For T2N0 anal squamous cell carcinoma, RTOG 0529 used 50.4/42Gy in 28 fractions. However, for nodal disease >3cm, 54Gy in 30 fractions is used (and similar dosing in the UK trial).
What is the rationale for treating nodes >3cm to a higher dose but not treat primaries >3cm (without nodal involvement) to the same higher dose?
If you treat primary T2 tumors greater than 3cm to 54 Gy (or some dose greater than 50.4 Gy), what dose coverage do you then use for nodes?
As usual, @Christopher H. Crane nails it.