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Purpose: To evaluate the use of hyperpolarized [1- 13 C]pyruvate magnetic resonance spectroscopic imaging (HP- 13 C MRSI) for quantitative measurement of early changes in glycolytic metabolism and its ability to predict response to pan-tyrosine kinase inhibitor (Pan-TKI) therapy in gastric cancer (GCa)., Procedures: Pan-TKI afatinib-sensitive NCI-N87 and resistant SNU16 human GCa cells were assessed for GLUT1, hexokinase-II (HKII), lactate dehydrogenase (LDHA), phosphorylated AKT (pAKT), and phosphorylated MAPK (pMAPK) at 0-72 h of treatment with 0.1 μM afatinib. Subcutaneous NCI-N87 tumor-bearing nude mice underwent [ 18 F]FDG PET/MRI and HP- 13 C MRSI at baseline and 4 days after treatment with afatinib 10 mg/kg/day or vehicle (n = 10/group). Changes in PET and HP- 13 C MRSI metabolic parameters were compared between the two groups. Imaging findings were correlated with tumor growth and histopathology over 3 weeks of treatment., Results: In vitro analysis showed a continuous decrease in LDHA, pAKT, and pMAPK in NCI-N87 compared to SNU16 cells within 72 h of treatment with afatinib, without a significant change in GLUT1 and HKII in either cell type. [ 18 F]FDG PET of NCI-N87 tumors showed no significant change in PET measures at baseline and day 4 of treatment in either treatment group (SUVmean day 4/day 0: 2.7 ± 0.42/2.34 ± 0.38, p = 0.57 in the treated group vs. 1.73 ± 0.66/2.24 ± 0.43, p = 0.4 in the control group). HP- 13 C MRSI demonstrated significantly decreased lactate-to-pyruvate ratio (L/P) in treated tumors (L/P day 4/day 0: 0.83 ± 0.30/1.10 ± 0.20, p = 0.012 vs. 0.94 ± 0.20/0.98 ± 0.30, p = 0.75, in the treated vs. control group, respectively). Response to afatinib was confirmed with decreased tumor size over 3 weeks (11.10 ± 16.50 vs. 293.00 ± 79.30 mm 3 , p < 0.001, treated group vs. control group, respectively) and histopathologic evaluation., Conclusions: HP- 13 C MRSI is a more representative biomarker of early metabolic changes in response to pan-TKI in GCa than [ 18 F]FDG PET and could be used for early prediction of response to targeted therapies., (© 2022. World Molecular Imaging Society.)

Purpose: Radiation therapy (RT) is an effective treatment for unresectable cholangiocarcinoma (CC). Accurate tumor volume delineation is critical in achieving high rates of local control while minimizing treatment-related toxicity. This study compares 18 F-FDG PET/MR to MR and CT for target volume delineation for RT planning., Methods: We retrospectively included 22 patients with newly diagnosed unresectable primary CC who underwent 18 F-FDG PET/MR for initial staging. Gross tumor volume (GTV) of the primary mass (GTV M ) and lymph nodes (GTV LN ) were contoured on CT images, MR images, and PET/MR fused images and compared among modalities. The dice similarity coefficient (DSC) was calculated to assess spatial coverage between different modalities., Results: GTV M PET/MR (median: 94 ml, range 16-655 ml) was significantly greater than GTV M MR (69 ml, 11-635 ml) (p = 0.0001) and GTV M CT (96 ml, 4-564 ml) (p = 0.035). There was no significant difference between GTV M CT and GTV M MR (p = 0.078). Subgroup analysis of intrahepatic and extrahepatic tumors showed that the median GTV M PET/MR was significantly greater than GTV M MR in both groups (117.5 ml, 22-655 ml vs. 102.5 ml, 22-635 ml, p = 0.004 and 37 ml, 16-303 ml vs. 34 ml, 11-207 ml, p = 0.042, respectively). The GTV LN PET/MR (8.5 ml, 1-27 ml) was significantly higher than GTV LN CT (5 ml, 4-16 ml) (p = 0.026). GTV PET/MR had the highest similarity to the GTV MR , i.e., DSC PET/MR-MR (0.82, 0.25-1.00), compared to DSC PET/MR-CT of 0.58 (0.22-0.87) and DSC MR-CT of 0.58 (0.03-0.83)., Conclusion: 18 F-FDG PET/MR-based CC delineation yields greater GTVs and detected a higher number of positive lymph nodes compared to CT or MR, potentially improving RT planning by reducing the risk of geographic misses., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Purpose: To compare the diagnostic performance of qualitative and quantitative 18F-FDG PET/CT in detection of regional and distant lymph node metastasis in patients with anal cancer., Methods: Between 2004 and 2017, 28 patients with anal cancer who had staging PET/CT and pathological assessment of suspicious lymph nodes were included. For qualitative analysis, positive lymph nodes were defined as uptake visually higher than the liver reference uptake. For quantitative study, lymph nodes were contoured to determine maximum standard uptake value (SUV max ) and metabolic tumor volume (MTV). Receiver operating characteristic (ROC) curves were plotted to extract the optimal cut-offs and area under the curve (AUC) of SUV max , lesion to background (L/B) ratio, short axis diameter (SAD), and MTV of lymph nodes. Histopathologic analysis was a reference standard., Results: A total of 28 lymph nodes (24 inguinal, 2 external iliac, 1 internal iliac, and 1 paraaortic nodes) in 28 patients on PET/CT were included. With the qualitative visual analysis, 19 patients were categorized as positive for nodal metastasis with sensitivity, specificity, and accuracy of 85%, 75%, and 82%. The optimal SUV max and L/B ratio cut-offs were 2.6 and 1.0 with both sensitivity and specificity of 95% and 75% (AUC of SUV max  = 0.893, AUC of L/B ratio = 0.912). Using the best cut-off of 1.6 cm for SAD and 3.65 cm 3  for MTV, both sensitivity and specificity were 80% and 100% (AUC of SAD = 0.950, AUC of MTV = 0.931)., Conclusions: SUV max optimization may be helpful in enhancing the diagnostic accuracy of 18F-FDG PET/CT in nodal staging patients with anal cancer.

Esophageal cancer is the third most common malignancy of the alimentary tract. The incidence of esophageal cancer has steadily increased over the past three decades. Almost all therapeutic modalities for esophageal cancer are associated with a considerable mortality and morbidity. Consequently, there has been growing concern regarding effective management of esophageal cancer. 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET) is playing an increasing role in the management of esophageal cancer, offering potential advantages in the accuracy of disease assessment at a number of decision points in the management pathway. This review evaluates the critical role of FDG-PET in (i) diagnosis, (ii) preoperative staging, (iii) monitoring of response to neoadjuvant therapy, (iv) assessment of recurrence and (v) prediction of prognosis of esophageal cancer. We have also compared diagnostic performance of FDG-PET and other current technologies such as computed tomography scan and endoscopic ultrasonography based on available evidence.