ABSTRACT
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.