Prognostic Value of Positron Emission Tomography (PET) Scan in Patients with Relapsed Hodgkin Lymphoma or Aggressive Non-Hodgkin Lymphoma Receiving Salvage Chemotherapy Followed by Reduced-Intensity Allogeneic Stem Cell Transplantation.

Positron emission tomography (PET) scan using 18-fluorodeoxyglucose [¹⁸F-FDG] has a prognostic value in patients (pts) with Hodgkin Lymphoma (HL) or aggressive Non-Hodgkin lymphoma (NHL) receiving chemotherapy. Chemosensitive disease is a critical prognostic factor for the success of both autologous and allogeneic stem cell transplantation (allo-SCT). We have recently shown a lower risk of death or progression for pts in CR versus those in PR before reduced-intensity conditioning (RIC) allo-SCT (Corradini P, Leukemia 2007). Thus, to better assess the value of pre-transplant disease response, we retrospectively assessed the prognostic role of PET scan before allotransplant. Between 2000 and 2007, 64 consecutive patients with a histologically proven diagnosis of aggressive NHL [n=30: diffuse large B cell lymphoma (n=18), peripheral T-cell lymphomas (n=11), Burkitt lymphoma (n=1)] or HL [n=34], responding to salvage therapy, were evaluated with a PET scan before and after allo-SCT. PET scans were performed at 3 different Nuclear Medicine Units. Presence (PET-positive) or absence (PET-negative) of abnormal ¹⁸F-FDG uptake was correlated to progression-free survival (PFS) and overall survival (OS) curves. Patients’ median age was 37 years (range, 17–65 years). Thirty-three pts (52%) were allografted from a HLA-identical sibling donor, 14 from a haploidentical donor and 17 from an unrelated donor. Pts had relapsed disease: 52 pts (81%) had failed autologous SCT, the median number of prior chemotherapy regimens was 3 (range, 1–6). All pts received a RIC regimen followed by allo-SCT. PET scans were performed at a median of 30 days prior to allograft (range, 3–90 days): 34 out of 64 pts showed an abnormal ¹⁸F-FDG uptake [NHL (n=16), HL (n=18)] whereas 30 were completely negative [NHL (n=14), HL (n=16)]. Patients with PET-positive or PET-negative scans were balanced in terms of diagnosis, previous treatments, and type of donor. At a median follow-up of 24 months (range, 6–86 months), 41 pts are alive and 23 died [toxicity n=10 (n= 5 NHL, n=5 HL), disease n=13 (n=8 NHL, n=5 HL)]. Overall, the estimated 3-year PFS in pts with negative or positive PET scans were 64% (95% CI, 42%–86%) versus 28% (95% CI, 8%–48%), respectively (p<0.005). A statistically significant higher cumulative risk of relapse was observed in pts with a positive PET scan before allografting as compared to the PET negatives (53% versus 21%, p< 0.022). The estimated 3-year OS in pts with negative or positive PET scans were 69% (95% CI; 51%–87%) versus 44% (95% CI;23%-65%), respectively (p=0.05). For NHL pts, the estimated 3-year PFS was 59% for PET-negative as compared to 38% for PET-positive (p<0.04). For HL pts, the estimated 3-year PFS was 70% for PET-negative as compared to 23% for PET-positive (p<0.05). PET scan has a clinical relevance before allo-SCT. Pts with a positive PET scan have a worse outcome, and should receive experimental therapies to target chemoresistant tumor cells.