END OF TREATMENT PET-CT PREDICTS PROGRESSION-FREE SURVIVAL IN DLBCL AFTER FIRST-LINE TREATMENT: RESULTS FROM THE PHASE III GOYA STUDY

PET/CT in Non-Hodgkin Lymphoma: An Update

Non-Hodgkin lymphomas represents a heterogeneous group of lymphoproliferative disorders characterized by different clinical courses, varying from indolent to highly aggressive. ¹⁸F-FDG-PET/CT is the current state-of-the-art diagnostic imaging, for the staging, restaging and evaluation of response to treatment in lymphomas with avidity for ¹⁸F-FDG, despite it is not routinely recommended for surveillance. PET-based response criteria (using five-point Deauville Score) are nowadays uniformly applied in FDG-avid lymphomas. In this review, a comprehensive overview of the role of ¹⁸F-FDG-PET in Non-Hodgkin lymphomas is provided, at each relevant point of patient management, particularly focusing on recent advances on diffuse large B-cell lymphoma and follicular lymphoma, with brief updates also on other histotypes (such as marginal zone, mantle cell, primary mediastinal- B cell lymphoma and T cell lymphoma). PET-derived semiquantitative factors useful for patient stratification and prognostication and emerging radiomics research are also presented.

Positron emission tomography/computed tomography in the management of Hodgkin and B-cell non-Hodgkin lymphoma: An update

¹⁸ F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is now an integral part of lymphoma staging and management. Because of its greater accuracy compared with CT alone, PET/CT is currently routinely performed for staging and for response assessment at the end of treatment in the vast majority of FDG-avid lymphomas and is the cornerstone of response classification for these lymphomas according to the Lugano classification. Interim PET/CT, typically performed after 2 to 4 of 6 to 8 chemotherapy/chemoimmunotherapy cycles with or without radiation, is commonly performed for prognostication and potential treatment escalation or de-escalation early in the course of therapy, a concept known as response-adapted or risk-adapted treatment. Quantitative PET is an area of growing interest. Metrics, such as the standardized uptake value, changes (Δ) in the standardized uptake value, metabolic tumor volume, and total lesion glycolysis, are being investigated as more reproducible and potentially more accurate predictors of response and prognosis. Despite the progress made in standardizing the use of PET/CT in lymphoma, challenges remain, particularly with respect to its limited positive predictive value, emphasizing the need for more specific molecular probes. This review highlights the most relevant applications of PET/CT in Hodgkin and B-cell non-Hodgkin lymphoma, its strengths and limitations, as well as recent efforts at implementing PET/CT-based metrics as promising tools for precision medicine.

Long-term results of PET-guided radiation in patients with advanced-stage diffuse large B-cell lymphoma treated with R-CHOP

Consolidative radiation therapy (RT) for advanced-stage diffuse large B-cell lymphoma (DLBCL) remains controversial, with routine practice continuing to include RT in patients with initial bulky disease or residual masses. Positron emission tomography (PET)-computed tomography is a sensitive modality for detecting the presence of residual disease at the end of treatment (EOT). A PET-guided approach to selectively administering RT has been the policy in British Columbia since 2005. Patients with advanced-stage DLBCL diagnosed from 1 January 2005 to 1 March 2017 and treated with at least 6 cycles of R-CHOP (cyclophosphamide, doxorubicin, vincristine, and prednisolone plus rituximab), who underwent EOT PET, were included in this analysis. Those with complete metabolic response (PET-negative [PET-NEG]) were observed; those with PET-positive (PET-POS) scans were offered consolidative RT, when feasible. Of the patient records reviewed, 723 were identified, with median follow-up of 4.3 years: 517 (72%) were PET-NEG; 206 (28%) were PET-POS. Time to progression (TTP) and overall survival (OS) at 3 years were 83% vs 56% and 87% vs 64%, in patients with PET-NEG and PET-POS scans, respectively. PET-POS patients with nonprogressing disease treated with consolidative RT (109 and 206; 53%) had outcomes approaching those of PET-NEG patients, with 3-year estimates of 76% and 80% for TTP and OS. PET-NEG patients who had bulky disease (≥10 cm) at diagnosis had outcomes indistinguishable from those without bulk, despite the omission of RT. These data suggest that patients with advanced-stage DLBCL who are PET-NEG at EOT and receive no RT have excellent outcomes. 18F-fluorodeoxyglucose-PET can reliably guide selective administration of consolidative RT, even in patients with initially bulky disease.