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Case Report |
1 Western Australia PET/Cyclotron Service, Sir Charles Gairdner Hospital,
Nedlands, Western Australia 6009, Australia.
2 Department of Nuclear Medicine, Royal Perth Hospital, Perth, Western Australia
6000, Australia.
Received October 17, 2003; accepted after revision November 25, 2003.
Address correspondence to N. P. Lenzo
(Nat.Lenzo{at}health.wa.gov.au).
Case Report
A 28-year-old man presented with malaise, weight loss, and a lump in the left neck typical for an enlarged supraclavicular lymph node. He had been treated 4 years earlier for a stage III metastatic seminoma. He had been left with residual paraaortic lymphnode masses in the mediastinum and paraaortic region of the abdomen. These masses had remained stable on the basis of CT criteria since completion of treatment.
Excision biopsy of the supraclavicular lymph node revealed recurrent seminoma. A repeat CT scan showed persistent but unchanged mediastinal and paraaortic adenopathy. The liver and spleen appeared normal on CT (Figs. 1A and 1B). A staging FDG PET study was performed (370 MBq of FDG, images obtained 1 hr after administration on an Allegro GSO PET camera [Philips Medical Systems]; 4-min emission; 2-min transmission per bed; blood glucose level, 92 mg/dL at the time of administration) to more accurately delineate the extent of active disease. The PET scan revealed extensive metabolically active sites of likely recurrent disease present in the paraaortic, mediastinal, and cervical lymph nodes with diffuse splenic radiotracer uptake and several osseous sites of likely disease (Fig. 1C). On the basis of the PET study and the result of the biopsy, the patient was started on salvage platinum-based chemotherapy, and a repeat PET study was scheduled for 2 months after the beginning of chemotherapy.
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The repeat PET scan (370 MBq of FDG, images obtained 1 hr after administration on the Allegro GSO PET camera; 4-min emission; 2-min transmission per bed; blood glucose level, 104 mg/dL at the time of administration) revealed a complete metabolic response to treatment with all previously documented sites of likely disease now showing normal physiologic FDG uptake (Figs. 1D and 1E). In particular, the previously documented mediastinal, paraaortic, and splenic uptake was no longer evident. The patient had also responded clinically with resolution of systemic symptoms.
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Discussion
This case is of interest for several reasons. It shows the potential utility and sensitivity of FDG PET in the restaging of metastatic seminoma and in assessing residual masses after therapy for metastatic seminoma. Also, according to FDG PET criteria, the spleen was diffusely infiltrated, but it had a normal CT appearance. A biopsy was not performed to confirm disease because of the potential risk to the patient, and the appearances were very likely those of widespread metastatic involvement including splenic disease. The patient's clinical response to salvage chemotherapy and the complete metabolic response of the sites of active nodal and splenic tissue FDG uptake suggest that the initial PET study was depicting active metastatic disease.
Although splenic metastases are supposedly rare, this case raises the question of how often extranodal disease may be present in metastatic seminoma yet not visualized by anatomic imaging methods alone. Whether this question in fact alters prognosis has not been determined.
Finally the rapid metabolic response to therapy visualized on FDG PET may be significant. Other studies have suggested that the rapid response is a good prognostic feature both in seminoma [6] and in other nontesticular cancers [7, 8]. This patient will probably continue to have residual masses, which again make early assessment of relapse on CT difficult in the future. However, FDG PET, which assesses the metabolism of possible tumor in the residual mass, is likely to continue to be useful and should be considered as the primary method of reassessing the same patient for potential relapse.
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