When would you consider testicular RT prior to TBI for BMT?

In children with ALL treated with systemic chemotherapy alone (no transplant), the risk of testicular recurrence is ~15-20% (Br J Haematol 2003;123:396, Br J Haematol 1998;102:656). In adults with AML treated with standard chemotherapy, with or without transplant using a chemotherapy alone conditioning regimen, the risk of testicular recurrence is 0-3% (Cancer 1990;66:2095; Cancer 2004;101:845). Thus, there seems to be a predilection for ALL to recur in the testicle (another sanctuary site) but ...