Early-stage pediatric classic Hodgkin lymphoma was treated with response-adapted involved-field radiotherapy (IFRT) instead of systemic treatment in the Children’s Oncology Group (COG) study AHOD0431. For a study, researchers sought to determine the effects of PET1 (positron emission tomography response after 1 cycle) on IFRT results and relapse patterns.
After AVPC, patients in AHOD0431 had their PET1 responses evaluated (doxorubicin, vincristine, prednisone, and cyclophosphamide). PET1 results for “slow early responders” (SERs) were positive PET1 (PET1+), whereas those for “rapid early responders” (RERs) were negative PET1 (PET1–). After 3 chemotherapy cycles, patients who showed a partial response on computed tomographic and functional imaging got a 21-Gy IFRT, but those who showed a complete response did not. The progression-free survival (PFS) of RERs and SERs receiving IFRT was assessed. Recurrence sites might have been original, fresh, or both. The terms “within the PET1+site” and “originally involved but outside the PET1+ site” were used to describe relapses involving initial locations.
The average follow-up time was 118 months. While SERs had a 10-year PFS rate of 80.9% with IFRT and 64.0% without IFRT (P=.03), RERs had a 10-year PFS rate of 96.6% with IFRT and 84.1% without IFRT (P=.10). All 14 relapses among the 90 RERs who did not get IFRT had an original site. Fourteen out of 16 relapses in the original site (9 PET1+ site alone) among 45 SERs who did not get IFRT. Five out of 10 relapses in the PET1+ location were among the 58 patients who had IFRT. RERs demonstrated positive outcomes after 3 cycles of AVPC alone. In contrast, SERs performed poorly with AVPC alone but better with 21-Gy IFRT. RT played a significant part in treating SERs.