PET/CT is a standard imaging modality in MCL, an FDG-avid lymphoma, but uptake varies in different patients with differing forms and presentations of MCL. For those with more aggressive or larger volumes of disease, PET can be quite useful and can help identify areas of involvement. I obtain PET/CT imaging for most of my patients with MCL, particularly those who are candidates for aggressive treatment. Clinical presentation patterns in MCL vary from nodal, to splenomegaly with leukemia, to gastrointestinal involvement, and it is important to know the location and the extent of extranodal involvement before starting any treatment. For those with very indolent types of MCL, with a low perforation rate and limited disease, PET is not always helpful in detecting lesions (eg, in a patient with a small amount of bone marrow involvement and possibly limited gastrointestinal involvement). 

PET imaging is also useful for assessing responses to treatment, and it has become an important part of clinical research involving the absence of minimal residual disease (MRD). For instance, there is interest in patients who are PET negative and MRD negative in their blood or bone marrow after their initial therapy, and this stems from the desire to identify subsets of patients who might not require autologous stem cell transplantation (ASCT) for a durable response. Additionally, there is a separate issue of subsets of patients with high-risk MCL who do not benefit substantially from ASCT and for whom alternative targeted approaches are being examined.

A few recent reports from the EHA2021 Virtual Congress were relevant to PET/CT in MCL. For example, a retrospective study suggested that ¹⁸F-FDG PET/CT was not optimal in detecting gastric lesions, with researchers noting the value of esophagogastroduodenoscopy with biopsy in MCL. Additionally, in another retrospective study presented at EHA2021, Tan et al found in their small cohort that patients with MCL achieving PET/CT-confirmed complete metabolic response and MRD negativity after induction therapy with rituximab plus cyclophosphamide, vincristine, doxorubicin, and dexamethasone (R-hyper-CVAD) had excellent long-term outcomes and might reasonably avoid consolidative ASCT. Thus, a phase 3 randomized trial comparing the benefits of ASCT following intensive chemoimmunotherapy in MRD-negative patients with MCL who achieve complete remission is needed.