An external validation of the Candiolo nomogram in a cohort of prostate cancer patients treated by external-beam radiotherapy

Abstract

Backgroundthe aim of this study is to perform an external validation for the Candiolo nomogram, a predictive algorithm of biochemical and clinical recurrences in prostate cancer patients treated by radical Radiotherapy, published in 2016 on the journal “Radiation Oncology”.Methods561 patients, treated by Radiotherapy with curative intent between 2003 and 2012, were classified according to the five risk-classes of the Candiolo nomogram and the three risk-classes of the D’Amico classification for comparison. Patients were treated with a mean prostatic dose of 77.7 Gy and a combined treatment with Androgen-Deprivation-Therapy in 76% of cases. The end-points of the study were biochemical-Progression-Free-Survival (bPFS) and clinical-Progression-Free-Survival (cPFS). With a median follow-up of 50 months, 56 patients (10%) had a biochemical relapse, and 30 patients (5.4%) a clinical progression. The cases were divided according to D’Amico in low-risk 21%, intermediate 40%, high-risk 39%; according to Candiolo very-low-risk 24%, low 37%, intermediate 24%, high 10%, very-high-risk 5%. Statistically, the Kaplan-Meier survival curves were processed and compared using Log-Rank tests and Harrell-C concordance index.ResultsThe 5-year bPFS for the Candiolo risk-classes range between 98% and 38%, and the 5-year cPFS between 98% and 50% for very-low and very-high-risk, respectively. The Candiolo nomogram is highly significant for the stratification of both bPFS and cPFS (P < 0.0001), as well as the D’Amico classification (P = 0.004 and P = 0.001, respectively). For the Candiolo nomogram, the C indexes for bPFS and cPFS are 75% and 80%, respectively, while for D'Amico classification they are 64% and 69%, respectively. The Candiolo nomogram can identify a greater number of patients with low and very-low-risk prostate cancer (61% versus 21% according to D'Amico) and it better picks out patients with high and very-high-risk of recurrence, equal to only 15% of the total cases but subject to 48% (27/56) of biochemical relapses and 63% (19/30) of clinical progressions.Conclusionsthe external validation of the Candiolo nomogram was overall successful with C indexes approximately 10% higher than the D'Amico control classification for bPFS and cPFS. Therefore, its clinical use is justified in prostate cancer patients before radical Radiotherapy.Trial registrationretrospectively registered.

Comparison of Different Machine Learning Models in Prediction of Postirradiation Recurrence in Prostate Carcinoma Patients

“…The Candiolo nomogram appeared to be better and capable of predicting PC recurrence following a patient's radiotherapy than the traditional D'Amico risk classes [33]. An external validation study of this nomogram which was recently conducted also indicated that clinical use of Candiolo nomograms could be justified in PC patients prior to receiving radical radiotherapy [34].…”

“…D'Amico's risk classification first suggested a risk stratification system based on threegroups in order to predict a 2-year PSA failure rate following radical prostatectomy or EBRT. It categorizes patients into low, intermediate, and high risk groups based on their initial PSA, clinical stage, and biopsy GS [29,34]. In order to develop an algorithm to predict recurrence in PC patients treated with radical radiotherapy, Gabriele et al carried out a Candiolo nomogram that separated patients according to five risk groups that incorporated age, pretreatment PSA, clinical-radiological staging, GS, and the percentage of positive cores from the biopsy.…”