Recommendations on the use of 18F-FDG PET in oncology.

The rationale was to develop recommendations on the use of (18)F-FDG PET in breast, colorectal, esophageal, head and neck, lung, pancreatic, and thyroid cancer; lymphoma, melanoma, and sarcoma; and unknown primary tumor. Outcomes of interest included the use of (18)F-FDG PET for diagnosing, staging, and detecting the recurrence or progression of cancer. METHODS: A search was performed to identify all published randomized controlled trials and systematic reviews in the literature. An additional search was performed to identify relevant unpublished systematic reviews. These publications comprised both retrospective and prospective studies of varied methodologic quality. The anticipated consequences of false-positive and false-negative tests when evaluating clinical usefulness, and the impact of (18)F-FDG PET on the management of cancer patients, were also reviewed. Results and CONCLUSION: (18)F-FDG PET should be used as an imaging tool additional to conventional radiologic methods such as CT or MRI; any positive finding that could lead to a clinically significant change in patient management should be confirmed by subsequent histopathologic examination because of the risk of false-positive results. (18)F-FDG PET should be used in the appropriate clinical setting for the diagnosis of head and neck, lung, or pancreatic cancer and for unknown primary tumor. PET is also indicated for staging of breast, colon, esophageal, head and neck, and lung cancer and of lymphoma and melanoma. In addition, (18)F-FDG PET should be used to detect recurrence of breast, colorectal, head and neck, or thyroid cancer and of lymphoma.     

18F-氟脱氧葡萄糖PET在靶区确定和放疗计划制定中的价值

PET是一种功能性影像技术,能够提供丰富的肿瘤生物学信息,在肿瘤靶区确定和放疗计划制定中有其应用空间。18F-氟脱氧葡萄糖(18F-FDG)具有高度的敏感性和特异性,在非小细胞肺癌、头颈部鳞状细胞癌、食管癌确定放疗靶区和制定放疗计划时具有较大作用,但尚缺乏在直肠癌等肿瘤靶区确定中的价值的相关研究。18F-FDGPET应用于放射治疗在很多方面存在问题,能否作为制定放疗计划的标准,尚无大量前瞻性临床研究,有待进一步研究和证实。     

Prospective comparison of 18F-FDG PET with conventional imaging modalities (MRI, CT, and 67Ga scintigraphy) in assessment of combined intraarterial chemotherapy and radiotherapy for head and neck carcinoma.

To preserve the oral organs and functions in patients with head and neck carcinoma, accurate determination of the appropriate treatment after neoadjuvant chemotherapy and radiotherapy is of critical importance. We evaluated the diagnostic accuracy of (18)F-FDG PET relative to that of other conventional imaging modalities in the assessment of therapeutic response after combined intraarterial chemotherapy and radiotherapy as an organ preservation protocol. METHODS: The study was prospectively performed on 23 consecutive patients with head and neck squamous cell carcinoma who completed the treatment regimen and underwent 2 (18)F-FDG PET studies before and after neoadjuvant chemoradiotherapy. (67)Ga scintigraphy (only before therapy) as well as MRI and CT (both before and after therapy) were also performed. All images were blindly and independently interpreted without knowledge of histologic findings. The level of confidence in image interpretation was graded by means of a 5-point rating system (0 = definitely no tumor to 4 = definite tumor). RESULTS: Before treatment, (18)F-FDG PET detected primary tumors in all 23 patients and was more sensitive (100%) than MRI (18/23; 78.3%), CT (15/22; 68.2%), and (67)Ga scintigraphy (8/20; 40%), with a confidence level of 3 or 4 as a positive tumor finding. After chemoradiotherapy, residual tumors were histologically confirmed in 4 patients (pathologic complete response rate, 19/23; 82.6%). Although posttreatment (18)F-FDG PET showed almost equal sensitivity (4/4; 100%) compared with MRI (3/3; 100%) or CT (3/4; 75%), its specificity (17/19; 89.5%) was superior to MRI (7/17, 41.2%) and to CT (10/17; 58.8%) for primary lesions. Regarding metastases to neck lymph nodes, only specificity for posttreatment images was calculated because no metastasis was confirmed in any patients after treatment. Six subjects had (18)F-FDG PET-positive lymph nodes, which had pathologically no tumor cells and suggested an inflammatory reactive change after therapy. Therefore, the specificity of posttreatment (18)F-FDG PET (17/23; 73.9%) was almost identical to that of MRI (17/20; 85%) and CT (16/21; 76.2%) for neck metastasis. With combined chemoradiotherapy monitored with (18)F-FDG PET, 8 patients avoided surgery and the remaining 15 patients underwent a reduced form of surgery. CONCLUSION: (18)F-FDG PET facilitates differentiation of residual tumors from treatment-related changes after chemoradiotherapy, which may be occasionally difficult to characterize by anatomic images. (18)F-FDG PET has a clinical impact for the management of patients with head and neck cancers after neoadjuvant chemoradiotherapy by optimizing surgical treatment for each patient and contributes to the improvement of the patient's quality of life.     

Prognostic value of tumor 18F-FDG uptake in patients with untreated extranodal natural killer/T-cell lymphomas of the head and neck

Although 18F-FDG PET has been used to monitor patients with lymphoma, its usefulness has not been determined in patients with extranodal natural killer/T-cell lymphoma (ENKTL). Therefore, we evaluated whether pretreatment 18F-FDG uptake was a predictor of survival in patients with ENKTL of the head and neck. METHODS: Pretreatment staging work-ups, including whole-body 18F-FDG PET, were performed on 21 patients with previously untreated head and neck ENKTL. Fourteen patients received combined chemoradiotherapy (n = 14), and 7 received chemotherapy or radiotherapy alone. We assessed the relationship of maximum standardized uptake value (SUVmax) of the tumor to disease-specific survival (DSS) and to clinical parameters, including sex, age, Ann Arbor stage, performance status, International Prognostic Index score, presence of B symptoms, lactate dehydrogenase level, local tumor invasion (LTI), and lymph node involvement. RESULTS: Mean tumor SUVmax was 5.5 and was significantly higher in patients with elevated lactate dehydrogenase level, LTI, or poor response to initial therapy (P < 0.05). All 5 nonresponders to therapy had an SUVmax greater than 5.5, whereas 11 of 16 responders (69%) had an SUVmax less than or equal to 5.5 (mean SUVmax, 8.4 vs. 4.5). Univariate analysis showed that an International Prognostic Index score greater than or equal to 2, LTI, and SUVmax category were significant predictors of 3-y DSS, although only the SUVmax category remained an independent determinant of DSS on multivariate analysis (P = 0.023). CONCLUSION: High tumor 18F-FDG uptake was closely associated with local tumor invasion, contributing to unfavorable treatment and survival outcomes in patients with ENKTL of the head and neck.     

Comparison of 18F-FLT PET and 18F-FDG PET in esophageal cancer.

18F-FDG PET has gained acceptance for staging of esophageal cancer. However, FDG is not tumor specific and false-positive results may occur by accumulation of FDG in benign tissue. The tracer 18F-fluoro-3'-deoxy-3'-L-fluorothymidine (18F-FLT) might not have these drawbacks. The aim of this study was to investigate the feasibility of 18F-FLT PET for the detection and staging of esophageal cancer and to compare 18F-FLT PET with 18F-FDG PET. Furthermore, the correlation between 18F-FLT and 18F-FDG uptake and proliferation of the tumor was investigated. METHODS: Ten patients with biopsy-proven cancer of the esophagus or gastroesophageal junction were staged with CT, endoscopic ultrasonography, and ultrasound of the neck. In addition, all patients underwent a whole-body 18F-FLT PET and 18F-FDG PET. Standardized uptake values were compared with proliferation expressed by Ki-67 positivity. RESULTS: 18F-FDG PET was able to detect all esophageal cancers, whereas 18F-FLT PET visualized the tumor in 8 of 10 patients. Both 18F-FDG PET and 18F-FLT PET detected lymph node metastases in 2 of 8 patients. 18F-FDG PET detected 1 cervical lymph node that was missed on 18F-FLT PET, whereas 18F-FDG PET showed uptake in benign lesions in 2 patients. The uptake of 18F-FDG (median standardized uptake value [SUV(mean)], 6.0) was significantly higher than 18F-FLT (median SUV(mean), 3.4). Neither 18F-FDG maximum SUV (SUV(max)) nor 18F-FLT SUV(max) correlated with Ki-67 expression in the linear regression analysis. CONCLUSION: In this study, uptake of 18F-FDG in esophageal cancer is significantly higher compared with 18F-FLT uptake. 18F-FLT scans show more false-negative findings and fewer false-positive findings than do 18F-FDG scans. Uptake of 18F-FDG or 18F-FLT did not correlate with proliferation.     

PET imaging of osteosarcoma.

During the past decade the clinical value of PET imaging has been investigated for many different tumors. As knowledge of the advantages and limitations of this modality increased, PET has gained acceptance in tumor imaging. (18)F-FDG PET is now successfully used and approved for procedure reimbursement in many types of cancer-for example, lung cancer, melanoma, lymphoma, head and neck tumors, brain tumors, esophageal cancer, and colorectal cancer. In osteosarcoma, the introduction of neoadjuvant chemotherapy has dramatically improved survival rates, thus changing the demands for state-of-the-art imaging to provide detailed information on tumor staging and grading, evaluating treatment, and detecting recurrences. In this review, the available literature on PET imaging in osteosarcoma patients is critically summarized with respect to diagnosis, staging, therapy monitoring, and follow-up focusing on the clinically used tracers (18)F-FDG and (18)F-fluoride ion. Potential and probable indications are outlined. Because of the relatively small number of patients enrolled in clinical trials published to date, further research needs to be done in larger, prospective patient series to determine the full utility of PET in osteosarcoma.     

18F-氟脱氧葡萄糖PET及PET-CT在食管癌中的应用价值

食管癌的预后较差,切除术的致死率和致残率较高,术前正确分期对确定治疗方案尤为重要。PET是对CT、MRI、食管镜等常规检查的有益补充。受分辨率的影响,PET较难确定肿瘤的浸润程度,但对远处转移灶的诊断明显优于CT、MRI等常规检查,诊断复发性食管癌准确率较高,能有效鉴别手术瘢痕和复发,有效评价放疗、化疗的疗效。结合传统影像学检查,18F-氟脱氧葡萄糖PET及PET-CT能较为准确地进行术前分期,纠正不正确的治疗方案,改善食管癌患者的预后。     

PET/CT在食管癌放射治疗中的应用进展

食管癌是最常见的恶性肿瘤之一,放射治疗是其治疗的重要手段.然而,目前的CT、食管内镜超声(EUS)等影像检查手段只能从肿瘤的解剖形态信息上来进行食管癌的放射治疗模拟定位及分期、疗效评价.18F-FDG PET/CT作为集功能和解剖信息于一身的一种新的检查方式,在食管癌的诊断分期及放化疗预后的监测中已经得到了日益广泛的应用.笔者就18F-FDG PET/CT在食管癌的诊断分期及放射治疗方面的应用进展进行综述.     

18F-FDG PET对原发性食管癌和复发性食管癌的诊断价值

食管癌的预后较差,手术的致死率和致残率均较高,术前正确分期对确定治疗方案显得尤为重要.PET是继CT、MRI、食管镜等常规检查的有益补充.受分辨率的影响,PET较难确定肿瘤的局部浸润程度,在局部淋巴结转移方面其价值有待于进一步的研究,但对远处转移灶的诊断明显优于CT、MRI等常规检查,诊断复发性食管癌准确率较高,能有效鉴别手术疤痕和复发,有效评价放化疗的疗效.结合传统影像学检查,18F-FDG能较为准确地进行术前分期,纠正不正确的治疗方案,改善食管癌的预后.     

18F-FET PET compared with 18F-FDG PET and CT in patients with head and neck cancer.

Recent studies suggest a somewhat selective uptake of O-(2-[18F]fluoroethyl)-L-tyrosine (FET) in cerebral gliomas and in squamous cell carcinoma (SCC) and a good distinction between tumor and inflammation. The aim of this study was to investigate the diagnostic potential of 18F-FET PET in patients with SCC of the head and neck region by comparing that tracer with 18F-FDG PET and CT. METHODS: Twenty-one patients with suspected head and neck tumors underwent 18F-FET PET, 18F-FDG PET, and CT within 1 wk before operation. After coregistration, the images were evaluated by 3 independent observers and an ROC analysis was performed, with the histopathologic result used as a reference. Furthermore, the maximum standardized uptake values (SUVs) in the lesions were determined. RESULTS: In 18 of 21 patients, histologic examination revealed SCC, and in 2 of these patients, a second SCC tumor was found at a different anatomic site. In 3 of 21 patients, inflammatory tissue and no tumor were identified. Eighteen of 20 SCC tumors were positive for both 18F-FDG uptake and 18F-FET uptake, one 0.3-cm SCC tumor was detected neither with 18F-FDG PET nor with 18F-FET PET, and one 0.7-cm SCC tumor in a 4.3-cm ulcer was overestimated as a 4-cm tumor on 18F-FDG PET and missed on 18F-FET PET. Inflammatory tissue was positive for 18F-FDG uptake (SUV, 3.7-4.7) but negative for 18F-FET uptake (SUV, 1.3-1.6). The SUVs of 18F-FDG in SCC were significantly higher (13.0 +/- 9.3) than those of 18F-FET (4.4 +/- 2.2). The ROC analysis showed significantly superior detection of SCC with (18)F-FET PET or 18F-FDG PET than with CT. No significant difference (P = 0.71) was found between 18F-FDG PET and 18F-FET PET. The sensitivity of 18F-FDG PET was 93%, specificity was 79%, and accuracy was 83%. 18F-FET PET yielded a lower sensitivity of 75% but a substantially higher specificity of 95% (accuracy, 90%). CONCLUSION: 18F-FET may not replace 18F-FDG in the PET diagnostics of head and neck cancer but may be a helpful additional tool in selected patients, because 18F-FET PET might better differentiate tumor tissue from inflammatory tissue. The sensitivity of 18F-FET PET in SCC, however, was inferior to that of 18F-FDG PET because of lower SUVs.     

喉癌18F-FDG PET/CT显像的临床应用价值

目的探讨18F-脱氧葡萄糖(FDG)PET/CT显像相对于单独的18F-FDG PET显像在喉癌诊断中的临床价值以及评价平均标准化摄取值(SUVmean)在喉癌和喉生理性显像鉴别中的作用。方法疑似喉癌患者23例。男19例,女4例,年龄30～70岁。空腹6H以上,静脉注射7.4MBq/kg 18F-FDG后40min后仰卧位行头颈部或全身扫描。分别评价18F-FDG PET和18F-FDG PET/CT显像对病灶诊断的灵敏度和特异性。19例病理为鳞癌的喉癌患者与15例喉生理性显像患者作为对照,测定显像部位的SUVmean,试用受试者工作曲线特征(Receivrer Operation Characteristic,ROC)及阳性似然比(positive likelihood ratio,+LR)确定SUVmean阈值。结果 23例喉癌患者,108处病灶。18 F-FDGPET显像和18F-FDG PET/CT显像对病灶诊断的灵敏度分别为85.1%(40/47)和89.4%(42/47),差异无统计学意义(P>0.05),特异性分别为和72.1%(44/61)和91.8%(56/61),差异有统计学意义(P<0.05)。19例病理为鳞癌的喉癌患者SUVmean均数为7.3±2.9,15例喉生理性显像SUVmean均数为4.9±1.1,差异有统计学意义(P<0.05)。SU-Vmean阈值选定为6.1,18 F-FDG PET/CT显像喉癌诊断的灵敏性为63.2%,特异性为86.7%。结论 18 F-FDG PET/CT显像明显改善18F-FDG PET显像的特异性。SUVmean阈值选定为6.1,有利于喉癌和喉生理性显像的鉴别。     

Application of fluorodeoxyglucose positron emission tomography in the management of head and neck cancers

The use of fluorodeoxyglucose positron emission tomography (FDG PET) scan technology in the management of head and neck cancers continues to increase. We discuss the biology of FDG uptake in malignant lesions and also discuss the physics of PET imaging. The various parameters described to quantify FDG uptake in cancers including standardized uptake value, metabolic tumor volume and total lesion glycolysis are presented. PET scans have found a significant role in the diagnosis and staging of head and neck cancers. They are also being increasingly used in radiation therapy treatment planning. Many groups have also used PET derived values to serve as prognostic indicators of outcomes including loco-regional control and overall survival. FDG PET scans are also proving very useful in assessing the efficacy of treatment and management and follow-up of head and neck cancer patients. This review article focuses on the role of FDG-PET computed tomography scans in these areas for squamous cell carcinoma of the head and neck. We present the current state of the art and speculate on the future applications of this technology including protocol development, newer imaging methods such as combined magnetic resonance and PET imaging and novel radiopharmaceuticals that can be used to further study tumor biology.     

The role of PET in head and neck cancer

PET and PET/CT are the procedures of choice for molecular imaging in the head and neck area. The current data of the literature show, that functional imaging with fluorine-18-deoxyglucose ((18)F-FDG) provides the possibility to obtain information about the viability of malignant lesions. The use of hybrid systems, PET/CT, enables physicians to assess both, morphology and function, and achieve a high diagnostic accuracy exceeding 90%. PET with (18)F-FDG is the most sensitive method to detect tumor recurrence. However, false positive results must be considered due to unspecific changes following treatment, especially radiotherapy. The use of quantitative PET scans as well as the application of a second tracer, enhance the capability of PET to assess questionable masses more accurately. Follow up examinations with PET and (18)F-FDG provide data about early changes in the tumor metabolism due to chemotherapeutic treatment. Studies in patients undergoing surgery and radiotherapy demonstrated, that PET with (18)F-FDG can be used for the prediction of individual survival.     

~(18)F-FDG PET/CT在食管癌的应用进展

食管癌恶性程度高、预后差,严重威胁了人类健康,18F-FDG PET/CT集功能和解剖信息于一身,这种医学影像技术在食管癌的应用优势日益受到广大医务工作者的关注。本文综述了18F-FDG PET/CT在食管癌的诊断、分期、复发、疗效和预后评估、放射治疗计划制定等方面的研究进展。     

Clinical utility of 18F-FDG PET for patients with salivary gland malignancies.

The clinical utility of 18F-FDG PET in evaluating salivary gland malignancies has not been well defined. We therefore evaluated the utility of 18F-FDG PET in management for patients with salivary gland cancers. METHODS: Thirty-four patients with newly diagnosed salivary gland cancers underwent CT and 18F-FDG PET before surgical resection with radiotherapy. The diagnostic accuracies of CT and 18F-FDG PET for detecting primary tumors and neck metastases were compared with a histopathologic reference. We determined the relationship between the maximum standardized uptake value (SUV) of the tumor and clinicopathologic parameters such as sex, age, local tumor invasion, T and N categories, TNM stage, and histologic grade, as well as their associations with disease-free survival (DFS). RESULTS: 18F-FDG PET was more sensitive than CT for the detection of primary tumors (91.2% vs. 79.4%; P < 0.05), cervical metastases (80.5% vs. 56.1%; P < 0.05), and distant metastases in 2 patients at initial staging. High-grade malignancies had higher mean maximum SUVs than did low- and intermediate-grade malignancies (4.6 vs. 2.8; P = 0.011). T and N categories were independent determinants of DFS (P < 0.05), but the maximum SUV (4.0) was not. During a mean follow-up of 25.1 mo, 18F-FDG PET correctly diagnosed local-regional recurrences in 6 patients and new distant metastases in 9 patients. CONCLUSION: Our findings indicate that, in patients with salivary gland malignancies, 18F-FDG PET is clinically useful in initial staging, histologic grading, and monitoring after treatment but not in predicting patient survival.     

Early prediction of response to chemotherapy in metastatic breast cancer using sequential 18F-FDG PET.

Chemotherapy is currently the treatment of choice for patients with high-risk metastatic breast cancer. Clinical response is determined after several cycles of chemotherapy by changes in tumor size as assessed by conventional imaging procedures including CT, MRI, plain film radiography, or ultrasound. The aim of this study was to evaluate the use of sequential 18F-FDG PET to predict response after the first and second cycles of standardized chemotherapy for metastatic breast cancer. METHODS: Eleven patients with 26 metastatic lesions underwent 31 (18)F-FDG PET examinations (240-400 MBq of 18F-FDG; 10-min 2-dimensional emission and transmission scans). Clinical response, as assessed by conventional imaging after completion of chemotherapy, served as the reference. 18F-FDG PET images after the first and second cycles of chemotherapy were analyzed semiquantitatively for each metastatic lesion using standardized uptake values (SUVs) normalized to patients' blood glucose levels. In addition, whole-body 18F-FDG PET images were viewed for overall changes in the 18F-FDG uptake pattern of metastatic lesions within individual patients and compared with conventional imaging results after the third and sixth cycles of chemotherapy. RESULTS: After completion of chemotherapy, 17 metastatic lesions responded, as assessed by conventional imaging procedures. In those lesions, SUV decreased to 72% +/- 21% after the first cycle and 54% +/- 16% after the second cycle, when compared with the baseline PET scan. In contrast, 18F-FDG uptake in lesions not responding to chemotherapy (n = 9) declined only to 94% +/- 19% after the first cycle and 79% +/- 9% after the second cycle. The differences between responding and nonresponding lesions were statistically significant after the first (P = 0.02) and second (P = 0.003) cycles. Visual analysis of 18F-FDG PET images correctly predicted the response in all patients as early as after the first cycle of chemotherapy. As assessed by 18F-FDG PET, the overall survival in nonresponders (n = 5) was 8.8 mo, compared with 19.2 mo in responders (n = 6). CONCLUSION: In patients with metastatic breast cancer, sequential 18F-FDG PET allowed prediction of response to treatment after the first cycle of chemotherapy. The use of 18F-FDG PET as a surrogate endpoint for monitoring therapy response offers improved patient care by individualizing treatment and avoiding ineffective chemotherapy.     

Clinical utility of 18F-FDG PET/CT in assessing the neck after concurrent chemoradiotherapy for Locoregional advanced head and neck cancer.

For patients with locoregional advanced head and neck squamous cell carcinoma (HNSCC), concurrent chemoradiotherapy is a widely accepted treatment, but the need for subsequent neck dissection remains controversial. We investigated the clinical utility of 18F-FDG PET/CT in this setting. METHODS: In this Institutional Review Board (IRB)-approved and Health Insurance Portability and Accountability Act (HIPPA)-compliant retrospective study, we reviewed the records of patients with HNSCC who were treated by concurrent chemoradiation therapy between March 2002 and December 2004. Patients with lymph node metastases who underwent 18F-FDG PET/CT > or = 8 wk after the end of therapy were included. 18F-FDG PET/CT findings were validated by biopsy, histopathology of neck dissection specimens (n = 18), or clinical and imaging follow-up (median, 37 mo). RESULTS: Sixty-five patients with a total of 84 heminecks could be evaluated. 18F-FDG PET/CT (visual analysis) detected residual nodal disease with a sensitivity of 71%, a specificity of 89%, a positive predictive value (PPV) of 38%, a negative predictive value (NPV) of 97%, and an accuracy of 88%. Twenty-nine heminecks contained residual enlarged lymph nodes (diameter, > or =1.0 cm), but viable tumor was found in only 5 of them. 18F-FDG PET/CT was true-positive in 4 and false-positive in 6 heminecks, but the NPV was high at 94%. Fifty-five heminecks contained no residual enlarged nodes, and PET/CT was true-negative in 50 of these, yielding a specificity of 96% and an NPV of 98%. Lack of residual lymphadenopathy on CT had an NPV of 96%. Finally, normal 18F-FDG PET/CT excluded residual disease at the primary site with a specificity of 95%, an NPV of 97%, and an accuracy of 92%. CONCLUSION: In patients with HNSCC, normal 18F-FDG PET/CT after chemoradiotherapy has a high NPV and specificity for excluding residual locoregional disease. In patients without residual lymphadenopathy, neck dissection may be withheld safely. In patients with residual lymphadenopathy, a lack of abnormal 18F-FDG uptake in these nodes also excludes viable tumor with high certainty, but confirmation of these data in a prospective study may be necessary before negative 18F-FDG PET/CT may become the only, or at least most-decisive, criterion in the management of the neck after chemoradiotherapy.     

Evaluation of head and neck cancer with 18F-FDG PET: a comparison with conventional methods

The aim of this study was to evaluate the usefulness of 18F-FDG PET in the diagnosis and staging of primary and recurrent malignant head and neck tumours in comparison with conventional imaging methods [including ultrasonography, radiography, computed tomography (CT) and magnetic resonance imaging (MRI)], physical examination, panendoscopy and biopsies in clinical routine. A total of 54 patients (13 female, 41 male, age 61.3+/-12 years) were investigated retrospectively. Three groups were formed. In group I, 18F-FDG PET was performed in 15 patients to detect unknown primary cancers. In group II, 24 studies were obtained for preoperative staging of proven head and neck cancer. In group III, 18F-FDG PET was used in 15 patients to monitor tumour recurrence after radiotherapy and/or chemotherapy. In all patients, imaging was obtained at 70 min after the intravenous administration of 180 MBq 18F-FDG. In 11 of the 15 patients in group I, the primary cancer could be found with 18F-FDG, yielding a detection rate of 73.3%. In 4 of the 15 patients, CT findings were also suggestive of the primary cancer but were nonetheless equivocal. In these patients, 18F-FDG showed increased 18F-FDG uptake by the primary tumour, which was confirmed by histology. One patient had recurrence of breast carcinoma that could not be detected with 18F-FDG PET, but was detected by CT. In three cases, the primary cancer could not be found with any imaging method. Among the 24 patients in group II investigated for staging purposes, 18F-FDG PET detected a total of 13 local and three distant lymph node metastases, whereas the conventional imaging methods detected only nine local and one distant lymph node metastases. The results of 18F-FDG PET led to an upstaging in 5/24 (20.8%) patients. The conventional imaging methods were false positive in 5/24 (20.8%). There was one false positive result using 18F-FDG PET. Among the 15 patients of group III with suspected recurrence after radiotherapy and/or chemotherapy, 18F-FDG was true positive in 7/15 (46.6%) and true negative in 4/15 (26.6%). The conventional imaging methods were true positive in 5/15 (33.3%) and true negative in 4/15 (26.6%). One false negative (6.6%) and three false positive findings (20%) on 18F-FDG PET were due to inflamed tissue. The conventional imaging methods were false positive in three (20%) and false negative in three cases (20%). It is concluded that in comparison to conventional diagnostic methods, 18F-FDG PET provides additional and clinically relevant information in the detection of primary and metastatic carcinomas as well as in the early detection of recurrent or persistent head and neck cancer after radiotherapy and/or chemotherapy. 18F-FDG PET should therefore be performed early in clinical routine, usually before CT or MRI.     

Detection of pelvic lymph node metastases in gynecologic malignancy: a comparison of CT, MR imaging, and positron emission tomography.

OBJECTIVE: Accurate assessment of lymph node status before treatment is critical in the treatment of gynecologic cancers because the 5-year survival and treatment of women is influenced by lymph node involvement. The aims of this study were to investigate the ability of X-ray CT, MR imaging, and (18)F-FDG positron emission tomography (PET) to detect pelvic lymph node metastases by comparing imaging with histopathologic findings after lymph node dissection. MATERIALS AND METHODS: Eighteen patients with gynecologic cancers were studied by all three imaging methods before surgery. The images were initially reviewed with routine diagnostic conditions and then, subsequently, by two observers who were unaware of the clinical and histopathologic findings of the patients. The nodal sites were split into upper (aortic to common iliac bifurcations) and lower (common iliac bifurcations to inguinal ligament) iliac chains. All observers' results were statistically analyzed with specificity, sensitivity, positive and negative predictive values, Fisher's exact test (individual observers) or chi-square test (combined observers), and Cohen's kappa test. RESULTS: Eight of 18 patients had lymph node metastases at histology. Findings of all three modalities agreed in full in only one patient. CT correctly revealed 10 node-negative patients, whereas MR imaging was correct in eight of these patients. (18)F-FDG PET correctly depicted one patient with lymph nodes negative for tumor. CT was the most specific imaging modality (97.0%), with MR imaging and PET rendering values of 90.7% and 77.3%, respectively, but sensitivity of all modalities was low (CT, 48.1%; MR imaging, 53.7%; PET, 24.5%). Observer agreement for each modality was good; kappa values among all observers were 0.88 for CT, 0.85 for MR imaging, and 0.72 for PET. CONCLUSION: CT is the most specific modality for detecting lymph nodes positive for tumor in gynecologic cancers, whereas MR imaging is the most sensitive. The poor results of PET in the pelvis are attributed to urinary (18)F-FDG in the ureters or bladder, which may mask or imitate lymph node metastases.     

Monitoring response to treatment in patients utilizing PET

Establishing new surrogate end points for monitoring response to treatment is needed for current therapy modalities and for new therapeutic strategies including molecular targeted cancer therapies. PET as a functional imaging technology provides rapid, reproducible, noninvasive in vivo assessment and quantification of several biologic processes targeted by these therapies. PET is useful in a variety of clinical relevant applications, including distinguishing between radiation necrosis and tumor recurrence, determining the resectability of recurrent tumor, and evaluating response to therapy. FDG-PET has demonstrated efficacy for monitoring therapeutic response in a wide range of cancers, including breast, esophageal, lung, head and neck, and lymphoma. FDG-PET can assess tumor glucose use with high reproducibility. Following therapy, the decrease of glucose use correlates with the reduction of viable tumor cells. FDG-PET allows the prediction of therapy response early in the course of therapy and determining the viability of residual masses after completion of treatment. The molecular basis for the success of FDG-PET is the rapid reduction of tumor glucose metabolism in effective therapies. Of even higher clinical relevance is the accurate identification of nonresponders in patients without a significant change in tumor glucose metabolism after initiation of therapy. PET imaging can easily visualize these changes in metabolic activity and indicate, sometimes within hours of the first treatment, whether or not a patient will respond to a particular therapy. In contrast to CT, MR imaging, or ultrasound, PET imaging allows identification of responding and nonresponding tumors early in the course of therapy. With this information, physicians can rapidly modify ineffective therapies for individual patients and thereby potentially improve patient outcomes and reduce cost. One of the major limitations for the routine application of FDG-PET imaging for therapy monitoring is that no generally accepted cutoff values have been established to differentiate optimally between responders and nonresponders. The patient series are still relatively small and frequently consist of different tumor types and different therapy regimens. Prospective studies including a sufficient number of patients are needed to define cutoff values to differentiate between responder and nonresponder for different tumors and different treatment regimes. In the future, PET imaging can also serve in the evaluation of new therapeutic agents, new experimental treatments, and specifically in monitoring clinical phase II studies.