ITA-IMMUNO-PET: The Role of [18F]FDG PET/CT for Assessing Response to Immunotherapy in Patients with Some Solid Tumors

Granzyme B PET/CT Imaging Evaluates Early Response to Immunotherapy in Gastric Cancer

In several malignancies, only a limited number of patients respond to immune checkpoint inhibitors. Predicting and monitoring responses to these inhibitors represent an unmet clinical need. Here, we developed a PET/CT probe targeting granzyme B, [68Ga]Ga-NOTA-Gly-Gly-Gly-Ile-Glu-Pro-Asp-CHO (GSI), and aimed to investigate whether it can be used to monitor the effects of immune checkpoint inhibitors early in the course of therapy. Methods: Seventy-two patients with gastric cancer (stages III-IV) were recruited for [68Ga]Ga-NOTA-GSI PET/CT imaging after 2 or 3 cycles of the immunotherapy, and 40 patients were included in the final analysis. The SUVmax of primary tumors (SUVmax-t), SUVmax of metastatic lymph nodes (SUVmax-LN), and SUVmax of normal tissues (liver and blood pool) were measured, and their target-to-liver background ratio (TLR) and target-to-blood background ratio (TBR) were denoted for primary tumors as TLRtumor and TBRtumor and for metastatic lymph nodes as TLRLN and TBRLN, respectively. The treatment responses were assessed within 1 wk after full-course treatment according to RECIST version 1.1. Wilcoxon rank-sum tests were used to compare the PET/CT parameters between responders and nonresponders. Receiver operating characteristic curve analysis was used to assess the diagnostic efficacy of [68Ga]Ga-NOTA-GSI PET/CT parameters in identifying responders. Two-tailed P value of less than 0.05 was considered statistically significant. Results: We found that SUVmax-t, TLRtumor, TBRtumor, SUVmax-LN, and TBRLN were higher in responders than in nonresponders (2.49 ± 0.58 vs. 1.55 ± 0.48, P = 0.000; 2.24 ± 0.48 vs. 1.74 ± 0.67, P = 0.007; 1.38 ± 0.43 vs. 0.90 ± 0.23, P = 0.000; 2.24 ± 0.99 vs. 1.42 ± 0.55, P = 0.003; and 1.28 ± 0.68 vs. 0.83 ± 0.32, P = 0.012, respectively). According to receiver operating characteristic curve analysis, the area under the curve for SUVmax-t, TBRtumor, TLRtumor, SUVmax-LN, TLRLN, and TBRLN was 0.886, 0.866, 0.746, 0.772, 0.648, and 0.731, respectively. The threshold of SUVmax-t was 2.05, and its sensitivity and specificity were 81.0% and 84.2%, respectively. In addition, multivariate logistic regression indicated that TBRtumor was an independent predictor of treatment response (P = 0.03). Conclusion: Our results indicated that [68Ga]Ga-NOTA-GSI PET/CT is a promising tool for predicting early response to combined immunotherapy in gastric cancer patients.

Outcome prediction based on [18F]FDG PET/CT in patients with pleural mesothelioma treated with ipilimumab and nivolumab +/- UV1 telomerase vaccine

PURPOSE

The introduction of immunotherapy in pleural mesothelioma (PM) has highlighted the need for effective outcome predictors. This study explores the role of [18F]FDG PET/CT in predicting outcomes in PM treated with immunotherapy.

METHODS

Patients from the NIPU trial, receiving ipilimumab and nivolumab +/- telomerase vaccine in second-line, were included. [18F]FDG PET/CT was obtained at baseline (n = 100) and at week-5 (n = 76). Metabolic tumour volume (MTV) and peak standardised uptake value (SUVpeak) were evaluated in relation to survival outcomes. Wilcoxon rank-sum test was used to assess differences in MTV, total lesion glycolysis (TLG), maximum standardised uptake value (SUVmax) and SUVpeak between patients exhibiting an objective response, defined as either partial response or complete response according to the modified Response Criteria in Solid Tumours (mRECIST) and immune RECIST (iRECIST), and non-responders, defined as either stable disease or progressive disease as their best overall response.

RESULTS

Univariate Cox regression revealed significant associations of MTV with OS (HR 1.36, CI: 1.14, 1.62, p < 0.001) and PFS (HR 1.18, CI: 1.03, 1.34, p = 0.02), while multivariate analysis showed a significant association with OS only (HR 1.35, CI: 1.09, 1.68, p = 0.007). While SUVpeak was not significantly associated with OS or PFS in univariate analyses, it was significantly associated with OS in multivariate analysis (HR 0.43, CI: 0.23, 0.80, p = 0.008). Objective responders had significant reductions in TLG, SUVmax and SUVpeak at week-5.

CONCLUSION

MTV provides prognostic value in PM treated with immunotherapy. High SUVpeak was not associated with inferior outcomes, which could be attributed to the distinct mechanisms of immunotherapy. Early reductions in PET metrics correlated with treatment response.

STUDY REGISTRATION

The NIPU trial (NCT04300244) is registered at clinicaltrials.gov. https://classic.

CLINICALTRIALS

gov/ct2/show/NCT04300244?cond=Pleural+Mesothelioma&cntry=NO&draw=2&rank=4.

The Prognostic Role of [18F]FDG PET/CT in Patients with Advanced Cutaneous Squamous Cell Carcinoma Submitted to Cemiplimab Immunotherapy: A Single-Center Retrospective Study

Background: Baseline 2-deoxy-2[18F]fluoro-d-glucose ([18F]FDG) positron emission tomography (PET)-derived parameters and 12-week metabolic response were investigated as prognostic factors in advanced cutaneous squamous cell carcinoma (cSCC) submitted to cemiplimab immunotherapy. Materials and Methods: Clinical records of 25 cSCC patients receiving cemiplimab, submitted to [18F]FDG positron emission tomography/computed tomography (PET/CT) at baseline and after ∼12 weeks, were retrospectively reviewed. The Kaplan-Meier (KM) method was applied to analyze differences in event-free survival (EFS), and Cox regression analysis was employed to identify the prognostic factors. Results: At the 12-week PET/CT evaluation, 16 patients (64%) were classified as responders (complete or partial response) and 9 (36%) as nonresponders ("unconfirmed progressive metabolic disease") according to immune PET Response Criteria in Solid Tumors (iPERCIST). By KM analysis, baseline metabolic tumor volume (MTV) and total lesion glycolysis (TLG) significantly correlated with the EFS (p < 0.05). Furthermore, the KM analysis showed that the lack of metabolic response at 12 weeks was associated with meaningfully shorter EFS (7.2 ± 1 months in nonresponders vs. 20.3 ± 2.3 months in responders). In Cox multivariate analysis, metabolic response at 12 weeks remained the only predictor of the EFS (p < 0.05). Conclusions: Baseline tumor load (i.e., MTV and TLG) and metabolic response at 12 weeks may have a prognostic impact in cSCC patients treated with cemiplimab.

The evolution of PET imaging in renal, bladder, upper urinary tract urothelial, testicular and penile carcinoma - Today's impact, tomorrow's potential

INTRODUCTION

The advancement of hybrid PET/CT or PET/MRI imaging for non-prostate genitourinary cancers has not experienced the rapid progress of prostate cancer. Nevertheless, these neoplasms are aggressive and reliable imaging plays a pivotal role in enhancing patients' quality of life and prognosis.

AREAS COVERED

the main evidence regarding [18F]FDG and non-[18F]FDG PET/CT or PET/MRI in non-prostate uro-oncological malignancies are summarized and discussed. Moreover, potential future directions concerning PET imaging in these neoplasms are debated, with the aim to stimulate future research projects covering these fields.

EXPERT OPINION

In Renal Cell Carcinoma (RCC), [18F]FDG PET/CT demonstrates varying efficacy in staging, restaging, and prognostic stratification, but PSMA PET/CT is emerging as a potential game-changer, particularly in advanced, high-grade aggressive clear cell RCC. [18F]FDG PET/CT may see an increased use in N and M-staging of bladder cancer, as well as for detecting recurrence and response to neoadjuvant chemotherapy. Preliminary data regarding [68Ga]-FAPI also looks promising in this context. [18F]FDG PET/MRI could be useful for the T-staging of bladder cancer, while upper tract urothelial carcinoma still lacks of molecular imaging literature reports. In testicular and penile cancer [18F]FDG PET/CT has demonstrated its usefulness in several clinical settings, although experiences with non-[18F]FDG radiotracers are lacking.

Can physiologic colonic [18F]FDG uptake in PET/CT imaging predict response to immunotherapy in metastatic melanoma?

AIM

The development of biomarkers that can reliably and early predict response to immune checkpoint inhibitors (ICIs) is crucial in melanoma. In recent years, the gut microbiome has emerged as an important regulator of immunotherapy response, which may, moreover, serve as a surrogate marker and prognosticator in oncological patients under immunotherapy. Aim of the present study is to investigate if physiologic colonic [18F]FDG uptake in PET/CT before start of ICIs correlates with clinical outcome of metastatic melanoma patients. The relation between [18F]FDG uptake in lymphoid cell-rich organs and long-term patient outcome is also assessed.

METHODOLOGY

One hundred nineteen stage IV melanoma patients scheduled for immunotherapy with ipilimumab, applied either as monotherapy or in combination with nivolumab, underwent baseline [18F]FDG PET/CT. PET/CT data analysis consisted of standardized uptake value (SUV), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) calculations in the colon as well as measurements of the colon-to-liver SUV ratios (CLRmean, CLRmax). Visual grading of colon uptake based on a four-point scale was also performed. Moreover, the spleen-to-liver SUV ratios (SLRmean, SLRmax) and the bone marrow-to-liver SUV ratios (BLRmean, BLRmax) were calculated. We also measured serum lipopolysaccharide (LPS) levels as a marker for bacterial translocation and surrogate for mucosal defense homeostasis. The results were correlated with patients' best clinical response, progression-free survival (PFS), and overall survival (OS) as well as clinical signs of colitis.

RESULTS

Median follow-up [95%CI] from the beginning of immunotherapy was 64.6 months [61.0-68.6 months]. Best response to treatment was progressive disease (PD) for 60 patients, stable disease (SD) for 37 patients, partial response (PR) for 18 patients, and complete response (CR) for 4 patients. Kaplan-Meier curves demonstrated a trend for longer PFS and OS in patients with lower colonic SUV and CLR values; however, no statistical significance for these parameters as prognostic factors was demonstrated. On the other hand, patients showing disease control as best response to treatment (SD, PR, CR) had significantly lower colonic MTV and TLG than those showing PD. With regard to lymphoid cell-rich organs, significantly lower baseline SLRmax and BLRmax were observed in patients responding with disease control than progression to treatment. Furthermore, patients with lower SLRmax and BLRmax values had a significantly longer OS when dichotomized at their median. In multivariate analysis, PET parameters that were found to significantly adversely correlate with patient survival were colonic MTV for PFS, colonic TLG for PFS, and BLRmax for PFS and OS.

CONCLUSIONS

Physiologic colonic [18F]FDG uptake in PET/CT, as assessed by means of SUV, before start of ipilimumab-based treatment does not seem to independently predict patient survival of metastatic melanoma. On the other hand, volumetric PET parameters, such as MTV and TLG, derived from the normal gut may identify patients showing disease control to immunotherapy and significantly correlate with PFS. Moreover, the investigation of glucose metabolism in the spleen and the bone marrow may offer prognostic information.

The prognostic value of [18F]FDG PET/CT based response monitoring in metastatic melanoma patients undergoing immunotherapy: comparison of different metabolic criteria

PURPOSE

To investigate the prognostic value of [18F]FDG PET/CT as part of response monitoring in metastatic melanoma patients treated with immune checkpoint inhibitors (ICIs).

METHODS

Sixty-seven patients underwent [18F]FDG PET/CT before start of treatment (baseline PET/CT), after two cycles (interim PET/CT) and after four cycles of ICIs administration (late PET/CT). Metabolic response evaluation was based on the conventional EORTC and PERCIST criteria, as well as the newly introduced, immunotherapy-modified PERCIMT, imPERCIST5 and iPERCIST criteria. Metabolic response to immunotherapy was classified according to four response groups (complete metabolic response [CMR], partial metabolic response [PMR], stable metabolic disease [SMD], progressive metabolic disease [PMD]), and further dichotomized by response rate (responders = [CMR] + [PMR] vs. non-responders = [PMD] + [SMD]), and disease control rate (disease control = [CMR] + [PMR] + [SMD] vs. [PMD]). The spleen-to-liver SUV ratios (SLRmean, SLRmax) and bone marrow-to-liver SUV ratios (BLRmean, BLRmax) were also calculated. The results of PET/CT were correlated with patients' overall survival (OS).

RESULTS

Median patient follow up [95% CI] was 61.5 months [45.3 - 66.7 months]. On interim PET/CT, the application of the novel PERCIMT demonstrated significantly longer survival for metabolic responders, while the rest criteria revealed no significant survival differences between the different response groups. Respectively on late PET/CT, both a trend for longer OS and significantly longer OS were observed in patients responding to ICIs with metabolic response and disease control after application of various criteria, both conventional and immunotherapy-modified. Moreover, patients with lower SLRmean values demonstrated significantly longer OS.

CONCLUSION

In patients with metastatic melanoma PET/CT-based response assessment after four ICIs cycles is significantly associated with OS after application of different metabolic criteria. The prognostic performance of the modality is also high after the first two ICIs cycles, especially with employment of novel criteria. In addition, investigation of spleen glucose metabolism may provide further prognostic information.