In a patient with pancreatic cancer who is heterozygous for the ATM c.875C>T (Pro292Leu) mutation with functional impairment in the gene product, is there any data or recommendation to support using SBRT vs. chemo-RT?

Ablative-dose radiation (100 Gy BED) is a curative option, with LC and OS similar to surgery. Everything else is palliative. 50 Gy in 5 fx with MRgRT is an evolving standard. The patient should be informed that this option is available at many centers. Otherwise, any palliative dose is fine.

With the ATM mutation, standard chemoradiation (50.4 Gy in 28 fx + capecitabine with IMRT) is preferred over low-dose palliative SBRT (e.g., 33 Gy in 5 fx) because it would better facilitate re-irradiation after a year or so. That may be offered with 39 Gy in 26 fx, BID.