Would you include the tract in your treatment field in a patient with squamous cell carcinoma of the anal canal presenting with an ano-cutaneous fistula?

I don't know that there is an evidence-informed answer, but I just had this in a patient recently. We had him get a diverting colostomy prior to starting CRT, then treated him with standard CRT with 5FU/MMC. I included the fistula tract in an intermediate dose, but with a margin on the boost to tumo...