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

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 (¹⁸F-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.

Fifty-five patients (mean age 56.6 y) diagnosed with penile squamous cell carcinoma were prospectively evaluated from 2012 to 2014. All subjects underwent ¹⁸F-FDG PET/CT before treatment and were regularly followed after surgery.

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 ¹⁸F-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).

This study showed promising results on the use of ¹⁸F-FDG PET/CT as a prognostic tool for PC, using specific cutoff values of pSUV_max and nSUV_max.