Is there any role for post chemotherapy (R CHOP x 6) radiation therapy after a splenectomy for a stage IE diffuse large B-cell lymphoma involving only the spleen?

Quite an interesting presentation in terms of extranodal site and age. I would say no for consolidative RT here.

For Lugano PET CR after R-CHOPx6, the added benefit of ISRT in a young patient is low and counterbalanced by a real long term 2nd malignacy risk.

Other than bulky >7.5cm sites, 'special' sites for benefit of RT even after CR would seem to be skeletal sites (German post hoc in JCO from prospective trials Held et al), testicular DLBCL, and potentially craniofacial sites (though a post hoc from the German prospective trials experiene didn't show a particular benefit for RT and even allowing for unaccounted confounding it's possible benefit is nil or low in some of these cases).