Is it safe and appropriate to palliatively treat abdominal or thoracic tumors with concurrent chemotherapy when using fractions of 250-300 cGy?
I have routinely given 250cGy per fraction to total doses of 3500-3750cGy with single-agent radiosensitizing chemotherapy (usually 5-FU or capecitabine) without apparent significant toxicity, though we have not reviewed our data. So I generally consider this to be a safe regimen and consider it for relatively high-performance-status patients where a more durable palliative effect is desired, though I agree with @Dr. First Last that hard evidence for improved efficacy or durability is lacking.
I have personally not done this. At last ASTRO, there was presentation of a randomised international study for esophageal cancer comparing RT (30 to 35 Gy in 10-15 fractions) to chemoRT (same RT with cis and 5FU) for palliation showing no difference in symptom relief, QOL and survival but increased acute GI toxicities as expected.