89Zr-DFO-durvalumab PET/CT prior to durvalumab treatment in patients with recurrent or metastatic head and neck cancer

Background: In the PINCH study we performed ⁸⁹Zr-DFO-durvalumab (anti-PD-L1) PET/CT in patients with recurrent or metastatic squamous cell carcinoma of the head and neck (SCCHN) prior to monotherapy durvalumab treatment. The primary aims were to assess safety and feasibility of ⁸⁹Zr-DFO-durvalumab PET-imaging and predict disease control rate during durvalumab treatment. Secondary aims were to correlate ⁸⁹Zr-DFO-durvalumab uptake to tumor PD-L1 expression, ¹⁸F-FDG uptake, and treatment response of individual lesions. Methods: In this prospective multicenter phase I-II study (NCT03829007), patients with incurable R/M SCCHN underwent baseline [¹⁸F]FDG PET and CT or MRI imaging. Subsequently, PD-L1 PET-imaging was performed 5 days after 37MBq [⁸⁹Zr]Zr-DFO-durvalumab administration. To optimize imaging conditions, dose-finding was performed in the first 14 patients. For all patients, durvalumab treatment (1500mg/4 weeks, IV) was started <1 week after PD-L1 PET imaging and continued until disease progression or unacceptable toxicity (maximum 24 months). CT evaluation was assessed according to RECIST 1.1 every 8 weeks. PD-L1-expression was determined by combined positive score (CPS) on (archival) tumor-tissue. [⁸⁹Zr]Zr-DFO-durvalumab uptake was measured in [¹⁸F]FDG-positive lesions, primary and secondary lymphoid organs, and bloodpool. Results: In total, 33 patients with locoregional recurrent (n = 12) or metastatic SCCHN (n = 21) were enrolled. [⁸⁹Zr]Zr-DFO-durvalumab injection was safe. A dose of 10mg durvalumab resulted in highest tumor-to-blood-ratios. After a median follow-up of 12.6 months, overall response rate was 26%. The disease control rate at 16 weeks was 48% with a mean duration of 7.8 months (range 1.7-21.1). On a patient level, [⁸⁹Zr]Zr-DFO-durvalumab-SUVpeak or tumor-to-blood ratio could not predict treatment response (HR 1.4 (95%CI 0.5-3.9, P = 0.54) and (HR 1.3 (95%CI 0.5-3.6, P = 0.61) respectively). Also, on a lesion level, [⁸⁹Zr]Zr-DFO-durvalumab-SUVpeak showed no substantial correlation to treatment response (Spearman ρ= 0.45, P = 0.051). Lesional [⁸⁹Zr]Zr-DFO-durvalumab-uptake did not correlate to PD-L1 CPS score, but did correlate to [¹⁸F]FDG SUV peak (Spearman ρ= 0.391, P = 0.005). Conclusion: PINCH is the first PD-L1 PET/CT study in patients with R/M SCCHN and has shown the feasibility and safety of [⁸⁹Zr]Zr-DFO-durvalumab PET/CT in a multi-center trial. [⁸⁹Zr]Zr-DFO-durvalumab-uptake did not correlate to durvalumab treatment response.

Factors for differential outcome across cancers in clinical molecular-targeted fluorescence imaging

Clinical imaging performance using a fluorescent antibody was compared across three cancers to elucidate physical and biological factors contributing to differential translation of epidermal growth factor receptor (EGFR) expression to macroscopic fluorescence in tumors. Methods: Thirty-one patients with high-grade glioma (HGG, n = 5), head-and-neck squamous cell carcinoma (HNSCC, n = 23) or lung adenocarcinoma (LAC, n = 3) were systemically infused with 50 mg panitumumab-IRDye800, 1 - 3 days prior to surgery. Intraoperative open-field fluorescent images of the surgical field were acquired, where imaging device settings and operating room lighting conditions were tested on tissue-mimicking phantoms. Fluorescence contrast and margin size were measured on resected specimen surface. Antibody distribution and EGFR immunoreactivity were characterized in macroscopic and microscopic histological structures. Integrity of the blood-brain barrier (BBB) was examined via tight junction protein (claudin-5) expression with immunohistochemistry. Stepwise multivariate linear regression of biological variables was performed to identify independent predictors of panitumumab-IRDye800 concentration in tissue. Results: Optimally acquired at the lowest gain for tumor detection with ambient light, intraoperative fluorescence imaging enhanced tissue-size dependent tumor contrast by 5.2-fold, 3.4-fold and 1.4-fold in HGG, HNSCC and LAC, respectively. Tissue surface fluorescence target-to-background ratio correlated with margin size and identified 78 - 97% of at-risk resection margins ex vivo. In 4 µm-thick tissue sections, fluorescence detected tumor with 0.85 - 0.89 areas under the receiver operating characteristic curves. Preferential breakdown of BBB in HGG improved tumor specificity of intratumoral antibody distribution relative to that of EGFR (96% vs 80%) despite its reduced concentration (3.9 ng/mg tissue) compared to HNSCC (8.1 ng/mg) and LAC (6.3 ng/mg). Cellular EGFR expression, tumor cell density, plasma antibody concentration and delivery barrier were independently associated with local intratumoral panitumumab-IRDye800 concentration with 0.62 goodness-of-fit of prediction. Conclusion: In multi-cancer clinical imaging of receptor-ligand based molecular probe, plasma antibody concentration, delivery barrier, as well as intratumoral EGFR expression driven by cellular biomarker expression and tumor cell density, led to heterogeneous intratumoral antibody accumulation and spatial distribution while tumor size, resection margin, and intraoperative imaging settings substantially influenced macroscopic tumor contrast.

Differential tumor biology between locoregional and distant metastasis in a patient with TENIS with TKI-resistant aggressive recurrent disease: a comparative evaluation with FDG, 68Ga-DOTATATE and 68Ga-PSMA-11 PET-CT

The molecular PET-CT imaging profile of an interesting case of differentiated thyroid carcinoma, later transformed into with thyroglobulin elevation and negative iodine scintigraphy (TENIS) with tyrosine kinase inhibitor (TKI) resistant recurrent aggressive disease, is presented. The patient was evaluated to assess SSTR-2 or PSMA expression to explore the possibility of any effective targeted nuclear therapy. 18F-FDG, 68Ga-DOTATATE and 68Ga-PSMA-11 PET/CT was performed, which revealed tracer avidity in all 3 scans in the extensive loco-regional disease of large ill-defined retropharyngeal and retro-tracheal soft tissue eroding cricoid cartilage, extending into tracheal lumen and left sided strap muscles. On the contrary, there was no definite uptake in the multiple bilateral lung nodules, the scan findings indicating a differential tumor biology between loco-regional and distant metastasis.

Head-to-head comparison of 68Ga-FAPI-46 and 18F-FDG PET/CT for evaluation of head and neck squamous cell carcinoma: a single-center exploratory study

⁶⁸Ga-conjugated fibroblast activation protein inhibitor (⁶⁸Ga-FAPI) has become an attractive agent for positron emission tomography (PET). This study aimed to compare ⁶⁸Ga-FAPI-46 PET/computed tomography (CT) with ¹⁸F-fluorodeoxy-D-glucose (¹⁸F-FDG) PET/CT for detecting primary cancer and metastatic lesions in patients with head and neck squamous cell carcinoma (HNSCC). Methods: Twelve patients and twenty-eight patients with HNSCC underwent ⁶⁸Ga-FAPI-46 and ¹⁸F-FDG PET/CT for initial staging and recurrence detection, respectively. Concordance and diagnostic accuracy of both tracers were analyzed. Semiquantitative parameters, including the maximum and mean of standardized uptake value (SUV_max and SUVmean) and tumor-to-background ratio (T/B) were compared. FAP expression tumor volume (FTV) and total lesion FAP expression (TLF) of ⁶⁸Ga-FAPI-46 were compared with metabolic tumor volume (MTV) and total lesion glycolysis (TLG) of ¹⁸F-FDG, respectively. Differences between semiquantitative parameters were analyzed using paired t-tests. Results: ⁶⁸Ga-FAPI -46 PET/CT was 83.3% and 96.4% concordant with ¹⁸F-FDG PET/CT for initial staging and recurrence detection, respectively. Eighteen lesions had histopathological validation and both tracers displayed 100% sensitivity, 50% specificity, and 94.4% accuracy for lesion-based analysis. FTV was greater than MTV (P < 0.05), but no significant differences were observed for the other parameters. Conclusion: ⁶⁸Ga-FAPI-46 PET/CT showed good concordance and comparable diagnostic performance compared with ¹⁸F-FDG PET/CT for initial staging and recurrence detection in patients with HNSCC.

The Added Value of 68Ga-FAPI-04 PET/CT in Patients with Head and Neck Cancer of Unknown Primary with 18F-FDG Negative Findings

¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) plays an important role in locating of primary tumor for patients with head and neck cancer of unknown primary (HNCUP). Nevertheless, it can be challenging to locate the primary malignancy in ¹⁸F-FDG-PET/CT scan in some cases. As ⁶⁸Ga-radiolabeled fibroblast activation protein inhibitor (FAPI) PET/CT has promising results in detecting different tumor entities, our study aimed to evaluate the performance of ⁶⁸Ga-FAPI-PET/CT for detecting the primary tumor in HNCUP patients with negative ¹⁸F-FDG findings. Methods: A total of eighteen patients (16 males and 2 females; median age, 55 years; range, 24-72 years) with negative ¹⁸F-FDG findings were enrolled in this study. All patients underwent ¹⁸F-FDG and ⁶⁸Ga-FAPI-PET/CT within one week. Biopsy and histopathological examinations were done in the sites with positive ⁶⁸Ga-FAPI-PET/CT findings. Results: ⁶⁸Ga-FAPI-PET/CT detected the primary tumor in 7 out of 18 patients (38.89%). Among the 7 patients, in respect of the primary tumor sites, 1 was in nasopharynx, 2 were in palatine tonsil, 2 were in submandibular gland, and 2 were in hypopharynx. The primary tumors showed moderate to intensive uptake of FAPI (mean SUV_max, 8.79; range, 2.60-16.50) and excellent tumor-to-contralateral normal tissue ratio (mean SUV_max ratio, 4.50; range, 2.17-8.21). In lesion-based analysis, a total of 65 lymph nodes and 17 bone metastatic lesions were identified. The mean SUV_max of lymph node metastases were 9.05 ± 5.29 for FDG and 9.08 ± 4.69 for FAPI (P = 0.975); as for bone metastases, the mean SUV_max were 8.11 ± 3.00 for FDG and 6.96 ± 5.87 for FAPI, respectively (P = 0.478). The mean tumor-to-background ratio (TBR) values of lymph node and bone metastases were 10.65 ± 6.59 vs. 12.80 ± 8.11 (P = 0.100) and 9.08 ± 3.35 vs. 9.14 ± 8.40 (P = 0.976), respectively. Conclusion: We presented first evidence of diagnostic role of ⁶⁸Ga-FAPI-PET/CT in HNCUP, and our study demonstrated that ⁶⁸Ga-FAPI-PET/CT had the potential to improve the detection rate of primary tumor in HNCUP patients with negative FDG findings. Moreover, ⁶⁸Ga-FAPI had similar performance in assessing metastases with ¹⁸F-FDG.

Epidermal growth factor receptor targeted fluorescence molecular imaging for postoperative lymph node assessment in patients with oral cancer

Rationale: In most oral cancer patients, surgical treatment includes resection of the primary tumor combined with the excision of lymph nodes (LN), either for staging or treatment. All LNs harvested during surgery require tissue processing and subsequent microscopic histopathological assessment to determine the nodal stage. In this study, we investigated the use of the fluorescent tracer cetuximab-800CW to discriminate between tumor-positive and tumor-negative LNs before histopathological examination. Methods: Here, we report a retrospective ad hoc analysis of a clinical trial designed for resection margin evaluation of oral squamous cell carcinoma patients (NCT02415881). Two days prior to surgery, patients were intravenously administered with 75 mg cetuximab followed by 15 mg cetuximab-800CW, an Epidermal Growth Factor Receptor (EGFR)-targeting fluorescent tracer. Fluorescence images were obtained of excised, formalin-fixed LNs and correlated with histopathological assessment. Results: Fluorescence molecular imaging of 514 LNs (61 pathologically positive nodes) can detect tumor-positive LNs ex vivo with 100% sensitivity and 86.8% specificity (AUC 0.97). In this cohort, the number of LNs that require microscopic assessment was decreased by 77.4%, without missing any metastasis. Additionally, in 7.5% of the fluorescence false-positive LNs, we identified metastases missed by standard histopathological analysis. Conclusion: Our findings suggest that EGFR-targeted fluorescence molecular imaging can aid in the detection of LN metastases in the ex vivo setting in oral cancer patients. This image-guided concept can improve the efficacy of postoperative LN examination and identify additional metastases, which safeguards appropriate postoperative therapy and may improve patient prognosis.