How would you treat an older patient with B symptoms and biopsy consistent with grade 3 follicular lymphoma but noted to have a PET scan with SUV readings of > 20?

If an adequate biopsy was performed of the most active (high SUV) mass/node and results as follicular grade 3 A, then can treat as you would a follicular lymphoma with BR. I have seen high SUVs with follicular lymphoma. Mir et al., PMID 31961926

However, if it is follicular grade 3 B or has high Ki67 >30% then it should be treated like DLBCL. Based on the age of the patient if age >75, could use mini RCHOP.

Moreover, de novo transformed DLBCL does much better prognostically when compared to previously treated indolent lymphoma/CLL that has recently transformed to DLBCL.