Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is an uncommon subtype of Hodgkin lymphoma. Data are limited regarding FDG-PET-CT scan (PET-CT) use in NLPHL. We are reporting our experience with PET-CT utility in staging and response assessment of patients with NLPHL and compare this with conventional contrast enhanced CT scan (CT).
Using prospectively collected lymphoma data base and Hospital Tumor Registry, all pediatrics and adult patients with NLPHL seen at our institution from 2003 to 2016 were captured. Patients who underwent pre-treatment CT and PET-CT, during the course of chemotherapy, at the end of planned treatment or for relapsed /refractory disease prior to have new treatment were included in this study. PET-CT response was assessed using both visual assessment method (mediastinal blood pool activity was used as a reference for normal uptake) and Deauville criteria. Both methods were compared (5-point Deauville Criteria; a score of 1-3 as negative-disease and 4-5 as positive-disease).
We identified 67 NLPHL who met the inclusion criteria. Median age at diagnosis was 27 years (6-56 years) and median follow-up was 30.7 months (5.95-157.4) with a male: female ratio of 4.1:1. Median SUV-max was 8.8 (2.0 to 18.8). In 30 pediatrics patients (age <21 years), median SUV-max was 8.7 (4.0 to 18.8).
In the per-scan analysis, the sensitivity, specificity and positive predictive value of pre-treatment PET-CT was 100 %, 99% and 98% respectively. Among the total of 79 pre-therapeutic PET-CT, 948 sites were analyzed, 238 sites were true-positive (1 bone/3 bone marrow involvement, 4 parotids, 4 nasopharynx, 3 liver, 2 lungs, and 221 nodal involvement), 5 were false positive (4 were progressive transformation of germinal center and 1 was reactive lymph node) and 705 sites were true negative. In 5 patients, PET-CT revealed extra nodal disease that was subsequently confirmed on follow-up, but was not picked by CT. There was an agreement between the CT and the PET-CT staging in 68 scans (86%). The staging was changed in 11 (14%) patients; 8 (10%) were upstaged (7 nodal and 1 bone marrow) and 3 (4%) were down staged by PET-CT.
A total of 33 bone marrow biopsies (BMBx) were performed and PET-CT confirmed all BMBx results (32 BMBx negative and PET-CT negative, 1 patient BMBx positive and PET-CT positive) showing 100% concordance and suggesting a positive PET-CT for bone or bone marrow is adequate to designate advanced stage. In 2 patients, pre-therapeutic PET-CT revealed bone marrow involvement that was unsuspected before the PET-CT examination.
A total of 83 end of treatment PET-CT were carried out, 72 scans were negative (score 1-3) and 11 scans were positive (score 4-5). Treatment consisted of local treatment in the form of surgery/radiation in 7 patients, 2-4 cycles of ABVD +/- radiotherapy in 43 patients, and 6-8 cycles of ABVD +/- radiotherapy in 17 patients. Of the 238 previously involved sites, 204 became true negative, 31 remained true positive, and 3 sites had false negative results with no false positives, showing the negative predictive value of 98.6% with specificity of 100%. Deauville criteria correlated very well with visual assessment criteria. 83 post treatment CT scans showed that out of 238 previously involved sites, 180 became true negative, 24 sites were false positive with specificity of 88%. Two year progression free survival of the entire cohort was 83%.
Twenty one patients with stage II, III and IV patients whom were planned to receive 6-8 cycles of chemotherapy underwent mid-treatment PET-CT that were assessed based on Deauville Criteria. 13 patients had negative-disease with none failed primary treatment. 8 had positive-disease; out of which 4 failed primary treatment (numbers are too small for statistics) (Table1).
Our data suggest that baseline PET scan is far superior to CT staging. A negative pre-therapy PET-CT for bone/bone marrow is sufficient to omit BMBx. Mid-treatment PET-CT response may have a prognostic role. The validity of the Deauville Score for interpretation of the end of treatment response assessment scans in adult and pediatric patients has been confirmed by the present study. PET-CT has much better specificity for response assessment than CT. Deauville criteria are in concordance with visual assessment criteria and can be applied in real practice.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.