Usefulness of PET/CT for the Differentiation and Characterization of Periampullary Lesions

Preoperative 2-[18F]FDG PET-CT aids in the prognostic stratification for patients with primary ampullary carcinoma

OBJECTIVES

We sought to investigate whether preoperative dual-phase 2-[¹⁸F]FDG PET-CT identify predictors for poor survival in patients with ampullary carcinoma receiving pancreaticoduodenectomy.

METHODS

The preoperative PET-CT images of patients with resected ampullary carcinoma from June 2007 to July 2017 were analyzed. Survival curves were analyzed using the Kaplan-Meier method and compared with the log-rank test. Cox proportional hazard model was used to identify potential prognostic factors associated with disease-free survival (DFS) and overall survival (OS).

RESULTS

Fifty-four subjects (26 men, 28 women) were enrolled with a median tumor size of 20 mm. All patients were followed for a median period of 36.9 months with 3- and 5-year DFS of 50.3% and 44.2%, and OS of 77.0% and 68.2%, respectively. Parameters associated with DFS in multivariate analysis were lymphovascular invasion (hazard ratio [HR]: 9.45, p < 0.001), involved margin in pathology (HR: 7.67, p < 0.001), and tumor retention index (RI) from the dual-phase PET (HR: 2.41, p = 0.03), whereas involved margin (HR: 13.14, p < 0.001), post-recurrence chemotherapy (HR: 0.10, p < 0.001), and metabolic tumor volume (MTV) (HR: 4.62, p = 0.009) emerged as independent prognostic factors for OS.

CONCLUSIONS

Preoperative 2-[¹⁸F]FDG PET-CT offered independent prognostic biomarkers in patients with ampullary carcinoma receiving standard surgical resection.

KEY POINTS

• 2-[¹⁸F]FDG PET-CT offers good survival prediction before operation in primary malignant neoplasms at ampulla of Vater. • Dual-phase PET scan with bowel distention can better delineate Ampulla of Vater and characterize tumor physiology. • Preoperative risk stratification might aid in better treatment planning.

Evaluation of the clinical and economic impact of delays to surgery in patients with periampullary cancer

Background

Early treatment is the only potential cure for periampullary cancer. The pathway to surgery is complex and involves multiple procedures across local and specialist hospitals. The aim of this study was to analyse variability within this pathway, and its impact on cost and outcomes.

Methods

Patients undergoing surgery for periampullary cancer (2011–2016) were identified retrospectively and their pathway to surgery was analysed. Patients who had early surgery (shortest quartile, Q1) were compared with those having late surgery (longest quartile, Q4).

Results

A total of 483 patients were included in the study, with 121 and 124 patients in Q1 and Q4 respectively. The median time from initial CT to surgery was 21 days for Q1 versus 112 days for Q4 (P < 0·001). Diagnostic delays were common in Q4; these patients required significantly more investigations than those in Q1 (endoscopic ultrasonography (EUS): 74·2 versus 18·2 per cent respectively, P < 0·001; MRI: 33·6 versus 20·6 per cent, P = 0·036). The median time to diagnostic EUS was 13 days in Q1 versus 59 days in Q4 (P < 0·001). Some 42·1 per cent of jaundiced patients in Q1 underwent preoperative biliary drainage, compared with all patients in Q4. There were significantly more unplanned admissions and associated longer duration of hospital stay per patient and costs in Q4 than in Q1 (median: 8 versus 3 days respectively; €5652 versus €2088; both P < 0·001). There was a higher likelihood of potentially curative surgery in Q1 (82·6 per cent versus 66·9 per cent in Q4; P = 0·005).

Conclusion

There is wide variation across the entire pathway, suggesting that multiple strategies are required to enable early surgery. Defining an effective pathway by anticipating the need for investigations and avoiding biliary drainage reduces unplanned admissions and costs and increases resection rates.

18F-fluorodeoxyglucose positron emission tomography (18FDG-PET) for patients with biliary tract cancer: Systematic review and meta-analysis

BACKGROUND & AIMS

The role of ¹⁸F-fluorodeoxyglucose positron emission tomography (¹⁸FDG-PET) in the diagnosis and staging of patients with biliary tract cancers (BTCs) remains controversial, so we aimed to provide robust information on the utility of ¹⁸FDG-PET in the diagnosis and management of BTC.

METHODS

This systematic review and meta-analysis explored the diagnostic test accuracy of ¹⁸FDG-PET as a diagnostic tool for diagnosis of primary tumour, lymph node invasion, distant metastases and relapsed disease. Subgroup analysis by study quality and BTC subtype were performed. Changes in management based on ¹⁸FDG-PET and impact of maximum standardised uptake values (SUVmax) on prognosis were also assessed. A random effects model was used for meta-analyses.

RESULTS

A total of 2,125 patients were included from 47 eligible studies. The sensitivity (Se) and specificity (Sp) of ¹⁸FDG-PET for the diagnosis of primary tumour were 91.7% (95% CI 89.8-93.2) and 51.3% (95% CI 46.4-56.2), respectively, with an area under the curve (AUC) of 0.8668. For lymph node invasion, Se was 88.4% (95% CI82.6-92.8) and Sp was 69.1% (95% CI 63.8-74.1); AUC 0.8519. For distant metastases, Se was 85.4% (95% CI 79.5-90.2) and Sp was 89.7% (95% CI86.0-92.7); AUC 0.9253. For relapse, Se was 90.1% (95% CI 84.4-94.3) and Sp was 83.5% (95% CI 74.4-90.4); AUC 0.9592. No diagnostic threshold effect was identified. Meta-regression did not identify significant sources of heterogeneity. Sensitivity analysis revealed no change in results when analyses were limited to studies with low risk of bias/concern. The pooled proportion of change in management was 15% (95% CI 11-20); the majority (78%) due to disease upstaging. Baseline high SUVmax was associated with worse survival (pooled hazard ratio of 1.79; 95% CI 1.37-2.33; p <0.001).

CONCLUSIONS

There is evidence to support the incorporation of ¹⁸FDG-PET into the current standard of care for the staging (lymph node and distant metastases) and identification of relapse in patients with BTC to guide treatment selection; especially if the identification of occult sites of disease would change management, or if diagnosis of relapse remains unclear following standard of care imaging. The role for diagnosis of the primary tumour remains controversial due to low sensitivity and ¹⁸FDG-PET should not be considered as a replacement for pathological confirmation in this setting.

LAY SUMMARY

A positron emission tomography (PET scan), using ¹⁸F-fluorodeoxyglucose (¹⁸FDG), can help doctors identify areas of cancer in the body by highlighting "hot spots". These hotspots may be cancerous (true positive) but may also be non-cancerous, like inflammation (false positive). We show that PET scans are useful to assess how far advanced the cancer is (by assessing spread to lymph glands and to other organs) and also to identify if the cancer has recurred (for example after surgery), thus helping doctors to make treatment decisions. However, a biopsy is still needed for the initial diagnosis of a biliary tract cancer, because of the high chance of a "false positive" with PET scans.

Prospective comparison of (4S)-4-(3-18F-fluoropropyl)-L-glutamate versus 18F-fluorodeoxyglucose PET/CT for detecting metastases from pancreatic ductal adenocarcinoma: a proof-of-concept study

PURPOSE

(4S)-4-(3-¹⁸F-Fluoropropyl)-L-glutamate (FSPG) positron emission tomography (PET) reflects system x_C^- transporter (xCT) expression. FSPG PET has been used to detect brain, lung, breast and liver cancer with only modest success. There is no report on the use of FSPG PET in pancreatic ductal adenocarcinoma (PDAC), presumably because of normal xCT expression in the pancreas. Nonetheless, the tissue-specific expression of xCT in the pancreas suggests that FSPG PET may be ideal for identifying metastasized PDAC.

METHODS

The performance of FSPG in detecting PDAC metastases was compared with that of ¹⁸F-fluorodeoxyglucose (FDG) in small-animal PET studies in seven PDAC tumour-bearing mice and in prospective PET/computed tomography (CT) studies in 23 patients with tissue-confirmed PDAC of stage III or stage IV. All PET/CT results were correlated with the results of histopathology or contrast-enhanced CT (ceCT) performed 3 and 6 months later.

RESULTS

In the rodent model, FSPG PET consistently found more PDAC metastases earlier than FDG PET. FSPG PET showed a trend for a higher sensitivity, specificity and diagnostic accuracy than FDG PET in detecting PDAC metastases in a patient-based analysis: 95.0%, 100.0% and 95.7%, and 90.0%, 66.7% and 90.0%, respectively. In a lesion-based analysis, FSPG PET identified significantly more PDAC metastases, especially in the liver, than FDG PET (109 vs. 95; P = 0.0001, 95% CI 4.9-14.6). The tumour-to-background ratios for FSPG and FDG uptake on positive scans were similar (FSPG 4.2 ± 4.3, FDG 3.6 ± 3.0; P = 0.44, 95% CI -1.11 to 0.48), despite a lower tumour maximum standardized uptake value in FSPG-avid lesions (FSPG 4.2 + 2.3, FDG 7.7 + 5.7; P = 0.002, 95% CI 0.70-4.10). Because of the lower physiological activity of FSPG in the liver, FSPG PET images of the liver are more easy to interpret than FDG PET images, and therefore the use of FSPG improves the detection of liver metastasis.

CONCLUSION

FSPG PET is superior to FDG PET in detecting metastasized PDAC, especially in the liver.

Imaging modalities for characterising focal pancreatic lesions

BACKGROUND

Increasing numbers of incidental pancreatic lesions are being detected each year. Accurate characterisation of pancreatic lesions into benign, precancerous, and cancer masses is crucial in deciding whether to use treatment or surveillance. Distinguishing benign lesions from precancerous and cancerous lesions can prevent patients from undergoing unnecessary major surgery. Despite the importance of accurately classifying pancreatic lesions, there is no clear algorithm for management of focal pancreatic lesions.

OBJECTIVES

To determine and compare the diagnostic accuracy of various imaging modalities in detecting cancerous and precancerous lesions in people with focal pancreatic lesions.

SEARCH METHODS

We searched the CENTRAL, MEDLINE, Embase, and Science Citation Index until 19 July 2016. We searched the references of included studies to identify further studies. We did not restrict studies based on language or publication status, or whether data were collected prospectively or retrospectively.

SELECTION CRITERIA

We planned to include studies reporting cross-sectional information on the index test (CT (computed tomography), MRI (magnetic resonance imaging), PET (positron emission tomography), EUS (endoscopic ultrasound), EUS elastography, and EUS-guided biopsy or FNA (fine-needle aspiration)) and reference standard (confirmation of the nature of the lesion was obtained by histopathological examination of the entire lesion by surgical excision, or histopathological examination for confirmation of precancer or cancer by biopsy and clinical follow-up of at least six months in people with negative index tests) in people with pancreatic lesions irrespective of language or publication status or whether the data were collected prospectively or retrospectively.

DATA COLLECTION AND ANALYSIS

Two review authors independently searched the references to identify relevant studies and extracted the data. We planned to use the bivariate analysis to calculate the summary sensitivity and specificity with their 95% confidence intervals and the hierarchical summary receiver operating characteristic (HSROC) to compare the tests and assess heterogeneity, but used simpler models (such as univariate random-effects model and univariate fixed-effect model) for combining studies when appropriate because of the sparse data. We were unable to compare the diagnostic performance of the tests using formal statistical methods because of sparse data.

MAIN RESULTS

We included 54 studies involving a total of 3,196 participants evaluating the diagnostic accuracy of various index tests. In these 54 studies, eight different target conditions were identified with different final diagnoses constituting benign, precancerous, and cancerous lesions. None of the studies was of high methodological quality. None of the comparisons in which single studies were included was of sufficiently high methodological quality to warrant highlighting of the results. For differentiation of cancerous lesions from benign or precancerous lesions, we identified only one study per index test. The second analysis, of studies differentiating cancerous versus benign lesions, provided three tests in which meta-analysis could be performed. The sensitivities and specificities for diagnosing cancer were: EUS-FNA: sensitivity 0.79 (95% confidence interval (CI) 0.07 to 1.00), specificity 1.00 (95% CI 0.91 to 1.00); EUS: sensitivity 0.95 (95% CI 0.84 to 0.99), specificity 0.53 (95% CI 0.31 to 0.74); PET: sensitivity 0.92 (95% CI 0.80 to 0.97), specificity 0.65 (95% CI 0.39 to 0.84). The third analysis, of studies differentiating precancerous or cancerous lesions from benign lesions, only provided one test (EUS-FNA) in which meta-analysis was performed. EUS-FNA had moderate sensitivity for diagnosing precancerous or cancerous lesions (sensitivity 0.73 (95% CI 0.01 to 1.00) and high specificity 0.94 (95% CI 0.15 to 1.00), the extremely wide confidence intervals reflecting the heterogeneity between the studies). The fourth analysis, of studies differentiating cancerous (invasive carcinoma) from precancerous (dysplasia) provided three tests in which meta-analysis was performed. The sensitivities and specificities for diagnosing invasive carcinoma were: CT: sensitivity 0.72 (95% CI 0.50 to 0.87), specificity 0.92 (95% CI 0.81 to 0.97); EUS: sensitivity 0.78 (95% CI 0.44 to 0.94), specificity 0.91 (95% CI 0.61 to 0.98); EUS-FNA: sensitivity 0.66 (95% CI 0.03 to 0.99), specificity 0.92 (95% CI 0.73 to 0.98). The fifth analysis, of studies differentiating cancerous (high-grade dysplasia or invasive carcinoma) versus precancerous (low- or intermediate-grade dysplasia) provided six tests in which meta-analysis was performed. The sensitivities and specificities for diagnosing cancer (high-grade dysplasia or invasive carcinoma) were: CT: sensitivity 0.87 (95% CI 0.00 to 1.00), specificity 0.96 (95% CI 0.00 to 1.00); EUS: sensitivity 0.86 (95% CI 0.74 to 0.92), specificity 0.91 (95% CI 0.83 to 0.96); EUS-FNA: sensitivity 0.47 (95% CI 0.24 to 0.70), specificity 0.91 (95% CI 0.32 to 1.00); EUS-FNA carcinoembryonic antigen 200 ng/mL: sensitivity 0.58 (95% CI 0.28 to 0.83), specificity 0.51 (95% CI 0.19 to 0.81); MRI: sensitivity 0.69 (95% CI 0.44 to 0.86), specificity 0.93 (95% CI 0.43 to 1.00); PET: sensitivity 0.90 (95% CI 0.79 to 0.96), specificity 0.94 (95% CI 0.81 to 0.99). The sixth analysis, of studies differentiating cancerous (invasive carcinoma) from precancerous (low-grade dysplasia) provided no tests in which meta-analysis was performed. The seventh analysis, of studies differentiating precancerous or cancerous (intermediate- or high-grade dysplasia or invasive carcinoma) from precancerous (low-grade dysplasia) provided two tests in which meta-analysis was performed. The sensitivity and specificity for diagnosing cancer were: CT: sensitivity 0.83 (95% CI 0.68 to 0.92), specificity 0.83 (95% CI 0.64 to 0.93) and MRI: sensitivity 0.80 (95% CI 0.58 to 0.92), specificity 0.81 (95% CI 0.53 to 0.95), respectively. The eighth analysis, of studies differentiating precancerous or cancerous (intermediate- or high-grade dysplasia or invasive carcinoma) from precancerous (low-grade dysplasia) or benign lesions provided no test in which meta-analysis was performed.There were no major alterations in the subgroup analysis of cystic pancreatic focal lesions (42 studies; 2086 participants). None of the included studies evaluated EUS elastography or sequential testing.

AUTHORS' CONCLUSIONS

We were unable to arrive at any firm conclusions because of the differences in the way that study authors classified focal pancreatic lesions into cancerous, precancerous, and benign lesions; the inclusion of few studies with wide confidence intervals for each comparison; poor methodological quality in the studies; and heterogeneity in the estimates within comparisons.

Current clinical status of 18F-FLT PET or PET/CT in digestive and abdominal organ oncology

Positron emission tomography (PET) or PET/computed tomography (CT) using ¹⁸F-3'-fluoro-3'-deoxythymidine (¹⁸F-FLT) offers noninvasive assessment of cell proliferation in human cancers in vivo. The present review discusses the current status on clinical applications of ¹⁸F-FLT-PET (or PET/CT) in digestive and abdominal oncology by comparing with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG)-PET (or PET/CT). The results of this review show that although ¹⁸F-FLT uptake is lower in most cases of digestive and abdominal malignancies compared with ¹⁸F-FDG uptake, ¹⁸F-FLT-PET can be used to detect primary tumors. ¹⁸F-FLT-PET has shown greater specificity for N staging than ¹⁸F-FDG-PET which can show false-positive uptake in areas of inflammation. However, because of the high background uptake in the liver and bone marrow, it has a limited role of assessing liver and bone metastases. Instead, ¹⁸F-FLT-PET will be a powerful tool for monitoring response to treatment and provide prognostic information in digestive and abdominal oncology.

FLT PET/CT Is Better Than FDG PET/CT in Differentiating Benign From Malignant Pancreatobiliary Lesions

PURPOSE

F-fluorothymidine (FLT), unlike FDG, is incorporated exclusively into DNA and is considered a specific marker of cell proliferation. The role of FLT PET/CT scan in differentiating benign from malignant pancreatobiliary tumors is unknown.

PATIENTS AND METHODS

Twenty-five suspected pancreatobiliary tumors on contrast-enhanced CT (CECT) scan in 23 patients were evaluated by FDG PET/CT and FLT PET/CT scans. The histopathology or fine-needle aspiration cytology was considered as criterion standard for the diagnosis. Surgeons were blinded to FLT PET/CT results. Management decision was guided by clinical and CECT scan and FDG PET/CT.

RESULTS

Five of 23 patients had metastatic disease on CECT imaging. The remaining 18 underwent exploratory laparotomy. Two of them had synchronous lesions. Histopathology/fine-needle aspiration cytology confirmed malignancy in 17 lesions and benign disease in the remaining 8 lesions. All 8 benign lesions were negative on FLT PET/CT. Seven of the 8 benign lesions were clinically diagnosed as malignancy on CECT and FDG PET/CT. The specificity, positive predictive value, and accuracy were higher for FLT PET/CT (100%, 100%, and 92%) compared with CECT (12.5%, 70.83%, and 72%) and FDG PET/CT (12.50%, 69.57%, and 68%). However, the sensitivity of FLT PET/CT (88.24%) was similar to CECT (100%) and FDG PET/CT (94.12%).

CONCLUSIONS

Molecular-based FLT PET/CT is a better imaging than FDG PET/CT in differentiating benign from malignant lesions in the pancreatobiliary region. It has a potential to bring down the incidence of preventable radical resection in suspected pancreatobiliary tumors.

Prognostic significance of standardized uptake value on preoperative ¹⁸F-FDG PET/CT in patients with ampullary adenocarcinoma

PURPOSE

The purpose of this study was to investigate the prognostic value of (18)F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patients with ampullary adenocarcinoma (AAC) after curative surgical resection.

METHODS

Fifty-two patients with AAC who had undergone (18)F-FDG PET/CT and subsequent curative resections were retrospectively enrolled. The maximum standardized uptake value (SUVmax) and tumor to background ratio (TBR) were measured on (18)F-FDG PET/CT in all patients. The prognostic significances of PET/CT parameters and clinicopathologic factors for recurrence-free survival (RFS) and overall survival (OS) were evaluated by univariate and multivariate analyses.

RESULTS

Of the 52 patients, 19 (36.5%) experienced tumor recurrence during the follow-up period and 18 (35.8%) died. The 3-year RFS and OS were 62.3 and 61.5%, respectively. Preoperative CA19-9 level, tumor differentiation, presence of lymph node metastasis, SUVmax, and TBR were significant prognostic factors for both RFS and OS (p < 0.05) on univariate analyses, and patient age showed significance only for predicting RFS (p < 0.05). On multivariate analyses, SUVmax and TBR were independent prognostic factors for RFS, and tumor differentiation, SUVmax, and TBR were independent prognostic factors for OS.

CONCLUSION

SUVmax and TBR on preoperative (18)F-FDG PET/CT are independent prognostic factors for predicting RFS and OS in patients with AAC; patients with high SUVmax (>4.80) or TBR (>1.75) had poor survival outcomes. The role of and indications for adjuvant therapy after curative resection of AAC are still unclear. (18)F-FDG uptake in the primary tumor could provide additive prognostic information for the decision-making process regarding adjuvant therapy.