Early prediction of response to chemotherapy and survival in malignant pleural mesothelioma using a novel semiautomated 3-dimensional volume-based analysis of serial 18F-FDG PET scans.

UNLABELLED: The aim of chemotherapy for mesothelioma is to palliate symptoms and improve survival. Measuring response using CT is challenging because of the circumferential tumor growth pattern. This study aims to evaluate the role of serial (18)F-FDG PET in the assessment of response to chemotherapy in patients with mesothelioma. METHODS: Patients were prospectively recruited and underwent both (18)F-FDG PET and conventional radiological response assessment before and after 1 cycle of chemotherapy. Quantitative volume-based (18)F-FDG PET analysis was performed to obtain the total glycolytic volume (TGV) of the tumor. Survival outcomes were measured. RESULTS: Twenty-three patients were suitable for both radiological and (18)F-FDG PET analysis, of whom 20 had CT measurable disease. After 1 cycle of chemotherapy, 7 patients attained a partial response and 13 had stable disease on CT assessment by modified RECIST (Response Evaluation Criteria in Solid Tumors) criteria. In the 7 patients with radiological partial response, the median TGV on quantitative PET analysis fell to 30% of baseline (range, 11%-71%). After 1 cycle of chemotherapy, Cox regression analysis demonstrated a statistically significant relationship between a fall in TGV and improved patient survival (P = 0.015). Neither a reduction in the maximum standardized uptake value (P = 0.097) nor CT (P = 0.131) demonstrated a statistically significant association with patient survival. CONCLUSION: Semiquantitative (18)F-FDG PET using the volume-based parameter of TGV is feasible in mesothelioma and may predict response to chemotherapy and patient survival after 1 cycle of treatment. Therefore, metabolic imaging has the potential to improve the care of patients receiving chemotherapy for mesothelioma by the early identification of responding patients. This technology may also be useful in the assessment of new systemic treatments for mesothelioma.

F-18 FDG uptake associated with Elastofibroma dorsi.

A patient with a history of colon carcinoma and computed tomography (CT) evidence suggestive of a liver metastasis underwent an F-18 FDG PET scan. The PET scan confirmed a metastasis in the left lobe of the liver. The study also demonstrated bilateral symmetric uptake involving the inferior subscapular regions. Correlation with the previous CT showed this to correspond to bilateral elastofibroma dorsi, which had been prospectively reported on the CT. Elastofibroma dorsi is a rare benign mass consisting of fibroelastic tissue and fat. It has been previously described on PET, CT, ultrasound, and magnetic resonance imaging (MRI). On CT, the masses are of soft tissue density, similar to adjacent musculature, and may contain linear areas of low density secondary to fat. On MRI, elastofibroma dorsi has been shown to have variable enhancement, which may reflect increased vascularity of the lesion. In this case, the masses demonstrated low-grade diffuse F-18 FDG uptake.

Discordant response to chemotherapy detected by PET scanning: unveiling of a second primary cancer.

Positron emission Tomography (PET) is commonly used to stage malignancies and monitor response to treatment. This report describes two patients, one with metastatic breast cancer and the other with aggressive non-Hodgkin's lymphoma (NHL) whose responses to treatment were monitored by serial computed tomography and PET scans. In both cases after completion of systemic chemotherapy, repeat PET scanning revealed residual metabolically active tissue at the base of the neck. Because of differential therapeutic response, the possibility of different pathologic lesions was raised. In each case, further investigation with an ultrasound scan and needle biopsy revealed carcinoma of the thyroid. Both patients were subsequently treated with definitive surgery. In both described cases, a second primary malignancy was found that affected further management and in the second patient altered prognosis. This report concludes that residual metabolically active tissue on PET scans after treatment is not necessarily resistant primary disease. A mixed response requires further investigation, particularly in the case of persisting solitary abnormalities in the neck.