P094: Long-term outcomes of bulky classic Hodgkin lymphoma managed with a PET-adapted approach demonstrate excellent outcomes in PET-negative cases

Figure 1: Freedom from treatment failure in bulky advanced stage cHL pts by post-ABVD chemotherapy PET scan (A) and Deauville score (B). Overall survival in bulky advanced stage cHL pts by post-ABVD chemotherapy PET scan (C) and Deauville score (D). Background: With concerns of long-term complications due to radiotherapy (RT), recent studies have evaluated ABVD alone in patients (pts) with bulky classic Hodgkin lymphoma (cHL) with an end of treatment (EOT) PET-negative (neg) scan. However, variable definitions of bulky disease are used, and long-term follow-up remains limited. Since 2005, advanced stage (stage 2B/3/4, bulky (≥10cm) stage 1/2) cHL pts in British Columbia (BC) have been managed with PET-guided consolidative RT. Methods: The BC Cancer Lymphoid Cancer Database was screened to identify all pts >16 years (y) with bulky (≥10cm) cHL treated with 6 cycles of ABVD chemotherapy. Pts with progressive disease on interim scan or at EOT were excluded. Pts with an EOT PET-positive (pos) scan received consolidative RT. PET scans assessed by the IHP criteria were re-reviewed to assign a Deauville (D) score (PET-neg=D1-3, DX; PET-pos=D4-5). Freedom from treatment failure (FFTF) was measured from diagnosis to relapse/ progression of HL, or death due to HL or treatment toxicity. Results: From 2005–2020, 215 patients (115M, 100F) were identified. Median age was 29 years (y) (17-72y), median mass size was 11cm (10-21cm), 94% had bulky mediastinal mass, and 2%, 65%, 8%, and 25% had stage 1, 2, 3 and 4 disease, respectively. At EOT, 176 (82%) had a PET-neg scan (none received RT), and 39 (18%) had a PET-pos scan (34 received RT to residual mass; 5 were observed: false pos n=3, refused n=1, not radioencompassable n=1). With a median follow-up of 6.75y (0.8–15.75y), pts with a PET-neg scan had 5y FFTF of 94% (stage 1/2–94%, stage 3/4–96%) vs 65% with a PET-pos scan (p<0.001). Overall survival (OS) was similar in PET-neg and pos (97% vs 90%, p=0.191). The 5y FFTF was similar by D score in PET-neg cases (DX-100%; D1-90.5%; D2-97%; D3-100%, p=0.213) but inferior in D4 (58%) and D5 (42%) (p<0.001). The 5y OS was similar between PET-neg and D4 (DX-93%, D1-97%, D2-100%, D3-100%, D4-94%), but inferior in D5 cases, with 5y OS 60% (p=0.015). There were 23 relapses: 10 PET-neg (7 in what would have been the RT field (residual mass), 3 inside and outside field); 13 PET-pos (5 in field, 8 included sites outside the RT field). Conclusion: With a median follow-up of almost 7y, bulky cHL with an EOT PET-neg scan have excellent outcomes, regardless of initial stage. A large proportion of D4 PET-pos cases are salvaged with RT and maintain an excellent OS. Both FFTF and OS are inferior in those with an EOT D5 scan.