Predictors of Toxicity in a Randomized Study of Consolidation Chemoradiation Versus Observation After First Line...

Gall bladder cancers (GBC) usually presents in advanced stage. First-line chemotherapy (CT) is the standard of care, and there is no other option for responders than to wait for disease progression. We conducted a randomized study of consolidation chemoradiation (CTRT) versus observation in responders to first line CT (NCT05493956), which showed an improvement in overall survival by 6 months and therefore is practice changing. We are reporting the toxicity and factors predicting toxicity due to CTRT so that it informs appropriate patient selection.

Responders to first line CT (partial response, stable disease) were randomized to CTRT versus observation after 4 cycles. CTRT was delivered by 3D conformal radiotherapy (along-with concurrent capecitabine at 1250 mg/m²) to a dose of 45 Gy in 25 fractions to GBC and lymphatics followed by a boost of 9 Gy in 5 fractions to the GBC. Toxicities documented during CTRT were recorded using the Radiation Therapy Oncology Group criteria. Dose volume data were correlated with the radiation induced side effects.

Among 135 patients enrolled both arms are well balanced demographically, and 58% patients had T4 tumors, 42% had N2 and 15% had paraaortic lymph node, and 27% underwent upfront stenting. Grade 3 adverse events, such as anemia, dyspepsia, hepatotoxicity (Child Pugh B), and gastrointestinal bleed due to CTRT was observed in 9%, 1.5%, 13%, and 5.8%, respectively. Age >58 years (P = .02), planning target volume (PTV) 1 volume (>919 cc, P = .02), PTV2 volume (>380 cc, P = .01), mean liver dose (>28 Gy, P = .07), and liver V40 (>50%, P = .02) predicted radiation-induced liver disease. A receiver operating curve analysis revealed a cut-off value of PTV1 volume of 800 cc (sensitivity and specificity of 75% and 54%) and PTV2 volume of 300 cc (sensitivity and specificity of 81% and 65%) for prediction of hepatotoxicity. Duodenum V45 >45% (P = .02) predicted grade 3 anemia. Numerically high V15 duodenum (98%, P = .11), large PTV2 volume >484 cc (P = .06) and prior stenting had predilection for gastrointestinal bleed.

Consolidation CTRT is tolerable in those with PTV1 volume less than 800 cc.