Pilot Evaluation of the Value of FDG PET-CT after One and Two Cycles of Salvage Chemotherapy in Relapsed/Refractory Aggressive Non-Hodgkin’s and Hodgkin’s Lymphoma
Authors: Hodson Andrew , Barwick Tara , Marson Brigitta , Maisey Nick , Raj Kavita , Mikhaeel George , Kazmi Majid A. , Nunan Tom , O’Doherty Michael , Fields Paul 
Published: April 2020

Introduction The currently accepted standard of care for patients with relapse/refractory NHL is dose escalation and consolidation with Stem Cell Transplantation. The ability to predict those patients who may benefit or not from this approach would be beneficial. Whole-body Positron Emission Tomography using 18F-fluorodeoxyglucose (FDG) is now recognised to have predictive ability in those patients at high risk of relapse and shortened overall survival in De novo High grade lymphoma. In the salvage setting it is unknown whether the appearance of PET scan after 1 cycle of salvage treatment may predict similarly for outcome post transplant and whether early scanning is indicated before cycle 2 salvage chemotherapy.

Aim: The aim of this study is to assess whether the PET-CT after one cycle or two cycles of dose escalation was predictive of outcome in patients with relapse/refractory NHL.

Methods: We collected the data prospectively of all patients with relapsed or refractory aggressive NHL or HD treated in our institution over a 2 year period who were considered suitable for salvage therapy followed by Stem Cell Transplantation. We identified 14 male and 10 female patients with a mean age of 44 years (range 24–66). 12 patients had disease refractory to first line treatment and 12 patients had relapsed disease with a median interval from completion of treatment to relapse of 20 months (range 2–60). All patients were initially treated with DHAP as salvage therapy.22/24 patients proceeded to a stem cell transplant. 16/22 had an autologous transplant conditioned with BEAM and 6/22 had allogeneic transplants.FDG PET- CT scans were performed (all positive) prior to salvage chemotherapy and then assessed after 1 cycle of salvage chemotherapy and then after the second cycle using a 5 point visual scoring system as follows:

CMR - no uptake at disease sites, MRU1 – visually uptake below level of mediastinum, MRU2 – visually between mediastinum and liver Stable/persistent metabolically active disease and Progressive disease (either new lesions or increased uptake in the same sites.

Results FDG-PET Data was collected from 24 patients (14 male and 10 female) and read by two independent observers. The patients had the distribution shown in table:

Visual response criteria Appearance PET 1 : Patient Numbers Appearance PET 2 : Patient Numbers CMR 1 6 MRU1 0 2 MRU2 1 3 Stable/persistent 16 5 Progressive 6 8

The median progression free survival of the patients with progression after one cycle of chemotherapy was 1.5 months with 3/6 deaths. Progression on PET1 was seen only in refractory cases pre salvage and was associated with a significant risk of relapse (p=0.014). The median progression free survival of the patients with stable disease after one cycle was 9.5 months. After two cycles of chemotherapy the median progression free survival of patients with CMR/MRU1/MRU2 was 9 months, compared with stable disease of 8 months and progressive disease 6 months.

Conclusions: Patients with progressive disease on PET after one cycle of chemotherapy have a poor outcome with 50% early deaths and would be candidates for targeted/experimental therapies. Longer follow up will be required to assess the significance of stable or persistent disease on PET after one cycle and two cycles of salvage chemotherapy.