Positron Emission Tomography in Lymphoma: Comparison with Computed Tomography and Gallium-67 Single Photon Emission Computed Tomography

With the advent of positron emission tomography (PET), metabolic imaging has become a reality for tumor staging and monitoring response to therapy in lymphoma. Increased Fluorine-18 fluorodeoxyglucose ([¹⁸F]FDG) uptake in lymphomas has been well documented in the literature; it is based upon elevated glycolysis and longer residence time of FDG in malignant cells compared to most normal tissues. This suggests that in tumor staging, FDG-PET may be more sensitive and specific than the anatomic imaging modalities. Computed tomography (CT) is the standard imaging modality for the staging and restaging of lymphoma, and Gallium-67 (⁶⁷Ga) scintigraphy has played an important role in monitoring response to therapy and follow-up of patients. Published results suggest that FDG-PET is superior to ⁶⁷Ga imaging and may be equal or superior to CT for the detection of nodal as well as extranodal involvement in lymphoma.     

The Registration of Diagnostic versus Planning Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Radiotherapy Planning for Non-small Cell Lung Cancer

AimsRadiotherapy for non-small cell lung cancer (NSCLC) increasingly utilises fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) fusion. However, it is unknown whether a PET/CT scan conducted in the treatment position results in more accurate registration to the radiotherapy planning CT (rCT) than a diagnostic PET/CT scan. The aim of this study was to compare the accuracy of registration of the CT components of the planning PET/CT scan (pCT) and diagnostic PET/CT scan (dCT) scan with the rCT.Materials and methodsTen patients with stage I–III NSCLC underwent an rCT immediately followed by a planning PET/CT scan, both carried out with arms placed above the head and immobilisation in the treatment position. All previously underwent a diagnostic FDG PET/CT, which was carried out with the arms above the head, but without custom immobilisation. dCT and pCT were registered to the rCT using a rigid body mutual information algorithm. Four observers identified 12 anatomical points on each scan and differences in their absolute location were analysed.ResultsAt the carina, the mean absolute error (MAE) for pCT–rCT compared with dCT–rCT was 4.37 versus 5.73 mm (P = 0.028). However, there was no significant difference in the root mean squared error (RMSE) for that point. There were no significant differences in MAE or RMSE for all other anatomical points. The MAE for all points was 4.11 versus 4.15 mm (P = NS) and RMSE was 4.40 versus 4.48 mm for pCT–rCT compared with dCT–rCT (P = NS).ConclusionsThere is an average of 4 mm of misregistration when registering the CT components of PET/CT scans to the rCT for NSCLC. Using a rigid registration technique, the registration of a diagnostic PET/CT is as good as the registration of a planning PET/CT.     

Granulomatous Slack Skin: Assessment of Disease Progression and Treatment Response Using Positron Emission Tomography/Computed Tomography

Granulomatous slack skin (GSS) is an extremely rare subtype of cutaneous T-cell lymphoma. A 14-year-old boy had suffered from progressive infiltrative erythema and plaques that gradually evolved into lax masses and pendulous skin on his axilla, anterior wall of the abdomen, bilateral inguinal region, and thighs. Histopathologic examination of the skin lesion and inguinal lymph node demonstrated granulomatous infiltration with multinucleated giant cells. Positron emission tomography (PET)/computed tomography (CT) scan was performed after acute exacerbation and exhibited slightly high fluorodeoxyglucose (FDG) distribution of skin lesions, without any evidence of abnormality in the metabolism of FDG in lymph nodes or other extralymphatic organs. Concurrent use of corticosteroid and recombinant interferon-α successfully controlled the disease, and posttreatment PET/CT scan confirmed the response to the therapy with decreased levels of FDG uptake. PET/CT is suggested to be helpful in the assessment of disease progression and treatment response in the management of patients with GSS.     

Positron Emission Tomography/Computed Tomography and Biomarkers for Early Treatment Response Evaluation in Metastatic Colon Cancer

Background.

Treatment options for metastatic colon cancer (mCC) are widening. We prospectively evaluated serial 2-deoxy-2-[18F]fluoro-d-glucose positron-emission tomography/computed tomography (PET/CT) and measurements of tissue inhibitor of metalloproteinases-1 (TIMP-1), carcinoembryonic antigen (CEA), and liberated domain I of urokinase plasminogen activator receptor (uPAR(I)) for early assessment of treatment response in mCC patients.

Methods.

Thirty-three mCC patients scheduled for first-line chemotherapy with capecitabine and oxaliplatin (CAPOX) and bevacizumab participated; 27 were evaluated by PET/CT before treatment, after one and four treatment series. Morphological and metabolic response was independently assessed according to Response Evaluation Criteria in Solid Tumors and European Organization for Research and Treatment of Cancer PET criteria. Plasma TIMP-1, plasma uPAR(I), and serum CEA were determined.

Results.

Metabolic response after one treatment course predicted the ability of CAPOX and bevacizumab to induce morphological response after four treatment series with a sensitivity of 80%, specificity of 69%, and odds ratio of 13.9 (95% confidence interval [CI] 1.9; 182). Early metabolically stable or progressive disease was associated with shorter progression-free survival (hazard ratio [HR] = 3.2 [CI 1.3; 7.8]). Biomarker levels at early evaluation were associated with shorter OS (TIMP-1 per unit increase on a log-2-transformed ng/mL scale: HR = 2.6 [CI 1.4; 4.9]; uPAR(I) per 25 fmol/mL increase: HR = 1.5 [CI 1.1; 2.1]).

Conclusion.

This monocentric study demonstrated predictive value of early metabolic PET response and prognostic value of TIMP-1 and uPAR(I) levels in mCC treated with CAPOX and bevacizumab. Results support investigation of PET/CT, TIMP-1, and uPAR(I) guided early treatment adaptation in mCC.     

18-Fluorodeoxy-Glucose Positron Emission Tomography- Computed Tomography (18-FDG-PET/CT) for Gross Tumor Volume (GTV) Delineation in Gastric Cancer Radiotherapy

Purpose: Evaluation of the 18-fluorodeoxy-glucose positron emission tomography-computed tomography (18-FDG-PET/CT) for gross tumor volume (GTV) delineation in gastric cancer patients undergoing radiotherapy. Methods: In this study, 29 gastric cancer patients (17 unresectable and 7 inoperable) were initially enrolled for radical chemoradiotherapy (45Gy/25 fractions + chemotherapy based on 5 fluorouracil) or radiotherapy alone (45Gy/25 fractions) with planning based on the 18-FDG-PET/CT images. Five patients were excluded due to excess blood glucose levels (1), false-negative positron emission tomography (1) and distant metastases revealed by 18-FDG-PET/CT (3). The analysis involved measurement of metabolic tumor volumes (MTVs) performed on PET/CT workstations. Different threshold levels of the standardized uptake value (SUV) and liver uptake were set to obtain MTVs. Secondly, GTVPET values were derived manually using the positron emission tomography (PET) dataset blinded to the computed tomography (CT) data. Subsequently, GTVCT values were delineated using a radiotherapy planning system based on the CT scans blinded to the PET data. The referenced GTVCT values were correlated with the GTVPET and were compared with a conformality index (CI). Results: The mean CI was 0.52 (range, 0.12-0.85). In 13/24 patients (54%), the GTVPET was larger than GTVCT, and in the remainder, GTVPET was smaller. Moreover, the cranio-caudal diameter of GTVPET in 16 cases (64%) was larger than that of GTVCT, smaller in 7 cases (29%), and unchanged in one case. Manual PET delineation (GTVPET) achieved the best correlation with GTVCT (Pearson correlation = 0.76, p <0.0001). Among the analyzed MTVs, a statistically significant correlation with GTVCT was revealed for MTV10%SUVmax (r = 0.63; p = 0.0014), MTVliv (r = 0.60; p = 0.0021), MTVSUV2.5 (r = 0.54; p = 0.0063); MTV20%SUVmax (r = 0.44; p = 0.0344); MTV30%SUVmax (r = 0.44; p = 0.0373). Conclusion: 18-FDG-PET/CT in gastric cancer radiotherapy planning may affect the GTV delineation.     

Positron Emission Tomography/Computed Tomography Predictors of Overall Survival in Stage IIIC/IV Ovarian Cancer

OBJECTIVE: To evaluate the role of 2-deoxy-2-(F)fluoro-D-glucose (FDG) positron emission tomography/computed tomography (PET/CT) for selecting patients with extensive ovarian cancer (OC) for neoadjuvant chemotherapy by evaluating predictors of overall survival in patients with stage IIIC/IV OC. MATERIALS AND METHODS: From September 1, 2004, to November 20, 2011, 514 consecutive patients with a pelvic tumor underwent preoperative PET/CT; 179 patients had stage IIIC/IV OC. Patients' characteristics were collected from 153 patients with stage IIIC/IV OC who underwent primary surgery. In 152 patients with stage IIIC/IV OC, clinical predictors and PET/CT predictors of survival were evaluated. RESULTS: Median age was 64 years (range, 38-88 years); 87% (113) of the 153 patients had a performance status of less than 2; 55% (84) of the 153 patients had PET/CT stage III, and 45% (69) of the 153 patients had PET/CT stage IV. Using univariate analysis, incomplete debulking (P = 0.0001), pleural exudates (P = 0.001), postmenopausal state (P = 0.01), WHO performance status greater than 2 (P = 0.01), PET/CT stage IV (P = 0.01), and large bowel mesentery implants (P = 0.02) were statistically significant prognostic variables. Using multivariate Cox regression analysis, incomplete debulking was the only statistically significant independent prognostic variable (P = 0.0001). Median overall survival was significantly longer in the 53 patients with no residual tumor than in the 99 patients with residual tumor (33.3 vs 25.5 months; P = 0.0001) CONCLUSION: Suggested PET/CT criteria for referral of patients with advanced OC to neoadjuvant chemotherapy are PET/CT stage IV, pleural exudates, and PET-positive large bowel mesentery implants. Evaluation of selection criteria for neoadjuvant chemotherapy should be promoted in prospective clinical trials, with survival as the primary end point.     

The Clinical Significance of Preoperative 18F-Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography for Predicting Distant Recurrence in Thymoma

AimsThymomas sometimes require treatment for various recurrence patterns, despite their relatively good survival rates after resection. We focused on their maximum standardised uptake value (SUVmax) on preoperative 18F-fluorodeoxyglucose positron emission tomography as a tumour recurrence predictor in completely resected thymomas. Those with a high SUVmax might be at an increased recurrence risk, irrespective of tumour size. We categorised cases into axes (tumour size and SUVmax) and determined whether cluster analysis predicts recurrence patterns and freedom from recurrence (FFR).Materials and methodsOf the 115 patients who underwent primary surgery for thymoma between 2005 and 2018, 66 were evaluated. According to the Masaoka stage and World Health Organization (WHO) histological type, all histological diagnoses were obtained after resection. All recurrences were diagnosed using computed tomography and categorised into three patterns: distant, local and regional recurrences. A multiple regression analysis was carried out to identify predictors for each recurrence pattern. Cluster analysis was carried out based on tumour size and SUVmax. The FFR rate was evaluated.ResultsAll patients with preoperative SUVmax <3.4 were free from recurrence regardless of Masaoka stage, WHO histological classification and tumour size. Multiple regression analysis revealed that the SUVmax was the only significant predictor for distant recurrence. All cases were divided into three clusters. Cluster 3, with average tumour size and a high SUVmax, showed a higher risk of distant recurrence rate (60%) and a significantly lower FFR rate (P = 0.003).ConclusionsThe preoperative positron emission tomography/computed tomography SUVmax could be a useful thymoma recurrence predictor, especially for distant recurrences. In addition, cluster analysis revealed that cases with average tumour sizes and extremely high SUVmax were identified to have a higher recurrence risk and a significantly lower FFR rate than those in other clusters. Even after complete resection, such cases should be closely followed-up and screened for distant recurrence.     

Clinical Value of 18F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Response Evaluation after Primary Treatment of Advanced Epithelial Ovarian Cancer

Aims

To prospectively evaluate the use of ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG-PET/CT) in the definition of the treatment response after primary treatment of advanced epithelial ovarian cancer (EOC).

Positron Emission Tomography in Tumor Diagnosis and Treatment Follow-Up

The technique of positron emission tomography (PET) is described. PET is an in vivo imaging and quantitative technique which allows the visualization of various functional and biochemical parameters. PET is a tracer technique in which bioactive tracer substances are labelled with short-lived positron emitting radionuclides. The most important of these are ¹⁵O, ¹³N, ¹¹C and ¹⁸F with decay times ranging from 2 min to 2 h. The radiolabeled substance is injected intravenously and the distribution, uptake and binding are registered externally with the PET camera using of the order of 4 000 small detectors. The camera produces simultaneously 15 tomographic slices in which the absolute concentration of the tracer substance can be measured. Using a dynamic imaging sequence starting after the injection of the tracer, the dynamics of the tracer uptake is recorded and can be used to deduce functional parameters, such as perfusion flow, tracer distribution, binding to receptor or enzyme systems, etc. depending on the choice of tracer substance. The great versatility of PET and its potential of direct noninvasive study of tumor function will make it a very important clinical and research tool in oncology. With the choice of substances selective for a certain aspect of a tumor's biochemistry the potential opens for a better diagnosis, improved differential diagnosis and, especially with the use of metabolic tracers, an improved possibility to evaluate the response to treatment.