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| |  Fluorodeoxyglucose-PET May Identify Occult Metastases: Presented at ASCO-GU By Fred Gebhart SAN FRANCISCO -- March 9, 2010 -- A small phase 2 study suggests that 17-fluorodeoxyglucose positron-emission tomography (FDG-PET) may help identify occult masses after orchiectomy for stage 1 seminoma, said researchers here at the 2010 Genitourinary Cancers Symposium (ASCO-GU). Current treatment standards for stage 1 seminoma call for adjuvant radiotherapy, adjuvant chemotherapy, or surveillance after orchiectomy. Because all 3 options offer cure rates of 90% to 100%, avoiding unnecessary treatment and the associated toxicity has become a priority for clinicians and researchers as well as for patients. Computed tomography (CT) is often used to identify metastases in the pelvis, abdomen, and thorax, but a small percentage of patients experience relapse despite negative CT findings. FDG-PET has already been shown to identify residual masses after chemotherapy in advanced seminoma, prompting researchers to investigate the technique in less-advanced disease. Yohan Loriot, MD, Institut Gustave Roussy, Villejuif, France, presented the findings here on March 7. Dr. Loriot and colleagues performed an FDG-PET scan on 56 patients with stage 1 seminoma after orchiectomy and a negative CT scan of the pelvis, abdomen, and thorax. Patients were scanned between March 2004 and June 2008 and followed for a mean of 40 months. Five of the patients had a positive FDG-PET, all with abnormalities in the retroperitoneum. All of these positive patients were treated with immediate chemotherapy. One patient had a doubtful FDG-PET, relapsed, and was also treated with adjuvant chemotherapy. None of the patients showed any further signs of relapse. Of the 50 FDG-PET-negative patients, 7 requested adjuvant chemotherapy and 2 requested adjuvant radiotherapy. None of the 9 treated patients relapsed. Of the remaining 41 FDG-PET-negative patients, 5 relapsed with tumours in the retroperitoneum at 6, 8, 10, 16, and 18 months. One of the 5 was given radiotherapy, and the other 4 had chemotherapy; all remained disease free throughout the study period. The 2-year relapse rate for FDG-PET-negative patients who did not request adjuvant treatment was 12.29%. With a median follow up of 40 months, the survival rate was 100%. Researchers concluded that FDG-PET could help most postorchiectomy patients with stage 1 seminoma avoid unnecessary adjuvant treatment and the associated toxicities. Although a negative scan does not offer 100% assurance that the patient is free from occult metastases, FDG-PET was able to identify 55% (6 of 11) of patients with a disseminated seminoma that was not detected by conventional CT scan. The conference is sponsored by the American Society of Clinical Oncology (ASCO), the American Society for Therapeutic Radiation Oncology (ASTRO), and the Society of Urologic Oncology (SUO). [Presentation title: Stage 1 Seminoma: Can 17Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) Predict Occult Dissemination: Preliminary Results of a Phase II Study. Abstract 263]
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