18F-FDG PET/CT as a prognostic factor in penile cancer

PurposePenile cancer (PC) is a rare neoplasm with an aggressive behavior and variable prognosis. Lymph node (LN) involvement and pathological features of the primary lesion have been proven to be the most important survival factors. Positron emission tomography/computed tomography with fluorodeoxyglucose labelled with fluorine-18 (F-18-FDG PET/CT) provides information on tumor staging and works as a prognostic factor, with promising results in other carcinomas. The aim of the present study is to evaluate PET/CT as a prognostic factor in PC.MethodsFifty-five patients (mean age 56.6 y) diagnosed with penile squamous cell carcinoma were prospectively evaluated from 2012 to 2014. All subjects underwent F-18-FDG PET/CT before treatment and were regularly followed after surgery.ResultsOut of the 53 patients selected, 17 (32.1%) had localized disease (cT1-2) and 24 (45.3%) had palpable nodes (cN+). Partial penile amputation was performed in 38 patients (71.7%) and inguinal lymphadenectomy (LND) in 30 (56.6%). From the LND group, 16 (53.3%) presented with positive neoplastic cells (pN+). Patients with more aggressive disease had a significantly (p=0.019) higher F-18-FDG tumor uptake (pSUV(max)), while inguinal LN uptake (nSUV(max)) was able to recognize metastatic LN (p=0.039). Some pathological prognostic features, when presented, have shown significant changes in pSUV(max) values. Receiver operating characteristic (ROC) curves were performed and specific cutoff values of pSUV(max) were evaluated to determine sensitivity and specificity. Regarding regional LNs, PET/CT presented a 76.2% accuracy in cN+ patients. After a 39-month follow up, pSUV(max) of 16.6 (p=0.0001) and nSUV(max) of 6.5 (p=0.019) were established as the ideal values to predict cancer-specific survival. The multivariate analysis confirmed nSUV(max) as a predictor for LN metastasis (p=0.043) and pSUV(max) as a mean to estimate survival rate (p=0.05).ConclusionThis study showed promising results on the use of F-18-FDG PET/CT as a prognostic tool for PC, using specific cutoff values of pSUV(max) and nSUV(max).