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

Abstract

Purpose: Penile 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 ( 18 F-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. Methods: Fifty-five patients (mean age 56.6 y) diagnosed with penile squamous cell carcinoma were prospectively evaluated from 2012 to 2014. All subjects underwent 18 F-FDG PET/CT before treatment and were regularly followed after surgery. Results: Out 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 18 F-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). Conclusion: This study showed promising results on the use of 18 F-FDG PET/CT as a prognostic tool for PC, using specific cutoff values of pSUV max and nSUV max .