Time benefit in the assessment of recurrences following fractionated radiotherapy in an experimental tumour system using positron-emission tomography with 18F-fluorodeoxyglucose

PURPOSE: To determine the sensitivity and specificity of 18F-fluorodeoxyglucose-positron-emission tomography (FDG-PET) in the diagnosis of R1H tumours after fractionated radiotherapy, and the dependency of sensitivity and specificity on time after therapy. In addition, the time benefit of FDG-PET concerning early recognition of recurrences after fractionated radiotherapy was assessed. MATERIAL AND METHODS: Subcutaneously growing rat rhabdomyosarcoma R1H tumours were irradiated by applying total doses of 80 or 85 Gy after reaching a start volume of 0.8 cm3. Twenty animals were treated. Tumour volume was determined twice a week. FDG-PET was performed weekly before, during and for 6 months after therapy using a conventional full-ring whole-body PET scanner. In total, 600 PET results were evaluated qualitatively using a six-scale score. PET results and actual tumour volumes were compared. The sensitivity and specificity of tumour detection by PET was calculated for different times after the onset of therapy. The optimal score for tumour detection and the influence of time after therapy on the quality of PET (time benefit) was evaluated using receiver-operating characteristics. RESULTS: After irradiation, 8/20 tumours (40%) were locally controlled, while 12/20 recurred. In this tumour model, evidence of relapse is assured when a volume of 0.1 cm3 is reached. Sensitivity of tumour diagnosis by PET increases with time, i.e. with the volume of recurrent tumours after the onset of therapy, mounting to > 0.95 after 100 days. Specificities of 0.95-1.0 were determined after therapy, showing no increase with time. Tumour diagnosis by PET is highly accurate when performed 80 days after the start of treatment. On average, tumours were recognized by PET on 31, 62, 74 and 81 days (median) before approaching volumes of 0.2, 0.5, 0.8 or 1.0 cm3, respectively. CONCLUSION: An experimental system was implemented that allows reproducible detection of recurrent R1H tumours after radiotherapy using FDG-PET. The usefulness of PET as a diagnostic test for R1H tumours is very good and a reliable resolution for PET is demonstrated for volumes < 1 cm3. The results indicate that FDG-PET enables early recognition of recurrences after fractionated radiotherapy.     

Time benefit in the assessment of recurrences following fractionated radiotherapy in an experimental tumour system using positron‐emission tomography with 18F‐fluorodeoxyglucose

Purpose: To determine the sensitivity and specificity of ¹⁸F‐fluorodeoxyglucose‐positron‐emission tomography (FDG‐PET) in the diagnosis of R1H tumours after fractionated radiotherapy, and the dependency of sensitivity and specificity on time after therapy. In addition, the time benefit of FDG‐PET concerning early recognition of recurrences after fractionated radiotherapy was assessed.

Material and methods: Subcutaneously growing rat rhabdomyosarcoma R1H tumours were irradiated by applying total doses of 80 or 85?Gy after reaching a start volume of 0.8?cm³. Twenty animals were treated. Tumour volume was determined twice a week. FDG‐PET was performed weekly before, during and for 6 months after therapy using a conventional full‐ring whole‐body PET scanner. In total, 600 PET results were evaluated qualitatively using a six‐scale score. PET results and actual tumour volumes were compared. The sensitivity and specificity of tumour detection by PET was calculated for different times after the onset of therapy. The optimal score for tumour detection and the influence of time after therapy on the quality of PET (time benefit) was evaluated using receiver‐operating characteristics.

Results: After irradiation, 8/20 tumours (40%) were locally controlled, while 12/20 recurred. In this tumour model, evidence of relapse is assured when a volume of 0.1?cm³ is reached. Sensitivity of tumour diagnosis by PET increases with time, i.e. with the volume of recurrent tumours after the onset of therapy, mounting to >0.95 after 100 days. Specificities of 0.95–1.0 were determined after therapy, showing no increase with time. Tumour diagnosis by PET is highly accurate when performed 80 days after the start of treatment. On average, tumours were recognized by PET on 31, 62, 74 and 81 days (median) before approaching volumes of 0.2, 0.5, 0.8 or 1.0?cm³, respectively.

Conclusion: An experimental system was implemented that allows reproducible detection of recurrent R1H tumours after radiotherapy using FDG‐PET. The usefulness of PET as a diagnostic test for R1H tumours is very good and a reliable resolution for PET is demonstrated for volumes<1?cm³. The results indicate that FDG‐PET enables early recognition of recurrences after fractionated radiotherapy.     

The detection of local recurrent head and neck cancer with fluorine-18 fluorodeoxyglucose dual-head positron emission tomography.

Primary tumors of the larynx and hypopharynx are preferably treated with high-dose radiation therapy. In these patients, it may be difficult to distinguish recurrent disease from post-treatment reactions. The aim of the present study was to assess the value of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in the detection of local relapses of laryngeal or hypopharyngeal carcinoma after radiotherapy using a dual-head PET camera. Forty-eight patients (43 male, 5 female; mean age +/-SD, 61+/-9.5 years) with suspected recurrent laryngeal or hypopharyngeal cancer were prospectively studied. The mean interval between initial treatment and suspicion of recurrent disease was 14.6 months (range: 3-100 months). FDG dual-head PET was followed by endoscopy with or without biopsy under general anaesthesia within a period of 2 months in all patients. The mean period of follow-up after FDG dual-head PET was 13.7 months. In 19 out of 31 patients with focally increased uptake, tumour recurrence (mean diameter: 2.4 cm; range 0.4-6.5 cm) was found at initial endoscopy. In five patients recurrence was found during follow-up with a mean interval of 6.6 months. Seven patients had a false-positive study due to benign lesions or swallowing artefacts. In none of the patients with a normal PET study was tumour recurrence found during follow-up. The sensitivity and specificity of FDG dual-head PET were 100% and 71%, respectively. It is concluded that FDG dual-head PET is highly sensitive for the detection of local recurrence of laryngeal and hypopharyngeal carcinoma after radiotherapy. Some lesions were detected with a mean interval of 6.6 months before histological confirmation. In patients suspected of having recurrent laryngeal or hypopharyngeal cancer in whom FDG-PET is negative, endoscopy may be omitted for at least 6 months and possibly for up to 1 year.     

The detection of local recurrent head and neck cancer with fluroine-18 fluorodeoxyglucose dual-head positron emission tomography

Primary tumors of the larynx and hypopharynx are preferably treated with high-dose radiation therapy. In these patients, it may be difficult to distinguish recurrent disease from post-treatment reactions. The aim of the present study was to assess the value of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) in the detection of local relapses of laryngeal or hypopharyngeal carcinoma after radiotherapy using a dual-head PET camera. Forty-eight patients (43 male, 5 female; mean age ±SD, 61±9.5 years) with suspected recurrent laryngeal or hypopharyngeal cancer were prospectively studied. The mean interval between initial treatment and suspicion of recurrent disease was 14.6 months (range: 3–100 months). FDG dual-head PET was followed by endoscopy with or without biopsy under general anaesthesia within a period of 2 months in all patients. The mean period of follow-up after FDG dual-head PET was 13.7 months. In 19 out of 31 patients with focally increased uptake, tumour recurrence (mean diameter: 2.4 cm; range 0.4–6.5 cm) was found at initial endoscopy. In five patients recurrence was found during follow-up with a mean interval of 6.6 months. Seven patients had a false-positive study due to benign lesions or swallowing artefacts. In none of the patients with a normal PET study was tumour recurrence found during follow-up. The sensitivity and specificity of FDG dual-head PET were 100% and 71%, respectively. It is concluded that FDG dual-head PET is highly sensitive for the detection of local recurrence of laryngeal and hypopharyngeal carcinoma after radiotherapy. Some lesions were detected with a mean interval of 6.6 months before histological confirmation. In patients suspected of having recurrent laryngeal or hypopharyngeal cancer in whom FDG-PET is negative, endoscopy may be omitted for at least 6 months and possibly for up to 1 year. Received 27 January and in revised form 15 March 1999     

FDG positron emission tomography in the surveillance of hepatic tumors treated with radiofrequency ablation

PURPOSE: Radiofrequency thermal ablation (RFA) is an emerging technique in the treatment of focal hepatic tumors. Magnetic resonance imaging (MRI) and computed tomography (CT) are currently used to monitor hepatic tumors after RFA for residual disease and recurrence. Fluorodeoxyglucose (FDG) positron emission tomography (PET) is an excellent imaging method for the detection of liver metastases, but it has not been thoroughly evaluated as an alternative to anatomic imaging in the surveillance of liver tumors treated with RFA. The purpose of this investigation was to determine the role of FDG-PET imaging in the surveillance of liver tumors treated with RFA. METHODS: Thirteen patients with histories of malignant tumors of the liver treated with RFA and who had received post-treatment FDG-PET scans were assessed retrospectively. One patient had two post-RFA FDG-PET scans, eight patients had concurrent MRI scans, and six patients had concurrent CT scans. Imaging findings were compared with the results of clinical follow-up. RESULTS: There were either recurrent tumors at the ablation site (8 patients) or new metastases (3 patients) in 11 patients. FDG-PET identified all 11 cases and did not misidentify any cases. Of the seven patients with positive PET findings who received an MRI scan, three were also positive on MRI (42.9%); the other four cases were either negative or equivocal. Of the four patients with positive PET findings who received a CT scan, only two had positive CT scan findings (50%). All recurrences diagnosed by PET were confirmed on clinical follow-up. CONCLUSION: In this preliminary study, FDG-PET was superior to anatomic imaging in the surveillance of patients treated with RFA for malignant hepatic tumors.     

Roles of positron emission tomography with fluorine-18-deoxyglucose in the detection of local recurrent and distant metastatic sarcoma

Sarcomas are a heterogeneous group of tumors comprising approximately 1% of all malignancies. Definitive treatment of sarcoma is surgical resection. However, after surgical removal, 40% to 60% of the patients will develop local or distant recurrence. Therefore, the early detection and treatment of recurrence is an important part of modern sarcoma therapy. Positron emission tomography with fluorine-18-deoxyglucose (FDG-PET) has been highly successful in detecting and staging a variety of malignancies. However, its use in the management of patients with sarcoma is less defined. The purpose of our study was to assess the potential roles of FDG-PET in the detection of local recurrence and distant metastases. In this retrospective study, the images of 33 FDG-PET scans, reports of 29 computed tomography (CT) scans, and 8 magnetic resonance imaging (MRI) scans from 28 patients were compared with surgical pathology or clinical follow up for at least 6 months. FDG-PET detected all 25 cases of local and distant recurrences with 100% sensitivity. CT was able to detect 18 of the 22 possible cases of recurrent disease, whereas MRI was able to detect 5 of 7 cases of recurrent disease. PET was particularly useful in patients with extensive histories of surgery and radiation therapy, precisely the setting in which CT and MRI have the lowest specificity and sensitivity. In conclusion, FDG-PET was a sensitive test to detect local and distant recurrences of sarcoma and this warrants further investigation.     

Oxygenation of Tumor Recurrences Following Fractionated Radiotherapy of Primary Tumors

BACKGROUND AND PURPOSE: Tumor oxygenation is well recognized as a major factor of tumor response to radiotherapy. In this respect, a number of studies have examined the response of primary tumors, whereas little is known about the oxygenation of tumor recurrences after radiotherapy. It was the aim of this study to investigate the oxygenation of tumor recurrences after preceding irradiation of the primary tumor. MATERIAL AND METHODS: Tumor oxygenation in primary tumors and recurrences of rat rhabdomyosarcomas R1H was measured by using pO(2) probes and Eppendorf pO(2) histography. Primary tumors were irradiated at a (60)Co radiotherapy facility with a total dose of 75 Gy, given in 30 fractions over 6 weeks. Oxygenation was measured in R1H tumors before and directly after completion of irradiation. In R1H recurrences oxygenation was determined, when they reached the same size as the previously treated primary tumors (V(o) = 3.1 +/- 0.5 cm(3)). Additionally, tumor microvessel density and the intercapillary distance of tumor blood vessels were determined on histological sections using a counting grid. RESULTS: Tumor oxygenation in R1H recurrences was significantly lower when compared to primary R1H tumors. In primary tumors a median pO(2) of 17 +/- 7 mmHg was measured. By contrast, the median pO(2) in R1H recurrences was only 5 +/- 5 mmHg (p < 0.05). The high frequency of pO(2) values < 5 mmHg indicated that R1H recurrences were significantly more hypoxic (58 +/- 5%) in comparison to primary tumors (22 +/- 4%). The histological sections of the R1H recurrences showed a higher heterogeneity in their tissue structure than primary nonirradiated tumors. The morphometric studies demonstrated a reduced microvessel density (91 +/- 21/9.04 mm(2) in the tumor periphery; p = 0.0001) compared with recurrent tumors (68 +/- 26) and an enhanced mean distance of tumor blood vessels, especially in the center of the R1H recurrences (184 +/- 20 vs. 243 +/- 70 mm; p = 0.0001). CONCLUSION: In R1H rhabdomyosarcomas tumor oxygenation in recurrent tumors following radiation therapy is significantly lower than in primary tumors. This observation has to be taken into account in cases of tumor recurrences where repeated radiotherapy, chemotherapy or combined treatment modalities are used.     

PET-CT-Bildgebung bei Kopf-Hals-Tumoren

AIM: To evaluate the usefulness of combined PET/CT examinations for detection of malignant tumors and their metastases in head and neck oncology. METHODS: 51 patients received whole body scans on a dual modality PET/CT system. CT was performed without i.v. contrast. The results were compared concerning the diagnostic impact of native CT scan on FDG-PET images and the additional value of fused imaging. RESULTS: From 153 lesions were 97 classified as malignant on CT and 136 on FDG/PET images, as suspicious for malignancy in 33 on CT and 7 on FDG-PET and as benign in 23 on CT and 10 on FDG-PET. With combined PET/CT all primary and recurrent tumors could be found, the detection rate in patients with unknown primary tumors was 45%. Compared to PET or CT alone the sensitivity, specifity and accuracy could be significantly improved by means of combined PET/CT. CONCLUSION: Fused PET/CT imaging with [F18]-FDG and native CT-scanning enables accurate diagnosis in 93% of lesions and 90% of patients with head and neck oncology.     

Fluorodeoxyglucose-PET in the management of breast cancer

FDG-PET can be helpful in the diagnosis of primary breast cancer, especially in patients with dense breast tissue, significant fibrocystic changes, fibrosis after radiotherapy, and inconclusive results from MR imaging and other imaging modalities. PET has a limited role in patients with very small tumors and with well-differentiated and lobular types of breast cancer. In preoperative staging, FDG-PET has a low sensitivity for detection of regional lymph node involvement. Also, current PET imaging techniques can easily miss micrometastases. FDG-PET, however, has high positive predictive value for the axillary lymph node involvement, especially patient with advanced tumors. Compared with conventional imaging modalities, FDG-PET provides high diagnostic accuracy in detecting recurrent or metastatic breast carcinoma. FDG-PET seems to be highly useful for monitoring response to therapeutic interventions. This technique can identify response to therapy earlier than any other imaging method currently available. Obviously, identification of nonresponding patients could greatly improve patient management by allowing termination of ineffective and toxic therapies.     

Stellenwert der PET/CT zur Bildgebung des kolorektalen Karzinoms

CLINICAL/METHODICAL ISSUE: Fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) has emerged as a very useful imaging modality in the management of colorectal carcinoma. Data from the literature regarding the role of PET/CT in the initial diagnosis, staging, radiotherapy planning, response monitoring and surveillance of colorectal carcinoma is presented. Future directions and economic aspects are discussed. STANDARD RADIOLOGICAL METHODS: Computed tomography (CT), magnetic resonance imaging (MRI) and FDG-PET for colorectal cancer and endorectal ultrasound for rectal cancer. METHODICAL INNOVATIONS: Combined FDG-PET/CT. PERFORMANCE: While other imaging modalities allow superior visualization of the extent and invasion depth of the primary tumor, PET/CT is most sensitive for the detection of distant metastases of colorectal cancer. ACHIEVEMENTS: We recommend a targeted use of PET/CT in cases of unclear M staging, prior to metastasectomy and in suspected cases of residual or recurrent colorectal carcinoma with equivocal conventional imaging. The role of PET/CT in radiotherapy planning and response monitoring needs to be determined. Currently there is no evidence to support the routine use of PET/CT for colorectal screening, staging or surveillance. PRACTICAL RECOMMENDATIONS: To optimally exploit the synergy between morphologic and functional information, FDG-PET should generally be performed as an integrated FDG-PET/CT with a contrast-enhanced CT component in colorectal carcinoma.     

Diagnostic Accuracy of F-18 FDG-PET in the Assessment of Posttherapeutic Recurrence of Head and Neck Cancer

The purpose of this study was to compare whole-body fluorine-18-fluorodeoxyglucose positron emission tomography (F-18 FDG-PET) with conventional imaging modalities (CI: CT/MRI) in the detection of recurrent head and neck cancer. Whole-body F-18 FDG-PET was performed in 45 patients (recurrence = 39; no recurrence = 16) with previous head and neck cancer. We compared detectability by the period from initial cancer treatment and treatment modalities. Thirty were PET-positive and 15 were PET-negative. The sensitivity, specificity, and accuracy of PET were 97%, 88%, and 93%, respectively (corresponding figures of CI were 73%, 85%, and 77%). In 18 patients who underwent PET less than 3 months after the completion of cancer treatment, the sensitivity, specificity, and accuracy were 100%, 86%, and 94%, while for CI, the corresponding figures were 67%, 71%, and 69%. In 18 patients who had undergone surgery, PET results were 14 true positive and 4 were true negative; significantly higher detectability than CI. Among the patients who were evaluated for more than 6 months or treated by radiotherapy without surgery, diagnostic accuracy was almost the same. Whole body F-18 FDG-PET was a valuable tool in the evaluation of post-therapeutic recurrence of head and neck cancer.     

Positron emission tomography in gynecologic cancer

Most positron emission tomography (PET) imaging studies in gynecologic cancer are performed using (18)F-fluorodeoxyglucose (FDG). It contributes valuable information in primary staging of untreated advanced cervical cancer, in the post-treatment surveillance with unexplained tumor marker (such as squamous cell carcinoma antigen [SCC-Ag]) elevation or suspicious of recurrence, and restaging of potentially curable recurrent cervical cancer. Its value in early-stage resectable cervical cancer is questionable. In ovarian cancer, FDG-PET provides benefits for those with plateaued or increasing abnormal serum CA 125 (>35 U/mL), computed tomography and/or magnetic resonance imaging (CT-MRI) defined localized recurrence feasible for local destructive procedures (such as surgery, radiotherapy, or radiofrequency ablation), and clinically suspected recurrent or persistent cancer for which CT-guide biopsy cannot be performed. The role of FDG-PET in endometrial cancer is relatively less defined because of the lack of data in the literature. In our prospective study, FDG-PET coupled with MRI-CT may facilitate optimal management of endometrial cancer in well-selected cases. The clinical impact was positive in 29 (48.3%) of the 60 scans, 22.2% for primary staging, 73.1% for post-therapy surveillance, and 57.1% after salvage therapy, respectively. Scant studies have been reported in the management of vulvar cancer using FDG-PET. More data are needed. Gestational trophoblastic neoplasia is quite unique in biological behavior and clinical management. Our preliminary results suggest that FDG-PET is potentially useful in selected gestational trophoblastic neoplasia by providing a precise metastatic mapping of tumor extent up front, monitoring response, and localizing viable tumors after chemotherapy. The evaluation of a diagnostic tool, such as PET, is usually via comparing the diagnostic efficacy (sensitivity, specificity, etc), by using a more sophisticated receiver operating curve method, or the proportion of treatment been modified. Evaluating PET by clinical benefit is specific to the individual tumor and an attractive new endpoint.     

The clinical application of positron emission tomography to colorectal cancer management.

Colorectal cancer (CRC) is the second commonest cancer in the Western World. Successful treatment relies significantly on accurate detection and staging of primary disease as well as the early identification of the presence and extent of recurrence. Morphological imaging techniques, particularly computed tomography (CT), are well established and widely available to carry out these tasks in addition to predicting and monitoring response to therapy. This review analyses the current inadequacies for imaging CRC and critically assesses the potential role of functional imaging with positron emission tomography (PET). We review the current literature, use our experience from the first 1000 PET studies carried out at our Institution and the perspective of surgical colleagues. We find little evidence for the use of 2-[18F]fluoro-2-deoxy-D-glucose (FDG)-PET for screening asymptomatic individuals and current modalities appear better suited for detection of symptomatic primary CRC. There is evidence of increased accuracy for FDG-PET in staging primary disease, but this area remains controversial and larger studies are necessary. The situation is quite the reverse with respect to imaging suspected recurrent disease with FDG-PET being more sensitive and specific than conventional techniques. This benefit manifests itself through alteration in patient management and results in cost savings. PET also appears to have a specific place in the evaluation of patients undergoing radiotherapy and chemotherapy, a role that will expand. The evidence suggests that PET will ultimately become routinely incorporated into CRC patient management algorithms. Technological advances coupled with novel tracer research will facilitate this.     

F-18 FDG-PET for detection of osseous metastatic disease and staging, restaging, and monitoring response to therapy of musculoskeletal tumors

Recent advances in PET technology and applications have led to a proliferation in PET and PET/CT imaging, allowing correlation of both physiologic and anatomic information. This has also led to new and innovative ways to utilize PET imaging for the evaluation of musculoskeletal neoplasm. Currently, the most widely utilized musculoskeletal application of F-18 FDG-PET imaging is for the detection and characterization of osseous metastatic disease. The other notable potential role for FDG-PET imaging is for staging and restaging of primary bone tumors and soft tissue sarcomas. Precise staging and restaging of musculoskeletal neoplasm is critical to optimize treatment planning and to accurately determine patient prognosis. FDG-PET is also useful in evaluating response to therapy for musculoskeletal tumors. The future likely holds even more unique and potentially quite useful applications of PET imaging for primary osseous and soft tumors. This article will review the common and potentially useful applications of F-18 FDG-PET imaging for evaluating musculoskeletal tumors and malignancy.     

Monitoring chemotherapy and radiotherapy of solid tumors

PET imaging with the glucose analog fluorodeoxyglucose (FDG-PET) has been evaluated in numerous studies to monitor tumor response in patients undergoing chemo- and radiotherapy. The clinical value of FDG-PET for differentiation of residual or recurrent viable tumor and therapy-induced fibrosis or scar tissue has been documented for various solid tumors. Furthermore, there are now several reports suggesting that quantitative assessment of therapy-induced changes in tumor FDG uptake may allow prediction of tumor response and patient outcome very early in the course of therapy. In nonresponding patients, treatment may be adjusted according to the individual chemo- and radiosensitivity of the tumor tissue. Since the number of alternative treatments for solid tumors (e.g., second-line chemotherapy agents, protein kinase, or angiogenesis inhibitors) is continuously increasing, early prediction of tumor response to chemotherapy and radiotherapy by FDG-PET has enormous potential to "personalize" treatment and to reduce the side-effects and costs of ineffective therapy.     

Clinical value of PET with 18F-fluorodeoxyglucose and L-methyl-11C-methionine for diagnosis of recurrent brain tumor and radiation injury

We studied 15 patients clinically suspected to have recurrent brain tumor or radiation injury, using positron emission tomography (PET) with 18F-fluorodeoxyglucose (18FDG) and L-methyl-11C-methionine (11C-Met). PET with 11C-Met (Met-PET) clearly delineated the extent of recurrent brain tumor as focal areas of increased accumulation of 11C-Met, and was useful for early detection of recurrent brain tumor. PET with 18FDG (FDG-PET) showed focal 18FDG-hypermetabolism in one patient with malignant transformation of low grade glioma, and demonstrated its usefulness for evaluation of malignant transformation. 18FDG-hypometabolism was observed in all patients with radiation injury, but was also found in one patient with recurrent malignant brain tumor. 11C-Met uptake in 3 patients with radiation injury was similar to that of the normal cortical tissue. FDG-PET can be used to initially exclude recurrent brain tumor which is seen as 18FDG-hypermetabolism. The combined use of Met-PET in addition to FDG-PET can improve the accuracy of differentiation of recurrent brain tumor with 18FDG-hypometabolism from radiation injury.     

PET在颅内胶质瘤术后放射治疗后随访中的应用价值

目的：探讨PET在颅内胶质瘤术后,放射治疗后随诊中的作用。方法：对16例颅内胶质瘤术事并放射治疗后的病例采用双盲法将PET与CT／或MRI结果进行比较。结果：16例中14例（占87．5％）CT和／或MRI表现不规则环形或结节状明显强化,不能准确作出手术后改变和／或放射治疗后脑损伤,残存肿瘤或神经复发的诊断;其中9例残存肿瘤或肿瘤复发病灶^18F-FDG PET影像均表现为葡萄糖代谢率明显增高,另5例术后放射治疗后脑损伤病例和2例术后软化灶^18F-FDG PET影像均显示局部病变区为放射性分布缺损或明显低下。结论：与CT和MRI相比,PET在胶质瘤术后放射治疗后的脑损伤和肿瘤复发的定性诊断上具有明显的优势,若结合CT和MRI多种影像结果分析,更能提供病变解剖结构和功能改变的综合信息,尤其是对胶质瘤术后放射治疗后的临床随访非常重要。     

Kombinierte funktionelle und morphologische Bildgebung bei Sarkomen

¹⁸F-fluorodeoxyglucose positron-emission tomography (FDG-PET) and especially hybrid FDG-PET/CT is becoming more and more accepted for the clinical management of adult and pediatric patients with sarcomas. By integrating the CT component the specificity in particular but also the sensitivity of the modality are improved further. With PET/CT a complete staging including the detection of lung metastases is feasible in a single examination. For patients with primary bone and soft tissue sarcomas FDG-PET/CT is utilized for diagnosis, staging and restaging, metabolic tumor grading, guidance of biopsies, detection of tumor recurrence and therapy monitoring. Furthermore, it has been demonstrated that FDG uptake of the tumor prior to treatment and changes of FDG uptake after therapy significantly correlate with histopathologic response and survival of patients. Therefore, PET and PET/CT have a prognostic value. In the future new perspectives of hybrid PET/CT imaging will arise by introducing novel radiotracers and combined functional imaging of tumor metabolism and perfusion. High resolution MRI is essential for local evaluation of the primary tumor and preoperative planning with assessment of possible infiltration of vascular or neural structures. Contrast-enhanced MRI remains a key tool in the diagnosis of recurrent disease, especially in tumors which are not hypermetabolic. Dynamic contrast-enhanced MR sequences can significantly contribute to therapy monitoring. More research is necessary to prospectively compare dynamic contrast-enhanced MRI and FDG-PET/CT for evaluation of local and recurrent diseases.     

PET-imaging in tumors of the reproductive trac.

There is increasing evidence that metabolic imaging with positron-emission tomography (PET) using fluor-18 labeled fluorodeoxyglucose (18F FDG) is highly accurate for in vivo detection of a variety of malignancies. This quality gives FDG-PET an important role in the detection of malignant tumors and their metastases as well as for differentiation of tumors of unknown etiology. In the male and female reproductive tract, whole body imaging with FDG-PET is in particular capable of visualizing lymph-node and distant metastases before these changes become apparent on conventional cross-sectional imaging modalities. According to the incidence of tumors in the reproductive tract, FDG-PET-imaging has been evaluated in prostate cancer, ovarian cancer, cervical and testicular cancer. The role of PET is discussed with respect to the current management of patients. The presented data indicate that FDG-PET is more accurate for lymph-node staging in cervical cancer and testicular cancer. In ovarian cancer, FDG-PET may be helpful for detection of tumor recurrence. The role of FDG-PET is questionable in prostate cancer, due to the low metabolic activity of this type of cancer. Carbon-11 labeled acetate and carbon-11 or fluor-18 labeled choline are more promising than FDG for detection of recurrence in prostate cancer. In all other tumors of the reproductive tract there is limited experience with PET for a final conclusion.     

Relevance of Positron Emission Tomography (PET) in Oncology

BACKGROUND: The clinical use of positron emission tomography (PET) for detection and staging of malignant tumors is rapidly increasing. Furthermore, encouraging results for monitoring the effects of radio- and chemotherapy have been reported. METHODS: This review describes the technical principles of PET and the biological characteristics of tracers used in oncological research and patient studies. The results of clinical studies published in peer reviewed journals during the last 5 years are summarized and clinical indications for PET scans in various tumor types are discussed. RESULTS AND CONCLUSIONS: Numerous studies have documented the high diagnostic accuracy of PET studies using the glucose analogue F-18-fluordeoxyglucose (FDG-PET) for detection and staging of malignant tumors. In this field, FDG-PET has been particularly successful in lung cancer, colorectal cancer, malignant lymphoma and melanoma. Furthermore, FDG-PET has often proven to be superior to morphological imaging techniques for differentiation of tumor recurrence from scar tissue. Due to the high glucose utilization of normal gray matter radiolabeled amino-acids like C-11-methionine are superior to FDG for detection and delineation of brain tumors by PET. In the future, more specific markers of tumor cell proliferation and gene expression may allow the application of PET not only for diagnostic imaging also but for non-invasive biological characterization of malignant tumors and early monitoring of therapeutic interventions.