FDG-PET Guided Consolidative Radiotherapy in Patients with Advanced Stage Hodgkin Lymphoma with Residual Abnormalities on Post Chemotherapy CT Scan.

Abstract Consolidative radiotherapy (RT) is often administered following chemotherapy for advanced stage Hodgkin lymphoma (HL) with bulky disease at diagnosis or for residual abnormalities on post-chemotherapy CT imaging. It is unknown whether RT is necessary for such patients if the residual mass is FDG-PET-negative (PET-neg) following chemotherapy (CHT). Further, it has been previously shown that a post-therapy PET-positive (PET-pos) scan is highly predictive of future relapse; however, it is unclear whether consolidative RT can be used to salvage these cases. Methods Since July 2005, adult (> 16 y) patients in British Columbia (BC) with advanced stage HL (stage III /IV and/or the presence B symptoms and/or bulky disease (> 10cm)) have been treated with 6 cycles with ABVD followed by a PET scan for further treatment planning if residual abnormalities ≥2 cm were observed on CT imaging. Prior to this, post-treatment PET scans were obtained in some individuals by self-pay. If the PET scan was positive, RT was administered if feasible, otherwise, patients were observed. There were 68 eligible patients, including 7 self-pay patients, that were identified in the BC Lymphoid Cancer Database. 16 patients were excluded (PET not performed (5); palliative tx or refusal (3); composite lymphoma (1); progressive disease during CHT or at the time of PET scan (4); HIV + (1); PET mid-therapy (1); death due to unrelated cause prior to PET scan (n=1).), leaving a total of 52 patients who had a PET scan post-chemotherapy for a residual mass and who had adequate follow-up (median 19 m, 10–59 m). Patient characteristics include: M:F 1.1:1, Median age 29 (17–81); 55% stage II, 46% stage III/IV 44%; 49% bulky disease; 69% B symptoms; IPFP Prognostic score 0 8%; 1 39%; 2 26%; >3 26%. Results In total, 40/52 (77%) were PET-neg and 12/52 (23%) were PET-pos (SUV mean 4.4, 2.2–6.8). PET-pos patients had an inferior 2 y PFS compared to PET-neg patients (26% vs 91%, p=.001). In the PET-pos group, 10/12 received the planned RT and 5 have relapsed. In the PET-neg group, there was no difference in the 2 y PFS in patients with bulky (n=17) vs non-bulky disease (n=20) (86% vs 94%, p=.35). Conclusions Advanced stage HL patients who achieve a post-CHT PET-neg status are at a low risk of relapse and do not require additional consolidative RT thus avoiding potential long-term side effects. The majority of patients with bulky disease who have a PET-neg scan following CHT also remain in remission, however, longer follow-up is still needed. Although some patients with a positive PET-scan may be salvaged by consolidative RT, a high proportion ultimately relapse. Figure Figure Figure Figure

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