18F-FLT and 18F-FDG PET/CT in Predicting Response to Chemoradiotherapy in Nasopharyngeal Carcinoma: Preliminary Results

Head-to-Head Comparison of 68 Ga-DOTATATE and 18 F-FDG PET in EBV-Positive Nonkeratinizing Nasopharyngeal Carcinoma

PURPOSE

The aim of this study was to compare the clinical application value of 68 Ga-DOTATATE and 18 F-FDG PET/CT in Epstein-Barr virus (EBV)-positive nonkeratinizing nasopharyngeal carcinoma.

PATIENTS AND METHODS

Patients underwent 18 F-FDG and 68 Ga-DOTATATE PET scans. The lesion numbers, tracer parameters, and primary tumor volume derived from contrast-enhanced MRI, 18 F-FDG, and 68 Ga-DOTATATE PET were compared. The correlation between clinical characteristics and PET parameters as well as the predictive value of PET parameters were analyzed.

RESULTS

The median maximum standard uptake values (SUV max ) of 18 F-FDG and 68 Ga-DOTATATE in all 26 primary tumors was 15.00 and 9.73, respectively ( P = 0.001). 68 Ga-DOTATATE PET was superior to 18 F-FDG PET in detecting intracranial and skull base involvement. The primary tumor volume of 68 Ga-DOTATATE with 35% SUV max as the threshold had the highest consistency with that of contrast-enhanced MRI. 68 Ga-DOTATATE and 18 F-FDG PET/CT detected 103/108 (95.4%) and 101/108 (93.5%) regional lymph nodes metastases ( P = 0.552), and the median SUV max was 6.05 and 10.81, respectively ( P < 0.001). Furthermore, 68 Ga-DOTATATE PET/CT detected more distant metastases than 18 F-FDG (89/92 [96.7%] vs 54/92 [58.7%], respectively, P < 0.001). The plasma EBV DNA was positively correlated with the total metabolic tumor volume, lesion glycolysis, somatostatin receptor-expressing tumor volume, and lesion somatostatin receptor expression (all P values <0.05). The PET parameters in the non-objective response rate group were higher than those in the objective response rate group (all P values >0.05).

CONCLUSIONS

68 Ga-DOTATATE PET/CT is a promising imaging modality for detecting primary and metastatic EBV-positive nonkeratinizing nasopharyngeal carcinoma and delineating primary tumor boundary.

Nasopharyngeal Carcinoma in Children, Current Treatment Approach

Nasopharyngeal carcinoma (NPC) is a rare and locally aggressive form of childhood cancer. Treatment of pediatric NPC includes chemotherapy and radiotherapy. Most studies on the treatment of pediatric NPC are single-arm studies. With current treatment protocols survival rates for patients with nonmetastatic disease exceed 80%, although most children will have long-term treatment-related late effects. Efforts to reduce early and late toxicities include reduced radiotherapy doses in children with good responses to induction chemotherapy. Further studies are needed to evaluate the role of immunotherapy in both the primary setting and in children with progressive or relapsed disease. This review summarizes current clinical approaches to the treatment of pediatric NPC.

Biodistribution Assessment of a Novel 68Ga-Labeled Radiopharmaceutical in a Cancer Overexpressing CCK2R Mouse Model: Conventional and Radiomics Methods for Analysis

The aim of the present study consists of the evaluation of the biodistribution of a novel 68Ga-labeled radiopharmaceutical, [68Ga]Ga-NODAGA-Z360, injected into Balb/c nude mice through histopathological analysis on bioptic samples and radiomics analysis of positron emission tomography/computed tomography (PET/CT) images. The 68Ga-labeled radiopharmaceutical was designed to specifically bind to the cholecystokinin receptor (CCK2R). This receptor, naturally present in healthy tissues such as the stomach, is a biomarker for numerous tumors when overexpressed. In this experiment, Balb/c nude mice were xenografted with a human epidermoid carcinoma A431 cell line (A431 WT) and overexpressing CCK2R (A431 CCK2R+), while controls received a wild-type cell line. PET images were processed, segmented after atlas-based co-registration and, consequently, 112 radiomics features were extracted for each investigated organ / tissue. To confirm the histopathology at the tissue level and correlate it with the degree of PET uptake, the studies were supported by digital pathology. As a result of the analyses, the differences in radiomics features in different body districts confirmed the correct targeting of the radiopharmaceutical. In preclinical imaging, the methodology confirms the importance of a decision-support system based on artificial intelligence algorithms for the assessment of radiopharmaceutical biodistribution.

Pretreatment 18F-FDG uptake heterogeneity may predict treatment outcome of combined Trastuzumab and Pertuzumab therapy in patients with metastatic HER2 positive breast cancer

OBJECTIVE

Intra-tumoral heterogeneity of 18F-fluorodeoxyglucose (18F-FDG) uptake has been proven to be a surrogate marker for predicting treatment outcome in various tumors. However, the value of intra-tumoral heterogeneity in metastatic Human epidermal growth factor receptor 2(HER2) positive breast cancer (MHBC) remains unknown. The aim of this study was to evaluate 18F-FDG uptake heterogeneity to predict the treatment outcome of the dual target therapy with Trastuzumab and Pertuzumab(TP) in MHBC.

METHODS

Thirty-two patients with MHBC who underwent 18F-FDG positron emission tomography/computed tomography (PET/CT) scan before TP were enrolled retrospectively. The region of interesting (ROI) of the lesions were drawn, and maximum standard uptake value (SUVmax), mean standard uptake value (SUVmean), total lesion glycolysis (TLG), metabolic tumor volume (MTV) and heterogeneity index (HI) were recorded. Correlation between PET/CT parameters and the treatment outcome was analyzed by Spearman Rank Test. The ability to predict prognosis were determined by time-dependent survival receiver operating characteristic (ROC) analysis. And the survival analyses were then estimated by Kaplan-Meier method and compared by log-rank test.

RESULTS

The survival analysis showed that HI50% calculated by delineating the lesion with 50%SUVmax as threshold was a significant predictor of patients with MHBC treated by the treatment with TP. Patients with HI50% (≥ 1.571) had a significantly worse prognosis of progression free survival (PFS) (6.87 vs. Not Reach, p = 0.001). The area under curve (AUC), the sensitivity and the specificity were 0.88, 100% and 63.6% for PFS, respectively.

CONCLUSION

18F-FDG uptake heterogeneity may be useful for predicting the prognosis of MHBC patients treated by TP.

Predictive value of 18F-FDG PET/CT for evaluating the response to hypofractionated radiotherapy combined with PD-1 blockade in non-small cell lung cancer

Purpose

This retrospective study aimed to investigate ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG)-positron emission tomography/computed tomography (PET/CT) as a predictor of response to hypofractionated radiotherapy (HFRT) combined with programmed cell death-1 (PD-1) blockade for lung cancer.

Methods

We included 41 patients with advanced non-small cell lung cancer (NSCLC) in this study. PET/CT was performed before (SCAN-0) and one month (SCAN-1), three months (SCAN-2), and six months (SCAN-3) after treatment. Using the European Organization for Research and Treatment of Cancer 1999 criteria and PET response criteria in solid tumors, treatment responses were classified as complete metabolic response (CMR), partial metabolic response (PMR), stable metabolic disease (SMD), or progressive metabolic disease (PMD). Patients were further categorized as those with metabolic benefits (MB; SMD, PMR, and CMR) and those without MBs (NO-MB; PMD). We analyzed the prognosis and overall survival (OS) of patients with new visceral/bone lesions during treatment. Based on the findings, we generated a nomogram to predict survival. Receiver operating characteristics and calibration curves were used to evaluate the accuracy of the prediction model.

Results

The mean OS based on SCANs 1, 2, and 3 was significantly higher in patients with MB and those without new visceral/bone lesions. The prediction nomogram for survival had a high area under the curve and a high predictive value based on the receiver operating characteristics and calibration curves.

Conclusion

¹⁸FDG-PET/CT has the potential to predict the outcomes of HFRT combined with PD-1 blockade in NSCLC. Therefore, we recommend using a nomogram to predict patient survival.

Pre-treatment FLT-PET parameters as a prognostic tool for patients with locally advanced recurrent nasopharyngeal carcinoma salvaged by carbon-ion radiotherapy: a pilot study

Background

Although carbon-ion radiotherapy (CIRT) may improve outcome for patients with locoregionally recurrent nasopharyngeal carcinoma (LR-NPC), local progression still remains one of the major failure patterns. This suggests an unmet need of markers for predicting disease control after re-irradiation and potentially guiding tailored treatment. The purpose of this study was to explore the predictive value of pre-treatment 3'-deoxy-3'-[¹⁸F]fluorothymidine (FLT)-positron emission tomography (PET) for patients with locally advanced LR-NPC.

Methods

In this retrospective analysis, LR-NPC patients with locally advanced stage (stage III/IV) who received pre-treatment FLT-PET between June, 2015, and August, 2017, were retrospective reviewed and included in this study. OS and local progression-free survival (LPFS) were calculated using the Kaplan-Meier method. Univariable and multivariable Cox regression analyses of LPFS were performed. FLT-derived parameters, including SUV_max, metabolic tumor volume (MTV), and total lesion thymidine (TLT) were examined. The relationship between FLT-derived parameters and mucosal necrosis was tested by the Wilcoxon test.

Results

A total of 27 patients with a median follow-up of 31.3 months were included in this analysis. The 2-year OS and LPFS rates were 85.2% and 47.9%, respectively. In multivariable analysis, except for TLT-40% (P=0.059), all pre-treatment MTVs (P=0.040 for MTV-40%; P=0.021 for MTV-50%; P=0.026 for MTV-60%) and TLTs (P=0.043 for TLT-50%; P=0.048 for TLT-60%) were significantly related to LPFS. Moreover, MTVs and TLTs with various boundaries (except for MTV-40%) were also associated with the development of mucosal necrosis after CIRT.

Conclusions

In the current study, a significant association between pre-treatment FLT-PET and LPFS was observed in patients with locally advanced LR-NPC. Further investigations are warranted to confirm the predictive role of FLT-PET.

The role of PET/CT in radiotherapy for nasopharyngeal carcinoma

Radiotherapy has already been developed as the standard of care for patients with nasopharyngeal carcinoma (NPC), and precision staging, target volume delineation, prognosis prediction, and post-treatment surveillance are essential in the management of NPC. Positron emission tomography/computed tomography (PET/CT) is increasingly recognized as an imaging modality to guide precision radiotherapy in these areas. The feasibility and efficacy of 18F-FDG PET/CT have been confirmed in tumor diagnosis, treatment planning, prognosis, surveillance, and assessment. Coupled with the capability of revealing tumor metabolic information, 18F-FDG PET/CT is more accurate in identifying primary lesions and metastases of NPC than other conventional imaging methods including CT and MRI and shows the independently diagnostic and prognostic value for radiotherapy. However, 18F-FDG has limitations due to its physiological distribution in brain tissue and increasing uptake in post-radiation inflammation. Novel PET radiotracers including FAPI, NaF, CHO, and FLT are explored as alternatives with potential superiority for radiotherapy in NPC. In this review, we summarized the evolving role of PET/CT in the management of radiotherapy in NPC patients, aiming to facilitate precision radiotherapy from a molecular imaging aspect.

M1 stage subdivisions based on 18F-FDG PET-CT parameters to identify locoregional radiotherapy for metastatic nasopharyngeal carcinoma

Purpose

To establish a risk classification of de novo metastatic nasopharyngeal carcinoma (mNPC) patients based on ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET-CT) radiomics parameters to identify suitable candidates for locoregional radiotherapy (LRRT).

Methods

In all, 586 de novo mNPC patients who underwent ¹⁸F-FDG PET-CT prior to palliative chemotherapy (PCT) were involved. A Cox regression model was performed to identify prognostic factors for overall survival (OS). Candidate PET-CT parameters were incorporated into the PET-CT parameter score (PPS). Recursive partitioning analysis (RPA) was applied to construct a risk stratification system.

Results

Multivariate Cox regression analyses revealed that total lesion glycolysis of locoregional lesions (LRL-TLG), the number of bone metastases (BMs), metabolic tumor volume of distant soft tissue metastases (DSTM-MTV), pretreatment Epstein-Barr virus DNA (EBV DNA), and liver involvement were independent prognosticators for OS. The number of BMs, LRL-TLG, and DSTM-MTV were incorporated as the PPS. Eligible patients were divided into three stages by the RPA-risk stratification model: M1a (low risk, PPS_low + no liver involvement), M1b (intermediate risk, PPS_low + liver involvement, PPS_high + low EBV DNA), and M1c (high risk, PPS_high + high EBV DNA). PCT followed by LRRT displayed favorable OS rates compared to PCT alone in M1a patients (p < 0.001). No significant survival difference was observed between PCT plus LRRT and PCT alone in M1b and M1c patients (p > 0.05).

Conclusions

The PPS-based RPA stratification model could identify suitable candidates for LRRT. Patients with stage M1a disease could benefit from LRRT.

Glucose–Thymidine Ratio as a Metabolism Index Using 18F-FDG and 18F-FLT PET Uptake as a Potential Imaging Biomarker for Evaluating Immune Checkpoint Inhibitor Therapy

Immune checkpoint inhibitors (ICIs) are widely used in cancer immunotherapy, requiring effective methods for response monitoring. This study evaluated changes in 18F-2-fluoro-2-deoxy-D-glucose (FDG) and 18F-fluorothymidine (FLT) uptake by tumors following ICI treatment as potential imaging biomarkers in mice. Tumor uptakes of 18F-FDG and 18F-FLT were measured and compared between the ICI treatment and control groups. A combined imaging index of glucose–thymidine uptake ratio (GTR) was defined and compared between groups. In the ICI treatment group, tumor growth was effectively inhibited, and higher proportions of immune cells were observed. In the early phase, 18F-FDG uptake was higher in the treatment group, whereas 18F-FLT uptake was not different. There was no difference in 18F-FDG uptake between the two groups in the late phase. However, 18F-FLT uptake of the control group was markedly increased compared with the ICI treatment group. GTR was consistently higher in the ICI treatment group in the early and late phases. After ICI treatment, changes in tumor cell proliferation were observed with 18F-FLT, whereas 18F-FDG showed altered metabolism in both tumor and immune cells. A combination of 18F-FLT and 18F-FDG PET, such as GTR, is expected to serve as a potentially effective imaging biomarker for monitoring ICI treatment.

Tumor Blood Flow Is a Predictor of Radiotherapy Response in Patients With Nasopharyngeal Carcinoma

Purpose

The aim of this study was to evaluate tumor blood flow (TBF) as a predictor of radiotherapy response for nasopharyngeal carcinoma (NPC).

Materials and Method

A total of 134 patients were divided into two groups, the complete response (CR) group and the partial response (PR) group based on RECIST 1.1 recommendations. The statistical difference was evaluated for pre- and mid- or post-treatment TBF and changes of TBF for tumors and metastatic lymph nodes between CR and PR, respectively. The receiver operation characteristic (ROC) curve was utilized to evaluate the accuracy of TBF in predicting the response of radiation therapy. The association between TBF and SUVmax was also investigated.

Results

The reduction of TBF in CR was significantly lower than that in PR for primary tumors (P <0.001) and metastatic lymph nodes (P <0.001). The multivariate logistic regression analysis indicated that the reduction of TBF is an independent predictor of the response of radiation therapy for primary tumors (P <0.001) and metastatic lymph nodes (P <0.001). The accuracy of TBF reduction in predicting the response of radiation therapy was 0.817 in primary tumors and 0.924 in metastatic lymph nodes, respectively. No significant correlation was observed between the TBF values and SUVmax of primary tumors (r = -0.008, P = 0.954) and metastasis lymph nodes (r = -0.061, P = 0.652).

Conclusion

This study suggests that the reduction of TBF is a promising parameter for evaluating the response of radiation therapy.

Predictive value of 3'-deoxy-3'-18F-fluorothymidine PET in the early response to anti-programmed death-1 therapy in patients with advanced non-small cell lung cancer

Background

Anti-programmed death-1 (anti-PD-1) therapy has shown clinical success in patients with advanced non-small cell lung cancer (NSCLC). However, it is difficult to evaluate the early response to anti-PD-1 therapy. We determined whether changes in 3′-deoxy-3′-[¹⁸F]-fluorothymidine (¹⁸F-FLT) PET parameters before and soon after treatment initiation predicted the therapeutic effect of anti-PD-1 antibody.

Methods

Twenty-six patients with advanced NSCLC treated with anti-PD-1 antibody were enrolled prospectively and underwent ¹⁸F-FLT PET before and at 2 and 6 weeks after treatment initiation. Changes in maximal standardized uptake value (ΔSUV_max), proliferative tumor volume (ΔPTV) and total lesion proliferation (ΔTLP) of the lesions were calculated and evaluated for their associations with the clinical response to therapy.

Results

The disease control rate was 64%. Patients with non-progressive disease (non-PD) had significantly decreased TLP at 2 weeks, and decreased SUV_max, PTV, and TLP at 6 weeks, compared with those with PD, while three of eight (37.5%) patients who responded had increased TLP from baseline at 2 weeks (ie, pseudoprogression). Among the parameters that changed between baseline and 2 weeks, ΔPTV0-2 and ΔTLP0-2 had the highest accuracy (76.0%) to predict PD. Among the parameters that changed between baseline and 6 weeks, ΔSUV_max0-6, ΔPTV0-6 and ΔTLP0-6 had the highest accuracy (90.9%) to predict PD. ΔTLP0-2 (≥60%, HR 3.41, 95% CI 1.34–8.65, p=0.010) and ΔTLP0-6 (≥50%, HR 31.4, 95% CI 3.55 to 276.7, p=0.0019) were indicators of shorter progression-free survival.

Conclusions

Changes in ¹⁸F-FLT PET parameters may have value as an early predictive biomarker for the response to anti-PD-1 therapy in patients with NSCLC. However, it should be noted that pseudoprogression was observed in ¹⁸F-FLT PET imaging at 2 weeks after treatment initiation.

Trial registration number

jRCTs051180147.

Nasopharyngeal carcinoma in children and adolescents: The EXPeRT/PARTNER diagnostic and therapeutic recommendations

Nasopharyngeal carcinoma (NPC) is a rare pediatric tumor. Collaborative studies performed over the last decades showed improved results compared to historical data, but standardized guidelines for diagnosis and management of pediatric NPC are still unavailable. This study presents a European consensus guideline for the diagnosis and treatment of pediatric NPC developed by the European Cooperative Study Group for Pediatric Rare Tumors (EXPeRT). Main recommendations include induction chemotherapy with cisplatin and 5-flurouracil, concomitant chemoradiotherapy in advanced disease, and to consider maintenance treatment with interferon beta (IFN-β) for selected high-risk patients. Dose adjustments of radiotherapy based on response to induction chemotherapy may decrease the rates of long-term treatment-related complications that affect most of the survivors.

18F-FLT PET/CT imaging for early monitoring response to CDK4/6 inhibitor therapy in triple negative breast cancer

PURPOSE

Our study was to investigate 18F-FLT PET/CT imaging monitor the early response of CDK4/6 inhibitor therapy in triple negative breast cancer (TNBC).

METHODS

MDA-MB-231 and MDA-MB-468 cell lines and corresponding subcutaneous tumor models in CB17-SCID mice were used. Cell viability assay, cell-cycle analysis, and western blotting were performed in vitro experiments. 18F-FLT PET/CT imaging was performed and the value of tumor/muscle (T/M) of mice was measured before and 1-3 days after treatment in vivo experiments. Then, the tumor volume was recorded every day for 15 days.

RESULTS

In the presence of Palbociclib (CDK4/6 inhibitor), the results of in vitro experiments showed that protein pRB and E2F levels were significantly down-regulated in MDA-MB-231 cells leading to G0/G1 arrest with consumption in S phase compared with MDA-MB-468 cells. In PET/CT imaging, the 18F-FLT T/M ratio of treatment group was a significant and sustained reduction from 1 to 3 days (all p < 0.05) compared with control group in MDA-MB-231 section. However, there was no significant difference between treatment and control groups in MDA-MB-468 section. Compared with the control group, the tumor volume of the treatment group was significantly reduced from the 11th day in MDA-MB-231 section, but not in MDA-MB-468 section until 15 days.

CONCLUSION

18F-FLT PET/CT imaging can immediately and effectively monitor the early treatment response of CDK4/6 inhibitors in TNBC.

A Formula to Calculate the Threshold for Radiotherapy Targets on PET Images: Simulation Study

Background

Positron emission tomography (PET) images are being applied for defining radiotherapy targets. However, a recognized method for defining radiotherapy targets is lacking. We investigate the threshold to outline the radiotherapy target of a tumor on PET images and its influencing factors, and then expressed it by formula.

Methods

PET imaging for spherical tumors with a different tumor diameter (D), under different system resolutions [full width at half maximum (FWHM)], in different backgrounds with different pixel sizes, was simulated. PET images were analyzed to determine the relationship between the threshold and the factors mentioned above. Finally, the simulation results were verified by phantom experiments.

Results

The threshold decreased sharply with D for D < 2 FWHM, reached the minimum of 31% at D = 2 FWHM and then increased slowly, and it tended to constant for D > 8 FWHM. The threshold decreased with FWHM for FWHM < D/2, reached a minimum at FWHM = D/2, and then increased. The threshold increased with pixel size for D ≤ FWHM and decreased for D > FWHM. The threshold was independent of the background. The relationship between the threshold and its influencing factors was expressed as a formula. The results of the phantom verification indicated that the error of the target volume delineation that was calculated by the formula was less than 9%.

Conclusions

The threshold changes with tumor size, resolution of the PET system and pixel size according to certain rules. The formula to calculate the threshold could provide a method to estimate threshold to outline the radiotherapy target (tumor).

Volumetric parameters derived from FLT-PET performed at completion of treatment predict efficacy of Carbon-ion Radiotherapy in patients with locally recurrent Nasopharyngeal Carcinoma

The purpose of this study was to investigate the role of 3'-deoxy-3'-[¹⁸F]fluorothymidine (FLT)-PET for predicting the outcome of patients with locally recurrent nasopharyngeal carcinoma (LR-NPC) treated by carbon-ion radiotherapy (CIRT). Patients received FLT-PET/CT scan one-week prior to or after completion of CIRT were enrolled in the study. All patients were from prospective trials or treated using a standardized protocol. Time-dependent receiver operator characteristics (ROC) were used to determine the optimal cutoff values for FLT-PET parameters. Univariable and multivariable analyses of local progression-free survival (LPFS) were performed using Cox regression, to examine the prognostic value of FLT-PET parameters, including SUV_max, metabolic tumor volume (MTV) and total lesion thymidine (TLT). A total of 41 patients were enrolled. Elevated MTV and TLT were significantly associated with worse LPFS, in both univariable and multivariable analyses. ROC analysis revealed that both an MTV value higher than 8.6 and a TLT value higher than 14.9 were predictive of increased risk of developing local recurrence, the adjusted HRs were 5.59 (p=0.009) and 7.76 (p=0.002), respectively. In conclusion, FLT-PET was found to be a promising prognostic tool for LR-NPC patients and might play a role in the treatment guidance.

Predicting response to radiotherapy in tumors with PET/CT: when and how?

Radiotherapy is one of the main methods for tumor treatment, with the improved radiotherapy delivery technique to combat cancer, there is a growing interest for finding effective and feasible ways to predict tumor radiosensitivity. Based on a series of changes in metabolism, microvessel density, hypoxic microenvironment, and cytokines of tumors after radiotherapy, a variety of radiosensitivity detection methods have been studied. Among the detection methods, positron emission tomography-computed tomography (PET/CT) is a feasible tool for response evaluation following definitive radiotherapy for cancers with a high negative predictive value. The prognostic or predictive value of PET/CT is currently being studied widely. However, there are many unresolved issues, such as the optimal probe of PET/CT for radiosensitivity prediction, the selection of the most useful PET/CT parameters and their optimal cut-offs such as total lesion glycolysis (TLG), metabolic tumor volume (MTV) and standardized uptake value (SUV), and the optimal timing of PET/CT pre-treatment, during or following RT. Different radiosensitivity of tumors, modes of radiotherapy action and fraction scheduling may complicate the appropriate choice. In this study, we will discuss the diverse methods for evaluating radiosensitivity, and will also focus on the selection of the optimal probe, timing, cut-offs and parameters of PET/CT for evaluating the radiotherapy response.

FLT-PET At 6 Weeks Predicts Response Assessed by CT at 12 Weeks in Melanoma Patients Treated With Pembrolizumab

PURPOSE

Investigate the ability of F-fluorothymidine (FLT) PET combined with CT at 6 weeks to predict treatment response at 12 weeks after treatment with pembrolizumab.

METHODS

Five patients with unresectable stage IV melanoma were included in this single-institution pilot study. Patients underwent FLT-PET/CT (baseline and 6 weeks) and CT (baseline and 12 weeks). FLT-PET/CT response and CT response were assessed using PET Response Criteria in Solid Tumors and immune Response Evaluation Criteria in Solid Tumors, respectively. Patients were categorized as responders (complete response, partial response) and nonresponders (stable disease, progressive disease). Agreement between 6-week FLT-PET/CT and 12-week CT was calculated using Cohen kappa's agreement. Eight baseline FLT-PET/CT parameters were extracted: SUVmax, SUVpeak, SUVSD, SUVmean, proliferative tumor volume, total lesion proliferation, bone marrow-to-liver SUVmax ratio, and spleen-to-liver SUVmax ratio. Eight delta-parameters were extracted at 6 weeks by calculating variation in FLT uptake as percentage change from baseline.

RESULTS

Agreement between 6-week FLT-PET/CT and 12-week CT was kappa = 0.615, P = 0.025. Three of 5 patients were categorized as responders on CT by immune Response Evaluation Criteria in Solid Tumors. At baseline, responders had a lower mean proliferative tumor volume and a higher bone marrow-to-liver SUVmax ratio. At 6 weeks, responders demonstrated a decrease in tumor volume and tumor proliferation.

CONCLUSIONS

Our study illustrates the potential for FLT-PET/CT as an early predictor of response for patients with metastatic melanoma on anti-PD1 immunotherapy. Larger studies are indicated to confirm these findings.

Assessment of tumour hypoxia, proliferation and glucose metabolism in head and neck cancer before and during treatment

OBJECTIVE

The aim of the study was to assess the feasibility of multitracer positron emission tomography (PET) imaging before and during chemoradiation and to evaluate the predictive value of image-based factors for outcome in locally advanced head and neck cancers treated with chemoradiation.

METHODS

In the week prior to the treatment [¹⁸F]-2-flu-2-deoxy-D-glucose (FDG), [¹⁸F]-3'-flu-3'deoxythymidine (FLT) and [¹⁸F]-flumisonidazole (FMISO) imaging was performed. FLT scans were repeated at 14 and 28 Gy and FMISO at 36 Gy. Overall survival, disease-free survival and local control were correlated with subvolume parameters, and with tumour-to-muscle ratio for FMISO. For every tracer, total metabolic tumour volume was calculated.

RESULTS

33 patients were included. No correlation was found between pre-treatment maximum standardised uptake value for FDG, FLT, FMISO and outcomes. Tumour volume measured on initial CT scans and initial FLT volume correlated with disease-free survivall (p = 0.007 and 0.04 respectively). FDG and FLT metabolic tumour volumes correlated significantly with local control (p = 0.005 and 0.02 respectively). In multivariate Cox analysis only individual initial TMRmax correlated with overall survival.

CONCLUSION

PET/CT imaging is a promising tool. However, various aspects of image analysis need further clinical validation in larger multicentre study employing uniform imaging protocol and standardisation, especially for hypoxia tracer.

ADVANCES IN KNOWLEDGE

Monitoring of biological features of the tumour using multitracer PET modality seems to be a feasible option in daily clinical practice.Evaluation of hypoxic subvolumes is more patient dependent; thus, exploration of individual parameters of hypoxia is needed. tumour-to-muscle ratio seems to be the most promising so far.

Comparison of different images in gross target volume delineating on VX2 nasopharyngeal transplantation tumor models

Background: To determine the optimum conditions for diagnosis of nasopharyngeal carcinoma, we established VX2 rabbit model to delineate gross target volume (GTV) in different imaging methods. Methods: The orthotopic nasopharyngeal carcinoma (NPC) was established in sixteen New Zealand rabbits. After 7-days inoculation, the rabbits were examined by CT scanning and then sacrificed for pathological examination. To achieve the best delineation, different GTVs of CT, MRI, ¹⁸F-FDG PET/CT, and ¹⁸F-FLT PET/CT images were correlated with pathological GTV (GTVp). Results: We found 45% and 60% of the maximum standardized uptake value (SUV_max) as the optimal SUV threshold for the target volume of NPC in ¹⁸F-FDG PET/CT and ¹⁸F-FLT PET/CT images, respectively (GTV_FDG45% and GTV_FLT60%). Moreover, the GTV_MRI and GTV_CT were significantly higher than the GTVp (P ≤ 0.05), while the GTV_FDG45% and especially GTV_FLT60% were similar to the GTVp (R = 0.892 and R = 0.902, respectively; P ≤ 0.001). Conclusions: Notably, the results suggested that ¹⁸F-FLT PET/CT could reflect the tumor boundaries more accurately than ¹⁸F-FDG PET/CT, MRI and CT, which makes ¹⁸F-FLT PET-CT more advantageous for the clinical delineation of the target volume in NPC.

Feasibility of multiparametric imaging with PET/MR in nasopharyngeal carcinoma: A pilot study

OBJECTIVE

The aim of this pilot study was to explore the integrated positron emission tomography and magnetic resonance imaging scanner (PET/MR) for biological characterization of nasopharyngeal carcinoma (NPC) and potential therapeutic applications of dose painting (DP).

PATIENTS AND METHODS

Twenty-one NPC patients with PET/MR were included in this study. Overlap of tumor volumes was analyzed on T2-weighted images (volume of interest, VOI_T2), diffusion-weighted magnetic resonance imaging (VOI_DWI) and ¹⁸F-fluorodeoxyglucose positron emission tomography (VOI_PET). The overlap percentages of low-metabolic sub-region (cluster 1) and high-metabolic sub-region (cluster 2) in VOI_PET and VOI_DWI were analyzed by cluster analysis.

RESULTS

Both the VOI_DWI and VOI_PET were encompassed in the VOI_T2, respectively 99.6% and 97.5%. The median tumor overlap was 94.4% (VOI_DWI within VOI_PET). The median overlap of cluster 2 in VOI_PET and VOI_DWI was 43.61% (27.67-52.66%) and 21.86%(10.47-40.89%), respectively. The median overlap of cluster 1 in VOI_PET and VOI_DWI was 48.03% (23.91-63.15%) and 24.40% (7.44-51.44%), respectively. Separation between clusters appeared to be defined by a SUV value.

CONCLUSION

For NPC, the VOIs of DWI and FDG PET were not overlapped completely and the volume defined by cluster-analysis might be meaningful for DP.

Prospective evaluation of plasma Epstein-Barr virus DNA clearance and fluorodeoxyglucose positron emission scan in assessing early response to chemotherapy in patients with advanced or recurrent nasopharyngeal carcinoma

BACKGROUND

Plasma Epstein-Barr virus (pEBV) DNA and fluorodeoxyglucose positron emission (PET) reflect tumour burden in advanced NPC. This study hypothesised that a dual endpoint based on assessing pEBV DNA clearance and PET response could predict early drug response.

METHODS

Eligible patients underwent a computed tomography (CT) scan and dual PET-CT at baseline, a PET-CT at 4 weeks, and then a CT scan at 10 weeks after starting palliative or induction chemotherapy. Plasma EBV DNA clearance was determined.

RESULTS

Fifty-eight out of 70 enrolled patients completed all imaging and 50/58 had falling pEBV DNA level, which allowed calculation of the clearance. At a median follow-up of 29.1 months, the dual endpoint (pEBV DNA clearance ≤ 10 days and > 50% drop in sum of SUVmax of target lesions) was an independent indicator of overall survival (hazard ratio (HR) = 0.135, 95% CI = 0.039 to 0.466, p = 0.0015) and progression-free survival (HR = 0.136, 95% CI = 0.048 to 0.385, p = 0002). This dual endpoint could predict subsequent response by Response Evaluation Criteria In Solid Tumours (RECIST) criteria at 10 weeks after chemotherapy.

CONCLUSIONS

Early PET-CT response and pEBV DNA clearance could predict survival and subsequent response. This dual endpoint is an innovative tool for assessing early drug response.