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.