Household Cooking Fuel and Gallbladder Cancer Risk: A Multi-Centre Case Control Study in India

BACKGROUND-AIM: Evidence from India, a country with certain unique cancer patterns (e.g., high incidence of gallbladder cancers (GBC)) and distinct risk exposures such as ‘biomass burning’ for cooking, may offer insights into the role of indoor air pollution in cancer etiology. We evaluated the association between household cooking fuel and GBC risk in a case-control study conducted among long-term residents (i.e., at least 10-years) of North-East and East Indian regions of Assam and Bihar, with high-risk for GBC and intense ‘biomass burning’. We explored if these associations were accounted-for by healthy diet, fire-vents and ‘daily exposure duration’. METHODS: We recruited men and women aged 30-69 years from hospitals between 2019 and 2021, with newly diagnosed, biopsy-confirmed GBC (N=214) and unrelated controls frequency-matched by age, sex and region (N=166). Information about cooking fuel, lifestyle, personal and family history, socio-demographics and physical measurements was collected. We tested associations using multivariable logistic regression analyses adjusted-for confounders. RESULTS: All participants (73.4% women) were categorised based on lifetime use and duration of predominant cooking fuel. Group-1: LPG for ≥20 years (13.5%); Group-2: LPG for 1-19 years with no concurrent biomass (15.6%); Group-3: LPG 1-19 years with concurrent biomass (12.9%); and Group-4: Biomass for ≥20 years (57.9%). Compared to group-1, GBC risk was higher in group-3 [OR=2.69, 95%CI (1.07-6.72)] and group-4 [OR=2.44, 95%CI (1.07-5.56)] but not in group-2 (p-trend=0.020). The associations strengthened in women-only analysis; and attenuated with high daily consumption of fruits-vegetables, but did not alter with fire-vents or ‘daily exposure duration’. CONCLUSIONS: With cautious interpretation for residual confounding, sample-size limitations and possible errors in exposure, the findings identify ‘biomass burning’ as a modifiable risk factor for GBC in high-risk regions. It further highlights ‘clean fuel replacement’ can mitigate the risk; and a healthy diet can partially reduce the risk. KEY-WORDS: Gallbladder cancer, biomass, India