What dose and fractionation would you deliver to the sole of the foot in a patient with multifocal cutaneous DLBCL that is resistant to systemic therapy?

We need some more information here. Does multifocal mean the patient has multiple skin lesions? The diagnosis of cutaneous DLBCL is also somewhat ambiguous. Is this cutaneous DLBCL leg type, a specific entity in the WHO pathology classification, or perhaps the older WHO classification is being used where cutaneous DLBCL was a part of what is now termed primary cutaneous follicle center lymphoma? The latter has a much better prognosis than leg-type DLBCL. Finally, is one foot or both currently in...

Is this perhaps a leg-type DLBCL?

Leg-type DLBCLs tend to show an aggressive pattern of growth and recurrence.

The primary question is if you think there's still a chance to cure this patient. Even if resistance to systemic therapy is observed, there may still be options, including stem-cell transplant after HD chemotherapy and/or CAR-T-cell therapy and/or novel antibodies.

If so, I would treat this lymphoma aggressively, for instance with 25 x 2 Gy, opting for durable local control. There is a...