18F-FDG-PET/CT evaluation of response to treatment in lymphoma: When is the optimal time for the first re-evaluation scan?
Division of Nuclear Medicine, Stanford University Medical Center, 300 Pasteur Dr, Room H-0101, Stanford, CA 94305-5427, USA. Hellenic journal of nuclear medicine
(Impact Factor: 0.99).
Assessing the response to treatment as soon after treatment initiation is one of the key reasons for imaging lymphoma patients. The optimal time after initiating treatment for assessing response to treatment has yet to be determined. Therefore, we were prompted to review our experience with serial (18)F-FDG PET/CT in patients undergoing treatment for Hodgkin's disease (HD) and non Hodgkin's lymphoma (NHL). This is a retrospective study (Feb 2003 - Oct 2004) of 20 patients, 11 men and 9 women, with age range of 7-75 years with diagnosis of HD (10) and NHL (10), who had PET/CT at our institution prior, during and at the completion of therapy. Restaging PET/CT was done after 2 cycles of chemotherapy in 10 patients (group A) and after 4 cycles of chemotherapy in 10 pts (group B). A total of 60 scans were reviewed. The DeltaSUV from baseline to first PET/CT was on average 67.6% in group A and 75.1% in group B. This had no statistical significance (P value: 0.31). The DeltaSUV from baseline to post-therapy PET/CT was on average 72.9% in group A and 79.8% in group B. This difference also had no statistical significance (P value: 0.24). The correlation coefficient was 0.98 in group A and 0.80 in group B. Results of PET/CT after 2 cycles of chemotherapy did not statistically differ from the results of PET/CT after 4 cycles of chemotherapy. These results need to be confirmed in larger, prospective, randomized trials.
Available from: Ingeborg Goethals
- "Positron emission tomography (PET) imaging and the fusion of PET with computed tomography (CT) has emerged as a strong imaging tool for diagnosis of lymphoma and assessment of therapeutic response1234567. However, 18 F-FDG uptake by the thymus in children and young adults may complicate the assessment of mediastinal involvement. "
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ABSTRACT: To investigate the time-dependent changes in (18)F-FDG uptake by the thymus and marrow following combination chemotherapy for lymphoma in a paediatric study population.
Included in the study were 27 paediatric patients who were in complete metabolic remission after chemotherapy and who underwent off-therapy follow-up with serial whole-body PET-CT scans. A total of 142 PET-CT scans were recorded. (18)F-FDG uptake by the thymus and marrow was assessed both visually and semiquantitatively. Visual uptake was scored on the three-dimensional maximum intensity projection of the whole-body PET image according to a three-point scale. For the semiquantitative assessment, standard uptake values were measured. To find a pattern in the (18)F-FDG uptake by the thymus and marrow a moving average technique was applied.
Our time series analysis indicated that the marrow activity was highest at cessation of chemotherapy and declined thereafter. During an off-chemotherapy period of on average 6 months, marrow activity decreased quickly. From 6 months onward, the activity declined more slowly. The posttherapy changes in (18)F-FDG uptake by the thymus were quite different from the changes in uptake by the marrow. The lowest thymic FDG uptake was found at cessation of chemotherapy. Thereafter, thymic activity steadily increased, reached a peak on average 10 months after therapy, and then slowly decreased.
Knowledge of the time-dependent changes in metabolic activity in the thymus and marrow is important to avoid misinterpretation of increased (18)F-FDG uptake as disease in the off-therapy setting.
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ABSTRACT: To the Editor: The HJNM has published a paper and a letter on mucosa associated lymphoid tissue lymphoma where there was no reference to thyroid lymphoma. We do mention here a primary thyroid lymphoma which is a rare malignant tumor, occurring in 1%-5% of thyroid malignancies and in less than 2% of extranodal lymphomas. This tumor is frequently associated with Hashimoto's thyroiditis and is usually a non-Hodgkin's lymphoma (NHL). The most frequent histopathologic types of this lymphoma are extranodal marginal zone B-cell, diffuse large B-cell and marginal zone B cell of mucosa-associated lymphoid tissue (MALT). This lymphoma is most common in the sixth and seventh decade of life and in women, with a male/female ratio of 1:4. The main symptoms are a rapidly enlarging goiter which can cause dysphagia, stridor and hoarseness. Fine needle aspiration biopsy (FNAB) usually suggests NHL, while open biopsy is necessary to confirm the diagnosis. The treatment includes chemo and radiation treatment and the prognosis depends on histological results and the stage of the disease. A correct staging is pivotal in order to evaluate treatment response and the timing of the re-evaluation scans. MALT lymphomas tend to have a more indolent course and have better prognosis compared with the large B-cell types which are associated with an aggressive course. The accuracy of (18)F-FDG-PET/CT in diagnosing lymphomas is well established but up to now, few cases have been reported describing the role of PET in thyroid lymphomas. Such a case was a 67 years old woman with a rapidly growing goiter and laterocervical lymph nodes which were examined by echography and CT. FNAB of a supraclavicular lymph node suggested the presence of a marginal zone B-cell type NHL. The histologic examination of the latero-cervical lymph node showed an altered architecture with nodular aspect and accumulation of lymphoid elements (B phenotype CD20+,CD79a+, BCL6-) with round regular nucleus, without nucleolus. Conclusion: NHL-B marginal zone, nodal (OMS 2001). The examination of right and left thyroid lobe revealed the presence of high colloid cellularity be constituted by lymphoid polymorphic cells mixed with small lymphoid cells and large immunoblasts. In order to stage the disease, the patient underwent (18)F-FDG-PET/CT which showed a massive thyroid involvement with associated high uptake at cervical and mediastinal lymph nodes and on a pulmonary nodule at the upper left lobe.
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ABSTRACT: The purpose of this study was to evaluate prospectively, whether integrated 2-deoxy-2-[(18)F]fluoro-D: -glucose positron emission tomography-computed tomography (FDG-PET-CT) is more accurate for determination musculoskeletal tumors compared with separate interpretation of CT and FDG-PET, because most of the current clinical data come from patients studied with PET.
Eighty patients with newly diagnosed musculoskeletal tumors underwent FDG-PET-CT. CT, FDG-PET, and FDG-PET-CT were interpreted separately to determine the performance of each imaging modality.
Assuming that equivocal lesions are benign, performance of diagnostic tests was as follows: sensitivity, specificity and accuracy for CT alone was 81, 84, 83%, for PET 71, 82, 76, and for PET-CT 80, 83 and 86%. Assuming that equivocal lesions are malignant, sensitivity, specificity, and accuracy for CT was 61, 100, 70%, for PET 69, 100, 79, and for PET-CT 69, 100 and 79%.
Combined FDG-PET-CT reliably differentiates soft tissue and bone tumors from benign lesions. The value of the information provided by FDG-PET-CT for planning surgical procedures must be evaluated in further studies.
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