect of population size on incidence rates. For a registry of population size 300,000, the incidence rate of 6 can very well be unstable. There are many registries in the world with their population size less than 200,000. Even in the case of registries with high population (>or= 500,000) the practice is to report the cancer incidence by different ethnic groups with populations less than 200,000 and thereby introduce the problem of small numbers in reporting the incidences of various cancer sites. To overcome this problem, pooling of data over broad age groups or ten years age groups or 3 to 5 years periods is one immediate solution.