O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) PET as a potential selection tool for second surgery in glioblastoma patients.

BACKGROUND: Treatment-related changes still represent a diagnostic challenge in the management of patients with suspect of recurrent glioblastoma. The specificity of conventional MRI in detecting recurrence remains limited. Brain PET imaging provides information on tumor metabolism and can contribute to improving the diagnostic accuracy of cerebral neoplasms. We performed a retrospective analysis to evaluate the clinical value of O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) PET in the diagnosis of glioblastoma recurrence. METHODS: A retrospective analysis on patients considered suitable for salvage surgery for recurrence glioblastoma was performed. 18F-FET-PET was performed to investigate gadolinium enhancement suspected for recurrence. Static and kinetic 18F-FET parameters were analyzed and related to O-6-methylguanine-DNA methyltransferase (MGMT) status. RESULTS: Forty-two of the 51 patients who underwent 18F-FET-PET were re-operated. In each case, neuropathological diagnosis of tumor recurrence was confirmed. pMGMT hypermethylation was detected in 21 patients. Mean tumor-to-brain ratios (TBR) max was 3.87 (range 2.6-6.0). Static and kinetic 18F-FET parameters were similar according to MGMT status. CONCLUSIONS: 18FET-PET can be a reliable tool to improve the selection of patients suitable for salvage surgery for glioblastoma recurrence.

Innovative Approach to Isolate and Characterize Glioblastoma Circulating Tumor Cells and Correlation with Tumor Mutational Status.

Circulating tumor cells (CTCs) are one of the most important causes of tumor recurrence and distant metastases. Glioblastoma (GBM) has been considered restricted to the brain for many years. Nevertheless, in the past years, several pieces of evidence indicate that hematogenous dissemination is a reality, and this is also in the caseof GBM. Our aim was to optimize CTCs' detection in GBM and define the genetic background of single CTCs compared to the primary GBM tumor and its recurrence to demonstrate that CTCs are indeed derived from the parental tumor. We collected blood samples from a recurrent IDH wt GBM patient. We genotyped the parental recurrent tumor tissue and the respective primary GBM tissue. CTCs were analyzed using the DEPArray system. CTCs Copy Number Alterations (CNAs) and sequencing analyses were performed to compare CTCs' genetic background with the same patient's primary and recurrent GBM tissues. We identified 210 common mutations in the primary and recurrent tumors. Among these, three somatic high-frequency mutations (in PRKCB, TBX1, and COG5 genes) were selected to investigate their presence in CTCs. Almost all sorted CTCs (9/13) had at least one of the mutations tested. The presence of TERT promoter mutations was also investigated and C228T variation was found in parental tumors and CTCs (C228T heterozygous and homozygous, respectively). We were able to isolate and genotype CTCs from a patient with GBM. We found common mutations but also exclusive molecular characteristics.

Optimal detection of sentinel lymph node metastases by intraoperative radioactive threshold and molecular analysis in patients with melanoma.

UNLABELLED: The aim of this study was to optimize a protocol for radioguided biopsy of the sentinel lymph node (SLN) in patients with melanoma. The protocol was based on a combination of ex vivo counting of the nodes detected intraoperatively and analysis of the harvested nodes by hematoxylin and eosin staining plus immunohistochemistry (conventional histopathology [PATH]) and by molecular biology (reverse-transcriptase polymerase chain reaction [RT-PCR]). METHODS: A total of 124 patients with primary clinical stage I-II (according to the American Joint Committee on Cancer) cutaneous melanoma underwent successful radioguided SLN biopsy. SLNs harvested for analysis included any additional nodes whose ex vivo counting rate exceeded 20% of the hottest node. All removed SLNs were examined by conventional PATH and with RT-PCR analysis for the expression of messenger RNA for tyrosinase and the melanoma antigens recognized by T cells. Complete lymph node dissection (CLND) was performed only in the case of SLN metastasis detected by PATH. Different combinations of the intraoperative parameters (only the hottest node and all nodes harvested) and of analysis (PATH and RT-PCR) were tested as predictors of clinical outcome on the basis of long-term follow-up (12-81 mo; median, 55 mo). RESULTS: A total of 197 SLNs were harvested, 41 of which harbored metastasis as detected by RT-PCR analysis; PATH detected metastasis in only 24 of 41 metastatic SLNs. In 5 of 41 instances, metastasis was not in the hottest SLN. The main factor determining correct classification of the SLN status was RT-PCR, which significantly improved detection of metastasis, even if applied only to the hottest node (P < 0.0001 vs. PATH analysis of either the hottest SLN or all nodes above the 20% threshold). Metastatic disease recurred locally in 5 patients who had not undergone CLND; RT-PCR analysis showed metastasis in 4 of these patients. The false-negative rate of SLN biopsy progressively decreased when applying PATH only to the hottest node (32.1%), additional RT-PCR to the hottest node (21.4%), PATH to all nodes (17.9%), and RT-PCR to all nodes (3.6%, P = 0.015 vs. PATH analysis of only the hottest SLN). CONCLUSION: On the basis of long-term follow-up (the gold standard for final clinical outcome of SLN biopsy), both 20% threshold and RT-PCR analysis should be applied for optimal detection of nodal metastases in patients with melanoma.