Can Baseline [18F]FDG PET/CT Predict Response to Immunotherapy After 6 Months and Overall Survival in Patients with Lung Cancer or Malignant Melanoma? A Multicenter Retrospective Study.

Aim: To assess the role of baseline 18F-fluorodeoxyglucose ([18F]FDG)-positron emission tomography/computed tomography (PET/CT) in predicting response to immunotherapy after 6 months and overall survival (OS) in patients with lung cancer (LC) or malignant melanoma (MM). Materials and Methods: Data from a multicenter, retrospective study conducted between March and November 2021 were analyzed. Patients >18 years old with a confirmed diagnosis of LC or MM, who underwent a baseline [18F]FDG-PET/CT within 1-2 months before starting immunotherapy and had a follow-up of at least 12 months were included. PET scans were examined visually and semiquantitatively by physicians at peripheral centers. The metabolic tumor burden (number of lesions with [18F]FDG-uptake) and other parameters were recorded. Clinical response was assessed at 3 and 6 months after starting immunotherapy, and OS was calculated as the time elapsing between the PET scan and death or latest follow-up. Results: The study concerned 177 patients with LC and 101 with MM. Baseline PET/CT was positive in primary or local recurrent lesions in 78.5% and 9.9% of cases, in local/distant lymph nodes in 71.8% and 36.6%, in distant metastases in 58.8% and 84%, respectively, in LC and in MM patients. Among patients with LC, [18F]FDG-uptake in primary/recurrent lung lesions was more often associated with no clinical response to immunotherapy after 6 months than in cases without any tracer uptake. After a mean 21 months, 46.5% of patients with LC and 37.1% with MM had died. A significant correlation emerged between the site/number of [18F]FDG foci and death among patients with LC, but not among those with MM. Conclusions: In patients with LC who are candidates for immunotherapy, baseline [18F]FDG-PET/CT can help to predict response to this therapy after 6 months, and to identify those with a poor prognosis based on their metabolic parameters. For patients with MM, there was only a weak correlation between baseline PET/CT parameters, response to therapy, and survival.

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

AIM: To examine the role of [18F]FDG PET/CT for assessing response to immunotherapy in patients with some solid tumors. METHODS: Data recorded in a multicenter (n = 17), retrospective database between March and November 2021 were analyzed. The sample included patients with a confirmed diagnosis of a solid tumor who underwent serial [18F]FDG PET/CT (before and after one or more cycles of immunotherapy), who were >18 years of age, and had a follow-up of at least 12 months after their first PET/CT scan. Patients enrolled in clinical trials or without a confirmed diagnosis of cancer were excluded. The authors classified cases as having a complete or partial metabolic response to immunotherapy, or stable or progressive metabolic disease, based on a visual and semiquantitative analysis according to the EORTC criteria. Clinical response to immunotherapy was assessed at much the same time points as the serial PET scans, and both the obtained responses were compared. RESULTS: The study concerned 311 patients (median age: 67; range: 31-89 years) in all. The most common neoplasm was lung cancer (56.9%), followed by malignant melanoma (32.5%). Nivolumab was administered in 46.3%, and pembrolizumab in 40.5% of patients. Baseline PET and a first PET scan performed at a median 3 months after starting immunotherapy were available for all 311 patients, while subsequent PET scans were obtained after a median 6, 12, 16, and 21 months for 199 (64%), 102 (33%), 46 (15%), and 23 (7%) patients, respectively. Clinical response to therapy was recorded at around the same time points after starting immunotherapy for 252 (81%), 173 (56%), 85 (27%), 40 (13%), and 22 (7%) patients, respectively. After a median 18 (1-137) months, 113 (36.3%) patients had died. On Kaplan-Meier analysis, metabolic responders on the first two serial PET scans showed a better prognosis than non-responders, while clinical response became prognostically informative from the second assessment after starting immunotherapy onwards. CONCLUSIONS: [18F]FDG PET/CT could have a role in the assessment of response to immunotherapy in patients with some solid tumors. It can provide prognostic information and thus contribute to a patient's appropriate treatment. Prospective randomized controlled trials are mandatory.

[18F] Fluorothymidine Positron Emission Tomography Imaging in Primary Brain Tumours: A Systematic Review.

PURPOSE: This review aimed to summarize the available literature on the clinical application of [18F] FLT PET imaging in primary brain tumours. METHODS: A comprehensive search strategy based on Pubmed/Medline, Scopus, Web of Science, Cochrane Library, Google Scholar, and the Embase databases was carried on using the following search string: ('3` Fluorothymidine'/exp OR 'FLT' OR '[81F]-FLT' OR '[18F] Fluorothymidine') AND ('pet'/exp OR 'pet' OR 'positron emission tomography') AND ('glioma'/exp OR 'glioma' OR 'brain tumour'/exp OR 'brain tumour'). The search was updated till March 2021 and only articles in English and studies investigating the clinical applications of [18F] FLT PET and PET/CT in primary brain tumours were considered eligible for inclusion. RESULTS: The literature search ultimately yielded 52 studies included in the systematic review, with main results as follows: a) the uptake of [18F] FLT may guide stereotactic biopsy but does not discriminate between grade II and III glioma. b) [18F] FLT uptake and texture parameters correlate with overall survival (OS) in newly diagnosed gliomas. c) In patients with recurrent glioma, proliferative volume (PV) and tumour-to-normal brain (T/N) uptake ratio are independent predictors of survival. d) Patients demonstrating response to therapy at [18F] FLT PET scan show longer OS compared to non-responders. e) [18F] FLT PET demonstrated good performance in discriminating tumour recurrence from radionecrosis. However, controversial results exist in comparative literature examining the performance of [18F] FLT vs. other radiotracers in the assessment of recurrence. CONCLUSION: [18F] FLT PET imaging has demonstrated potential benefits for grading, diagnostic and prognostic purposes, despite the small sample size studies due to the relatively low availability of the radiotracer.

Performance of FDG PET/ceCT in the evaluation of patients with lung cancer.

AIM: The aim of this study was to assess the performance of FDG PET/ceCT simultaneously acquired, contemporary read and finally discussed by the radiologist and the nuclear medicine physician for staging and restaging lung cancer patients. METHODS: We analysed 17 consecutive patients (7F; 10M; mean age 68). Six patients were in staging, 8 patients were in restaging (1 during therapy, 2 after therapy and 5 during the follow-up) and 2 patients needed to characterise a suspect pulmonary mass. All the patients underwent combined FDG PET/CT and ceCT acquired simultaneously on the same tomograph. The images were read and reported together by the nuclear medicine physician and the radiologist. RESULTS: None of the patients had adverse reactions nor complained about the procedure. Thirteen FDG PET/ceCT turned out positive, while 4 were completely negative. Among positive patients, a significant SUV max was detected in all the cases (range 1.8-17.5). In the end, 9 patients had a true positive result, 4 true negative, 3 false positive and 1 false negative. Sensitivity, specificity and accuracy of the combined procedure were 90%, 57% and 76% respectively. In 7/17 patients FDG PET/CT and ceCT were completely concordant. FDG PET/CT provided a significant impact on the final interpretation in 7/17 patients while ceCT had a major impact in 3/17 patients. DISCUSSION: This preliminary study shows that FDG PET/ceCT is a feasible technique for lung cancer patients, providing an optimal sensitivity (90%). From our results it is advisable not to include patients without an histological diagnosis of cancer due to possible false positivity of the two methods, significantly reducing specificity. However, a proper patient selection is not easy and the future of this combined test relies essentially on the capacity to early identify only the subjects who would really benefit from both the procedures.