Positive Positron Emission Tomography (PET) Scan in Non-Hodgkin Lymphoma Pre-Transplant Had No Impact On Relapse and Survival After Allogenenic Transplantation

Abstract 1999

Allogeneic donor hematopoetic stem cell transplantation (HCT) is increasingly used for patients with non-Hodgkin lymphoma (NHL). Positron emission tomography (PET) has become a standard for lymphoma evaluation and a valuable prognostic tool to risk-stratify treatment and time of the autologous HCT. Role of PET imaging in allogeneic HCT setting is controversial.

We sought to investigate the value of PET status pre-transplantation and at day 100 post donor HCT as an indicator predictive of relapse and survival post allograft.

Seventy-three patients (median age 50 years [range 2–69 years]) with NHL received allogeneic HCT at University of Minnesota from 2004–2010 and had PET imaging within 4 weeks pre-transplant. All PET and CT images were reviewed centrally by nuclear medicine radiologist. Follicular lymphoma (n=26) was more common than large cell, mantle cell lymphoma and others. PET scan pre-transplant was positive in 44 patients (PET+ group 57% vs PET- group 43%). Two thirds of PET+ group were in partial remission (PR), 7% CR and 16% were chemo-refractory prior to transplant compared to 25% in PR, 68% in CR and 7% refractory in PET+ cohort (p<0.01). Forty percent had PET-avid extra-nodal involvement. In both PET positive and negative groups the two thirds received reduced intensity conditioning and related donor (52% and 51%) or umbilical cord blood grafts (55% and 41%, respectively).

5-years disease-free survival (DFS) and overall survival (OS) of the cohort was 51% (95%CI 35– 64%) and 60% (95%CI 44–73%). DFS and OS of PET+ group was similar to PET- group (DFS: 50% vs 52%, p=0.31; OS: 63% vs 56%, p=0.63). In univariate analysis, the lymphoma subtype, disease status at transplant, extranodal disease, elevated LDH, high B2 macroglobulin or marrow involvement at the time of transplant had no impact on survival or relapse rate.

At median follow-up of 3.33 years (range 1.00–6.74) the cumulative 2 year relapse rate was 17%; similar in PET+ and PET- groups (19% [95% CI 7– 31%] vs 15% [95% CI 1– 28%]; p=0.48). Transplant mortality at 1-year was low for entire cohort (11% [95% CI 3–18%]) and particularly low in follicular lymphoma (4% [95%CI 0–10%]) compared to DL/MCL (10% [95%CI 0–21%]) and other NHL (25% [95%CI 4–46%]; p=0.51). PET status (pos vs neg) had no impact on grade III-IV acute GVHD and chronic GVHD.

Fifty-four patients with available surveillance PET evaluation at day 100 post-transplant. The 1-year relapse rate and 5 yr DFS was significantly improved for those patient who were PET-negative (day 100 PET- vs PET+ group: relapse 9% vs 42%; p<0.01; DFS 57% vs 25%, p<0.01 and OS 68% vs 59%, p=0.63).

In conclusion, pre-allo HCT PET scan for NHL does not predict transplant outcomes, however negative PET scan 100 days post-allo SCT is a valuable tool predictive of superior transplant DFS. Future studies evaluating role of PET in patients with specific lymphoma subsets and development of novel peri-transplant or post-transplant interventions for patients at high relapse risk are warranted.