Accuracy of 18F fluorodeoxyglucose positron emission tomography/computed tomography in staging of pediatric sarcomas

Review on Lymph Node Metastases, Sentinel Lymph Node Biopsy, and Lymphadenectomy in Sarcoma

Soft tissue sarcomas (STS) originating from connective tissue rarely affect the lymph nodes. However, involvement of lymph nodes in STS is an important aspect of prognosis and treatment. Currently, there is no consensus on the diagnosis and management of lymph node metastases in STS. The key risk factor for nodal involvement is the histological subtype of sarcoma. Radiological and pathological evaluation seems to be the most effective method of assessing lymph nodes in these neoplasms. Thus, sentinel lymph node biopsy (SLNB), which has been shown to be valuable in the management of melanoma or breast cancer, may also be a beneficial diagnostic option in some high-risk STS subtypes. This review summarizes data on the risk factors and clinical characteristics of lymph node involvement in STS. Possible management and therapeutic options are also discussed.

Diagnostic performance of PET/CT in primary malignant bone tumors

Background

Nowadays, PET/CT plays a substantial role in the diagnosis of different types of tumor by its ability to provide combined functional and anatomic imaging in the same session. The purpose of this study is to evaluate the added value of PET/CT in staging and re-staging of primary malignant bone tumors.

Results

Out of the studied 40 patients, 7 patients were referred for primary staging of different types of histologically proven primary malignant bone tumors, their FDG-PET/CT studies yielded additional diagnostic information in 28.6% of them. Thirty three patients were referred either for assessment of treatment response or for follow-up to detect any viable lesions; FDG-PET/CT was more sensitive and specific than CT in follow-up and assessment of treatment response with PET/CT sensitivity 94.4%, specificity 86.7%, and total accuracy 90.9% and CT sensitivity 88.2%, specificity 81.2%, and total accuracy 84.8%.

Conclusions

PET/CT was an accurate imaging modality in evaluation of primary malignant bone tumors regarding tumor staging, assessment of therapeutic response and detection of metastatic disease as compared to CT.

SNMMI Procedure Standard/EANM Practice Guideline on Pediatric 18F-FDG PET/CT for Oncology 1.0

The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and professional organization founded in 1954 to promote the science, technology, and practical application of nuclear medicine. The European Association of Nuclear Medicine (EANM) is a professional nonprofit medical association founded in 1985 to facilitate communication worldwide among individuals pursuing clinical and academic excellence in nuclear medicine. SNMMI and EANM members are physicians, technologists, and scientists specializing in the research and practice of nuclear medicine.

The SNMMI and EANM will periodically put forth new standards/guidelines for nuclear medicine practice to help advance the science of nuclear medicine and improve service to patients. Existing standards/guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner, if indicated. Each standard/guideline, representing a policy statement by the SNMMI/EANM, has undergone a thorough consensus process, entailing extensive review. The SNMMI and EANM recognize that the safe and effective use of diagnostic nuclear medicine imaging requires particular training and skills, as described in each document. These standards/guidelines are educational tools designed to assist practitioners in providing appropriate and effective nuclear medicine care for patients. These guidelines are consensus documents, and are not inflexible rules or requirements of practice. They are not intended, nor should they be used, to establish a legal standard of care. For these reasons and those set forth below, the SNMMI and the EANM cautions against the use of these standards/guidelines in litigation in which the clinical decisions of a practitioner are called into question.

The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by medical professionals taking into account the unique circumstances of each case. Thus, there is no implication that action differing from what is laid out in the standards/guidelines, standing alone, is below standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set forth in the standards/guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources, or advances in knowledge or technology subsequent to publication of the standards/guidelines.

The practice of medicine involves not only the science, but also the art of dealing with the prevention, diagnosis, alleviation, and treatment of disease. The variety and complexity of human conditions make it impossible for general guidelines to consistently allow for an accurate diagnosis to be reached or a particular treatment response to be predicted. Therefore, it should be recognized that adherence to these standards/guidelines will not ensure a successful outcome. All that should be expected is that the practitioner follows a reasonable course of action, based on their level of training, the current knowledge, the available resources, and the needs/context of the particular patient being treated.

PET and computerized tomography (CT) have been widely used in oncology. ¹⁸F-FDG is the most common radiotracer used for PET imaging. The purpose of this document is to provide imaging specialists and clinicians guidelines for recommending, performing, and interpreting ¹⁸F-FDG PET/CT in pediatric patients in oncology. There is not a high level of evidence for all recommendations suggested in this paper. These recommendations represent the expert opinions of experienced leaders in this field. Further studies are needed to have evidence-based recommendations for the application of ¹⁸F-FDG PET/CT in pediatric oncology. These recommendations should be viewed in the context of good practice of nuclear medicine and are not intended to be a substitute for national and international legal or regulatory provisions.

Desmoplastic small round-cell tumour of the peritoneal cavity: case report and literature review

Desmoplastic small round-cell tumour is a very rare neoplasm, which usually arises from the abdominal or pelvic peritoneum of adolescents and young adults. Early diagnosis is difficult, because most tumours present with non-specific gastrointestinal symptoms after a long asymptomatic period. It is generally a very aggressive tumour, which grows rapidly with poor prognosis and an overall five-year survival rate of 15% despite multimodal treatment. Despite multiple treatment strategies, the management of desmoplastic small round-cell tumour still remains a clinical challenge and no consensus about a therapeutic protocol has been established. A 35-year-old man presented with mild abdominal pain, constipation and weight gain, and was eventually diagnosed with desmoplastic small round-cell tumour, which was shown to be limited to the abdomen. After incomplete debulking surgery, radiotherapy and chemotherapy, he developed multiple metastatic nodular foci in chest and the pleura and, unfortunately, he died due to disease progression.

Effectiveness of 18F-FDG PET/CT in the diagnosis, staging and recurrence monitoring of Ewing sarcoma family of tumors: A meta-analysis of 23 studies

BACKGROUND

To investigate the value of positron emission tomography (PET) and PET/computed tomography (CT) using fluorine-18-fluorodeoxyglucose (F-FDG) in the diagnosis, staging, restaging and recurrence monitoring of Ewing sarcoma family of tumors (ESFTs), a meta-analysis was performed through systematically searching PubMed, Embase, and Cochrane Central library to retrieve articles.

METHODS

After screening and diluting out the articles that met inclusion criteria to be used for statistical analysis the pooled evaluation indexes including sensitivity, specificity, and diagnostic odd ratio (DOR) as well as the summary receiver operating characteristic curve (SROC) were calculated involving diagnostic data (true positive, false positive, false negative, and true negative) extracted from original studies.

RESULTS

Screening determined that out of 2007, 23 studies involving a total of 524 patients were deemed viable for inclusion in the meta-analysis. The results of the analysis showed that the sensitivity and specificity were at 86% and 80%, respectively. Additionally, a satisfactory accuracy of F-FDG PET and PET/CT was observed in detecting ESFT recurrence, lung metastasis, and osseous metastasis.

CONCLUSION

This meta-analysis suggests that F-FDG PET and PET/CT with an extremely high accuracy could be considered a valuable method for detecting distant metastasis and post-operational recurrence of ESFT, which might have a profound impact on the development of treatment protocols for ESFT.

FDG uptake in cervical lymph nodes in children without head and neck cancer

BACKGROUND

Reactive cervical lymphadenopathy is common in children and may demonstrate increased ¹⁸F-fluoro-deoxyglucose (¹⁸F-FDG) uptake on positron emission tomography/computed tomography (PET/CT).

OBJECTIVE

We sought to evaluate the frequency and significance of ¹⁸F-FDG uptake by neck lymph nodes in children with no history of head and neck cancer.

MATERIALS AND METHODS

The charts of 244 patients (114 female, mean age: 10.4 years) with a variety of tumors such as lymphoma and post-transplant lymphoproliferative diseases (PTLD), but no head and neck cancers, who had undergone ¹⁸F-FDG PET/CT were reviewed retrospectively. Using the maximum standardized uptake value (SUVmax), increased ¹⁸F-FDG uptake by neck lymph nodes was recorded and compared with the final diagnosis based on follow-up studies or biopsy results.

RESULTS

Neck lymph node uptake was identified in 70/244 (28.6%) of the patients. In 38 patients, the lymph nodes were benign. In eight patients, the lymph nodes were malignant (seven PTLD and one lymphoma). In 24 patients, we were not able to confirm the final diagnosis. Seven out of the eight malignant lymph nodes were positive for PTLD. The mean SUVmax was significantly higher in malignant lesions (4.2) compared with benign lesions (2.1) (P = 0.00049).

CONCLUSION

¹⁸F-FDG uptake in neck lymph nodes is common in children and is frequently due to reactive lymph nodes, especially when the SUVmax is <3.2. The frequency of malignant cervical lymph nodes is higher in PTLD patients compared with other groups.

Assessing the role of ¹⁸F-FDG PET and ¹⁸F-FDG PET/CT in the diagnosis of soft tissue musculoskeletal malignancies: a systematic review and meta-analysis

PURPOSE

Twelve years ago a meta-analysis evaluated the diagnostic performance of (18)F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in assessing musculoskeletal soft tissue lesions (MsSTL). Currently, PET/CT has substituted PET imaging; however, there has not been any published meta-analysis on the use of PET/CT or a comparison of PET/CT with PET in the diagnosis of MsSTL. Therefore, we conducted a meta-analysis to identify the current diagnostic performance of (18)F-FDG PET/CT and determine if there is added value when compared to PET.

METHODS

A systematic review of English articles was conducted, and MEDLINE PubMed, the Cochrane Library, and Embase were searched from 1996 to March 2015. Studies exploring the diagnostic accuracy of (18)F-FDG PET/CT (or dedicated PET) compared to histopathology in patients with MsSTL undergoing investigation for malignancy were included.

RESULTS

Our meta-analysis included 14 articles composed of 755 patients with 757 soft tissue lesions. There were 451 (60 %) malignant tumors and 306 benign lesions. The (18)F-FDG PET/CT (and dedicated PET) mean sensitivity, specificity, accuracy, positive predictive value, and negative predictive value for diagnosing MsSTL were 0.96 (0.90, 1.00), 0.77 (0.67, 0.86), 0.88 (0.85, 0.91), 0.86 (0.78, 0.94), and 0.91 (0.83, 0.99), respectively. The posterior mean (95 % highest posterior density interval) for the AUC was 0.92 (0.88, 0.96). PET/CT had higher specificity, accuracy, and positive predictive value when compared to a dedicated PET (0.85, 0.89, and 0.91 vs 0.71, 0.85, and 0.82, respectively).

CONCLUSION

(18)F-FDG PET/CT and dedicated PET are both highly accurate in the diagnosis of MsSTL. PET/CT is more accurate and specific and has a higher positive predictive value than PET.

FDG PET/CT imaging of desmoplastic small round cell tumor: findings at staging, during treatment and at follow-up

BACKGROUND

Desmoplastic small round cell tumor (DSRCT) is a very uncommon soft-tissue tumor of children and young adults. It has an aggressive course with generally poor survival. In general the assessment of tumor burden and response has relied upon CT or MRI. However these tumors are often metabolically active and can be evaluated using FDG PET/CT imaging.

OBJECTIVE

The purpose of this study was to determine the metabolic activity of desmoplastic small round cell tumors using FDG PET/CT imaging and the potential utility of FDG PET/CT in this disease.

MATERIALS AND METHODS

Eight patients (seven male, one female; ages 2-20 years, median 11 years) with confirmed DSRCT underwent 82 positron emission tomography/computed tomography (PET/CT) scans. PET/CT was used for initial staging (seven patients, eight scans), monitoring response to therapy (eight patients, 37 scans) and for surveillance of DSRCT recurrence (six patients, 37 scans).

RESULTS

Each scan performed at diagnosis showed abnormally elevated uptake in the primary tumor. Five patients had abdominal pelvic involvement, and two of those also had thoracic disease. Six patients whose scans showed no abnormal sites of uptake at the end of therapy have had progression-free survivals of 2-10 years. One patient whose scan continued to show uptake during treatment died of disease 1.3 years from diagnosis. Another patient with persistent uptake remained in treatment 3 years after initial diagnosis. One surveillance scan identified recurrent disease.

CONCLUSION

FDG PET/CT identified elevated metabolic activity in each patient studied. Despite our small sample size, FDG PET/CT scans appear useful for the management of patients with DSCRT. Patients whose studies become negative during or following treatment may have a prolonged remission.

Value of 18F-FDG PET and PET/CT for evaluation of pediatric malignancies

Successful management of solid tumors in children requires imaging tests for accurate disease detection, characterization, and treatment monitoring. Technologic developments aim toward the creation of integrated imaging approaches that provide a comprehensive diagnosis with a single visit. These integrated diagnostic tests not only are convenient for young patients but also save direct and indirect health-care costs by streamlining procedures, minimizing hospitalizations, and minimizing lost school or work time for children and their parents. (18)F-FDG PET/CT is a highly sensitive and specific imaging modality for whole-body evaluation of pediatric malignancies. However, recent concerns about ionizing radiation exposure have led to a search for alternative imaging methods, such as whole-body MR imaging and PET/MR. As we develop new approaches for tumor staging, it is important to understand current benchmarks. This review article will synthesize the current literature on (18)F-FDG PET/CT for tumor staging in children, summarizing questions that have been solved and providing an outlook on unsolved avenues.

Pediatric bone sarcoma: diagnostic performance of ¹⁸F-FDG PET/CT versus conventional imaging for initial staging and follow-up

OBJECTIVE

The purpose of this study was to compare the diagnostic performance of (18)F-FDG PET/CT and conventional imaging for staging and follow-up of pediatric osteosarcoma and skeletal Ewing sarcoma.

MATERIALS AND METHODS

We calculated sensitivity, specificity, and accuracy of PET/CT and conventional imaging (CT, MRI, bone scanning) for sites of disease and number of lesions. Diagnostic benefit, defined as better characterization of lesions, was evaluated on a per-scan basis, comparing PET/CT and conventional imaging.

RESULTS

A total of 412 lesions were characterized by imaging in 64 patients (20, osteosarcoma; 44, Ewing sarcoma). For osteosarcoma patients PET/CT was available only at follow-up, where it proved more accurate than conventional imaging for the detection of bone lesions (accuracy, 95% vs 67% for CT and 86% for MRI) and complementary to CT in evaluating lung nodules (sensitivity, 84% vs 94%; specificity, 79% vs 71%) with diagnostic benefit in 18% of examinations. In patients with Ewing sarcoma, PET/CT tended to perform better during follow-up than at initial staging (accuracy, 85% vs 69%). For lung findings, PET/CT was more specific than CT but was less sensitive. The diagnostic benefit of PET/CT was greater at staging (28%) than during followup (9%). On a per-patient basis, PET/CT provided diagnostic benefit in 21 of 44 patients with Ewing sarcoma and nine of 20 patients with osteosarcoma at least once during clinical management.

CONCLUSION

FDG PET/CT provides diagnostic benefit in Ewing sarcoma and osteosarcoma, with the exception of small lung nodules. Prospective studies are needed to define the best imaging algorithm and combination of tests in the staging and follow-up of patients with pediatric bone sarcoma.

2-deoxy-2-(18F)fluoro-D-glucose positron emission tomography/computed tomography imaging in paediatric oncology

Positron emission tomography (PET) is a minimally invasive technique which has been well validated for the diagnosis, staging, monitoring of response to therapy, and disease surveillance of adult oncology patients. Traditionally the value of PET and PET/computed tomography (CT) hybrid imaging has been less clearly defined for paediatric oncology. However recent evidence has emerged regarding the diagnostic utility of these modalities, and they are becoming increasingly important tools in the evaluation and monitoring of children with known or suspected malignant disease. Important indications for 2-deoxy-2-(¹⁸F)fluoro-D-glucose (FDG) PET in paediatric oncology include lymphoma, brain tumours, sarcoma, neuroblastoma, Langerhans cell histiocytosis, urogenital tumours and neurofibromatosis type I. This article aims to review current evidence for the use of FDG PET and PET/CT in these indications. Attention will also be given to technical and logistical issues, the description of common imaging pitfalls, and dosimetric concerns as they relate to paediatric oncology.

Role of FDG-PET/CT for monitoring soft tissue tumors

The aim of the current study was to evaluate the limitations of 2-deoxy-2-F¹⁸-fluoro-D-glucose positron emission tomography combined with computed tomography (FDG-PET/CT) when monitoring soft tissue tumors. The diagnostic criteria of malignancy was defined as the tumor having a maximum standardized uptake value (SUVmax) ≥2.0 and a maximum diameter ≥5 cm as measured using FDG-PET/CT. One-hundred-and-thirteen patients, that were either included in the criteria or not, were compared. In addition, the values of SUVmax of the primary tumor and relapse in 12 patients were evaluated. The Kaplan-Meier analysis demonstrated that patients with tumors measuring ≥5 cm size and ≥2.0 SUVmax were associated with a worse survival rate. Among the 12 patients with relapse, statistical significances were detected in the tumor diameters, however, not in the SUVmax values. Thus, the criteria identified patients that were associated with a poor prognosis, and the SUVmax of distant metastases and local recurrences were identified to be significantly affected by tumor size.

The diagnostic and prognostic value of ¹⁸F-FDG PET/CT in the initial assessment of high-grade bone and soft tissue sarcoma. A retrospective study of 89 patients

PURPOSE

To evaluate the feasibility of (18)F-FDG PET/CT for initial assessment in high-grade bone sarcomas (BS) and soft tissue sarcomas (STS).

METHODS

During the years 2001-2010, 89 patients (30 BS, 59 STS) referred for further evaluation and surgical treatment of a high-grade BS or STS also had a PET/CT scan performed for staging preoperatively (n = 68) or within 1 month of surgery (n = 21). Metastatic lesions suggested on the PET/CT scan were confirmed or rejected by histological evaluation, by additional imaging or by follow-up. In 68 patients (28 BS, 40 STS) the relationship between the maximal standardized uptake value (SUVmax) of the primary tumour and survival was examined.

RESULTS

The PET/CT scan suggested the presence of 13 metastatic lesions in BS patients (5 lymph node, 8 distant) and 21 metastatic lesions (6 lymph node, 15 distant) in STS patients. The calculated sensitivity (SE) and specificity (SP) were 95 % and 96 % for detection of distant metastases, and the predictive value (PV) of a positive or a negative test was 87 % and 98 %, respectively. SE and SP were 100 % and 90 % for detection of lymph node metastases, and the PV of a positive or a negative test was 27 % and 100 %, respectively. The 5-year survival was 81 % among patients with SUVmax below the median value (≤ 10), but was 33 % among those with SUVmax >10.

CONCLUSION

FDG PET/CT for the initial assessment of patients with high-grade BS or STS was feasible with high SE and SP, but in those with lymph node metastases the PV of a positive test was low. The SUVmax of the primary tumour was a strong prognostic factor for survival.

Is there a need for dedicated bone imaging in addition to 18F-FDG PET/CT imaging in pediatric sarcoma patients?

PURPOSE

Many children with sarcomas undergo whole body 2-deoxy-2-((18)F)fluoro-D-glucose positron emission tomography/computed tomography ((18)F-FDG PET/CT) and technetium methylene diphosphonate ((99)Tc-MDP) studies. It is unknown whether the combination of both tests results in more accurate detection of bone lesions than (18)F-FDG- PET/CT alone.

METHODS

(99)Tc-MDP bone and (18)F-FDG PET/CT scans were each read by 2 "blinded" observers and then reviewed side-by-side by 3 readers. Bone lesions were graded qualitatively on a 5-point scale (from benign to malignant). Clinical and imaging follow-up (n = 21) and bone biopsy results (n = 8) served as reference standard.

RESULTS

A total of 39 paired (99)Tc-MDP and (18)F-FDG-PET/CT studies (cases) performed at a mean interval 4 ± 7 days, were performed on 29 patients (mean age 12 ± 5 y). Of these, 21 patients (72%) had bone sarcoma, whereas 8 patients (28%) had soft tissue sarcoma. By patient and case-based analysis, (18)F-FDG PET/CT had an accuracy of 100%. Tc-MDP had accuracies of 90% and 82% by patient and case-based analysis. The combined interpretation had an accuracy of 97%.

CONCLUSIONS

In this study, (99)Tc-MDP bone imaging does not provide an added diagnostic value for bone involvement over (18)F-FDG-PET/CT.

18F-fluorodeoxyglucose uptake of bone and soft tissue sarcomas in pediatric patients

A high (18)F-fluorodeoxyglucose (FDG) uptake by positron emission tomography/computed tomography (PET/CT) imaging in sarcomas of adults has been reported. The current study aimed at defining the degree of (18)F-FDG uptake of pediatric sarcomas. This retrospective study included 29 patients (23 males, 6 females; mean age 14 ± 5 years) with soft tissue (n = 9) or bone (n = 20) sarcomas. Twenty-two patients (76%) underwent (18)F-FDG PET/CT and 7 (24%) had dedicated (18)F-FDG PET studies. Tumor (18)F-FDG uptake was quantified by standard uptake value (SUV)(max) and tumor-to-liver ratios (SUV ratios; tumor SUV(max)/liver SUV(mean)). Tumor SUV(max) and SUV ratios were correlated with tumor Ki-67 expression. SUV(max) ranged from 1.4 to 24 g/mL (median 2.5 g/mL) in soft tissue sarcomas and 1.6 to 20.4 g/mL (median 6.9 g/mL) in bone sarcomas (P = .03), and from 1.6 to 9.2 g/mL (median 3.9 g/mL) and 3.5 to 20.4 g/mL (median 12 g/mL) in Ewing sarcoma and osteosarcoma, respectively (P = .009). Tumor SUV ratios ranged from 0.8 to 8.7 (median 1.9) in soft tissue sarcomas and 1.4 to 8.9 (median 3.8) in bone sarcomas (P = .08). Ewing sarcoma had a significantly lower tumor SUV ratio than osteosarcoma (P = .01). Ki-67 expression correlated significantly with the (18)F-FDG uptake in bone but not in soft tissue sarcomas. All sarcomas were visualized by (18)F-FDG PET/CT imaging. A higher (18)F-FDG uptake was observed in osteosarcoma than in Ewing and soft tissue sarcomas. The results of this study suggest that the degree of tumor (18)F-FDG uptake is sufficient to allow for monitoring of therapeutic responses in pediatric sarcomas.

Clinical applications of PET and PET/CT in pediatric malignancies

The common childhood cancers are leukemia, CNS tumors, lymphomas, soft-tissue tumors (such as rhabdomyosarcoma and fibrosarcoma), neuroblastoma, malignant bone tumors, germ cell tumors with neoplasms of gonads and hepatic tumors. Usually the conventional imaging modalities, such as x-ray, ultrasound, computed tomography (CT) and MRI, are being routinely used for the management of these pediatric malignancies. However, most of these modalities provide structural information and are lacking in functional/metabolic status of these malignancies. Recently, PET and PET/CT have emerged as a functional diagnostic imaging modality for the management of various cancers in adult population. Up to now most of the data published in the literature are on PET alone. PET used in conjunction with CT is useful as it provides an enhanced view of the anatomical details and the malignant focus then can be located with highest accuracy. PET and PET/CT has been found to be useful in, for example, CNS tumors, lymphomas, soft-tissue tumors, neuroblastoma, malignant bone tumors and germ cell tumors. PET/CT has a limited role in early diagnosis, however, it plays an important role in initial staging, treatment response evaluation and detection of metastatic disease in these cancers. Despite the fact that PET/CT has better diagnostic value when compared with conventional imaging, such as CT and MRI, in the management of many pediatric cancers, there are certain limitations. PET/CT has a limited role in detection of lesions smaller than 5 mm, well-differentiated tumors and tumors with low metabolic rate. Many infections and inflammation can lead to false-positive PET/CT results. In the present review we will discuss the various clinical indications of PET and PET/CT in pediatric cancers.

Sarcoma

Sarcomas are a diverse group of malignancies originating in the connective tissue. The approach of a patient with a mass suspect for sarcoma starts with performing a biopsy to obtain tissue for evaluation by pathology. The main role of the current imaging modalities, in general, is to recognize patients with typically benign disease, in whom further invasive staging can be omitted, and select patients with a suspected malignancy, who should be referred for biopsy. Since soft tissue sarcoma tends to be large and heterogeneous, there is growing interest in using imaging modalities to guide these biopsies. Together with pathology, imaging modalities are the basis for accurate staging, evaluation of locoregional extent of the primary lesion, screening for occult metastases, evaluation of response to cancer treatment, and the detection of tumor recurrence. In this chapter, an overview is given of the use of 18F-FDG PET in these settings, its strengths as well as its limitations.

FDG PET of alveolar soft part sarcoma

Alveolar soft part sarcoma (ASPS) is a very rare, but distinctive type of soft tissue sarcoma, whose name is derived from the pseudoalveolar appearance of its histology. In this report, the FDG PET/CT findings of ASPS are described in a 17-year-old asthmatic female who presented with worsening respiratory symptoms and a pelvic mass. The staging PET showed heterogeneous intense incorporation of FDG within the mass and variable FDG incorporation within the multiple lung nodules. In concordance with other soft tissue sarcomas, PET/CT helped to confirm the anatomic origin of the ASPS, to direct its biopsy, and to assess the distribution of disease.