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.

Conflicts of interest and sources of funding: The authors have no conflicts of interest to declare. This study has been supported by SOFIE by the provision of precursors for FAPI synthesis. A.D. discloses research support from Siemens Healthineers, Life Molecular Imaging, GE Healthcare, AVID Radiopharmaceuticals, SOFIE and Eisai; Speaker Honorary and/or Advisory Boards fees from Siemens Healthineers, Sanofi, GE Healthcare, Biogen, Novo Nordisk; Invicro Stock from Siemens Healthineers, Lantheus Holding, and a patent pending for 18 F-PSMA7 (PSMA PET imaging tracer). All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Informed consent to undergo imaging and RT was obtained from all individual participants included in the study. The local institutional review board waived requirement to obtain consent for retrospective data analysis.

Background Expression of CXCR4, a chemokine (C-X-C motif) receptor that plays a central role in tumor growth and metastasis of circulating tumor cells, has been described in a variety of solid tumors. A high expression of CXCR4 has a prognostic significance with regard to overall and progression-free survival and offers a starting point for targeted therapies. In this context, [68]Ga-Pentixafor-Positron Emission Tomography/Computer Tomography (PET/CT) offers promising possibility of imaging the CXCR4 expression profile. We set out to compare a [18F] fluorodeoxyglucose (FDG)-PET/CT and a [68Ga]Pentixafor-PET/CT in (re-)staging and radiation planning of patients with localized esophageal cancer. Materials and methods In this retrospective analysis, ten patients, with adeno- or squamous cell carcinoma of the esophagus (n = 3 and n = 7, respectively), which were scheduled for radio (chemo) therapy, were imaged using both Pentixafor and FDG PET/CT examinations. All lesions were visually rated as Pentixafor and FDG positive or negative. For both tracers, SUVmax was measured all lesions and compared to background. Additionally, immunohistochemistry of CXCR4 was obtained in patients undergoing surgery. Results FDG-positive tumor-suspicious lesions were detected in all patients and a total of 26 lesions were counted. The lesion-based analysis brought equal status in 14 lesions which were positive for both tracers while five lesions were FDG positive and Pentixafor negative and seven lesions were FDG negative, but Pentixafor positive. Histopathologic correlation was available in seven patients. The CXCR4 expression of four non-pretreated tumour lesion samples was confirmed immunohistochemically. Conclusion Our data shows that additional PET/CT imaging with Pentixafor for imaging the CXCR4 chemokine receptor is feasible but heterogeneous in both newly diagnosed and pretreated recurrent esophageal cancer. In addition, the Pentixafor PET/CT may serve as complementary tool for radiation field expansion in radiooncology.