Reply to B. Bennani-Baiti et al, H.J.A. Adams et al, E. Laffon et al, and E.A. Hawkes et al

Use of FDG PET/CT in identification of bone marrow involvement in diffuse large B cell lymphoma and follicular lymphoma: comparison with iliac crest bone marrow biopsy

Background Non-Hodgkin's lymphoma (NHL) accounts for around 4% of new cancer cases annually. Bone marrow involvement is important for staging and management. Fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) is used increasingly to identify this, in addition to bone marrow biopsy (BMB), which is seen as "gold" reference standard. Purpose To compare determination of bone marrow involvement by FDG PET/CT against BMB in diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL). Material and Methods This was a retrospective study of patients with histologically confirmed NHL at a single UK cancer center undergoing pre-treatment FDG PET/CT and BMB between June 2010 and February 2013. Information was collected from patient notes, cancer registry, histological and imaging reports. Diagnostic accuracy of FDG PET/CT was determined, compared to BMB as the reference standard. Results Twenty-four patients with DLBCL and 12 with FL were included. Five DLBCL patients had bone marrow involvement on PET/CT; all were confirmed on BMB. Three FL patients had marrow involvement on PET/CT but not on BMB; one FL patient had positive BMB but negative PET/CT. Using BMB as the reference standard, the sensitivity and specificity of FDG PET/CT for detecting bone marrow involvement in DLBCL were 100% and 100%, respectively, and in FL were 0% and 72.7%, respectively. Conclusion FDG PET/CT is accurate for detection of bone marrow involvement in newly diagnosed DLBCL, but not FL. In DLBCL, positive FDG PET/CT may negate the need for routine BMB, although BMB in addition or combination may be appropriate if this would influence management or prognosis.

PET Scans for Staging and Restaging in Diffuse Large B-Cell and Follicular Lymphomas

Positron emission tomography (PET)-CT was recommended in updated international guidelines for staging/restaging of diffuse large B-cell lymphoma (DLBCL) and follicular lymphoma (FL). In FL, PET was previously regarded as a research application only. This review concentrates on new publications related to PET in these diseases. In DLBCL, PET appears appropriate for staging using prognostic indices established with CT and baseline PET parameters, e.g. metabolic tumour volume, are prognostic of outcome. Early complete metabolic response (CMR) predicts end-of-treatment CMR with excellent prognosis. Patients without CMR at interim should not have treatment altered, but have a worse prognosis, and patients with other high risk features may need closer monitoring. The end-of-treatment scan is confirmed as the standard for remission assessment using Deauville criteria, which are also predictive for patients undergoing ASCT. In FL, PET is more sensitive for staging than CT but misses bone marrow involvement. PET-CT identifies patients at risk of progression after induction chemotherapy better than CT.