FDG PET判断鼻咽癌放疗后鼻咽病灶残留的临床价值

背景与目的：18F－2脱氧葡萄糖（FDG）正电子发射计算机断层显像（PET）在判断恶性肿瘤治疗后病灶残留上的应用是放射肿瘤学目前研究的热点之一,本文旨在探讨FDG PET显像在鼻咽癌放射治疗后鼻咽肿瘤残留中的应用。方法：25例鼻咽癌放疗后,临床疑咽肿瘤残留,均行FDG PET显像,显像时间为放疗后2－6个月,其中23例同期行CT检查,最后诊断依靠病理检查和临床随访。结果：25例患者中FDG PET显像阳性18例,其中4例假阳性,阴性7例,其中2例假阴性,FDG PET显像的准确率为76．0％（19／25）,CT检查的准确率为52．2％（12／23）,11例CT未见鼻咽肿瘤残留,FDG PET显示其中2例有鼻咽局部FDG异常浓聚;7例CT诊为肿瘤残留,FDG PET均显示局部病变有FDG异常浓聚,5例CT未能确定残留,PET显示3例FDG异常浓聚,12例FDG异常浓聚的病变处经活检病理证实为肿瘤残留。结论：判断鼻咽癌放疗后鼻咽肿瘤残留,FDG PET比CT有更高的准确性。     

18F-脱氧葡萄糖hPET显像诊断非小细胞肺癌放化疗后复发病灶的价值

目的：探讨^18F-脱氧葡萄糖(FDG)hPET在诊断非小细胞肺癌放化疗后复发的临床价值。方法：21例非小细胞肺癌患者，临床疑复发而行^18F-FDG hPET显像，21例患者同期行cT或MRI检查。最后诊断依靠病理检查和临床随访。结果：2l例患者中^18F-FDG hPET显像阳性17例，其中1例假阳性；阴性4例，其中假阴性1例。^18F-FDG hPET显像的灵敏度、特异性、准确度和阳性预测值分别为94．1％、75％、90．5％、94．1％：cT或MRI检查的灵敏度、特异性、准确度和阳性预测值分别为60％、66．7％、61．9％、81．8％。结论：评价放化疗后复发性非小细胞肺癌，^18F-FDG hPET显像比CT或MR1有更高的灵敏度、特异性和准确度；对复发性非小细胞肺癌放射治疗靶区的定义有较高价值，费用低于PET，值得在临床上推广应用。     

18 F-脱氧葡萄糖PET显像在原发灶不明转移癌中的应用

目的：探讨^18F-脱氧葡萄糖（FDG）正电子发射型体层摄影术（PET）全身显像在原发灶不明转移癌中的作用。方法：对29例原发灶不明转移癌患者行EDG PET全身显像，并与临床随诊、组织活检和手术病理结果对照。结果：29例原发灶不明转移癌患者，FDG PET发现可疑原发灶15例，其中13例为病理结果所证实，2例病理结果为阴性，FDG PET对原发灶的检出率为44．8％（13／29）。FDG PET全身显像另外检检出淋巴结转移和远地转移灶26个，CT和MRI只检出13个。14例FDG PET未确定原发灶者，经随访3－13个月,死亡率42．9％（6／14）。13例FDG PET确定原发灶者，经过有针对性的治疗，经随访2－13个月，死亡率为15．4％（2／13）。结论：FDG PET全身显像对原发灶不明转移癌原发灶的确定、临床分期、治疗方案的制定以及预后的改善均有一定的价值。     

18F-FDG PET判断头颈部癌复发的作用

目的：探讨^18F-氟脱氧葡萄糖（^18F-fluoro-deoxyglucose,^18F-FDG）正电子发射断层显像术（positron emission tomography,PET）在头颈部癌复发诊断中的作用。方法：54例临床上怀疑复发的头颈部癌患者同期均行^18F-FDGPET显像（25例全身显像,29例局部显像）和CT或MR检查,最后诊断依靠病理检查或临床随访。结果：54例患者中^18F-FDGPET显像阳性39例,其中假阳性2例;阴性15例,其中假阴性3例。^18F-FDGPET显像和CT或MR的敏感性分别为92.5%（37/40）和55.0%（22/40）,差异有统计学意义,χ^2=14.528,P〈0.05;特异性分别为85.7%（12/14）和85.7%（12/14）,差异无统计学意义,χ^2=1.875,P=0.483;阳性预测值、阴性预测值分别为94.9%（37/39）、80.0%（12/15）和100.0%（22/22）、52.2%（12/23）;准确率分别为90.7%（49/54）和63.0%（34/54）,差异有统计学意义,χ^2=11.711,P=0.001。在25例18F-FDGPET全身显像中,16例除头颈^18F-FDG异常浓聚外,9例还发现有远处转移。结论：判断头颈部癌治疗后复发,^18F-FDGPET比CT或MR更敏感和有更高的准确性,并且在临床分期上有一定价值。     

PET/CT显像在淋巴瘤分期及疗效评价中的价值

目的：探讨正电子发射型断层扫描技术（PET）融合计算机断层扫描（CT）即PET／CT显像在淋巴瘤诊断、分期及疗效评价中的价值。方法：对14例经病理学确诊的淋巴瘤患者行PET／CT显像，显像剂18F-脱氧葡萄糖（18F-FDG）用量10-14mCi（370—518MBq），并与同期CT、MRI或B超等影像检查结果（CI）进行对比分析，随访时间6个月以上。结果：14例PET／CT显像阳性13例（92．8％）。3例（21．4％）为淋巴瘤初诊治疗前检查，PET／CT显像均阳性，PET标准摄取值（SUV，正常〈2．5）分别为3．7、3．5和11．4；11例（78．5％）淋巴瘤治疗2—4疗程后行PET／CT显像，11例中3例（21．4％）肿块全部处于高代谢状态，临床确认有肿瘤明显残余或复发，SUV分别为11．7、10．1和5．7，8例（57．1％）临床疗效为完全缓解（CR）和部分缓解（PR）的患者中，PET／CT显像阳性7例并示肿块处于抑制状态，其中2例SUV升高分别为3．6和2．8，但术后病理证实为假阳性。共有3例（21．4％）淋巴瘤PET／CT显像新发现恶性病灶而提高临床分期，改变了进一步临床治疗方案。结论：18F-FDGPET／CT显像能灵敏、准确地检出淋巴瘤病灶特别是复发及残余病灶，对淋巴瘤诊断、分期、疗效评价及指导临床治疗有重要价值。     

^18F—FDG PET显像在鼻咽癌诊断治疗中的价值

目的：探讨^18F—FDG PET显像在鼻咽癌诊断治疗中的价值。方法：35例鼻咽癌PET与同期CT、MRI、骨ECT诊断结果比较分析，全部经病理组织学证实。结果：35例鼻咽癌PET与临床和CT、MRI、骨ECT诊断相符31例(88．6％)，诊断不符4例(11．4％)．其中真阴性2例和假阴性2例，1例ECT疑为多处骨转移，PET未发现核素浓聚改变，随访排除了骨转移；1例MRI疑为复发，PET未发现核素浓聚改变，病理及随访排除了复发：1例CT诊断肝转移，1例MRI诊断桥脑转移，PET均未发现核素浓聚改变。PET检测出CT、MRI和ECT未发现的转移灶6例(17．1％)。结论：^18F—FDG PET对鼻咽癌定性诊断具有较高的准确性和特异性，在诊断淋巴结和远处转移方面优于CT和MRI；诊断肝、脑转移有假阴性表现，提示PET应结合CT、MRI进行综合分析，才能作出正确的诊断。     

子宫颈癌治疗后18F-FDG PET/CT显像的临床价值

目的 探讨18F-脱氧葡萄糖(FDG) PET/CT显像在子宫颈癌治疗后监测有无肿瘤复发及转移灶中的临床应用价值.方法 子宫颈癌治疗后患者48例,行全身18F-FDG PET/CT检查,肿瘤复发和(或)转移病灶根据病理结果、多种影像学诊断及临床随访而确诊.随访时间＞1年.采用SPSS 11.5软件进行统计学处理.结果 48例患者共行54次PET/CT显像,真阳性26例次,真阴性24例次,假阴性1例次,假阳性3例次.18F-FDG PET/CT显像诊断子宫颈癌治疗后肿瘤复发和(或)转移病灶的敏感度、特异性、准确性、阳性预测值及阴性预测值分别为96.3％ (26/27)、88.9％(24/27)、92.6％ (50/54)、89.7％(26/29)、96.0％(24/25).检查后部分患者的诊断和治疗方案发生了改变,有24例(50.0％)患者改变了诊断,其中21例(43.8％)改变了治疗方案.结论 PET/CT显像可以较准确地早期探查子宫颈癌治疗后的复发病灶和转移灶,包括盆腔外的远处转移,明确再分期,有助于临床医生确定正确的治疗方案.尽管有其一定的局限性,PET/CT显像仍可作为子宫颈癌治疗后监测的常规检查手段.     

18F-FDG SPECT/CT同机融合在肝癌术后随访中的价值

目的 探讨^18F-FDG SPECT／CT同机融合显像在原发性肝癌术后随访中的临床价值。方法 对20例原发性肝细胞癌术后随访患者同期进行CT(MR)及FDG-SPECT／CT检查，并对结果进行对比分析。结果 经病理及临床确诊的15例术后复发患者中有12例表现为明显形态学改变及增强表现而明确诊断，但有3例CT或MR显示不规则或结节状不明显强化，不能准确作出术后改变或术后复发的诊断，而呈假阴性；而FDG显像中有14例均表现为局部FDG明显浓集而明确诊断，仅1例出现假阴性。5例未复发者中CT(MR)有2例为假阳性；而FDG显像无1例假阳性。CT(MR)和FDG诊断的灵敏度及特异性分别为80．0％(12／15)、60．0％(3／5)及93，3％(14／15)、100．0％(5／5)。结论 FDG显像对肝癌术后复发及转移的定性诊断具有明显的优势；SPECT／CT同机融合显像能准确定位复发病灶的解剖和功能信息。     

18F-FDG PET/CT在探测卵巢癌术后复发和转移中的价值

[目的]评价^18F-FDG PET/CT显像在探测卵巢癌术后复发病灶中的应用价值。[方法]采用仪器为Siemens Biograph Sensation 16 PET/CT，43例卵巢癌术后患者禁食4～6h，静脉注射^18F-FDG60min后进行PET/CT检查，采集方式为3D模式。PET/CT图像结果与血清CA125、B超及CT或MRI影像学资料进行比较。并与手术病理或临床随访结果比较判断其诊断的准确性。[结果]FDG PET/CT诊断卵巢癌复发的灵敏度、特异性和准确性分别为92.3%、100%和93.0%。血清CA125水平与FDG PET结果有一定相关性，33例CA125升高患者中31例PET显像阳性，10例CA125正常水平患者中仅有5例PET显像阳性。[结论]当常规影像学检查阴性或可疑时，PET/CT显像对卵巢癌复发的检测具有较高的灵敏度和准确性，特别术后患者CA125升高的情况下，FDG PET/CT有助于探测隐匿性复发或转移病灶，指导进一步的治疗。     

18F - FDG PET / CT 显像对多发性骨髓瘤诊断效能的回顾性研究

目的：回顾性分析评价18F—FDGPET／CT显像对多发性骨髓瘤的诊断效能。方法：选择本院2011年3月-2013年6月临床可疑多发性骨髓瘤患者39例,其中男性22例,女性17例,年龄44—78岁,平均年龄（51．3±0．5）岁。均行PET／CT检查及临床骨穿或病理活检证实,分别统计其真假阳性例数及真假阴性例数,并计算灵敏度、特异性及准确性指标,评价诊断效能。结果：39例患者中真阳性18例,假阳性2例,真阴性16例,假阴性3例。PET／CT诊断灵敏度为85．7％（18／21）,特异性为88．9％（16／18）,准确性为87．2％（34／39）,阳性预测值为90％（18／20）,阴性预测值为84．2％（16／19）。结论：18F—FDGPET／CT可用于多发性骨髓瘤的诊断,结合患者临床表现及生化检查可提高诊断符合率。     

Utility of 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography and positron emission tomography/computed tomography imaging in the preoperative staging of head and neck squamous cell carcinoma

The combination of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) and computed tomography (CT) has been reported to be more accurate than CT or PET alone in a preoperative setting. We compared the diagnostic utility of preoperative PET/CT, PET and CT/MRI in 167 patients with newly diagnosed head and neck squamous cell carcinoma (HNSCC), of whom 104 underwent FDG PET and 63 underwent combined PET/CT with all receiving CT/MRI. These preoperative PET, PET/CT, and CT/MRI results were reviewed and their accuracies were compared in patients in whom diagnosis was confirmed histopathologically. Age, sex, primary sites and stage, and nodal involvement were comparable between two groups. The accuracy of PET and PET/CT for detecting primary tumors and cervical metastases was comparable, but significantly higher than that of CT/MRI (98%-97% vs. 86-88% for primary; 92%-93% vs. 85%-86% for neck on a level-by-level basis; P<.05). PET and PET/CT gave false negative results: in 2 (2%) and 2 (3%) patients for primary tumors; in 6 (6%) and 3 (5%) patients for neck metastases, respectively. PET and PET/CT also gave false-positive results for cervical metastases in 5 (5%) and 4 (6%) patients, respectively. Compared with PET alone, preoperative FDG PET/CT may not yield significantly improved diagnostic accuracy in patients with HNSCC. Moreover, despite their high accuracy, PET and PET/CT may not abrogate the need for conventional imaging and pathologic staging based on primary resection and neck dissection.     

Utility of 18F-fluorodeoxyglucose positron emission tomography in the preoperative staging of squamous cell carcinoma of the oropharynx.

BACKGROUND: 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) has been reported to be superior to computed tomography (CT)/magnetic resonance imaging (MRI) in the evaluation of head and neck cancers, but little is known about its usefulness in oropharyngeal squamous cell carcinoma (SCC). We therefore compared FDG PET and CT/MRI in the preoperative staging of previously untreated oropharyngeal SCC. METHODS: Thirty-two consecutive patients with oropharyngeal SCC underwent FDG PET and CT/MRI before surgery. Each method was interpreted separately to assess primary tumor and cervical node status. Their sensitivity and specificity were compared relative to histopathologic analysis. RESULTS: Histopathology revealed metastases in 29 of 39 dissected neck sides and in 47 of 163 dissected cervical levels. FDG PET had higher sensitivities than CT/MRI for primary tumor detection (25/32 vs. 30/32, P=0.063) and for identification of cervical metastases on neck side (22/29 vs. 28/29, P<0.05) and level-by-level (37/47 vs. 45/47, P<0.05) bases. In contrast, the specificity of the two methods did not differ significantly (P>0.5). FDG PET correctly interpreted the false-negative results of CT/MRI in 6 of 7 primary tumors and 8 of 10 cervical levels. CONCLUSIONS: The improved preoperative staging of FDG PET may help in planning treatment, but its accuracy is insufficient to replace pathologic staging based on neck dissection.     

Combined [18F]fluorodeoxyglucose positron emission tomography and computed tomography for detecting contralateral neck metastases in patients with head and neck squamous cell carcinoma

We evaluated the clinical utility of combined [(18)F]fluorodeoxyglucose (FDG) positron emission tomography (PET) and computed tomography (CT), as well as CT and magnetic resonance imaging (MRI) in identifying nodal metastases in the contralateral neck in patients with head and neck squamous cell carcinoma (HNSCC). A total of 114 patients were preoperatively evaluated with PET/CT and CT/MRI. Histopathologic analysis from bilateral neck dissection tissues was used as the gold standard in assessing these imaging techniques. Of the 114 patients, 63 (55%) had neck metastases and 26 (23%) had contralateral neck metastases. On a per-level basis, FDG PET/CT was significantly more sensitive and accurate than CT/MRI in the ipsilateral (88% vs. 70%, P<0.01 and 93% vs. 89%, P<0.01, respectively) and contralateral (52% vs. 36%, P<0.01 and 91% vs. 90%, P=0.039, respectively) neck. PET/CT and CT/MRI were less sensitive in detecting contralateral than ipsilateral neck metastases due to the lower incidence of metastases and smaller nodes on the contralateral side. Combined PET/CT is superior to CT/MRI in detecting metastatic neck nodes in HNSCC patients. However, PET/CT may not abrogate the need for contralateral neck surgery or radiotherapy in these patients.     

18F-fluorodeoxyglucose positron emission tomography/computed tomography in the assessment of occult primary head and neck cancers--an audit and review of published studies

AimsTo assess the value of 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in patients with squamous cell and undifferentiated cancer neck nodes and no primary site on conventional assessment.Materials and methodsSeventy-eight patients with neck nodal metastases from an unknown primary cancer were studied. PET/CT was carried out in all patients, 1 h after FDG injection.ResultsUptake suspicious of an occult primary cancer was found in 46/78 (59.0%) patients. Subsequent investigations confirmed a primary site in the base of the tongue in 14, pharyngeal palatine tonsil in 14, post cricoid in one, lung in one. PET/CT diagnosed primary cancers in 30/78 patients (38.5%); sensitivity, specificity, positive predictive value, negative predictive value: 30/30 (100.0%), 32/48 (66.7%), 30/46 (65.2%), 32/32 (100.0%), respectively. PET/CT detected additional disease in four patients: contralateral nodal disease in two, mediastinal nodal disease in one and liver metastases in one.ConclusionsFDG PET/CT is of value in the assessment of patients with occult head and neck primary cancers. However, false-positive results remain a limitation of the investigation.     

Diagnostic accuracy of <Superscript>18</Superscript>F–FDG PET/CT and MR imaging in patients with adenoid cystic carcinoma

Background

The aim of this study was to evaluate the value of 18F–FDG PET/CT (PET/CT) and MRI for local and/or whole-body restaging of adenoid cystic carcinoma of the head and neck (ACC).

Methods

Thirty-six patients with ACC underwent conventional MRI of the head and neck and a whole-body PET/CT and were analysed with regards to detection of a local tumor recurrence, lymph node or distant metastases. A consensus interpretation of all available imaging data was used as reference standard. Sensitivity, specificity, diagnostic accuracy, positive and negative predictive values were calculated for MRI and PET/CT.

Results

The sensitivity of PET/CT and MRI was 96% (89%), specificity 89% (89%), PPV 96% (96%), NPV 89% (73%) and accuracy 94% (89%) for detection of local tumors. Additionally, PET/CT revealed lymph node metastases in one patient and distant metastases in 9/36 patients. In three patients secondary primaries were found.

Conclusions

Whole-body PET/CT in addition to MRI of the head and neck improves detection of local tumour and metastastic spread in ACC.

     

氟脱氧葡萄糖PET-CT常规及双时相显像检测食管癌术后复发转移的价值

目的 评价氟脱氧葡萄糖(FDG)PET-CT常规及双时相显像在监测食管癌术后复发转移中的应用价值.方法 回顾分析食管癌术后临床怀疑复发转移而行FDG PET-CT检查的48例患者临床资料,根据细胞学、病理或随访结果分析FDG PET-CT检查结果.两样本率比较采用Fisher's精确概率法检验.结果 48例患者中位随访21.5个月,34例出现复发转移,确定复发转移灶61处.FDG PET-CT常规显像对全部病灶诊断的敏感性、特异性和准确性分别为93.44%、74.29%和86.46%;对局部复发和区域淋巴结转移的敏感性、特异性、准确性分别为91.67%、57.14%、78.95%和90.48%、77.78%、84.62%.FDG PET-CT双时相显像诊断局部复发+区域淋巴结转移的敏感性、特异性、准确性均高于常规显像,分别为96.97%∶90.90%(P=0.613)、96.00%∶72.00%(P=0.049)、96.55%∶82.76%(P=0.029).结论 FDG PET-CT常规显像虽然检测食管癌术后局部复发及区域淋巴结转移的特异性和准确性较低,但仍是检测其术后复发转移的有效手段;双时相显像较常规显像更具优势,可有效提高检测的特异性及准确性.

Abstract：

Objective To evaluate the clinical value of regular and dual-time-point 18-fluorodeoxyglucose positron emission tomography-CT(FDG PET/CT)imaging for recurrence and metastasis in esophageal carcinoma(EC)after curative esophagectomy. Methods A retrospective study was done on 48 patients received curative esophagectomy, who underwent FDG PET/CT scans to detect doubtful recurrent or metastatic lesions. The diagnostic accuracy of FDG PET-CT was assessed with the help of pathological findings as well as clinical or follow-up data. Using Fisher's Exact Test from SPSS 11.5 to analyze the data.Results Of the 48 patients, after a median follow-up of 21.5 months, 61 sites of local and regional recurrence or metastasis were finally confirmed in 34 patients. The sensitivity, specificity and accuracy of regular FDG PET/CT imaging in detecting recurrence of all sites were 93.44%, 74.29% and 86.46%respectively. The specificity and accuracy of local recurrence and regional metastasis were 57.14% ,78.95% and 77.78% ,84.62%, respectively. The sensitivity, specificity and accuracy of dual-time-point FDG PET/ CT imaging in detecting local and regional recurrence(96.97% ,96.00% and 96.55%)were higher than those of regular FDG PET/CT(90.90%, 72.00% and 82.76%)and there were significant differences of specificity and accuracy(P = 0.049, P = 0.029). Conclusions Regular FDG PET/CT imaging is highly effective in detecting recurrence and metastasis in EC patients after curative esophagectomy despite the low specificity and accuracy. Dual-time-point FDG PET/CT imaging can elevate the specificity and accuracy.     

鼻咽癌放射治疗后FDG PET显像的临床价值

目的 探讨核医学影像诊断技术--FDG PET在鼻咽癌放射治疗后随诊中的临床价值。方法 12例鼻咽癌患者放射治疗后12～18个月同期行FDG PET和CT、MRI检查,并采用双盲法将PDG PET与CT和MRI结果进行比较,其中6例经活检病理证实,余6例经CT动态观察10个月后确诊。结果 9例CT和MRI未见肿瘤复发,PET显示其中3例有局灶性FDG代谢明显增高病变,2例CT和MRI提示肿瘤复发,FDG PET均显示局部病变有放射性摄取浓聚;该5例FDG摄取浓聚的病变处均经活检病理证实为肿瘤复发。另1例MRI提示鼻咽癌颅内转移,而FDG PET诊断为放射治疗后脑损伤,后经CT随访证实。结论 与CT和MRI检查相比,FDG PET在鼻咽癌放射治疗后肿瘤复发的早期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,更能提供局部病变结构与代谢改变的复合信息,尤其对局部复发病灶精确的适形放射治疗非常重要。     

Positron emission tomography (PET) in the management of oro-pharyngeal cancer

AimsTo investigate the specific role of FDG–PET in the management of head and neck cancer patients.MethodsIn a retrospective study, 112 patients with head and neck cancer treated over a 5-year period had FDG–PET scans. The image of the tumour (local, regional and distant) was compared to, clinical, CT/MRI examination, pathological findings and the clinical course of the disease.ResultsFDG–PET correctly identified 95.3% of primary lesions, and 94.1% of the recurrences at the primary site. FDG–PET data was supportive of intended treatment in 31 cases and sufficient to alter the management of seven patients.ConclusionsOverall FDG–PET has a useful role in the diagnosis of head and neck cancers, and in the demonstration of occult or hidden tumours, distant and metastatic disease.     

The impact of FDG PET on the management of occult primary head and neck tumours

Aims: The aim of this study was to investigate the impact of positron-emission tomography (PET) with 18F-labelled fluoro-2-deoxy-D-glucose (FDG) in the management of occult primary head and neck tumours.Materials and methods: We reviewed 16 patients with squamous cell carcinoma (SCC) and one patient with undifferentiated carcinoma of cervical lymph nodes (N1-4; N2a-9; N2b-2; N3-2). All patients had full clinical assessment, including examination under anaesthesia (EUA), with biopsy of all suspicious areas and random biopsies of sites likely to harbour an occult primary site. Nine patients underwent magnetic resonance imaging (MRI) of the head and neck, three underwent computed tomography (CT) and five underwent both CT and MRI. None of these studies were able to locate a primary tumour. Patients received 350 MBq FDG intravenously. Emission transmission scans of the extra-cranial head, neck and thorax were obtained using an ECAT Exact 47 at least 60 min after injection. The images were interpreted by the same radiologist experienced in PET, independent of the final outcome. The influence of FDG PET on management was assessed on review of the patients’ notes after treatment or when treatment had been deemed unnecessary.Results: FDG PET suggested a primary site in eight of the 17 patients (tongue base 5; nasopharynx 1; tonsil 1; supraglottis 1). Pathological confirmation was obtained in four patients and one patient died of progressive disease at the primary site. In nine patients, the primary site was not identified on FDG PET. In six of these patients, no primary site was found during follow-up (range 8–36 months; mean 20 months). One patient died before treatment commenced, and there were two histologically confirmed false-negative FDG PET results: one tonsil SCC and one lateral pharyngeal wall SCC. FDG PET affected treatment plans in nine of the 17 (53%) patients in whom a primary site was suggested (altered radiotherapy plan 6; radiotherapy with curative intent to palliative radiotherapy 1; radiotherapy to surgery and post-operative radiotherapy 1), and in one patient where no occult primary was localised (radiotherapy to surgery 1). FDG PET had a sensitivity, specificity, positive and negative predictive value of 62%, 66%, 62% and 62%, respectively.