Preoperative Positron Emission Tomography Scans Research Articles

Surgical Resection After Talimogene Laherparepvec for Melanoma: Persistent Fuorodeoxyglucose Avidity on Positron Emission Tomography Despite No Viable Disease

Talimogene laherparepvec (TVEC) is an injectable attenuated oncolytic herpes simplex virus (HSV-1) used in the treatment of loco regionally metastatic melanoma. Lesions managed by TVEC are generally considered unresectable at time of initiation of intralesional therapy; however, a subset of patients go on to have surgical resection of loco regionally controlled disease. We sought to review our experience with surgical excision of treated lesions to offer an insight into the radiologic correlate, treatment effect, and pathological findings of intralesional TVEC therapy. This is a retrospective descriptive case series of patients who underwent TVEC injection at Mayo Clinic, Rochester, MN, between October 2016 and July 2020. Institutional Institutional Review Board approval was obtained. Twenty-one patients underwent intralesional TVEC, met inclusion criteria, and were included in this series. Seven went on to surgical excision of the injected lesions after an initial course of TVEC. Of those 7 patients, 4 had residual melanoma in the specimen on final pathology, while 3 had a complete pathologic response. All 3 patients who had no residual disease on pathology continued to have fluorodeoxyglucose (FDG) avidity on preoperative positron emission tomography scan of the excised lesions. Despite ongoing FDG avidity on PET scan, patients who have well-controlled disease and stability over time of the injected lesions may benefit from surgical excision following a course of TVEC. This may render the patient clinically disease free and/or allow them a reprieve from TVEC treatment.

P04.07 Correlation of 18F-fluorethyl-L-tyrosine (18F-FET) uptake in positron emission tomography (PET) and MRI growth rate in low-grade glioma

Abstract BACKGROUND Low-grade gliomas (LGGs, WHO grade II) are a heterogeneous group of tumors of the central nervous system with diverse behavior in histopathology, genetics and growth patterns. Therefore, different therapeutic strategies are discussed ranging from watchful waiting to radical resection and adjuvant radio-/chemotherapy. For a better evaluation of tumor progression or malignant transformation, the O-(2-18F-fluoroethyl)-L-tyrosine (18F-FET) uptake in PET or the tumor growth rate assessed on MRI are used depending on the neurooncological center. Here, we correlated both methods. MATERIAL AND METHODS Inclusion criteria for this retrospective study were (1) newly diagnosed and neuropathologically confirmed low-grade glioma; (2) at least two MRIs at initial diagnosis and follow-up for calculation of the tumor growth rate (using IDS7 by Sectra AB, Sweden, 2018); (3) and an additional preoperative 18F-FET PET scan. RESULTS From 2008 to 2018, 34 patients were identified (mean age 39.7 years; 68% diffuse astrocytoma). The mean tumor growth rate on MRI was 0.091 cm3/d. The average mean 18F-FET uptake was 1.42; the average maximum 18F-FET uptake was 2.18. The Pearson correlation coefficient between the tumor growth rate and the mean and maximum 18F-FET uptake was r=0.19, and r=0.10. In the group of diffuse astrocytomas, the mean growth rate in tumors with a mean 18F-FET uptake of >1.5 was significantly higher than the mean growth rate of those with a mean 18F-FET uptake of ≤1.5 (p<0.1). CONCLUSION Data suggest that astrocytic LGGs with increased 18F-FET uptake may show a more aggressive behaviour, with a potentially higher risk for an earlier tumor progression or malignant transformation. For further elucidation of a correlation between the tumor growth rate and the 18F-FET uptake, larger prospective studies are needed. In the future, the combination of both methods in the management of low-grade gliomas could help to detect tumor progression as well as tumor malignization more precisely.

Pre-Operative Perihepatic Lymph Node Assessment in Colorectal Cancer Liver Metastasis—A Review of Current Literature

Objective: Perihepatic lymph node involvement in colorectal cancer liver metastases is a negative prognostic factor. Resection of certain nodal stations around the liver has been shown to possibly improve survival. The aim of this review is to interrogate current literature on pre-operative investigations in diagnosing lymph node involvement. Method: A systematic review was conducted of articles published since 2006 to determine usefulness of pre-operative imaging in diagnosing lymph node involvement in colorectal cancer liver metastases. Results: Only 2 papers met the inclusion criteria for this study. Computed tomography (CT) scans were found to have sensitivities of 33% and 40%, specificities of 94% and 92%, positive predictive values (PPV) of 56% and 30%, and negative predictive values (NPV) of 85% and 95%. Positron emission tomography (PET) was studied in one of the paper and was found to have sensitivity, specificity, PPV and NPV of 57%, 100%, 100%, and 88% respectively. Conclusion: There is a significant lack of research on pre-operative investigations of perihepatic lymph node involvement in colorectal cancer liver metastases. Pre-operative CT and PET scans in assessing perihepatic lymph nodes were shown to be inaccurate. Newer pre-operative imaging modalities and research would be needed.

Hope Is Palliative

The authors reflect on the palliative value of hope when dealing with illness.

False-positive rate of positron emission tomography/computed tomography for presumed solitary metastatic adrenal disease in patients with known malignancy.

The aim of this study was to determine the diagnostic accuracy of positron emission tomography (PET) in cancer patients undergoing adrenalectomy for presumed metastatic disease, utilizing the gold standard of histopathology. We retrospectively reviewed all adrenalectomies for metastatic disease performed at our institution over the last 12years. Preoperative PET scans were compared with final pathology reports. Statistical analyses were performed with Fisher's exact test for categorical variables and Student's t test for continuous variables. Forty-nine adrenalectomies were performed for metastatic disease. Thirty had preoperative PET imaging and were included in this analysis. Mean age was 65.5±13.6years (29-91) and 54% were male. Mean size was 3.8cm (0.4-7.1). Primary tumor distribution was 61% (n=17) pulmonary; 11% (n=3) breast; 7% (n=2) gastric; 7% (n=2) renal; and 4% (n=1) each of brain, lymphoma, melanoma, and uterine. Mean standardized uptake value (SUV) was 11±7.3 (3.2-30.0). Final pathology revealed that 80% (25/30) were positive for metastatic disease and 20% (5/30) were negative. The positive predictive value of PET in correctly identifying adrenal metastatic disease was 83% (24 true-positive cases and 5 false-positive cases); there was one false-negative PET. False-positive PET results were not correlated with sex (p=0.35), age (p=0.24), or maximum SUV units (p=0.26). The 20% false-positive rate for PET-positive adrenalectomies performed for metastatic disease should warrant its inclusion in preoperative counseling to the patient and interaction with the treating oncologist.

Thoracoscopic approach to bilateral pulmonary metastasis: is it justified?

There are few reports on optimal surgical approaches to bilateral pulmonary metastasis and the sequences used in the operation. The aim of this study was to evaluate the feasibility of the thoracoscopic bilateral approach to pulmonary metastasis. From June 2006 to February 2013, 61 patients underwent a planned bilateral pulmonary metastasectomy with one- (n = 52) or two-stage (n = 9) thoracoscopic surgery. We retrospectively analysed the outcomes of this group of patients to define the role and limitation of thoracoscopic surgery in bilateral disease. In 17 patients with bilateral single lesions on the computed tomography (CT) scans, we were able to resect more nodules than initially imaged in 7 patients (41.2%), and there were 2 patients (11.8%) who had more true metastatic lesions than expected. Among 44 patients who showed more than two bilateral multiple lesions on the CT scan, we were able to resect more than 10 nodules in 2 patients (4.5%). The overall accuracy rate for resected malignant nodules was 76.6%, and 9 patients (14.8%) actually had the disease confined to the unilateral thorax, with solitary (n = 8) and multiple (n = 1) metastases after bilateral exploration. The prognostic factors for unilateral disease were unilateral lesion on the positron emission tomography (PET) scan (P = 0.024). The values of FVC and FEV1 were, respectively, 14.4 and 15.4% reduction at 6 months postoperatively in patients who had three or more nodules resected. Sarcomatous histology (P = 0.039), a diameter larger than 3 cm (P = 0.042) and bilateral lesion on PET (P = 0.035) were the prognostic factors for intrathoracic recurrences. Bilateral pulmonary metastasectomy was performed safely with thoracoscopy in patients with bilateral oligo-metastatic sub-pleural lesions and the one-stage approach was a feasible option in bilateral single lesions. Preoperative PET scan could help predict intrathoracic recurrence after thoracoscopic metastasectomy.

Abstract W P101: Surgical Revascularization Reverses Decreased Cerebral Oxygen Metabolism in Young Patients with Moyamoya Disease

Purpose: This prospective study was aimed to evaluate the effects of surgical revascularization on cerebral oxygen metabolism in moyamoya disease. Methods: This study included totally 41 patients who underwent STA-MCA anastomosis and indirect bypass for moyamoya disease between 2000 and 2011. There were 12 children and 29 adults. Totally 67 hemispheres underwent surgery. MR imaging and 15O-gas positron emission tomography (PET) were performed before and 3 to 4 months after surgery. Hemodynamic and metabolic parameters were precisely quantified. Results: Preoperative PET scans revealed that cerebral metabolic rate for oxygen (CMRO2) was kept normal in 15 hemispheres (22%), but decreased in other 52 (78%). The incidence did not differ between pediatric and adult patients. Pronounced cerebral ischemia was observed in all hemispheres with decreased CMRO2. After surgery, CMRO2 value significantly improved to the normal level in 20 (38%) of 52 hemispheres, but did not change in other 32 (62%). Multivariate analysis showed that the predictors for postoperative CMRO2 normalization were patient’s age (younger than 40 years) and no parenchymal damage on MRI. Conclusion: These findings strongly suggest that cerebral oxygen metabolism is often depressed in response to dense and chronic cerebral ischemia in moyamoya disease. The phenomenon may be advantageous to protect the involved hemispheres against ischemia. Surgical revascularization may readily normalize oxygen metabolism in young patients without any parenchymal damage.

Brain opioid receptor density predicts motor cortex stimulation efficacy for chronic pain

The clinical effects of motor cortex stimulation (MCS) for neuropathic pain (NP) is thought to be mediated primarily by the secretion of endogenous opioids in humans and in animal models. Because opioid receptor density is itself decreased in patients with NP, we investigated whether the magnitude and distribution of the remaining opioid receptors in patients with NP could be biological predictors of the pain-relieving effects of MCS. Using 11C-diprenorphine positron emission tomography scans, opioid receptor availability was assessed in 15 patients suffering refractory NP, who subsequently received chronically implanted MCS. All patients underwent 2 preoperative baseline scans at 2-wk intervals and were clinically assessed after 7mo of chronic MCS. The levels of preoperative opioid-binding in the insula, thalamus, periaqueductal gray, anterior cingulate, and orbitofrontal cortex were significantly and positively correlated with postoperative pain relief at 7mo. Patients with receptor density values below the lower limits in age-matched controls in the thalamus, periaqueductal gray and contralateral insula were the least likely to benefit from MCS. Opioid-receptor availability as shown in preoperative positron emission tomography scans appears to be related to the efficacy of MCS in NP and may help clinicians to select the candidates most likely to benefit from this procedure.

Interictal PET and ictal subtraction SPECT: Sensitivity in the detection of seizure foci in patients with medically intractable epilepsy

Interictal positron emission tomography (PET) and ictal subtraction single photon emission computed tomography (SPECT) of the brain have been shown to be valuable tests in the presurgical evaluation of epilepsy. To determine the relative utility of these methods in the localization of seizure foci, we compared interictal PET and ictal subtraction SPECT to subdural and depth electrode recordings in patients with medically intractable epilepsy. Between 2003 and 2009, clinical information on all patients at our institution undergoing intracranial electroencephalography (EEG) monitoring was charted in a prospectively recorded database. Patients who underwent preoperative interictal PET and ictal subtraction SPECT were selected from this database. Patient characteristics and the findings on preoperative interictal PET and ictal subtraction SPECT were analyzed. Sensitivity of detection of seizure foci for each modality, as compared to intracranial EEG monitoring, was calculated. Fifty-three patients underwent intracranial EEG monitoring with preoperative interictal PET and ictal subtraction SPECT scans. The average patient age was 32.7 years (median 32 years, range 1-60 years). Twenty-seven patients had findings of reduced metabolism on interictal PET scan, whereas all 53 patients studied demonstrated a region of relative hyperperfusion on ictal subtraction SPECT suggestive of an epileptogenic zone. Intracranial EEG monitoring identified a single seizure focus in 45 patients, with 39 eventually undergoing resective surgery. Of the 45 patients in whom a seizure focus was localized, PET scan identified the same region in 25 cases (56% sensitivity) and SPECT in 39 cases (87% sensitivity). Intracranial EEG was concordant with at least one study in 41 cases (91%) and both studies in 23 cases (51%). In 16 (80%) of 20 cases where PET did not correlate with intracranial EEG, the SPECT study was concordant. Conversely, PET and intracranial EEG were concordant in two (33%) of the six cases where the SPECT did not demonstrate the seizure focus outlined by intracranial EEG. Thirty-three patients had surgical resection and >2 years of follow-up, and 21 of these (64%) had Engel class 1 outcome. No significant effect of imaging concordance on seizure outcome was seen. Interictal PET and ictal subtraction SPECT studies can provide important information in the preoperative evaluation of medically intractable epilepsy. Of the two studies, ictal subtraction SPECT appears to be the more sensitive. When both studies are used together, however, they can provide complementary information.

Accuracy of PET‐CT in Predicting Survival in Patients with Esophageal Cancer

Positron emission tomography (PET) is an integral part of tumor staging for patients with esophageal cancer. Recent studies suggest a role for PET scan in predicting survival in these patients, but this relationship is unclear in the setting of neoadjuvant therapy. We examined pretreatment maximum standard uptake value (SUV(max)) of the primary tumor in patients treated with and without neoadjuvant therapy. All patients undergoing esophagectomy with a preoperative PET scan over a nine-year period (2001-2010) were identified from a prospectively maintained database. Positron emission tomography data were obtained from computers housing the original PET scans. Overall survival was correlated with SUV(max) of the primary tumor. A total of 191 patients were identified, and 103 patients met inclusion criteria. Eighty-two had an adenocarcinoma (80%), and 21 (20%) had a squamous cell carcinoma. Fifty-seven (55%) patients received neoadjuvant therapy. In the surgery alone group, a SUV(max) of > 5.0 in the primary tumor was associated with poor prognosis [Hazard Ratio (HR) 0.32; p = 0.007], but this factor did not retain its significance on multivariate analysis (HR 0.65; p = 0.43). Pretreatment SUV(max) in patients who underwent neoadjuvant therapy was not significant in predicting overall survival (p = 0.10). This study does not support the use of SUV(max) on pretreatment PET scans as a prognostic tool for patients with esophageal cancer, especially in those who have received neoadjuvant therapy. Lymph node status is a more accurate predictor of outcome, and efforts to improve pretreatment staging should focus on this factor.

The Role of the (18)F-Fluorodeoxyglucose-Positron Emission Tomography Scan in the Nederlands Leuvens Longkanker Screenings Onderzoek Lung Cancer Screening Trial

In computed tomography lung cancer screening programs, up to 30% of all resections are futile. To investigate whether a preoperative positron emission tomography (PET) after a conclusive or inconclusive nonsurgical workup will reduce the resection rate for benign disease in test-positive participants of a lung cancer screening program. ¹⁸F-Fluorodeoxyglucose-PET scans were made in 220 test positives. Nodules were classified as positive, indeterminate, or negative based on visual comparison with background activity. Gold standard for a positive PET was the presence of cancer in the resection specimen or the detection of cancer during more than 2 years follow-up. Sensitivity, specificity, positive predictive value, and negative predictive value (NPV) were calculated at participant level and 95% confidence intervals (CIs) constructed. The sensitivity of PET to detect cancer was 84.2% (95% CI: 77.6-90.7%), the specificity 75.2% (95% CI: 67.1-83.3), the positive predictive value 78.9% (95% CI: 71.8-86.0), and the NPV 81.2% (95% CI: 73.6-88.8). The resection rate for benign disease was 23%, but 26% of them had a diagnosis with clinical consequences. A preoperative PET after an inconclusive nonsurgical workup reduced the resection rate for benign lesions by 11 to 15%, at the expense of missing 12 to 18% lung cancer cases. A preoperative PET after a conclusive nonsurgical workup reduced the resection rate by 78% at the expense of missing 3% lung cancer cases. A preoperative PET scan in participants with an inconclusive nonsurgical workup is not recommended because of the very low NPV, but after a conclusive nonsurgical workup, the resection rate for benign disease can be decreased by 72%.

Novel handheld PET probes provide intraoperative localization of PET-avid lymph nodes

The accurate intraoperative localization of malignant nodes can pose a challenge to the surgical oncologist. Positron emission tomography (PET) scanning has significantly increased our ability to detect suspicious lesions. We investigated the ability of a novel, handheld tool to evaluate suspicious nodes intraoperatively and to correlate its findings with those seen on preoperative PET scan. Ten nude rats were inoculated with a lymphogenic mesothelioma tumor line and followed weekly with PET scan studies. When suspicious lymph nodes were found, animals were dissected and the intraoperative amount of tissue radiation was analyzed as "tumor-to-background ratio" (TBR) using the PET probes. The intraoperative probe was used to guide dissections and select high-risk nodes based on their specific radiotracer uptake. A total of 52 nodes were harvested; eight of these were suspicious on preoperative PET scan studies. Using a TBR of 2.5, the intraoperative probes were able to localize all suspicious nodes previously seen on PET scan. Both gamma (sensitivity: 100%; specificity: 86%; positive predictive value (PPV): 57%; negative predictive value (NPV): 100%) and beta (sensitivity: 88%; specificity: 91%; PPV: 64%; NPV: 98%) probes showed an excellent area under the curve (AUC) in the receiver operating characteristic analysis (ROC). Both probes had an AUC of 0.95 for localizing suspicious nodes on PET scan. Furthermore, the AUC for detecting malignancy for the gamma probe was 0.90 (95% confidence interval (CI), 0.83-0.99), and for the beta probe it was 0.97 (95% CI, 0.94-1.0), suggesting a better performance of the beta probe for detecting malignancy. This novel tool may be used synergistically with the PET scan examination to maximize intraoperative nodal selection and sampling.

Existing General Population Models Inaccurately Predict Lung Cancer Risk in Patients Referred for Surgical Evaluation

Patients undergoing resections for suspicious pulmonary lesions have a 9% to 55% benign rate. Validated prediction models exist to estimate the probability of malignancy in a general population and current practice guidelines recommend their use. We evaluated these models in a surgical population to determine the accuracy of existing models to predict benign or malignant disease. We conducted a retrospective review of our thoracic surgery quality improvement database (2005 to 2008) to identify patients who underwent resection of a pulmonary lesion. Patients were stratified into subgroups based on age, smoking status, and fluorodeoxyglucose positron emission tomography (PET) results. The probability of malignancy was calculated for each patient using the Mayo and solitary pulmonary nodules prediction models. Receiver operating characteristic and calibration curves were used to measure model performance. A total of 189 patients met selection criteria; 73% were malignant. Patients with preoperative PET scans were divided into four subgroups based on age, smoking history, and nodule PET avidity. Older smokers with PET-avid lesions had a 90% malignancy rate. Patients with PET-nonavid lesions, PET-avid lesions with age less than 50 years, or never smokers of any age had a 62% malignancy rate. The area under the receiver operating characteristic curve for the Mayo and solitary pulmonary nodules models was 0.79 and 0.80, respectively; however, the models were poorly calibrated (p<0.001). Despite improvements in diagnostic and imaging techniques, current general population models do not accurately predict lung cancer among patients referred for surgical evaluation. Prediction models with greater accuracy are needed to identify patients with benign disease to reduce nontherapeutic resections.

Evaluation of PET imaging in treatment decision making for early stage head and neck squamous cell cancer

e17017 Background: Positron emission tomography (PET) scanning is widely used in staging of patients (pts.) with head and neck squamous cell cancers (HNSCC). However, the role of PET scan in pts. with early stage disease and clinically negative nodes remains controversial. The purpose of our study was to correlate preoperative PET scan findings in early stage disease with operative pathological findings of neck dissection. Methods: A retrospective review of medical records of all pts. treated at Long Island Jewish Medical Center with T1N0 HNSCC from 2002 to 2008 was undertaken. Institutional Review Board approval was obtained for this study. Eligibility criteria included: clinically staged T1N0, documented pre-operative PET scans and primary surgical management including a neck lymph node dissection as part of initial treatment. Data collected included age, gender, physical examination findings, PET scan results, operative pathology and modalities of treatment. Results: Sixty six pts with early stage T1N0 HNSCC were identified. Twelve of sixty six pts met eligibility criteria for this study. Median age was 61 years (range: 27 to 84 yrs), M:F ratio was 1:1. Primary sites of tumor were: tongue (n = 8) 67%; oral cavity (n = 3) 25%; larynx (n = 1) 8%. Preoperative PET scan was positive at primary sites in all pts (n = 12). Additionally, PET positivity was noted in regional lymph node sites in six of twelve pts. Operative pathology confirmed tumor presence in all primary sites. However, nodal involvement was not found in any pt. Median numbers of lymph nodes dissected were 25 (range:13–34). Based on these clinical data, the calculated statistical parameters for preoperative PET scan in detecting occult neck lymph node metastases were: negative predictive value: 100%; positive predictive value: 50%: specificity: 50%; sensitivity: 0%. Conclusions: The clinical application of PET scans in early stage (T1N0) HNSCC may be limited by its high false positive rate. A high negative predictive value suggests that a negative result can exclude metastatic lymph nodes involvement in this group of pts. with early stage disease. Correlation with SUV values of the PET scans and comparisons between the relative PET avidity of the primary tumors and the nodal uptake are ongoing. No significant financial relationships to disclose.

Correlation between FDG PET/CT and the expression of Ki-67, MMP-2, micro-vessel density (MVD), and pathological grading in squamous cell carcinoma of the esophagus

e15556 Background: Variable uptake of 18FDG has been noticed in positron emission tomography (PET) studies of patients with esophageal squamous cell carcinoma (ESCC). The aim of the present study was to determine if 18F-FDG PET/CT standardized uptake value (SUV) could quantitatively reflect tumor proliferation, invasion and angiogenesis, and to reveal the relationship between SUV and pathological grading of ESCC. Methods: Preoperative PET scans were performed in 47 patients with histologically proven ESCC. 18FDG uptake was semiquantitatively measured by SUV.Tumour sections were HE stained to determine the pathological grading,and were stained by immunohistochemistry for proliferation marker (Ki67), invasion marker (MMP-2), and angiogenic marker (CD34). The correlations between FDG SUVmax and Ki67 expression, MMP-2 expression, corresponding MVD were statistically analysed respectively. Results: Among all the 47 cases,there were 13 well- differentiated squamous cell tumors, 16 moderately differentiated tumors and 18 poorly differentiated tumors,45 of 47 tumors revealed FDG. accumulation in primary tumor foci confirmed by subsequently histopathologically. The mean FDG SUVmax value was 12.504 ± 6.805. Average Ki-67 index was (7.837±29.798) %, average MMP-2 index was (71.551%±27.126) % and average MVD was (18.429±9.603) accordingly. The SUV and Ki-67 index, MMP-2 index were positively correlated (r=0.581,0.594), and it was not correlated with MVD(P&gt;0.05). The mean SUV of well-differentiated, moderately differentiated and poorly differentiated tumors were 9.787±1.477, 12.313±0.479, 15.053±2.147 respectively, and a significant difference could be determined between them by statistical analysis(P=0.000). Conclusions: A significant positive correlation is demonstrated between FDG PET/CT SUV and Ki-67 index, MMP-2 index of the primary ESCC. SUV could reflect proliferation and invasion potential of tumor. However, there is no significant correlation between SUV and MVD, thus it could not reflect tumor angiogenesis in ESCC. To some extent, SUV could reflect pathologic grading of ESCC. No significant financial relationships to disclose.

18F-FDG-Uptake of Hepatocellular Carcinoma on PET Predicts Microvascular Tumor Invasion in Liver Transplant Patients

Vascular invasion of hepatocellular carcinoma (HCC) is a major risk factor for poor outcome after liver transplantation (LT). The aim of this retrospective analysis was to assess the value of preoperative positron emission tomography (PET) using (18)F-fluorodeoxyglucose ((18)F-FDG) in liver transplant candidates with HCC for predicting microvascular tumor invasion (MVI) and posttransplant tumor recurrence. Forty-two patients underwent LT for HCC after PET evaluation. Sixteen patients had an increased (18)F-FDG tumor uptake on preoperative PET scans (PET +), while 26 recipients revealed negative PET findings (PET-) pre-LT. PET- recipients demonstrated a significantly better 3-year recurrence-free survival (93%) than PET + patients (35%, p < 0.001). HCC recurrence rate was 50% in the PET + group, and 3.8% in the PET-population (p < 0.001). PET + status was identified as independent predictor of MVI [hazard ratio: 13.4]. Patients with advanced PET negative tumors and patients with HCC meeting the Milan criteria had a comparable 3-year-recurrence-free survival (80% vs. 94%, p = 0.6). Increased (18)F-FDG uptake on PET is predictive for MVI and tumor recurrence after LT for HCC. Its application may identify eligible liver transplant candidates with tumors beyond the Milan criteria.

Portable PET probes are a novel tool for intraoperative localization of tumor deposits

BackgroundPositron emission tomography (PET) identifies cancer deposits by detecting sites of gamma emissions that are released from radioactively labeled molecules targeting tumor to formulate a PET image. Correlating preoperative PET scans with intraoperative findings remains a challenge. We investigated whether high-energy gamma emissions detected by a novel hand-held PET probe would detect tumors and offer a real-time method to localize tumor intraoperatively. Furthermore, we investigated the novel beta probe, which detects emissions at a shorter range than gamma emissions, making them undetectable by PET scanners, but potentially valuable for close range intraoperative detection of tumor deposits.MethodsSix-to-eight-week-old athymic mice were injected with one of four possible tumor cell lines: gastric, pancreas, squamous cell and breast cancer. After tumors reached at least 1 cm in size, they were euthanized and imaged with a micro-PET imager. Hand-held gamma and beta probes were then used in vivo and ex vivo to measure high-energy gamma and beta emissions.ResultsThe portable PET probes detected high-energy gamma and beta emissions from all tumors evaluated. These emissions were reproducible and we established that beta emissions correlate with high-energy gamma emissions and conventional PET scans. There was a strong positive correlation (R = 0.8) between gamma and beta counts. Beta emission showed a stronger correlation than gamma emission with overall tissue radioactivity.ConclusionThis study is the first to demonstrate that gamma emission detected by conventional PET imaging correlates with beta emissions. This study shows that compared to detection of gamma emissions, beta counts may offer superior real-time localization of tumor deposits. Intraoperative portable PET probe may become a useful way to exploit tumor biology and PET technology to guide real-time tissue characterization during surgery.

Post-operative changes of cerebral circulation and metabolism in the acute stage of low-grade aneurysmal subarachnoid hemorrhage

Objective: Pre- and post-operative cerebral circulation and metabolism were evaluated in patients with low-grade acute aneurysmal subarachnoid hemorrhage (SAH) who underwent early surgery to investigate the effects on brain dysfunction.Methods: Positron emission tomography (PET) was performed to measure the regional cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO2), oxygen extraction fraction (OEF) and cerebral blood volume in four patients (one male and three females, mean age: 60.3 years) with low-grade SAH within 30 hours of onset. Post-operative PET was performed on the seventh post-operative day. No patient suffered clinical deterioration during the study. Pre-operative PET scans demonstrated significant global reduction of CBF and CMRO2, compared to 16 normal control subjects, and no significant change in OEF. CBF and CMRO2 reduction post-operatively improved to the normal control values. Post-operative OEF was significantly increased compared to the normal control value.Conclusions: Patients with low-grade SAH have impairment of cerebral circulation and metabolism in the acute period, which improves after surgery. Early surgery for low-grade SAH, necessary to avoid rerupture of the aneurysm, did not worsen the impairment of cerebral circulation and metabolism. However, measures to protect the brain from perioperative damage are necessary to achieve the optimum outcome.

Impact of preoperative positron emission tomography scans on survival after liver resection for metastatic colorectal cancer

Aim: Positron emission tomography (PET) has been used to detect extrahepatic disease in patients in order to determine their suitability for liver resection from colorectal metastases. Our hypothesis is that PET scanning would result in a better 5‐year survival after liver resection due to better patient selection through downstaging of disease.Methods: Between 1997 and 2005 there were 467 patients undergoing potentially curative liver resections in three cohorts. PET scanning was available to our patients without restriction from 2002. There were 215 patients in the pre‐PET era (Group 1), 188 in the PET era where a PET scan was not performed (Group 2) and 64 patients with preoperative PET scanning (Group 3). Our three cohorts were followed up at 1, 3, 6 and 12 months postoperatively with a median follow up of 24, 21 and 20 months, respectively.Results: The 5‐year survival rate for patients with preoperative PET scanning was 68%. The 5‐year survival rate for patients without preoperative PET scanning was 40% in the PET era and 30% in the pre‐PET era (P = 0.0113). The disease‐free interval was 35% in the PET group and 20% without PET scans at 3 years (P &lt; 0.05).Conclusion: The usage of preoperative PET scanning has led to an improved overall survival because of better patient selection from detection of occult extrahepatic disease missed by traditional staging techniques.

A prospective study evaluating 18F-Fluorodeoxyglucose (18FDG) positron emission tomography (PET) in the assessment of axillary nodal spread in women undergoing sentinel lymph node biopsy (SLNB) for breast cancer

533 Background: In women with operable breast cancer, SLNB is often used to assess the axilla. 18FDG PET imaging is potentially useful because of preferential uptake of 18FDG by metabolically active tumor cells. Prior studies of PET in breast cancer have not included many women undergoing SLNB. Methods: Women with operable breast cancer diagnosed within the previous 3 months underwent 18FDG PET followed by SLNB. Axillary node assessment (ANA) consisted of SLNB alone if negative, SLNB with axillary lymph node dissection (ALND) if the SLNB or preoperative PET scan was positive or ALND alone if sentinel nodes were not identified. We considered that PET would be useful if the specificity was 95% or better. Based on a 30% prevalence of women with positive axillary nodes, 320 women were needed so that the lower boundary of the 95% CI for specificity would exclude 91%. Patients were scanned at one of 5 study centers in Ontario, using either a PET scanner or PET/CT instrumentation. Results: Between January 2005 and March 2007, 336 women were entered; 11 were not analyzable. Sentinel nodes were found for 312/325 women (96%) and were positive for tumor by H&E stain in 92 (30%). ALND was performed in 177 (54%) and was positive for tumor in 43 cases (25%): Using logistic regression, age, BMI, number of nodes, and tumor size were assessed as predictors of prevalence, positive PET, and sensitivity. Only tumor size was predictive (p<0.05) for prevalence (OR=1.6), PET positivity (OR=1.7) and PET sensitivity (OR=1.4). Conclusions: 18FDG PET is not sufficiently sensitive to detect positive axillary lymph nodes. However, the very high positive predictive value (96%) in our trial suggests that PET could be used in women with large primary tumors to identify those in whom SLNB may be avoided prior to therapeutic ALND. Parameter Estimate 95% CI Sensitivity 23.0% 15.2% - 32.5% Specificity 99.6% 97.6% - 99.9% Positive Predictive Value 95.8% 78.9% - 99.9% Negative Predictive Value 74.4% 69.1% - 79.3% Prevalence 30.8% 25.8% - 36.1% Author Disclosure Employment or Leadership Consultant or Advisory Role Stock Ownership Honoraria Research Expert Testimony Other Remuneration Aventis, Biomera, Ortho Biotech, Pfizer, Pharmacia, Roche, YM Biosciences AstraZeneca, Aventis, Pfizer, Pharmacia AstraZeneca, Aventis