The role of FDG PET/CT in testicular cancer

Objectives To ascertain the potential role of FDG PET/CT in the management of testicular cancer.

Methods We have reviewed the impact of FDG PET/CT in 42 patients with testicular cancer (17 non-seminomatous germ cell tumours (NSGCT), 19 seminomas, 5 mixed and 1 Mullerian remnant carcinoma). 15 patients underwent FDG PET/CT for primary staging (PS) (10 with equivocal para-aortic lymphadenopathy on CT and 5 to aid decisions for surveillance vs adjuvant chemotherapy in higher risk patients with stage 1 CT scans). 21 patients had indeterminate residual masses on CT following chemotherapy and 6 patients had rising tumour markers with negative CT scans following primary treatment .

Results Of the 10 PS patients with equivocal CT scans, FDG PET/CT downstaged 8 to stage 1 (all disease free between 1 and 5 years follow up) and upstaged 2 patients leading to chemotherapy. All 5 patients with increased risk and stage 1 CT scans had negative PET/CT scans and underwent surveillance. One relapsed at 3 years. Of 21 patients with residual post treatment masses, 7 FDG PET/CT scans were true negative. 14 scans showed FDG activity in the residual masses. 7 were true positive, 2 were treated without further investigation and 5 were false positive (3 seminoma, 2 NSGCT) with uptake that declined on subsequent follow up scans. FDG PET/CT identified sites of recurrence in 4 of 6 patients with rising tumour markers after primary treatment. 2 remained negative on serial follow up scans up to 5 and 27 months later.

Conclusions FDG PET/CT can guide management in testicular cancer patients in whom CT is equivocal at baseline. It may also be helpful in identifying sites of disease relapse when there are raised tumour markers in patients with negative CT scans. False positive scans reduce the reliability of FDG PET/CT for the assessment of residual masses but follow up scans showing declining uptake are reassuring in this scenario