PET/CT in malignant bone disease

The most commonly used positron emission tomography (PET) tracer in clinical practice, fluorine-18 fluorodeoxyglucose ( (18)F-FDG) is a glucose analogue that directly gains entry in excess into tumor cells. It is therefore sensitive for the detection of early bone marrow involvement prior to any identifiable bone changes. The introduction of (18)F-FDG-PET in the imaging algorithms of various malignant diseases often obviates the need to perform a separate assessment of malignant bone involvement with conventional bone scintigraphy. After therapy, disappearance of (18)F-FDG accumulation indicates success even when the bone remains morphologically abnormal. Novel hybrid systems composed of PET and computed tomography (CT) allow for acquisition of both modalities in the same clinical setting and the generation of fused functional-anatomical images. This technique has been found to improve the diagnostic accuracy of PET in detecting malignant bone involvement. This article discusses the role of PET/CT, primarily (18)F-FDG PET/CT, in the assessment of malignant bone involvement in patients with primary bone sarcomas, common solid malignancies, lymphoma, and multiple myeloma.     

全身MRI与PET/CT在淋巴瘤骨髓浸润诊断及预后中的作用

淋巴瘤是一种血液系统恶性肿瘤。淋巴瘤骨髓浸润(BMI)使疾病分期上升至IV期, 是疾病进展、预后较差的标志。常规部位的骨髓活检(BMB)具有创伤性, 且检出率低。PET/CT与全身MRI的出现, 丰富了BMI的检测手段。PET/CT与全身MRI对于淋巴瘤, 尤其是侵袭性淋巴瘤BMI均具有较高的检出率, 二者孰高孰低, 尚未定论。对于红骨髓、良性骨髓病变(炎症等)、淋巴瘤BMI病灶以及肿瘤治疗后骨髓的变化与骨髓残留或复发病灶, 全身MRI很难区分, 而PET/CT却可以很好地鉴别这些病灶。但是, PET/CT存在电离辐射; 对于惰性淋巴瘤的BMI, 超出PET/CT分辨率的病灶, 可能出现假阴性; 某些情况会限制PET/CT的使用, 包括18F-FDG生理性摄取量可能发生改变的正常组织、18F-FDG摄取相关性炎症、高血糖或高胰岛素血症导致的18F-FDG分布的改变、肿瘤患者治疗后出现的骨髓活化等。然而, 这些情况可以使用全身MRI。因此, 全身MRI和PET/CT相辅相成, 优势互补, 但二者均不能代替BMB。对于常规BMB阴性, 但影像学提示阳性的患者, 在影像学引导下进行BMB, 可以提高BMI的检出率。另外, 全身MRI阳性的淋巴瘤BMI患者与全身MRI阴性的淋巴瘤BMI患者相比, 前者预后可能较差。     

Assessment of malignant skeletal disease: initial experience with 18F-fluoride PET/CT and comparison between 18F-fluoride PET and 18F-fluoride PET/CT.

18F-fluoride PET/CT was performed on 44 oncologic patients to evaluate its diagnostic accuracy in assessing malignant osseous involvement and in differentiating malignant from benign bone lesions. METHODS: (18)F-fluoride PET and (18)F-fluoride PET/CT were interpreted separately. Lesions showing increased (18)F-fluoride uptake were categorized as malignant, benign, or inconclusive. The final diagnosis of lesions was based on histopathology, correlation with contemporaneous diagnostic CT or MRI, or clinical follow-up of at least 6 mo (mean, 10 +/- 3 mo). RESULTS: Increased (18)F-fluoride uptake was detected at 212 sites, including 111 malignant lesions, 89 benign lesions, and 12 lesions for which the final diagnosis could not be determined. In a lesion-based analysis, the sensitivity of PET alone in differentiating benign from malignant bone lesions was 72% when inconclusive lesions were considered false negative and 90% when inconclusive lesions were considered true positive. On PET/CT, 94 of 111 (85%) metastases presented as sites of increased uptake with corresponding lytic or sclerotic changes, and 16 of the 17 remaining metastases showed normal-appearing bone on CT, for an overall sensitivity of 99% for tumor detection. For only 1 metastasis was PET/CT misleading, suggesting the false diagnosis of a benign lesion. The specificity of PET/CT was significantly higher than that of PET alone (97% vs. 72%, P < 0.001). PET/CT identified benign abnormalities at the location exactly corresponding to the scintigraphic increased uptake for 85 of 89 (96%) benign lesions. In a patient-based analysis, the sensitivity of PET and PET/CT was 88% and 100%, respectively (P < 0.05) and the specificity was 56% and 88%, respectively (not statistically significant). Among the 12 patients referred for (18)F-fluoride assessment because of bone pain despite negative findings on (99m)Tc-methylene diphosphonate bone scintigraphy, (18)F-fluoride PET/CT suggested malignant bone involvement in all 4 patients with proven skeletal metastases, a potential benign cause in 4 of 7 patients who had no evidence of metastatic disease, and a soft-tissue tumor mass invading a sacral foramen in 1 patient. CONCLUSION: The results indicate that (18)F-fluoride PET/CT is both sensitive and specific for the detection of lytic and sclerotic malignant lesions. It accurately differentiated malignant from benign bone lesions and possibly assisted in identifying a potential cause for bone pain in oncologic patients. For most lesions, the anatomic data provided by the low-dose CT of the PET/CT study obviates the performance of full-dose diagnostic CT for correlation purposes.     

18F-Fluoride positron emission tomography and positron emission tomography/computed tomography

(18)F-Fluoride is a positron-emitting bone-seeking agent, the uptake of which reflects blood flow and remodeling of bone. Assessment of (18)F-fluoride kinetics using quantitative positron emission tomography (PET) methods allows the regional characterization of lesions of metabolic bone diseases and the monitoring of their response to therapy. It also enables the assessment of bone viability and discrimination of uneventful and impaired healing processes of fractures, bone grafts and osteonecrosis. Taking advantage of the favorable pharmacokinetic properties of the tracer combined with the high performance of PET technology, static (18)F-fluoride PET is a highly sensitive imaging modality for detection of benign and malignant osseous abnormalities. Although (18)F-fluoride uptake mechanism corresponds to osteoblastic activity, it is also sensitive for detection of lytic and early marrow-based metastases, by identifying their accompanying reactive osteoblastic changes, even when minimal. The instant fusion of increased (18)F-fluoride uptake with morphological data of computed tomography (CT) using hybrid PET/CT systems improves the specificity of (18)F-fluoride PET in cancer patients by accurately differentiating between benign and malignant sites of uptake. The results of a few recent publications suggest that (18)F-fluoride PET/CT is a valuable modality in the diagnosis of pathological osseous conditions in patients also referred for nononcologic indications. (18)F-fluoride PET and PET/CT are, however, not widely used in clinical practice. The limited availability of (18)F-fluoride and of PET and PET/CT systems is a major factor. At present, there are not enough data on the cost-effectiveness of (18)F-fluoride PET/CT. However, it has been stated by some experts that (18)F-fluoride PET/CT is expected to replace (99m)Tc-MDP bone scintigraphy in the future.     

^18F-FDG PET／CT显像全身骨髓代谢弥漫增高原因分析

目的分析^18F—FDG PET／CT所示全身骨髓代谢弥漫性增高临床原因。方法收集2005年8月至2009年11月期间在该院行^18F-FDG PET／CT检查,发现全身骨髓代谢弥漫性增高且已确诊的病例66例,分析影像学表现,并进行临床病程随访和病理结果分析。选择79名健康人作为对照组;分别测量骨髓代谢增高组和对照组的骨髓SUVmax和SUVmean以及纵隔SUVmax和SUVmean,并计算最大值比（SUVmax／纵隔SUVmax）及平均值比（骨髓SUVmean／纵隔SUVmean）,采用单因素方差分析对结果进行分析。结果（1）全身骨髓代谢弥漫l生增高原因有：近期升白细胞药物注射史27例,血液病21例,发热18例。（2）将上述3组及对照组SUVmean比（3．076±1．955,3．633±2．405,2．546±0．791,1．026±0．190）进行方差分析,F=34．465,P〈0．001,差异有统计学意义。健康对照组与3组骨髓代谢增高组进行多重比较,P均〈0．001,提示对照组与骨髓代谢增高组的SUVmean比差异均有统计学意义。（3）根据SUVmean比将骨髓代谢增高的程度分为2级：轻度（SUVmean比2．0—3．0）和重度（SUVmean大于3．0）。（4）3组骨髓代谢弥漫增高组中部分患者会伴有肝脾肿大及代谢增高,较常见的为血液病和发热。结论^18F-FDG PET／CT显像可以较敏感和准确地观察全身骨髓代谢的改变情况,良性和恶性病变均可引起骨髓代谢不同程度增高。     

Increased (18)F-fluorodeoxyglucose uptake in benign, nonphysiologic lesions found on whole-body positron emission tomography/computed tomography (PET/CT): accumulated data from four years of experience with PET/CT

The use of (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) in the field of oncology is rapidly evolving; however, (18)F-FDG is not tumor specific. Aside from physiological uptake (18)F-FDG also may accumulate in benign processes. Knowledge of these (18)F-FDG-avid nonmalignant lesions is essential for accurate PET interpretation in oncologic patients to avoid a false-positive interpretation. Through the systematic review of the reports of PET/computed tomography (CT) studies performed in oncologic patients during a 6-month period, we found benign nonphysiological uptake of (18)F-FDG in more than 25% of studies. In half of these, (18)F-FDG uptake was moderate or marked in intensity, similar to that of malignant sites. A total of 73% of benign lesions were inflammatory in nature, with post-traumatic bone and soft-tissue abnormalities (including iatrogenic injury) and benign tumors accounting for the remainder. The differentiation of benign from malignant uptake of (18)F-FDG on PET alone may be particularly challenging as a result of the low anatomical resolution of PET and paucity of anatomical landmarks. Fusion imaging, namely PET/CT, has been shown to improve not only the sensitivity of PET interpretation but also its specificity. Aside from better anatomical localization of lesions on PET/CT, morphological characterization of lesions on CT often may improve the diagnostic accuracy of nonspecific (18)F-FDG uptake. Correlation with CT on fused PET/CT data may obviate the need for further evaluation or biopsy in more than one-third of scintigraphic equivocal lesions. Familiarity with (18)F-FDG-avid nonmalignant lesions also may extend the use of (18)F-FDG-PET imaging beyond the field of oncology. We have tabulated our experience with benign entities associated with increased (18)F-FDG uptake on whole-body PET/CT from 12,000 whole-body (18)F-FDG-PET/CT studies performed during a 4-year period.     

The role of 18F-FDG PET in staging and early prediction of response to therapy of recurrent gastrointestinal stromal tumors.

Gastrointestinal stromal tumors (GISTs) are gaining the interest of researchers because of impressive metabolic response to the targeted molecular therapeutic drug imatinib mesylate. Initial reports suggest an impressive role for (18)F-FDG PET in follow-up of therapy for these tumors. However, the role of (18)F-FDG PET versus that of CT has not been established. Therefore, we compared the roles of (18)F-FDG PET and CT in staging and evaluation of early response to imatinib mesylate therapy in recurrent or metastatic GIST. METHODS: The study included 54 patients who underwent (18)F-FDG PET and CT scans within 3 wk before initiation of imatinib mesylate therapy. Forty-nine of these patients underwent repeat scans 2 mo after therapy. The numbers of sites or organs containing lesions on (18)F-FDG PET and CT scans were compared. Corresponding lesions on (18)F-FDG PET and CT scans or those confirmed to be malignant in appearance by other imaging modalities or on follow-up were considered true positives. Lesions seen on (18)F-FDG PET or CT scans but not seen or confirmed to be of benign appearance with other imaging modalities or on follow-up were considered false positives. Measurements of the maximum standard uptake value (SUV) on (18)F-FDG PET scans and tumor size on CT scans were used for quantitative evaluation of early tumor response to therapy. RESULTS: A total of 122 and 114 sites and/or organs were involved on pretherapy (18)F-FDG PET and CT scans, respectively. The sensitivity and positive predictive values (PPVs) for CT were 93% and 100%; whereas these values for (18)F-FDG PET were 86% and 98%. However, the differences between these values for CT and (18)F-FDG PET were not statistically significant (P = 0.27 for sensitivity and 0.25 for PPV). This suggests comparable performance of (18)F-FDG PET and CT in staging GISTs. Repeat scans at 2 mo after therapy showed agreement between (18)F-FDG PET and CT scans in 71.4% of patients (57.1% having a good response to therapy and 14.3% lacking a response). Discrepant results between (18)F-FDG PET and CT were recorded for 28.6% of the patients. (18)F-FDG PET predicted response to therapy earlier than did CT in 22.5% of patients during a longer follow-up interval (4-16 mo), whereas CT predicted lack of response to therapy earlier than (18)F-FDG PET in 4.1%. One patient did not undergo long-term follow-up. These findings suggest that (18)F-FDG PET is superior to CT in predicting early response to therapy in recurrent or metastatic GIST patients. CONCLUSION: The performances of (18)F-FDG PET and CT are comparable in staging GISTs before initiation of imatinib mesylate therapy. However, (18)F-FDG PET is superior to CT in predicting early response to therapy. Thus, (18)F-FDG PET is a better guide for imatinib mesylate therapy.     

Rhabdomyosarcoma with widespread bone marrow infiltration: beneficial management role of F-18 FDG PET

Alveolar rhabdomyosarcoma (RMS) accounts for 20% to 30% of childhood RMS and is associated with a prognosis worse than embryonal RMS. Disseminated RMS can present with extensive bone marrow involvement. Assessing the extent of the tumor is critical, because therapy and prognosis depend on the degree to which the mass has spread beyond the primary site. The value of F-18 FDG PET in patients with RMS has been reported in some series but none specifically involving bone marrow. Children have a highly cellular hematopoietic bone marrow and differentiation of a highly cellular marrow from neoplastic infiltration may be difficult. Various other conditions associated with diffuse FDG uptake in the bone marrow include marrow hyperplasia resulting from hemolytic/iron-deficiency/blood-loss anemia, after chemotherapy with granulocyte/macrophage colony-stimulating factor and recombinant erythropoietin treatment, leukemia, non-Hodgkin lymphoma, and myelodysplasia. It is therefore important to consider the above differential diagnoses in mind when evaluating cases of unexpected marrow uptake in F-18 FDG PET studies. We report here a case of RMS with diffuse bone marrow involvement detected on F-18 FDG PET wherein FDG PET was useful in determining the true extent (primary and metastases) of RMS before definitive therapy and the valuable adjunct role it has with structural imaging in management.     

Positron Emission Tomography in Diagnosis and Therapy Monitoring of Patients with Lymphoma

In contrast to conventional imaging modalities, positron emission tomography using fluorodeoxyglucose detects malignant tumors by their increased glucose metabolism. In patients with Hodgkin's disease or non-Hodgkin's lymphoma, FDG-PET imaging has been shown to sensitively identify enhanced tracer uptake in involved lymph nodes and infiltrated tissue. This brief review will summarize the currently available information on staging of lymphoma patients in comparison with other imaging modalities. In addition, FDG PET imaging has been suggested for differentiation of viable residual or recurrent tumor and scar after tumor therapy. One of the most promising applications of PET in the future will be the metabolic evaluation of early response to tumor therapy. It is hypothesized that changes in tumor metabolism occur before significant decrease of tumor mass. Early assessment of chemotherapy might help to avoid the toxicity of an ineffective therapy. In summary, the results concerning various clinical applications of PET imaging are encouraging for further prospective trials to document the advantage of PET in diagnosis and therapy of lymphoma patients as compared to conventional strategies.     

Value of FDG PET in the assessment of patients with multiple myeloma

OBJECTIVE: Our objective was to evaluate if whole-body PET with FDG is able to detect bone marrow involvement in patients with multiple myeloma and to assess its appearance and distribution pattern. MATERIALS AND METHODS: Seventeen whole-body FDG PET scans were performed in 13 patients with multiple myeloma. Four patients were referred for evaluation of extent of disease pretherapy and nine patients were referred for assessment of therapy response (chemotherapy, radiation therapy, bone marrow transplant). FDG PET images were evaluated for distribution and uptake pattern. Standardized uptake values were obtained to quantify FDG uptake. Results of other imaging examinations (MRI, CT, radiography), laboratory data, biopsies, and the clinical course were used for verification of detected lesions. RESULTS: FDG PET was able to detect medullary involvement of multiple myeloma. There were two false-negative results. In one patient, the radiographic skeletal survey showed subcentimeter lytic lesions within the ribs that were not detected on FDG PET and in the other patient, a lytic lesion detected on radiographs showed only mildly increased FDG uptake that was not identified prospectively. There was one false-positive FDG PET result in a patient who had undergone radiation therapy 3 weeks before PET. FDG PET was helpful in differentiating between posttherapeutic changes and residual/recurrent tumor and in assessing response to therapy. FDG PET resulted in upstaging of disease in four patients, which influenced subsequent management and prognosis. Sensitivity of FDG PET in detecting myelomatous involvement was 85% and specificity was 92%. CONCLUSION: FDG PET is able to detect bone marrow involvement in patients with multiple myeloma. FDG PET is useful in assessing extent of disease at time of initial diagnosis, contributing to staging that is more accurate. FDG PET is also useful for evaluating therapy response.     

PET/CT和MRI在多发性骨髓瘤中的应用与进展

多发性骨髓瘤（MM）是一种恶性B细胞肿瘤,其主要累及骨髓,部分也可出现髓外浸润。影像学检查是全面评估MM不可或缺的手段,X射线与CT对病灶的检出率低、定量能力差。PET/CT与MRI对MM的评估具有较大的价值,特别是18F-FDG及其他新型分子探针,全身扩散加权成像、动态增强MRI及水脂分离等MRI新技术。笔者就PET/CT及MRI在MM中的应用与进展进行综述。     

Prospective study of bone marrow infiltration in aggressive lymphoma by three independent methods: whole-body MRI, PET/CT and bone marrow biopsy

PURPOSE: Initial lymphoma staging requires bone marrow assessment in aggressive lymphomas. Bone marrow lymphoma infiltration is routinely assessed by bone marrow biopsy (BMB), considered as the "gold standard". The aim of this study was to compare the performance of BMB, whole-body MRI and PET/CT for evaluation of BM infiltration. METHODS: Patients with newly diagnosed aggressive lymphoma were evaluated by BMB, MRI and PET/CT. Two radiologists, two nuclear medicine physicians and one pathologist independently assessed the results of the three modalities. Bone was considered as involved if BM was positive or if PET/CT or MRI was positive and if there was a resolution of the abnormal image shown on PET/CT or MRI halfway or at the end of therapy. RESULTS: Both MRI and PET/CT detected bone marrow lesions in the 9/43 patients, but two patients with multiple lesions had more lesions detected by PET/CT compared to MRI. Among these nine patients, two with an iliac crest lesion detected by both MRI and PET/CT had bone marrow involvement with large-cell lymphoma on histological examination. The other seven patients had focal MRI and PET/CT lesions in areas other than the iliac crest, where the blind BMB was done. The other patients had bone marrow without large-cell lymphoma involvement. In all cases, after lymphoma therapy bone marrow involvement regressed on histological examination, PET and MRI. CONCLUSION: These preliminary results suggest that non-invasive morphological procedures could be superior to BMB for bone marrow assessment in aggressive lymphomas. Ongoing study is underway to validate these results.     

Distinguishing stress fractures from pathologic fractures: a multimodality approach

Whereas stress fractures occur in normal or metabolically weakened bones, pathologic fractures occur at the site of a bone tumor. Unfortunately, stress fractures may share imaging features with pathologic fractures on plain radiography, and therefore other modalities are commonly utilized to distinguish these entities. Additional cross-sectional imaging with CT or MRI as well as scintigraphy and PET scanning is often performed for further evaluation. For the detailed assessment of a fracture site, CT offers a high-resolution view of the bone cortex and periosteum which aids the diagnosis of a pathologic fracture. The character of underlying bone marrow patterns of destruction can also be ascertained along with evidence of a soft tissue mass. MRI, however, is a more sensitive technique for the detection of underlying bone marrow lesions at a fracture site. In addition, the surrounding soft tissues, including possible involvement of adjacent muscle, can be well evaluated with MRI. While bone scintigraphy and FDG-PET are not specific, they offer a whole-body screen for metastases in the case of a suspected malignant pathologic fracture. In this review, we present select examples of fractures that underscore imaging features that help distinguish stress fractures from pathologic fractures, since accurate differentiation of these entities is paramount.     

18F-FDG PET evaluation of the response to therapy for lymphoma and for breast, lung, and colorectal carcinoma.

PET is a unique form of diagnostic imaging that observes in vivo biologic changes using radiopharmaceuticals that closely mimic endogenous molecules. (18)F-FDG, which allows the evaluation of glucose metabolism, is the most commonly used tracer in oncology because of the practical half-life of (18)F (110 min), compared with other short-lived positron emitters. (18)F-FDG uptake in tumors is proportional to the glycolytic metabolic rate of viable tumor cells indicating the increased metabolic demand of tumors for glucose. (18)F-FDG PET significantly improves the accuracy of imaging tumors in initial staging, management of recurrent cancer, and monitoring of therapy response. The information provided by this technique is more sensitive and specific than that provided by anatomic imaging modalities. (18)F-FDG PET is particularly superior to CT or MRI in the ability to evaluate the effectiveness of various treatment regimens early during therapy or after therapy. In this review, we discuss the role of (18)F-FDG PET in evaluating the response to therapy and the impact of this information on patient management.     

The bone scan

Bone imaging continues to be the second greatest-volume nuclear imaging procedure, offering the advantage of total body examination, low cost, and high sensitivity. Its power rests in the physiological uptake and pathophysiologic behavior of 99m technetium (99m-Tc) diphosphonates. The diagnostic utility, sensitivity, specificity, and predictive value of 99m-Tc bone imaging for benign conditions and tumors was established when only planar imaging was available. Currently, nearly all bone scans are performed as a planar study (whole-body, 3-phase, or regional), with the radiologist often adding single-photon emission computed tomography (SPECT) imaging. Here we review many current indications for planar bone imaging, highlighting indications in which the planar data are often diagnostically sufficient, although diagnosis may be enhanced by SPECT. (18)F sodium fluoride positron emission tomography (PET) is also re-emerging as a bone agent, and had been considered interchangeable with 99m-Tc diphosphonates in the past. In addition to SPECT, new imaging modalities, including (18)F fluorodeoxyglucose, PET/CT, CT, magnetic resonance, and SPECT/CT, have been developed and can aid in evaluating benign and malignant bone disease. Because (18)F fluorodeoxyglucose is taken up by tumor cells and Tc diphosphonates are taken up in osteoblastic activity or osteoblastic healing reaction, both modalities are complementary. CT and magnetic resonance may supplement, but do not replace, bone imaging, which often detects pathology before anatomic changes are appreciated. We also stress the importance of dose reduction by reducing the dose of 99m-Tc diphosphonates and avoiding unnecessary CT acquisitions. In addition, we describe an approach to image interpretation that emphasizes communication with referring colleagues and correlation with appropriate history to significantly improve our impact on patient care.     

Imaging gastric cancer with PET and the radiotracers 18F-FLT and 18F-FDG: a comparative analysis.

In this pilot study, we evaluated 3'-deoxy-3'-(18)F-fluorothymidine (FLT) PET for the detection of gastric cancer and compared the diagnostic accuracy with that of (18)F-FDG PET. METHODS: Forty-five patients (31 male and 14 female) with histologically proven locally advanced gastric cancer underwent attenuation-corrected whole-body (18)F-FLT PET and (18)F-FDG PET/CT (low-dose CT). (18)F-FLT emission images were acquired on a full-ring PET scanner 45 min after the injection of 270-340 MBq of (18)F-FLT. (18)F-FDG PET/CT was performed 60 min after the injection of 300-370 MBq of (18)F-FDG. Mean standardized uptake values for (18)F-FLT and (18)F-FDG were calculated using circular ROIs (diameter, 1.5 cm) in the primary tumor manifestation site, in a reference segment of the liver, and in the bone marrow and were compared on a lesion-by-lesion basis. RESULTS: According to the Lauren classification, 15 tumors (33%) were of the intestinal subtype and 30 (67%) of the nonintestinal subtype. (18)F-FLT PET images showed high contrast for the primary tumor and proliferating bone marrow. In all patients (45/45), focal (18)F-FLT uptake could be detected in the primary tumor. In contrast, 14 primary tumors were negative for (18)F-FDG uptake, with lesional (18)F-FDG uptake lower than or similar to background activity. The mean standardized uptake value for (18)F-FLT in malignant primaries was 6.0 +/- 2.5 (range, 2.4-12.7). In the subgroup of (18)F-FDG-positive patients, the mean value for (18)F-FDG was 8.4 +/- 4.1 (range, 3.8/19.0), versus 6.8 +/- 2.6 for (18)F-FLT (Wilcoxon test: P = 0.03). Comparison of mean (18)F-FLT and (18)F-FDG uptake in tumors with signet ring cells revealed no statistically significant difference between the tracers (6.2 +/- 2.1 for (18)F-FLT vs. 6.4 +/- 2.8 for (18)F-FDG; Wilcoxon test: P = 0.94). CONCLUSION: The results of this study indicate that imaging gastric cancer with the proliferation marker (18)F-FLT is feasible. (18)F-FLT PET was more sensitive than (18)F-FDG PET, especially in tumors frequently presenting without or with low (18)F-FDG uptake, and may improve early evaluation of response to neoadjuvant treatment.     

18F-FDG PET/CT bone/bone marrow findings in Hodgkin’s lymphoma may circumvent the use of bone marrow trephine biopsy at diagnosis staging

Purpose

Accurate staging of Hodgkin’s lymphoma (HL) is necessary in selecting appropriate treatment. Bone marrow trephine biopsy (BMB) is the standard procedure for depicting bone marrow involvement. BMB is invasive and explores a limited part of the bone marrow. ¹⁸F-FDG PET/CT is now widely used for assessing response to therapy in HL and a baseline study is obtained to improve accuracy. The aim of this retrospective analysis was to assess whether routine BMB remains necessary with concomitant ¹⁸F-FDG PET/CT.

Methods

Data from 83 patients (newly diagnosed HL) were reviewed. All patients had received contrast-enhanced CT, BMB and ¹⁸F-FDG PET/CT. Results of BMB were not available at the time of ¹⁸F-FDG PET/CT imaging.

Results

Seven patients had lymphomatous involvement on BMB. Four patients had bone involvement on conventional CT (two with negative BMB). All patients with bone marrow and/or bone lesions at conventional staging were also diagnosed on ¹⁸F-FDG PET/CT scan. PET/CT depicted FDG-avid bone/bone marrow foci in nine additional patients. Four of them had only one or two foci, while the other had multiple foci. However, the iliac crest, site of the BMB, was not involved on ¹⁸F-FDG PET/CT. Osteolytic/sclerotic lesions matching FDG-avid foci were visible on the CT part of PET/CT in three patients. MRI ordered in three other patients suggested bone marrow involvement. Interim and/or end-therapy ¹⁸F-FDG PET/CT documented response of FDG-avid bone/bone marrow foci to chemotherapy in every patient.

Conclusion

¹⁸F-FDG PET/CT highly improves sensitivity for diagnosis of bone/bone marrow lesions in HL compared to conventional staging.     

FDG PET can replace bone scintigraphy in primary staging of malignant lymphoma.

Recent studies indicated that 18F-fluorodeoxyglucose (FDG) PET may be more accurate than CT in staging nodal and extranodal malignant lymphoma. The objective of this study was to compare conventional bone scintigraphy as an established skeletal staging procedure with PET using FDG in the detection of osseous involvement in malignant lymphoma. METHODS: Whole-body PET-based staging studies of 56 consecutive patients with proven Hodgkin's disease (n = 34) or non-Hodgkin's lymphoma (n = 22) were compared with the results of bone scintigraphy. Positive PET or bone scintigraphic findings were confirmed, if possible, by biopsy, MRI, CT or radiographic investigations. RESULTS: Of the 56 patients studied, 12 were found to have skeletal involvement on both studies (PET, 30 regions; bone scintigraphy, 20 regions). Findings were confirmed in all 12 patients. FDG PET detected an additional 12 involved regions in 5 patients. This was subsequently verified in 3 patients, although the other 2 cases remained unresolved. Conversely, bone scintigraphy revealed five abnormalities compatible with lymphoma in 5 patients. Three of these lesions were found to be erroneous; final evaluation of the remaining two findings was not possible. CONCLUSION: FDG PET is suitable for identifying osseous involvement in malignant lymphoma with a high positive predictive value and is thereby more sensitive and specific than bone scintigraphy.     

Chemokine receptor-4 targeted PET/CT with 68 Ga-Pentixafor in assessment of newly diagnosed multiple myeloma: comparison to 18 F-FDG PET/CT

18F-FDG PET/CT has some limitations in the evaluation of multiple myeloma (MM). Since chemokine receptor-4 is overexpressed in MM, we perform a prospective cohort study to compare the performance of 68Ga-Pentixafor and 18F-FDG PET/CT in newly diagnosed MM. Thirty patients with newly diagnosed MM were recruited. All patients underwent 68Ga-Pentixafor and18F-FDG PET/CT within 1 week after enrollment. A positive PET/CT was defined as the presence of focal PET-positive lesions in bone marrow or diffuse bone marrow patterns (uptake > liver). Bone marrow uptake values in 68Ga-Pentixafor and18F-FDG PET/CT (total bone marrow glycolysis [TBmGFDG], total bone marrow uptake with 68Ga-Pentixafor [TBmUCXCR4], total bone marrow volume [TBmV], SUVmean, and SUVmax) were obtained by drawing total bone marrow volume of interest on PET/CT. The positive rates of the PET/CT scans were statistically compared, and the correlation between quantitative bone marrow uptake values and clinical characteristics, laboratory findings, and staging was analyzed. 68Ga-Pentixafor PET/CT had a higher positive rate than 18F-FDG PET/CT in recruited patients (93.3 vs. 53.3%, p = 0.0005). In quantitative analysis, bone marrow uptake values in 68Ga-Pentixafor (TBmUCXCR4, SUVmax, and SUVmean) were positively correlated with end organ damage, staging, and laboratory biomarkers related to tumor burden including serum β2-microglobulin, serum free light chain, and 24-h urine light chain (p < 0.05). In 18F-FDG PET/CT, only the SUVmean of total bone marrow was positively correlated with serum free light chain and 24-h urine light chain (p < 0.05). 68Ga-Pentixafor PET/CT is promising in assessment of newly diagnosed MM. NCT 03436342     

18F-FDG accumulation with PET for differentiation between benign and malignant lesions in the thorax.

Recent reports have indicated the value and limitations of (18)F-FDG PET and (201)Tl SPECT for determination of malignancy. We prospectively assessed and compared the usefulness of these scintigraphic examinations as well as (18)F-FDG PET delayed imaging for the evaluation of thoracic abnormalities. METHODS: Eighty patients with thoracic nodular lesions seen on chest CT images were examined using early and delayed (18)F-FDG PET and (201)Tl-SPECT imaging within 1 wk of each study. The results of (18)F-FDG PET and (201)Tl SPECT were evaluated and compared with the histopathologic diagnosis. RESULTS: Fifty of the lesions were histologically confirmed to be malignant, whereas 30 were benign. On (18)F-FDG PET, all malignant lesions showed higher standardized uptake value (SUV) levels at 3 than at 1 h, and benign lesions revealed the opposite results. Correlations were seen between (18)F-FDG PET imaging and the degree of cell differentiation in malignant tumors. No significant difference in accuracy was found between (18)F-FDG PET single-time-point imaging and (201)Tl SPECT for the differentiation of malignant and benign thoracic lesions. However, the retention index (RI) of (18)F-FDG PET (RI-SUV) significantly improved the accuracy of thoracic lesion diagnosis. Furthermore, (18)F-FDG PET delayed imaging measuring RI-SUV metastasis was useful for diagnosing nodal involvement and it improved the specificity of mediastinal staging. CONCLUSION: No significant difference was found between (18)F-FDG PET single-time-point imaging and (201)Tl SPECT for the differentiation of malignant and benign thoracic lesions. The RI calculated by (18)F-FDG PET delayed imaging provided more accurate diagnoses of lung cancer.