Reply to B. Bennani-Baiti et al, H.J.A. Adams et al, E. Laffon et al, and E.A. Hawkes et al
Authors: Sally F. Barrington, N. George Mikhaeel, Lale Kostakoglu, Michel Meignan, Martin Hutchings, Stefan Müeller, Lawrence H. Schwartz, Emanuele Zucca, Richard I. Fisher, Judith Trotman, Otto S. Hoekstra, Rodney J. Hicks, Michael J. O'Doherty, Roland Hustinx, Alberto Biggi, Franco Cavalli, T. Andrew Lister, Bruce D. Cheson
Journal: Journal of Clinical Oncology (2015)

We are pleased to have the opportunity to respond to colleagues regarding recent recommendations for staging and response assessment in lymphoma. 1,2 We have recommended that positron emission tomography-computed tomography (PET-CT) be used for the routine staging of [ 18 F]fluorodeoxyglucose (FDG) -avid lymphomas.However, we acknowledge that most published data regarding the role of PET or PET-CT for staging relate to the most common lymphoma subtypes, Hodgkin lymphoma (HL) and aggressive non-Hodgkin lymphoma.Bennani-Baiti et al 3 describe a patient for whom FDG PET-CT appearances prompted an excisional biopsy after two nondiagnostic skin biopsies, enabling the correct diagnosis of subcutaneous panniculitis-like T-cell lymphoma (SPTCL) to be made.Their review of several case reports in the literature indicates that others have also reported that PET-CT can help to differentiate SPTCL from other forms of panniculitis. [4]5][6] They point out that prompt diagnosis is important, especially considering the incidence of hemophagocytic syndrome, which can be rapidly fatal. 7 Extranodal involvement is rare in SPTCL but is important to detect, and PET-CT can also be useful in this regard. 8PET-CT has been used successfully to monitor response to chemotherapy in a few patients with FDG uptake at diagnosis with a good treatment response, 4,5,8 although we have observed that false-positive uptake may occur after treatment with macrophage infiltration on biopsy.It is difficult to make firm recommendations about the utility of imaging in rare diseases, and this was not the purpose of our guidelines, which were evidence based and did not report on rare subtypes for which evidence is lacking.However, we acknowledge that in lymphoma subtypes, including SPTCL, which have been reported to have variable FDG avidity, PET-CT may have a place if it will affect management in individual patients, although PET-CT cannot be routinely recommended.PET-CT at diagnosis to assess FDG avidity is important if the technique will be used in subsequent response assessment.Adams and Kwee 9 have raised the issue of whether or not routine bone marrow biopsy (BMB) is required in patients with diffuse large B-cell lymphoma (DLBCL) who undergo PET-CT during routine staging.Adams and Kwee agree that BMB can be avoided in HL on the grounds that it does not change risk assessment or treatment status.They disagree with this approach in DLBCL on the basis of concerns about reduced sensitivity of FDG PET-CT in DLBCL.In the guidelines, we acknowledged that PET-CT may miss low-volume involvement and discordant lymphoma in the marrow 1 ; however, overall PET-CT detects more cases of bone marrow involvement (BMI) than does BMB. 10 Changes to focal FDG uptake within marrow that occur in parallel with changes in lymph nodes during treatment for DLBCL are likely to indicate BMI. 11Diffuse uptake may indicate BMI or reactive