Descriptive report on pattern of variation in cancer cases within selected ethnic groups in Kamrup Urban District of Assam, 2009-2011.

BACKGROUND
The global burden of cancer is continuously increasing. According to recent report of the National Cancer Registry Programme (NCRP) on time trends it is estimated that future burden of cancer cases for India in 2020 will be 1,320,928. It is well known that knowledge of the incidence of cancer is a fundamental requirement of rational planning and monitoring of cancer control programs. It would help health planners to formulate public health policy if relevant ethnic groups were considered. North East-India alone contains over 160 Scheduled Tribes and 400 other sub-tribal communities and groups, whose cancer incidence rates are high compared to mainland India. As since no previous study was done focusing on ethnicity, the present investigation was performed.


MATERIALS AND METHODS
In this paper PBCR-Guwahati data on all cancer registrations from January 2009 to December 2011 for residents of the Kamrup Urban District, comprising an area of 261.8 sq. km with a total population of 900,518, including individual records with information on sex, age, ethnicity and cancer site are provided. Descriptive statistics including age adjusted rates (AARs) were taken as provided by NCRP. For comparison of proportional incidence ratios (PIR) the Student's t test was used, with p<0.05 considered as statistically significant.


RESULTS AND CONCLUSIONS
Differences in leading sites of Kamrup Urban District since from the beginning of the PBCR-Guwahati were revealed among different ethnic groups by this study. The results should help policy makers to formulate different strategies to control the level of burden as well as for treatment planning. This study also suggests that age is an important factor of cancer among different ethnic populations as well as for overall population of Kamrup District of Assam.


Introduction
Global burden of Cancer incidence is continuously increasing. As per the GLOBOCAN 2008 estimates, about 12.7 million cancer cases and 7.6 million cancer deaths are estimated to have occurred in 2008 (Jemal et al., 2011). According to recent report of National Cancer Registry Programme (NCRP, 2013) on time trends it is estimated that future burden of cancer cases for India in 2020 will be 13,20,928 (male 6,22,203, female 6,98,725). Knowledge of the incidence of cancer is a fundamental requirement of rational planning and monitoring of cancer control programs (Yang and Parkin et al., 2005). Globally cancer incidence pattern is varied widely and studies in migrant populations may help explain the relative contribution of genetic and environmental factors to these differences and aid our understanding of cancer aetiology (Parkin et al., 2004). Demographic, ecological, environmental, cultural, ethnicity and genetic variables all contribute to the heterogeneity of cancer incidence (Yong-Chuan Wang et al., 2012).
India is a hub of diverse ethnic residential population and disparities in pattern of cancer incidence rate is observed among different regions and among ethnic groups. North East-India alone comprise of over 160 Scheduled Tribes and over 400 other sub-tribal communities and groups (Taid et al., 2014), where cancer incidence rate is severely high compared to mainland India and also variation within ethnic residential population was observed, So it is necessary to observe the pattern among ethnic groups by different ways. However so far only a limited studies were done in India to observe the incidence pattern on ethnic populations.
Studies by (Cho et al., 1996;Nirmala et al., 2012) have suggested that ethnicity plays a significant role towards the differences in cancer rates among individual groups.
A study was carried out in UK to access the variation in incidence rate and rate ratio among British Indian and British Whites in Leicester (Ali et al., 2010). Similarly variation in incidence rate of cancer among ethnic groups was studied in Sikkim, India (Verma et al., 2012). However no previous study was conducted ethnicity wises for this region of India.
The Northeastern region is distinguished by a preponderance of the Tibeto Burman languages, and the population here is thought to comprise migrating peoples from East and Southeast Asia region (Kataki et al., 2011). Which may be a factor of versatile ethnic population in NE-India and diversity among cancer incident cases was observed. Therefore it is necessary to compare cancer incident rates among ethnic groups. In this paper an attempt was initiated to report the incidence and patterns of cancer including the ethnic variation observed in Kamrup Urban District during the last 3 years (2009-2011) of registry operation. However no previous study was done considering ethnicity for this part of the world.

Materials and Methods
The PBCR-Guwahati covers the Kamrup urban district comprising an area of 261.8 sq. km. The population as per the 2001 Census is 490 772 men and 409 746 women (total population 900 518) . In this paper PBCR-Guwahati provides data on all cancer registrations from January 2009 to December 2011 for residents of the Kamrup Urban District, including individual records with information on sex, age, ethnicity and cancer site.
The major ethnic groups were selected for the study while rest minors were clustered as others category. The site of the cancer was coded according to the International Classifications of Diseases, revision 10.

Statistical analysis
A descriptive study was conducted to figure out leading sites for major ethnic groups as well as overall population. Age Adjusted Rate (AAR) was taken as calculated by NCRP for their report 2009(NCRP, 2013 and provided to PBCR-GHY. Proportional Incidence Ratio (PIR) for leading sites of cancer for different ethnic groups (using all cases of Kamrup Urban district as Reference, cancer site wise), which is complete for sex and race. Proportional incidence ratios (PIR) were calculated by using the observed:expected ratio, where the observed number was the number of site-specific cancer cases in the worker cohort, and the expected number was calculated by multiplying the age-and period-specific number of all cancer cases in this worker cohort by the proportion of site-specific cancer relative to all cancers in the general population (Chapter 11. Statistical methods for registries, P. Boyle and D. M. Parkin-IARC, France). Student's t test was used to test difference between mean ages, p<0.05 considered as statistically significant at 95% Confidence interval (CI).

Results
A total of 4416 cancer cases was reported during the period of study 2009-2011, out of the total cases 2508 (56.79%) were males and 1908 (43.21%) were females, the male to female ratio was 1.31: 1.00. Almost equal male: female ratio was observed among koiborta community with 1.09:1.00. The average annual AAR per 100 000 population for all sites was 185.2 in males and 156.3 in females. Oesophagus was the most common cancer site in males which comprised 14.47% of all cancer cases and 10.42 % in Females, followed by Hypo pharynx (8.25%) in Male. In Female Breast cancer was the most common one comprised a total of 16.98%, followed by Oesophagus (10.43%). According to NCRP Report 2013 among the residents of Kamrup Urban region, Oesophagus (AAR Male=27.0, Female=18.3) was the top leading common cancer site for both males and females followed by Lung   For the study period a total of 242 number of cancer cases were reported from Tai Ahom community, 57.0% (n=138) were males and 43.0% (n=104) were females. Mean Age±SEM was 58.55±1.481, 55.91±1.253 respectively for Males and Females with a significant value of p=0.0193. In Tai Ahom population the common cancers among male were Oesophagus comprised with a total of 10.14% (i.e. 14 out of 138 cases) followed by Prostate 8.70% (12/138), Lung 7.25% (10/138) and Stomach 6.52% (9/138). In female Breast cancer alone accounts one third of the total cases i.e. 30.77% (32 out of 104 cases) of total female cases followed by Oesophagus 7.69% (8/104), Gallbladder 5.76% (6/104) and carcinoma of Ovary 5.76% (6/104). In males carcinoma of Colon was with a rise incidence of about PIR 2.18 (95%CI: 1.381, 2.981), rectum 1.957 (95%CI: 1.216, 2.698). Carcinoma of Tonsil was observed to be a significant high with PIR 2.202 (95%CI: 1.070, 3.333) followed by Corpus Uteri 1.498 (95%CI: 0.517, 2.478) in females.

Discussion
The study was conducted with a perception to formulate public health policy by considering relevant ethnic groups with incident pattern among cancer cases. Which will be useful for healthcare planners to formulate and decide how to manage and utilize the available resources as well as this study also provide knowledge, risk of different cancer incident pattern among communities. The overall Age Adjusted Incidence Rate (AAR) for the study period in males was observed as 185.6 and 156.2 in females. The most common cancer was Oesophagus as well as Lung in male, while Breast and Oesophagus was in female. A significant factor observed in the study that only 6.26% (n=157/2508) cases of all cases were from the age group 0-34, while remaining 93.74% (n=2351/2508) cases were from 35 and above age group. While in female it is observed as 9.33% cases from the previous age group while 90.67% cases from later age group. This also proves that age is an important risk factor for occurrences of cancer.
Among Ahom females observed that only 5% are form 0-34 age group while remaining 95% from other group, which is less than the overall Kamrup urban, while Boro, Kalita community it observed 11% and 10% from Koiborta community from previous age group and rest from later age group. So a difference in age was present in the communities to the total population of Kamrup Urban District. Among Kalita male found that PIR was high for carcinoma of rectum and Brain and Nervous where others were moderately less or above. While in female also found Rectum a little high. In Koiborta ethnic group, PIR in Hypopharynx female was found significantly high with 1.93, while Bladder also found significantly high among males. In Ahom found that Tonsil was with high proportional incidence ration among females while Colon, rectum and carcinoma of Pancreas was with high incidence.
In males Oesophagus was high in all ethnic groups ranging from 10 to 17 percent cases to the total cases of the respective ethnic group, observed 16.75% cases of total cases among Kalitas. Most of the cancer studies in North East India and Assam suggested that ethnic food like kolakhar, a locally made unique alkaline food additive, papad, very hot spicy food, chillies, chewing of betel nut with or without tobacco, high intake of alcohol, smoke and smokeless tobaccos are important risk factors (Rai et al., 2014;Sharma et al., 2014) among ethnic groups.
Hypopharynx was the another common site among the ethnic groups of Kamrup Urban District of Assam, studies in Kamrup Urban District has reflected that high consumption of tobacco and dietry habits of among the residents of these region was to be a factor for high incidence of hypopharyengal carcinoma . In males of Bodo and Koiborta ethnic group Hypopharynx was 11.92% and 11.70% to total cases. As feminine cancers are common among females of kamrup urban district but observed that among koiborta community the top leading site is Gallbladder, followed by Oesophagus.