Use of a nomogram for predicting positive PSMA-PET scan in patients with prostate cancer recurrence

A nomogram has been developed to predict PSMA-PET scan results for recurrent prostate
cancer. Medical nomograms use biologic and clinical variables, such as tumor grade and patient
age to graphically depict a statistical predictive model that generates a probability of a clinical
event. The nomogram represents an easy tool in the decision-making process of recurrent prostate cancer.

The treatment of prostate cancer patients with PSA failure after radiation therapy or radical
prostatectomy treatments is currently changing. Salvage therapies based on the hypothetical
risk of local versus systemic recurrence represented the standard practice for many years.

However, models based on clinical parameters cannot reliably predict recurrence sites and the
extent of metastatic disease. Location and number of lesions are parameters influencing
prognosis and represent key information for planning personalized treatment. The application
of new-generation imaging in prostate cancer significantly improved the clinical decision-
making process, leading to novel “imaging-guided” therapeutic approaches. These strategies
have the potential to improve patient outcome, delaying administration of systemic therapies.
PSMA-PET scans have emerged as the most accurate novel imaging procedure to restage
prostate cancer due to its high accuracy to correctly detect and localize prostate cancer lesions.

However, PSMA-PET imaging is not exempt from false negative results, especially in the early
stage of recurrence, when the tumor burden and PSA levels are low.
Moreover, recurrent or persistent prostate cancer patients represent a highly heterogeneous
group with different tumor sites, burdens, aggressiveness, and prognoses. Thus, patient
selection criteria for PSMA-PET are essential to optimize nuclear medicine resources that
cannot satisfy the demand for PSMA-PET scans.

Recently Lorenzo Bianchi et al., University of Bologna, proposed a nomogram to provide a
prediction model to identify patients at high risk of positive PSMA-PET results for recurrent
prostate cancer. The nomogram exhibited excellent characteristics on external validation. The
incidence of a false negative scan can be reduced if PSMA-PET is performed when the predicted
probability is ≥20%.
European Urology Oncology 2021 Dec. doi:org/10.1016/j.euo.2021.12.002