Radiation Therapy in Unresectable Gall Bladder Cancer

Inclusion Criteria: * Histologically proven (biopsy/cytology) adenocarcinoma of gall bladder. Gall bladder neck primaries with hilar block mimicking hilar cholangiocarcinoma will also be included. * Non metastatic at presentation as determined using cross sectional imaging and diagnostic laparoscopy if done as a part of standard work up recommended in the joint clinic. * Locally advanced disease with one or more of the following * Extensive liver infiltration not amenable for surgery but feasible for safe radiation delivery (Liver minus gross tumor volume at least 700cc) * Vascular involvement: encasement (\>180-degree angle) of one of the vessels: Hepatic artery, main portal vein, right or left portal vein * Obstructive jaundice with hilar involvement (type 2 non communicating block and higher blocks as per Bismuth-Corlette classification) * Stable disease or partial response (RECIST 1.1) after initial 3 months of Gemcitabine based chemotherapy * More than 18 years of age * Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2 fit for chemotherapy * Normal hematological and renal and hepatic functions allowing safe delivery of chemotherapy * Hematological- Hb\> 80 g/L, ANC ≥ 1.5 x 109/L, platelets ≥ 100 x 109/L. * Liver functions- bilirubin ≤ 2 x upper limit normal (ULN), AST/ALT ≤ 5 x ULN, alkaline phosphatase ≤ 6 x upper limit normal (ULN) S. albumin ≥ 30 g/L * Renal function- Creatinine ≤ 1.5 ULN, Creatinine clearance \>= 50 mL/min Exclusion Criteria: * Patients with distant metastasis (including nonregional lymph nodes metastasis) will be excluded. * Prior abdominal therapeutic radiation * Past or current history of other malignancies not curatively treated and without evidence of disease for more than 5 years, except for curatively treated basal cell carcinoma of the skin and in situ carcinoma of the cervix * Pregnancy/Lactating women