¹⁸F-FDG PET/CT for staging Hodgkin lymphoma may allow for accurate and reliable assessment of the metabolic tumor volume (MTV) as a baseline risk factor. Our aim was to analyze the prognostic impact of MTV measurements obtained by different means in advanced-stage Hodgkin lymphoma patients treated within the German Hodgkin Study Group HD18 trial. Methods: Within HD18, 310 patients underwent ¹⁸F-FDG PET/CT scanning for staging, which was available to the central review panel for quantitative analysis. We calculated the MTV by 4 different thresholding methods and performed receiver-operating-characteristic analysis to evaluate the potential for prediction of early response determined by PET after 2 cycles (PET-2) of dose-escalated bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (eBEACOPP). Logistic regression was used to evaluate its prognostic value concerning progression-free survival and overall survival. Results: All of the different MTV calculations predicted PET-2 response to a moderate and comparable degree (area under the curve, 0.62–0.63; P = 0.01–0.06). With none of the measuring methods did the receiver-operating-characteristic curves point to any unique cutoffs; rather, a wide range of possible cutoffs was indicated. None of the MTV measurements was prognostic for progression-free survival (hazard ratio, 1.2–1.5; P = 0.15–0.52) or overall survival (hazard ratio, 1.0–1.5; P = 0.95–0.27). Conclusion: Baseline MTV as determined by different means is a predictive factor for early response to eBEACOPP after 2 cycles. However, value as a prognostic factor after a highly effective PET-2–adapted treatment strategy could not be observed.

Bone marrow (BM) involvement defines advanced-stage Hodgkin lymphoma and thus has impact on the assignment to treatment. Our aim was to evaluate whether the established BM biopsy may be omitted in patients if ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) scanning is performed during staging. Our analysis set consisted of 832 Hodgkin lymphoma patients from the German Hodgkin Study Group trials HD16, HD17, and HD18 who underwent both PET scanning and BM biopsy before treatment. All PET studies were centrally reviewed and BM was categorized as showing focal involvement or not. Taking BM biopsy as reference standard, baseline PET showed a negative predictive value of 99.9% (95% confidence interval: 99.2-100%) with true-negative results in 702 of 703 cases. The sensitivity of PET for detecting BM involvement was 95.0% (95% confidence interval: 75.1-99.9%) as it could identify 19 out of 20 patients with positive BM biopsy. Moreover, PET found 110 additional subjects with focal BM lesions who would have been considered negative by biopsy. As compared to BM biopsy, PET was able to detect focal BM lesions in a large number of additional patients. This indicates that conventional BM biopsy may substantially underestimate the actual incidence of BM involvement. Given the high negative predictive value, baseline PET scanning can safely be used to exclude BM involvement in Hodgkin lymphoma. BM biopsy should be considered only in such patients in whom PET-detected lesions lead to a change of treatment protocol. The trials included in this analysis were registered at ClinicalTrials.gov: HD16 - NCT00736320, HD17 - NCT01356680, HD18 - NCT00515554.

Various factors have been identified that influence quantitative accuracy and image interpretation in positron emission tomography (PET). Through the continuous introduction of new PET technology—both imaging hardware and reconstruction software—into clinical care, we now find ourselves in a transition period in which traditional and new technologies coexist. The effects on the clinical value of PET imaging and its interpretation in routine clinical practice require careful reevaluation. In this review, we provide a comprehensive summary of important factors influencing quantification and interpretation with a focus on recent developments in PET technology. Finally, we discuss the relationship between quantitative accuracy and subjective image interpretation.

Key Points: DS4 is recommended as the cutoff value for PET-2 positivity after 2 cycles eBEACOPP for advanced-stage HL.

Since the mid-1990s, ¹⁸F-fluorodeoxglucose (FDG)-positron emission tomography (PET) in combination with computed tomography has come to play a prominent role in the management of malignant lymphomas. One of the first PET applications in oncology was the detection of lymphoma manifestations at staging, where it has shown high sensitivity. Nowadays, this imaging modality is also used during treatment to evaluate the individual chemosensitivity and adapt further therapy accordingly. If the end-of-treatment PET is negative, irradiation in advanced-stage Hodgkin lymphoma patients can be safely omitted after highly effective chemotherapy. Thus far, lymphoma response assessment has mainly been performed using visual criteria, such as the Deauville five-point scale, which became the international standard in 2014. However, novel measures such as metabolic tumor volume or total lesion glycolysis have recently been recognized by several working groups and may further increase the diagnostic and prognostic value of FDG-PET in the future.

Purpose: A primary analysis of the ongoing NIVAHL trial demonstrated unexpectedly high interim complete response rates to nivolumab-based first-line treatment in early-stage unfavorable Hodgkin lymphoma. However, biomarkers such as metabolic tumor volume (MTV) or total lesion glycolysis (TLG) and their change under treatment (ΔMTV and ΔTLG), measured on PET, might provide additional relevant information for response assessment in this setting. Hence, the current analysis aimed to investigate early response to checkpoint inhibitor therapy beyond conventional criteria. Patients and Methods: NIVAHL is a prospective, randomized phase II trial that recruited between April 2017 and October 2018. Patients in arms A and B were assessed for early treatment response after two courses of doxorubicin, vinblastine, and dacarbazine with two concomitant nivolumab infusions per cycle (2 × N-AVD) and 4 × nivolumab, respectively. In the current analysis, we included all 59 individuals with PET images available to the central review panel for quantitative analysis before April 30, 2019. Results: At interim restaging, we determined a mean ΔMTV and ΔTLG of −99.8% each in arm A after 2 × N-AVD, compared with −91.4% and −91.9%, respectively, for treatment group B undergoing 4 × nivolumab. This high decrease in MTV and TLG was observed regardless of the initial lymphoma burden. Conclusions: Our study showed that nivolumab-based first-line treatment leads to rapid, near-complete reduction of tumor metabolism in early-stage unfavorable Hodgkin lymphoma. Thus, PET-derived biomarkers might allow reduction or even omission of chemotherapy and radiotherapy. Furthermore, MTV and TLG could be also used to optimize immune checkpoint-targeting treatments in other cancers.