How would you approach treatment failures with squamous cell carcinoma-keratoacanthoma-type lesions that did not respond to a standard SRT regimen after many sessions?  

I wouldn't do XRT for KA unless it's inoperable. There is WAY too much SRT being done for tumors that don't need it.

Most keratoacanthoma-type cutaneous squamous cell carcinomas that I see are bulky, and superficial radiotherapy (SRT) would not provide an adequate depth of radiation penetration to eliminate the carcinoma cells. If radiotherapy is being used for a bulky tumor like this, a higher energy form of more...

Surgery is an option if the patient is amenable.  If the intent is to avoid surgery, then the keratoacanthomas can be treated with intralesional chemotherapy (methotrexate or 5FU), a chemo wrap with 5FU and occlusive zinc oxide and compression dressing if on an extremity, or radiation therapy ...