The value of dual-time-point 18F-FDG PET/CT for identifying axillary lymph node metastasis in breast cancer patients

Objective

The sensitivity of 18-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) for detecting axillary lymph node (ALN) metastases in breast cancer is reported to be low. Several studies have shown, however, that dual-time-point ¹⁸F-FDG PET imaging provides improved accuracy in the diagnosis of certain primary tumours when compared with single-scan imaging. The purpose of this study was to assess whether the use of dual-time-point ¹⁸F-FDG PET/CT scans could improve the diagnostic accuracy of ALN metastasis in breast cancer.

Method

The study included 171 breast cancer patients who underwent pre-operative ¹⁸F-FDG PET/CT scans at 2 time-points, the first at 1 h after radiotracer injection and the second 3 h after injection. Where ¹⁸F-FDG uptake was in the ALN perceptibly increased, the maximum standardised uptake values for both time-points (SUVmax1 and SUVmax2) and the retention index (RI) were calculated. Correlation between the PET/CT results and post-operative histological results was assessed.

Results

The performance of 1 h and 3 h PET/CT scans was equal, with sensitivity 60.3% and specificity 84.7%, in detecting ALN metastasis. Out of 171 patients, 60 had ALNs with increased ¹⁸F-FDG uptake on 1 h or 3 h images. There was no significant difference in RI between the metastatic ALN-positive group and the node-negative group. The area under the receiver operating characteristic (ROC) curve for SUVmax1 was 0.90 (p<0.001) and 0.87 for SUVmax2 (p<0.001).

Conclusion

Dual time-point imaging did not improve the overall performance of ¹⁸F-FDG PET/CT in detecting ALN metastasis in breast cancer patients.Axillary lymph node (ALN) involvement is the key prognostic factor in patients with breast cancer [1]. Accurate assessment of axillary node status is therefore essential for both predicting outcome and choosing a therapeutic plan. The most reliable and accurate procedure for the examination of ALN is standard axillary lymph node dissection (ALND). However, the complications associated with ALND, such as lymphoedema, numbness of the skin of the upper arm and impairment of shoulder movement, lead to decreased quality of life [2]. Moreover, a significant proportion of breast cancer patients, especially those with small tumours, are node negative [3,4]. Therefore, a non-invasive modality for accurate staging of ALNs is needed to avoid unnecessary ALND.¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET) and ¹⁸F-FDG PET/CT have a useful role in staging and therapeutic planning in breast cancer patients in that these modalities are used to identify unexpected metastasis and recurrence [5]. The sensitivity of ¹⁸F-FDG PET for detecting ALN metastasis in breast cancer staging is, however, reported to be relatively low [6,7]. Recently, immunohistochemistry and multistep section have improved the detection rate of axillary micrometastasis and the value of ¹⁸F-FDG PET in axillary staging has become more uncertain [6,8,9].Several studies have shown that ¹⁸F-FDG uptake by malignant tumours increases for hours after injection [10,11]. Thus, some investigators suggest advantages of using delayed PET or dual time-point PET images. In breast cancer, Boerner et al [12] reported that PET images made 3 h after ¹⁸F-FDG injection showed higher tumour-to-non-tumour and tumour-to-organ ratios, and enhanced lesion detectability when compared with 1.5 h images.The purpose of this study was to assess whether dual-time-point (1 h and 3 h) ¹⁸F-FDG PET/CT scans could improve the diagnostic accuracy of ALN metastasis in breast cancer.     

Diagnostic value of full-dose FDG PET/CT for axillary lymph node staging in breast cancer patients

Purpose

The aims of this study were (1) to evaluate FDG PET/CT and CT for the detection of axillary lymph node metastases in breast cancer (BC) patients and (2) to evaluate FDG PET/CT as a pre-test for the triage to sentinel lymph node biopsy (SLNB) versus axillary lymph node dissection (ALND).

Methods

The sensitivity, specificity, positive and negative predictive value (PPV, NPV), and accuracy of FDG PET/CT and CT for axillary lymph node metastases were determined in 61 patients (gold standard: histopathology). According to the equation “NPV = specificity ? (1-prevalence) / [specificity ? (1-prevalence) + (1-sensitivity) ? prevalence]” FDG PET/CT was evaluated as a triage tool for SLNB versus ALND.

Results

The sensitivity, specificity, PPV, NPV and accuracy of FDG PET/CT was 58, 92, 82, 77 and 79% and of CT 46, 89, 72, 71 and 72%, respectively. Patients with an up to ~60% risk for axillary lymph node metastases appear to be candidates for SLNB provided that the axilla is unremarkable on FDG PET/CT.

Conclusion

FDG PET/CT cannot replace invasive approaches for axillary staging but may extend the indication for SLNB.     

Diagnostic and prognostic value of <Superscript>18</Superscript>F-FDG PET/CT for axillary lymph node staging in patients with breast cancer

Purpose

To investigate the diagnostic and prognostic value of ¹⁸F-FDG-PET/CT for axillary lymph node (LN) staging in breast cancer patients, employing histologic evaluation as the reference.

Methods

Among 196 patients with biopsy-proven breast cancer who had undergone ¹⁸F-FDG-PET/CT before mastectomy or breast-conserving surgery with sentinel LN biopsy and/or axillary LN dissection, 200 axillae were retrospectively analyzed by visual assessment and quantitatively using SUVmax. LN SUVmax as well as other clinicopathological features were assessed for their prognostic value using the log-rank test and Cox method.

Results

Metastasis was diagnosed histopathologically in 56 (28 %) axillae. The sensitivity, specificity, and accuracy of visual PET/CT for diagnosing node metastasis were 55.4, 95.8, and 84.5 %, respectively. When the optimal discriminative SUVmax cutoff was 1.5, these figures were 51.8, 97.2, and 84.5 %, respectively. Fourteen of 55 patients (25.5 %) with LN metastases suffered a recurrence during follow-up (median 39 months). Patients with a high nodal SUVmax (≥1.7) had a significantly lower progression-free survival rate than those with a low SUVmax (p = 0.0499). Axillary nodal and primary tumor SUVmax as well as estrogen receptor status were significantly associated with recurrence.

Conclusion

Axillary nodal SUVmax may be a prognostic indicator of disease recurrence in patients with axillary LN metastases.

     

Early and delayed prediction of axillary lymph node neoadjuvant response by 18F-FDG PET/CT in patients with locally advanced breast cancer

Purpose

To determine the utility of ¹⁸F-FDG (FDG) PET/CT performed in an early and delayed phase during neoadjuvant chemotherapy in the prediction of lymph node histopathological response in patients with locally advanced breast cancer.

Methods

FDG PET/CT studies performed in 76 patients (mean age 53 years) at baseline (PET-1), after the second course of chemotherapy (PET-2) and after the last course of chemotherapy (PET-3) were prospectively analysed. Inclusion criteria were lymph node involvement detected by PET/CT and non-sentinel node biopsy before or after the baseline PET/CT scan. Following the recommendations of the 12th International Breast Conference (St. Gallen), the patients were divided into five subgroups in relation to biological prognostic factors by immunohistochemistry. For diagnosis visual and semiquantitative analyses was performed. Absence of detectable lymph node uptake on the PET-2 or PET-3 scan with respect to the PET-1 scan was considered metabolic complete response (mCR). Lymph nodes were histopathologically classified according the lymph node regression grade and in response groups as pathological complete response (pCR) or not pCR (type A/D or B/C of the Smith grading system, respectively). ROC analysis was performed to determine a cut-off value of Δ% SUV1–2 and SUV1–3 for prediction of nodal status after chemotherapy. An association between mCR and pCR was found (Cohen’s kappa analysis), and associations between phenotypes and metabolic behaviour and the final histopathological status were also found.

Results

Lymph node pCR was seen in 34 patients. The sensitivity, specificity, and positive and negative predictive values of PET-2 and PET-3 in establishing the final status of the axilla after chemotherapy were 52 %, 45 %, 50 % and 47 %, and 33 %, 84 %, 67 % and 56 %, respectively. No significant relationship was observed between mCR on PET-2 and PET-3 and pCR (p?=?0.31 and 0.99, respectively). Lymph node metabolism on PET-1 was not able to predict the final histopathological status, whereas basal carcinomas showed a higher rate of pCR (70.6 %) than the other groups (p?=?0.03).

Conclusion

FDG PET/CT seems to have limitations in both the early and delayed evaluation of lymph node status after chemotherapy, with reduced predictive values.     

Delayed (18)F-FDG PET for detection of paraaortic lymph node metastases in cervical cancer patients.

This prospective study investigated the usefulness of dual-phase (18)F-FDG PET scans (40 min and 3 h) in detecting paraaortic lymph node (PALN) metastasis for cervical cancer. METHODS: One hundred four consecutive cervical cancer patients (International Federation of Gynecology and Obstetrics staging Ib-IVb, recurrent or persistent tumors) were included. All patients received a whole-body (18)F-FDG PET scan at 40 min and an additional scan from the T11 level to the inguinal region at 3 h after injection of 370 MBq (18)F-FDG. The maximum standardized uptake value (SUV) and retention index (RI [%], obtained by subtracting the normalized SUV value obtained at 40 min from that at 3 h) of the lesions were determined. RESULTS: In all, 38 of the 104 patients were confirmed to have PALN metastases. For 31 patients (81.6%) with 13 upper (L1-L2 level) and 30 lower (L3-L4 level) PALNs, these metastases were detected with the 40-min scan. In addition, for 7 patients (18.4%) with 7 lower PALNs, metastases were found with the 3-h scan (RI = 12.6%). Two patients (3.0%) had 2 false-positive lesions initially (40 min) but were classified as benign with the 3-h scan. The sensitivity, specificity, and accuracy of (18)F-FDG PET scans at 40 min were 81.6%, 97.0%, and 91.3%, respectively. These quantities were all 100% when both the 40-min and 3-h scans were taken together. Eight patients (21.1%) had their treatment planning changed. We divided the 38 patients into 2 subgroups. Subgroup A included those with either only upper or only lower PALN metastases, and subgroup B included those with both upper and lower PALN metastases. In subgroup A, the SUV values were greater in the upper than in the lower PALNs in both the 40-min and 3-h images (P = 0.077). In subgroup B, there was no significant difference of SUV values between upper and lower PALNs in the 40-min (P = 0.433) and 3-h (P = 0.937) images. CONCLUSION: Our results showed that an additional 3-h scan is helpful for PALN detection of cervical cancer patients. A delayed image (3 h) is especially useful for lower PALN metastases.     

18F-FDG PET detection of lymph node metastases in medullary thyroid carcinoma.

Postsurgically elevated or increasing serum calcitonin levels strongly suggest the presence of residual or recurrent medullary thyroid carcinoma (MTC). Several imaging modalities (sonography, MRI, CT, scintigraphy with different types of radiolabeled ligands, etc.) are routinely used in an attempt to localize tumorous tissue, but such efforts often fail. In the search for a more reliable method, 18F-FDG PET was applied to detect tumor tissue of residual or recurrent MTC. METHODS: Forty patients with a postoperatively elevated plasma calcitonin level were included. These patients underwent routine diagnostic imaging procedures (CT, MRI, and 131I-metaiodobenzylguanidine [MIBG] whole-body planar scintigraphy or SPECT) and 18F-FDG PET examinations. Two independent experts visually analyzed the images provided by each method to detect pathologic lesions. Lymph nodes of > or = 1 cm in short diameter that were detected by radiologic methods were considered to be pathologic. 18F-FDG accumulation with a sharp contour reported by both independent observers was similarly regarded as pathologic. RESULTS: PET detected 270 foci with a high tracer accumulation, whereas only 116 lesions were detected by MRI and 141 by CT. The numbers of such foci determined by PET, MRI, and CT were 98, 34, and 34, respectively, in the neck; 25, 5, and 6, respectively, in the supraclavicular regions; and 117, 35, and 39, respectively, in the mediastinum. 131I-MIBG scintigraphy findings were positive for only 3 patients. CONCLUSION: For MTC patients with a postoperatively elevated plasma tumor marker level, PET was more sensitive and superior in localizing tumorous lymph node involvement than were the other imaging modalities, especially in the cervical, supraclavicular, and mediastinal lymphatic regions.     

Diagnosis supporting algorithm for lymph node metastases from colorectal carcinoma on 18F-FDG PET/CT

Objective We studied the improvement of the detect-ability of lymph node (LN) metastases from colorectal cancer in ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG PET)/computed tomography (CT) by analyzing the acquired counts with a statistical method. Methods Thirty-nine metastatic LNs from 32 cases with colorectal cancer were included in this study. “Uptake region” was defined as the site where counts were higher than the average plus 3 standard deviations (SDs) on each transaxial image of FDG PET. After the initial uptake regions were selected, these high accumulation areas were automatically excluded from consideration thereafter. This method was repeated and new uptake regions were identified. This method was repeated up to five times. After that, the stacked-up uptake regions were compared with computed tomography (CT) images, and the high accumulation areas that were superimposed on the normal structures, such as intestine, vessels, and ureters, were excluded from the consideration. The remaining uptake regions were diagnosed as metastatic LNs, and the detectability of LN metastases was calculated. We then compared these statistical results with the results obtained on the basis of visual assessments by radiologists. Results Our proposed method showed the best results when the procedures were repeated three times in the light of detectability. After being repeated three times, this method detected 15/23 (65.2%) metastatic LNs in the first LN group, 16/16 (100%) in the second-third LN groups and 31/39 (79.4%) in the total LNs, whereas the radiologists diagnosed 8/23 (34.8%) of metastatic first LNs, 12/16 (75.0%) in the second-third LNs and 20/39 (51.3%) in the total LNs. A statistically significant difference was observed between the result of iteration number 3 and that by radiologists as for the second—third LNs and the total LNs. Conclusions This study suggests that our proposed statistical method could improve the detectability of LN metastases from colorectal cancer. Our method will help radiologists to detect small metastatic lesions such as LN metastases.     

Assessment of lymph node metastases using 18F-FDG PET in patients with advanced gastric cancer

Purpose The aim of this study was to assess the diagnostic accuracy of ¹⁸F-fluoro-2-deoxyglucose (FDG) positron emission tomography (PET) with respect to lymph node (LN) metastasis in patients with advanced gastric cancer, and to ascertain the factors that affect this accuracy.Methods Seventy-three patients with advanced gastric cancer, verified in all cases by endoscopic biopsy, were enrolled in this prospective study. We conducted FDG PET and other routine preoperative studies, including abdominal computed tomography (CT). Patients underwent either curative-intent gastrectomy and lymphadenectomy (n=67) or exploratory laparotomy. The Japanese system for the classification of gastric cancer was used for LN assessment.Results FDG PET was able to detect primary lesions in 70 of the 73 cases. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value of FDG PET for LN metastasis were 40%, 95%, 91% and 56%, respectively. Signet-ring cell carcinoma was associated with the lowest sensitivity (15%), whereas other cell types could be detected with moderate sensitivity (30–71%) and high specificity (93–100%). According to multiple logistic regression, the standardised uptake value for primary tumours was the only independent variable to be significantly related to sensitivity for LN metastasis (p=0.02, odds ratio=1.14). CT was superior to PET in terms of sensitivity (p<0.0001), and PET was superior to CT in terms of specificity (p<0.0001) and PPV (p=0.05).Conclusion FDG PET exhibits good specificity for LN staging of gastric cancer, and FDG uptake in the primary tumour is significantly related to the accuracy of FDG PET. Despite some clear limitations, FDG PET proved useful in the LN staging of FDG-avid gastric cancer.Seok-Ki Kim and Keon Wook Kang contributed equally to this paper.     

Diagnostic accuracy of 18F-FDG PET/CT for detection of suspected recurrence in patients with oesophageal carcinoma

Purpose

To evaluate the role of ¹⁸F-FDG PET/CT in the detection of recurrence in patients with oesophageal carcinoma, suspected clinically or following conventional investigations.

Methods

This was a retrospective study. Data from 180 patients (age 56.3?±?10.4 years; 126 men, 54 women) with histopathologically proven oesophageal carcinoma (squamous cell 115, adenocarcinoma 59, neuroendocrine carcinoma 4, small cell 1, poorly differentiated 1) who had undergone 227 ¹⁸F-FDG PET/CT studies for suspected recurrence were analysed. Recurrence was suspected clinically or following conventional investigations. PET/CT images were revaluated by two nuclear medicine physicians in consensus. Findings were grouped into local, nodal and distant recurrence. Results were compared to those from contrast-enhanced (CE) CT when available (109 patients). Clinical/imaging follow-up (minimum 6 months) with histopathology (when available) was taken as the reference standard.

Results

Of the 227 ¹⁸F-FDG PET/CT studies,166 were positive and 61 were negative for recurrent disease. PET/CT showed local recurrence in 134, nodal recurrence in 115 and distant recurrence in 47, with more than one site of recurrence in 34. The PET/CT findings were true-positive in 153 studies, true-negative in 54, false-positive in 13 and false-negative in 7. The sensitivity of ¹⁸F-FDG PET/CT was 96 %, the specificity was 81 %, the positive and negative predictive values were 92 % and 89 %, respectively, and the accuracy was 91 %. PET/CT showed similar accuracy in patients with squamous cell carcinoma and in those with adenocarcinoma (P?=?0.181).¹⁸F-FDG PET/CT was more specific than CECT (67 % vs. 21 %; P?<?0.0001). PET/CT was superior to CECT for the detection of nodal recurrence (P?<?0.0001), but not local recurrence (P?=?0.093) or distant metastases (P?=?0.441).

Conclusion

¹⁸F-FDG PET/CT shows high accuracy in the detection of suspected recurrence in patients with oesophageal carcinoma. It is more specific than and is superior to CECT in the detection of nodal recurrence.     

Feasibility of FDG PET/CT to monitor the response of axillary lymph node metastases to neoadjuvant chemotherapy in breast cancer patients

Purpose  

The aim of this study was to assess the accuracy of ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT to visualize lymph node metastases before the start of neoadjuvant chemotherapy and to determine how often the visualization is sufficiently prominent to allow monitoring of the axillary response.     

Preoperative 18F-FDG PET/CT tumor markers outperform MRI-based markers for the prediction of lymph node metastases in primary endometrial cancer

European Radiology - To compare the diagnostic accuracy of preoperative 18F-FDG PET/CT and MRI tumor markers for prediction of lymph node metastases (LNM) and aggressive disease in endometrial...     

乳腺癌腋窝淋巴结转移18^F-FDG PET／CT半定量分析预测阈值的临床研究

目的探讨18^F-脱氧葡萄糖（FDG）PET／CT半定量分析方法预测乳腺癌腋窝淋巴结转移的最佳阈值及诊断效能。方法将56例接受腋窝淋巴结清扫术（ALND）的乳腺癌患者分成腋窝淋巴结转移阳性组（简称阳性组）和对照组（阴性组）,回顾其术前18^F-FDG PET／CT结果,测量乳腺癌原发灶（T）、腋窝淋巴结（L）及淋巴结镜像区本底（B）的最大标准摄取值（SUV-T、SUV-L、SUV-B）,计算L/B比值（L／B=SUV-L／SUV-B）。采用受试者工作特征（ROC）曲线确定SUV-T、SUV-L、L/B预测腋窝淋巴结转移的最佳阈值,采用Kappa法分别将最佳阈值下的判断结果与病理诊断结果进行一致性检验。结果56例患者共56个原发病灶,长径为（30±19）mm,SUV-T为5．5±3．5,其中阳性者38例（68％）,阳性组病灶长径[（36±19）mm]及SUV-T（6．3±3．5）明显高于对照组（t值分别为4．060和2．774,P〈0．001和P=0．008）。对628枚淋巴结进行病理活组织检查,检出阳性（转移性）淋巴结182枚（29％）、阴性（非转移性）淋巴结446枚（71％）。PET／CT所示与手术基本匹配的腋窝淋巴结共145枚（Ⅰ区132枚、Ⅱ区11枚、Ⅲ区2枚）,其中转移性淋巴结126枚（Ⅰ区103枚、Ⅱ区11枚、Ⅲ区2枚）。SUV-T、SUV-L、L/B比值ROC曲线下面积分别为0．756,0．821,0．765,最佳阈值分别为3．2,1．0,2．4。采用SUV-T≥3．2为阈值判断56例患者腋窝淋巴结转移的灵敏度、特异性、阳性预测值、阴性预测值、准确性分别为84％（32／38）、67％（12／18）、84％（32／38）、67％（12／18）、79％（44／56）;采用SUV-L≥1．0和L/B≥2．4的判断结果完全一致,分别为92％（35／38）、67％（12／18）、85％（35／41）、80％（12／15）、84％（47／56）;而目测法分析结果分别为95％（36／38）、50％（9／18）、80％（36／45）、82％（9／11）、80％（45／56）。SUV     

18F-FDG PET/CT不同诊断方法对乳腺癌及其淋巴结转移的应用价值

目的 探讨18F-脱氧葡萄糖(FDG)PET/CT显像在诊断乳腺癌及其区域淋巴结转移中的临床价值.方法 对27例疑原发性乳腺癌及经临床随访(＞12个月)证实的12例单发乳腺良性病变患者行18F-FDG PET/CT显像,患者均为女性.对显像结果分别行定性、半定量分析.27例疑乳腺癌患者均行手术治疗.结果 疑乳腺癌患者术后病理检查示24例为乳腺癌,共25个病灶;良性病灶7个.18F-FDG PET/CT显像定性分析诊断乳腺癌的灵敏度为76.0%(19/25),特异性为94.7%(18/19);以最大标准摄取值(SUVmax)＞2.5为界值,18F-FDG PET/CT诊断乳腺癌的灵敏度为72.0%(18/25),特异性为63.2%(12/19);以病灶SUVmax大于对侧正常乳腺腺体SUVmax的-x+2s为界值,PET/CT诊断乳腺癌的灵敏度为96.0%(24/25),特异性为63.2%(12/19),其灵敏度明显高于前2种分析方法(X2=4.15,4.14;P均＜0.05).定性方法的特异性明显高于半定量分析(X2值均为5.7,P均＜0.05).23例行区域淋巴结廓清术的患者病理检查示10例有淋巴结转移.18F-FDGPET/CT定性诊断乳腺癌区域淋巴结转移的灵敏度为60.0%(6/10),特异性为84.6%(11/13);以SUVmax＞2.5为界值,18F-FDG PET/CT诊断淋巴结转移的灵敏度为60.0%(6/10),特异性为92.3%(12/13).结论 在18F-FDG PET/CT诊断乳腺癌中,以病灶SUVmax大于正常乳腺腺体sUVmax的-x+2s为界值的半定量分析有较好的灵敏度;定性分析的诊断特异性优于半定量分析.     

Meta-analysis of diagnostic value of 18F-FDG PET or PET/CT for detecting lymph node and distant metastases in patients with nasopharyngeal carcinoma

Objective:

We performed this meta-analysis to comprehensively assess the diagnostic performance of positron emission tomography (PET) or PET/CT for detecting lymph node and distant metastases in patients with nasopharyngeal carcinoma (NPC).

Methods:

Through a search of four English and three Chinese databases (January 1990 to June 2013), pooled estimated sensitivity, specificity and diagnostic odds ratio (DOR) were calculated based on the data extracted from the included studies. We also constructed summary receiver operating characteristic curves, with the area under the curve (AUC) and obtained the Q* index. Heterogeneity and subgroup analysis were also performed.

Results:

In total, 18 articles consisting 20 studies were included in this meta-analysis. On a per-patient basis, the overall pooled estimates for sensitivity and specificity of PET or PET/CT in N and M staging of NPC were 0.89 [95% confidence interval (CI), 0.86–0.91] and 0.96 (95% CI, 0.95–0.96), respectively. The overall DOR, AUC and Q* index were 162.07 (95% CI, 90.72–289.55), 0.9689 and 0.9181, respectively. Subgroup analysis showed that AUC and Q* index were 0.9734 and 0.9255 for N staging and 0.9715 and 0.9223 for M staging, respectively.

Conclusion:

The present meta-analysis showed that PET or PET/CT has excellent diagnostic performance for detecting lymph node and distant metastases in patients with NPC.

Advances in knowledge:

To provide evidence to assess the role of PET or PET/CT in staging of NPC.In Western countries, nasopharyngeal carcinoma (NPC) is a rare form of squamous cell carcinoma, with incidence rates <1 per 10⁵ persons per year. However, it is a highly frequent epithelial malignancy of the head and neck in southern China and parts of Southeast Asia, with a reported annual incidence of 30–80 per 10⁵ persons in endemic regions, mainly owing to Asian ancestry and infection with the Epstein–Barr virus.^1–3 The mainstay of treatment for nasopharyngeal cancers is using 100 mg m⁻² of cisplatin on Days 1, 22 and 43 concurrent with radiotherapy, followed by adjuvant 80 mg m⁻² of cisplatin on Day 1 and 1000 mg m⁻² of 5-fluorouracil on Days 1–4 for three cycles.^4,5 It is known that stage-adapted therapy significantly improved the survival of patients with cancer.^6,7 In this regard, conventional CT and MRI, mainly providing anatomical information, are performed to assess staging site of NPC, especially for the primary site and local-regional metastases. However, owing to the lack of functional information, these modalities are limited in assessment of disease aggressiveness and distant metastases.⁸ Furthermore, it is difficult to diagnose residual or recurrent NPC owing to the presence of soft-tissue inflammation and oedema after radiotherapy.⁹ In addition, some small volume metastatic nodal lesions may be misinterpreted as reactive nodes when patients show reactive hyperplasia in lymph nodes.Positron emission tomography (PET) and in particular integrated PET/CT using fluorine-18 fludeoxyglucose (¹⁸F-FDG), the latter uniting metabolic function with anatomic form, are widely used techniques in the cancer staging assessment in recent years. Many studies on the staging value of PET or PET/CT for patients with NPC have been performed. For T staging of NPC, PET/CT was less sensitive than MRI, which is plausibly ascribed to the facts that early tumour invasion may have poor ¹⁸F-FDG uptake owing to low tumour burden, while these anatomic areas, including the intracranial area along the cranial nerve, the parapharyngeal space, the skull base and sphenoid sinuses, may be obscured by the spillover effect of ¹⁸F-FDG PET. On the other hand, compared with MRI, partial volume and lack of consensus of optimal strategy for tumour delineation on ¹⁸F-FDG PET may lead to T overstaging. MRI appeared to be superior to PET/CT in delineating primary tumour extent.¹⁰ The use of PET/CT without MRI may lead to inappropriate coverage by radiation portals or improper use of chemotherapy. PET or PET/CT did not have adequate contrast resolution to identity retropharyngeal lymph nodes that merged with adjacent primary tumour or to discriminate direct tumour invasion from metastases, which may result in incorrect N staging or improper use of chemotherapy.¹⁰ However, ¹⁸F-FDG PET/CT may be more accurate than conventional work-up for the determination of neck status and identifying cervical lymph node metastasis, which could facilitate a more appropriate treatment plann, especially for portal designation.^10–12 For those suspicious lymph nodes on conventional imaging or PET/CT, pathological examination may still be necessary. Ultrasound-guided fine-needle aspiration, allowing cytological examination of suspicious nodes as small as 2 mm in diameter, may be a minimally invasive procedure that can enable cytological examination of suspicious lymph nodes.¹³ It has good specificity and a high positive-predictive value but a poor negative-predictive value for identification of metastatic lymph nodes from NPC; furthermore, fine-needle aspiration cytology of the node frequently yields inconclusive results, and this is likely to be related to the increased fibrosis within these nodes after radiation.¹³ With regard to distant metastasis, PET/CT has an acceptable diagnostic yield and a low false-positive rate for the detection of distant malignancy and can replace conventional work-up for this aim.^10,14,15To our knowledge, the results of previous studies are controversial, mainly because of different study design, selection criteria and reference standard. Thus, we performed a meta-analysis of all available studies to comprehensively assess their value in detecting lymph node and distant metastases in patients with NPC.     

18F-FDG PET/CT对原发不明颈部淋巴结转移癌患者原发灶检出的价值

目的 探讨18F-FDG PET/CT在原发不明颈部淋巴结转移癌患者原发灶检出中的临床应用价值.方法 回顾性分析2007年至2012年间因颈部淋巴结细针穿刺活组织检查提示转移但原发不明而行18F-FDG PET/CT检查的患者78例,其中男48例,女30例,平均年龄(56.4±14.7)岁.在PET/CT图像上勾画ROI并计算SUVmax.将淋巴结分为Ⅰ～Ⅵ区、咽后区及锁骨上区,取淋巴结短径为其大小.患者均经病理、随访确诊.观察肿瘤原发灶部位、病理类型及转移淋巴结分布、大小及SUVmax.采用单因素方差分析及直线相关分析分析数据.结果 78例患者中,恶性75例,良性3例(手术切除后病理检查).56例患者由PET/CT检出原发灶,检出率为71.8％(56/78).其中头颈部肿瘤占57.1％(32/56),对应转移淋巴结多分布于Ⅱ、Ⅲ、Ⅳ区(90.6％,29/32);体部肿瘤占42.9％(24/56),对应转移淋巴结多分布于锁骨上区(95.8％,23/24).不同原发部位及不同病理类型的颈部转移淋巴结大小和SUVmax差异均无统计学意义(F=0.037～ 2.413,均P＞O.05).结论 18F-FDGPET/CT有利于判断原发不明肿瘤的大致部位,并了解全身病灶分布.     

18F-FDG PET and PET/CT for detection of pulmonary metastases from musculoskeletal sarcomas

OBJECTIVE: Sarcomas represent a significant therapeutic challenge and their potential for distant pulmonary metastases is well known. [(18)F]Fluorodeoxyglucose ((18)F-FDG) positron emission tomography (PET) has a role in differentiating sarcomas from benign tumours and assessing the response to therapy in advanced sarcomas. However, PET appears to be less accurate in detection of pulmonary metastases. We were therefore prompted to review our experience with PET and PET/computed tomography (CT) in osseous and soft tissue sarcomas (OSTSs). METHODS: This is a retrospective study (January 1995 to December 2004) of 106 patients with histological diagnosis of OSTS, who had PET and PET/CT at our institution. The group included 52 men and 54 women, aged 12-92 years (average, 45+/-20 years). RESULTS: For all the patients in the analysis, the sensitivity and specificity were 68.3% (95% CI: 53-80.4) and 98.4% (95% CI: 91.8-99.7) for PET, with 95.1% sensitivity (95% CI: 83.8-98.6) and 92.3% specificity (95% CI: 83.2-96.7) for CT. Pulmonary metastases were seen in 40 patients. CT identified 17 lesions larger than 1.0 cm, while PET identified 13 of them (76.5%). CONCLUSIONS: Chest CT is more sensitive than PET in detecting pulmonary metastases from OSTS. A significant portion of known pulmonary metastases greater than 1.0 cm on CT, are PET negative. Sub-centimetre CT lesions should not be considered false positive if inactive on PET. A negative PET scan in the presence of suspicious CT findings in the chest cannot reliably exclude pulmonary metastases from OSTS.