It starts local.
Top Line: Oh, HD16, that classic lymphoma trial that yet again failed to demonstrate equipoise between arms that did and did not receive radiation.
The Study: As a reminder, HD16 was the most aggressive de-escalation trial yet. Patients with favorable Hodgkin lymphoma received a restaging PET after only 2 cycles of ABVD. Just over half of patients achieved a negative (read: Deauville 1-2) PET at this time and were randomized to the standard 20 Gy involved field radiation versus observation with a resulting discrepancy in progression-free survival at 5 years of 93% versus 86%, respectively. Here’s an in-depth look at patterns of failure where fields were created for all 628 PET-negative patients. At a median follow-up of nearly 4 years, there were 15 failures (7 in-feld) in the radiation arm and 29 (26 in the potential field) in the observation arm. So radiation decreases recurrences by half and, unsurprisingly, it is due to a stark difference in local recurrences. While it may seem straight-forward enough, similar findings across a number of studies have been open to interpretation. But, at what toxicity expense does this advantage come? We know the short-term side effects of 20Gy/10 are almost negligible: grade 3 toxicities occurred in a total of 3% of patients. We’ve yet to see how many (or how few) late toxicities will occur after 20Gy of, most importantly, involved-site radiation reflective of modern techniques.
TBL: Consolidative 20 Gy involved-field radiation when a negative PET is achieved after ABVDx2 significantly decreases recurrences, predominantly local, with very few acute toxicities. | Baues, Int J Radiat Oncol Biol Phys 2021