Imaging Responses to Immunotherapy with Novel PET Tracers

Discordant Responses Between Imaging Examination and Surgical Pathology of Head and Heck Squamous Cell Carcinoma After Neoadjuvant Immunotherapy Combined With Chemotherapy

Background

We here investigated the value of imaging examination in evaluating tumor remission-based surgery in patients with head and neck squamous cell carcinoma (HNSCC), who had undergone neoadjuvant immunotherapy combined with chemotherapy (NICC).

Methods

HNSCC patients who underwent NICC and surgery from May 2021 to September 2023 were retrospectively analyzed. All patients had to undergo imaging examination evaluation, including enhanced computed tomography (CT) and enhanced magnetic resonance (MR) imaging before and after NICC. Data related to clinical parameters, complete response of the primary site (PrCR), complete response of the primary site and the lymph node (PLCR), complete response of the lymph node (LCR), and tumor response (TR), were gathered. The paired Chi-square test and t-test were conducted to analyze the differences in responses between imaging examination and pathology. Binary logistic regression was applied to analyze the relevant clinical factors of differences in responses.

Results

In total, data of 41 patients were included in this study. Significant discordant responses were observed between enhanced CT, magnetic resonance imaging (MRI), and pathology in PrCR (4.9%, 7.3% vs. 41.5%), LCR (12.2%, 7.3% vs. 53.7%), PLCR (0%, 0% vs. 31.7%), and TR (severe 29.3%,17.1% vs. 25.61%) (P < 0.05). Patients with hypopharyngeal cancer (odds ratio (OR): 7.04), oral cancer (OR: 3.64), higher neutrophil to lymphocyte ratio (NLR) (OR: 2.05), and earlier T stage (OR: 0.71) exhibited a larger response difference between enhanced CT and pathology. Patients with younger age (OR: 0.79) hypopharyngeal cancer (OR: 22.81), oral cancer (OR: 2.65), higher NLR (OR: 19.47), and earlier T stage (OR: 0.29) exhibited a larger response difference between enhanced MR and pathology.

Conclusions

Discordant responses were noted between the imaging examination and surgical pathology of HNSCC after NICC. Hypopharyngeal cancer, higher NLR, and earlier T stage may predict a higher response difference.

Th17.1 cell driven sarcoidosis-like inflammation after anti-BCMA CAR T cells in multiple myeloma

Pseudo-progression and flare-up phenomena constitute a novel diagnostic challenge in the follow-up of patients treated with immune-oncology drugs. We present a case study on pulmonary flare-up after Idecabtagen Vicleucel (Ide-cel), a BCMA targeting CAR T-cell therapy, and used single-cell RNA-seq (scRNA-seq) to identify a Th17.1 driven autoimmune mechanism as the biological underpinning of this phenomenon. By integrating datasets of various lung pathological conditions, we revealed transcriptomic similarities between post CAR T pulmonary lesions and sarcoidosis. Furthermore, we explored a noninvasive PET based diagnostic approach and showed that tracers binding to CXCR4 complement FDG PET imaging in this setting, allowing discrimination between immune-mediated changes and true relapse after CAR T-cell treatment. In conclusion, our study highlights a Th17.1 driven autoimmune phenomenon after CAR T, which may be misinterpreted as disease relapse, and that imaging with multiple PET tracers and scRNA-seq could help in this diagnostic dilemma.

Tumor response assessment on imaging following immunotherapy

In recent years, various systemic immunotherapies have been developed for cancer treatment, such as monoclonal antibodies (mABs) directed against immune checkpoints (immune checkpoint inhibitors, ICIs), oncolytic viruses, cytokines, cancer vaccines, and adoptive cell transfer. While being estimated to be eligible in 38.5% of patients with metastatic solid or hematological tumors, ICIs, in particular, demonstrate durable disease control across many oncologic diseases (e.g., in melanoma, lung, bladder, renal, head, and neck cancers) and overall survival benefits. Due to their unique mechanisms of action based on T-cell activation, response to immunotherapies is characterized by different patterns, such as progression prior to treatment response (pseudoprogression), hyperprogression, and dissociated responses following treatment. Because these features are not encountered in the Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST 1.1), which is the standard for response assessment in oncology, new criteria were defined for immunotherapies. The most important changes in these new morphologic criteria are, firstly, the requirement for confirmatory imaging examinations in case of progression, and secondly, the appearance of new lesions is not necessarily considered a progressive disease. Until today, five morphologic (immune-related response criteria (irRC), immune-related RECIST (irRECIST), immune RECIST (iRECIST), immune-modified RECIST (imRECIST), and intra-tumoral RECIST (itRECIST)) criteria have been developed to accurately assess changes in target lesion sizes, taking into account the specific response patterns after immunotherapy. In addition to morphologic response criteria, 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/computed tomography (18F-FDG-PET/CT) is a promising option for metabolic response assessment and four metabolic criteria are used (PET/CT Criteria for Early Prediction of Response to Immune Checkpoint Inhibitor Therapy (PECRIT), PET Response Evaluation Criteria for Immunotherapy (PERCIMT), immunotherapy-modified PET Response Criteria in Solid Tumors (imPERCIST5), and immune PERCIST (iPERCIST)). Besides, there is evidence that parameters on 18F-FDG-PET/CT, such as the standardized uptake value (SUV)max and several radiotracers, e.g., directed against PD-L1, may be potential imaging biomarkers of response. Moreover, the emerge of human intratumoral immunotherapy (HIT-IT), characterized by the direct injection of immunostimulatory agents into a tumor lesion, has given new importance to imaging assessment. This article reviews the specific imaging patterns of tumor response and progression and available imaging response criteria following immunotherapy.

Pilot study of a novel nanobody 68 Ga-NODAGA-SNA006 for instant PET imaging of CD8+ T cells

PURPOSE

Positron emission tomography (PET) with specific diagnostic probes for quantifying CD8⁺ T cells has emerged as a powerful technique for monitoring the immune response. However, most CD8⁺ T cell radiotracers are based on antibodies or antibody fragments, which are slowly cleared from circulation. Herein, we aimed to develop and assess ⁶⁸ Ga-NODAGA-SNA006 for instant PET (iPET) imaging of CD8⁺ T cells.

METHODS

A novel nanobody without a hexahistidine (His₆) tag, SNA006-GSC, was designed, site-specifically conjugated with NODAGA-maleimide and radiolabelled with ⁶⁸ Ga. The PET imaging profiles of ⁶⁸ Ga-NODAGA-SNA006 were evaluated in BALB/c MC38-CD8⁺/CD8^- tumour models and cynomolgus monkeys. Three volunteers with lung cancer underwent whole-body PET/CT imaging after ⁶⁸ Ga-NODAGA-SNA006 administration. The biodistribution, pharmacokinetics and dosimetry of patients were also investigated. In addition, combined with immunohistochemistry (IHC), the quantitative performance of the tracer for monitoring CD8 expression was evaluated in BALB/c MC38-CD8⁺/CD8^- and human subjects.

RESULTS

⁶⁸ Ga-NODAGA-SNA006 was prepared with RCP > 98% and SA > 100 GBq/μmol. ⁶⁸ Ga-NODAGA-SNA006 exhibited specific uptake in MC38-CD8⁺ xenografts tumours, CD8-rich tissues (such as the spleen) in monkeys and CD8⁺ tumour lesions in patients within 1 h. Fast washout from circulation was observed in three volunteers (t_1/2 < 20 min). A preliminary quantitative linear relationship (R² = 0.9668, p < 0.0001 for xenografts and R² = 0.7924, p = 0.0013 for lung patients) appeared between ⁶⁸ Ga-NODAGA-SNA006 uptake and CD8 expression. ⁶⁸ Ga-NODAGA-SNA006 was well tolerated by all patients.

CONCLUSION

⁶⁸ Ga-NODAGA-SNA006 PET imaging can instantly quantify CD8 expression with an ideal safety profile and is expected to be important for dynamically tracking CD8⁺ T cells and monitoring immune responses for individualised cancer immunotherapy.

TRIAL REGISTRATION

NCT05126927 (19 November 2021, retrospectively registered).

Immuno-Imaging (PET/SPECT)-Quo Vadis?

The use of immunotherapy has revolutionized the treatment regimen of certain cancer types, but response assessment has become a difficult task with conventional methods such as CT/MRT or FDG PET-CT and the classical response criteria such as RECIST or PERCIST which have been developed for chemotherapeutic treatment. Plenty of new tracers have been published to improve the assessment of treatment response and to stratify the patient population. We gathered the information on published tracers (in total, 106 individual SPECT/PET tracers were identified) and performed a descriptor-based analysis; in this way, we classify the tracers with regard to target choice, developability (probability to progress from preclinical stage into the clinic), translatability (probability to be widely applied in the 'real world'), and (assumed) diagnostic quality. In our analysis, we show that most tracers are targeting PD-L1, PD-1, CTLA-4, and CD8 receptors by using antibodies or their fragments. Another finding is that plenty of tracers possess only minor iterations regarding chelators and nuclides instead of approaching the problem in a new innovative way. Based on the data, we suggest an orthogonal approach by targeting intracellular targets with PET-activatable small molecules that are currently underrepresented.

Preclinical Evaluation of 89Zr-Df-IAB22M2C PET as an Imaging Biomarker for the Development of the GUCY2C-CD3 Bispecific PF-07062119 as a T Cell Engaging Therapy

Purpose

A sensitive and specific imaging biomarker to monitor immune activation and quantify pharmacodynamic responses would be useful for development of immunomodulating anti-cancer agents. PF-07062119 is a T cell engaging bispecific antibody that binds to CD3 and guanylyl cyclase C, a protein that is over-expressed by colorectal cancers. Here, we used ⁸⁹Zr-Df-IAB22M2C (⁸⁹Zr-Df-Crefmirlimab), a human CD8-specific minibody to monitor CD8+ T cell infiltration into tumors by positron emission tomography. We investigated the ability of ⁸⁹Zr-Df-IAB22M2C to track anti-tumor activity induced by PF-07062119 in a human CRC adoptive transfer mouse model (with injected activated/expanded human T cells), as well as the correlation of tumor radiotracer uptake with CD8+ immunohistochemical staining.

Procedures

NOD SCID gamma mice bearing human CRC LS1034 tumors were treated with four different doses of PF-07062119, or a non-targeted CD3 BsAb control, and imaged with ⁸⁹Zr-Df-IAB22M2C PET at days 4 and 9. Following PET/CT imaging, mice were euthanized and dissected for ex vivo distribution analysis of ⁸⁹Zr-Df-IAB22M2C in tissues on days 4 and 9, with additional data collected on day 6 (supplementary). Data were analyzed and reported as standard uptake value and %ID/g for in vivo imaging and ex vivo tissue distribution. In addition, tumor tissues were evaluated by immunohistochemistry for CD8+ T cells.

Results

The results demonstrated substantial mean uptake of ⁸⁹Zr-Df-IAB22M2C (%ID/g) in PF-07062119-treated tumors, with significant increases in comparison to non-targeted BsAb-treated controls, as well as PF-07062119 dose-dependent responses over time of treatment. A moderate correlation was observed between tumor tissue radioactivity uptake and CD8+ cell density, demonstrating the value of the imaging agent for non-invasive assessment of intra-tumoral CD8+ T cells and the mechanism of action for PF-07062119.

Conclusion

Immune-imaging technologies for quantitative cellular measures would be a valuable biomarker in immunotherapeutic clinical development. We demonstrated a qualification of ⁸⁹Zr-IAB22M2C PET to evaluate PD responses (mice) to a novel immunotherapeutic.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11307-021-01621-0.

Tumor Hypoxia as a Barrier in Cancer Therapy: Why Levels Matter

Simple Summary

Hypoxia is a common feature of solid tumors and associated with poor outcome in most cancer types and treatment modalities, including radiotherapy, chemotherapy, surgery and, most likely, immunotherapy. Emerging strategies, such as proton therapy and combination therapies with radiation and hypoxia targeted drugs, provide new opportunities to overcome the hypoxia barrier and improve therapeutic outcome. Hypoxia is heterogeneously distributed both between and within tumors and shows large variations across patients not only in prevalence, but importantly, also in level. To best exploit the emerging strategies, a better understanding of how individual hypoxia levels from mild to severe affect tumor biology is vital. Here, we discuss our current knowledge on this topic and how we should proceed to gain more insight into the field.

Abstract

Hypoxia arises in tumor regions with insufficient oxygen supply and is a major barrier in cancer treatment. The distribution of hypoxia levels is highly heterogeneous, ranging from mild, almost non-hypoxic, to severe and anoxic levels. The individual hypoxia levels induce a variety of biological responses that impair the treatment effect. A stronger focus on hypoxia levels rather than the absence or presence of hypoxia in our investigations will help development of improved strategies to treat patients with hypoxic tumors. Current knowledge on how hypoxia levels are sensed by cancer cells and mediate cellular responses that promote treatment resistance is comprehensive. Recently, it has become evident that hypoxia also has an important, more unexplored role in the interaction between cancer cells, stroma and immune cells, influencing the composition and structure of the tumor microenvironment. Establishment of how such processes depend on the hypoxia level requires more advanced tumor models and methodology. In this review, we describe promising model systems and tools for investigations of hypoxia levels in tumors. We further present current knowledge and emerging research on cellular responses to individual levels, and discuss their impact in novel therapeutic approaches to overcome the hypoxia barrier.