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CONTEXT: Within India, the incidence of gallbladder cancer (GBC) is characterized by marked geographical variation; however, the reasons for these differences are unclear. AIMS: To evaluate the role of place of birth, length of residence, and effect of migration from high‑ to low‑risk region on GBC development. SETTINGS AND DESIGN: Population‑based cancer registries (PBCRs); case–control study. SUBJECTS AND METHODS: Data of PBCRs were used to demonstrate geographical variation in GBC incidence rates. A case–control study data examined the role of birth place, residence length, and effect of migration in etiology of GBC. STATISTICAL ANALYSIS: Rate ratios for different PBCRs were estimated using Chennai Cancer Registry as the reference population. Odds ratios (ORs) for developing GBC in a high‑risk region compared to a low‑risk region and associated 95% confidence interval (CI) were estimated through unconditional logistic regression models using case–control study. RESULTS: GBC shows marked variation in incidence with risk highest in Northeast regions and lowest in South India. OR of 4.82 (95% CI: 3.87–5.99) was observed for developing GBC for individuals born in a high‑risk region compared to those born in a low‑risk region after adjusting for confounders. A dose–response relationship with increased risk with increased length of residence in a high‑risk region was observed (OR lifetime 5.58 [95% CI: 4.42–7.05]; Ptrend ≤ 0.001). The risk persisted even if study participant migrated from high‑ to low‑risk region (OR = 1.36; 95% CI: 1.02–1.82). CONCLUSIONS: The present study signifies the importance of place of birth, length of stay, and effect of migration from high‑ to low‑risk region in the development of GBC. The data indicate role of environmental and genetic factors in etiology of disease.
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Background. This paper investigates cancer trends in Chennai and predicts the future cancer burden in Chennai and Tamil Nadu state, India, using data on 89 357 incident cancers from the Chennai registry during 1982–2006, published incidence rates from the Dindigul Ambilikkai Cancer Registry during 2003–06 and population statistics during 1982–2016. Methods. Age-specific incidence rates were modelled as a function of age, period and birth cohort using the NORDPRED software to predict future cancer incidence rates and numbers of cancer cases for the period 2007–11 and 2012–16 in Chennai. Predictions for Tamil Nadu state were computed using a weighted average of the predicted incidence rates of the Chennai registry and current rates in Dindigul district. Results. In Chennai, the total cancer burden is predicted to increase by 32% by 2012–16 compared with 2002–06, with 19% due to changes in cancer risk and a further 13% due to the impact of demographic changes. The incidence of cervical cancer is projected to drop by 46% in 2015 compared with current levels, while a 100% increase in future thyroid cancer incidence is predicted. Among men, a 21% decline in the incidence of oesophageal cancer by 2016 contrasts with the 42% predicted increase in prostate cancer. The annual cancer burden predicted for 2012–16 is 6100 for Chennai, translating to 55 000 new cases per year statewide (in Tamil Nadu). Breast cancer would dislodge cervical cancer as the top-ranking cancer in the state, while lung, stomach and large bowel cancers would surpass cervical cancer in ranking in Chennai by 2016. Conclusion. In order to tackle the predicted increases in cancer burden in Tamil Nadu, concerted efforts are required to assess and plan the infrastructure for cancer control and care, and ensure sufficient allocation of resources.