[Prospective validation of a nomogram predictive of a positive initial prostate biopsy]. / Validación prospectiva de un nomograma predictivo de la presencia de cáncer de próstata en pacientes que se someten a biopsia transrectal ecodirigida de 10 cilindros.

INTRODUCTION: Ultrasound-guided transrectal prostate biopsy is currently an indispensable test for diagnosing prostate cancer. Many variables have been related to the presence of cancer in the biopsy (e.g. digital rectal examination [DRE], serum levels of prostate-specific antigen [PSA], free PSA fraction [PSAI/PSAt]). Multivariate mathematical models integrating these variables (nomograms, artificial network models) and improving the capacity to predict tests results are currently available. OBJECTIVE: To develop a nomogram for predicting the probability of a positive prostate biopsy in patients in whom this test is requested, and to use such nomogram in subsequent patients to assess its predictive ability. MATERIAL AND METHODS: A total of 410 consecutive patients undergoing biopsy due to a suspicious digital rectal examination or two serum PSA values higher than 4 ng/mL were enrolled into the study. Ten cores were taken in the prostate biopsy. Patients with both PSA levels >20 ng/ml and prior biopsies were excluded. The following variables were recorded in each patient: age, total PSA, free PSA fraction, prostate volume, transition zone volume, PSA density, PSA density adjusted by transition zone volume, digital rectal examination, and findings suggesting cancer during transrectal ultrasound (hypoechogenic nodules). Prospective external validation was performed with 185 patients who met the same inclusion criteria. Statistical analysis consisted of four phases: a univariate study, a multivariate logistic regression study which was used to develop the nomogram, internal validation, and prospective external validation. S-Plus#r Programme Design and SPSS 12.0#r software was used for the procedure. RESULTS: Variables found to be independently and significantly associated to the presence of cancer included age, digital rectal examination, trnsition zone volume, PSA density, and the presence of hypoechogenic nodules during transrectal ultrasound. Such variables were therefore used to develop the nomogram. The goodness-of-fit of the nomogram was 84%. Validation with an external sample showed a 73% concordance index. CONCLUSION: A nomogram having a satisfactory predictive ability and fit that allows for predicting the prostate biopsy result with a high accuracy rate was developed.

Validación prospectiva de un nomograma predictivo de la presencia de cáncer de próstata en pacientes que se someten a biopsia transrectal ecodirigida de 10 cilindros / Prospective validation of a nomogram predictive of a positive initial prostate biopsy

Introducción: la biopsia prostática transrectal ecodirigida es, hasta la fecha, la prueba ineludible en el diagnóstico del cáncer de próstata. Numerosas variables se han asociado de manera univariante y multivariante a la presencia de cáncer en la biopsia (tacto rectal [TR], antígeno prostático específico (PSA) sérico, fracción libre del PSA [PSAl/PSAt], etc.). Actualmente están en boga modelos matemáticos multivariantes que integran estas variables y que mejoran la capacidad predictiva del resultado de la prueba. Objetivo: desarrollar un modelo matemático particular que estime la probabilidad de los pacientes, a quienes se indique una biopsia de próstata, de que esta sea positiva. Del mismo modo aplicarlo a pacientes ulteriores y evaluar su capacidad predictiva. Material y método: incluimos 410 pacientes biopsiados de manera consecutiva por sospecha en el TR o por dos PSA séricos mayores de 4 ng/ml. La biopsia prostática se realizaba con toma de 10 cilindros. Se excluyeron los pacientes con PSA > 20 y aquellos con biopsias previas. Las variables registradas en cada paciente eran: edad, PSA total- fracción libre de PSA, volumen prostático, volumen de la zona transicional, densidad del PSA, densidad del PSA respecto de la zona transicional, TR, presencia de hallazgos sugestivos de cáncer durante la ecografía transrectal (nódulos hipoecoicos). La validación externa prospectiva se llevó a cabo con 185 pacientes con idénticos criterios de inclusión. El análisis estadístico consta de cuatro fases: un estudio univariante, uno multivariante por regresión logística mediante el cual se desarrolla el nomograma, una validación interna y una validación externa prospectiva. Se utilizaron los programas S-Plus(R) y SPSS 12.0(R) para el desarrollo matemático. Resultados: las variables que, en el modelo multivariante, se asociaban de manera independiente y significativa a la presencia de cáncer fueron: la edad, el TR, el volumen de la zona transicional, el PSA-densidad y la presencia de nódulos hipoecoicos durante la ecografía transrectal. Con dichas variables se desarrolló un modelo matemático gráfico, nomograma; dicho nomograma tenía una bondad de ajuste del 84%. Se procedió a la validación con una muestra externa en el que objetivamos un índice de concordancia del 73%. Conclusión: desarrollamos una herramienta matemática con una capacidad predictiva y ajuste satisfactorios que permite, con una alta tasa de aciertos, conocer el resultado de la biopsia de próstata(AU)

Introduction: Ultrasound-guided transrectal prostate biopsy is currently an indispensable test for diagnosing prostate cancer. Many variables have been related to the presence of cancer in the biopsy (e.g. digital rectal examination [DRE], serum levels of prostate-specific antigen [PSA], free PSA fraction [PSAI/PSAt]). Multivariate mathematical models integrating these variables (nomograms, artificial network models) and improving the capacity to predict tests results are currently available. Objective: To develop a nomogram for predicting the probability of a positive prostate biopsy in patients in whom this test is requested, and to use such nomogram in subsequent patients to assess its predictive ability. Material and methods: A total of 410 consecutive patients undergoing biopsy due to a suspicious digital rectal examination or two serum PSA values higher than 4 ng/mL were enrolled into the study. Ten cores were taken in the prostate biopsy. Patients with both PSA levels >20 ng/ml and prior biopsies were excluded. The following variables were recorded in each patient: age, total PSA, free PSA fraction, prostate volume, transition zone volume, PSA density, PSA density adjusted by transition zone volume, digital rectal examination, and findings suggesting cancer during transrectal ultrasound (hypoechogenic nodules). Prospective external validation was performed with 185 patients who met the same inclusion criteria. Statistical analysis consisted of four phases: a univariate study, a multivariate logistic regression study which was used to develop the nomogram, internal validation, and prospective external validation. S-Plus#r Programme Design and SPSS 12.0#r software was used for the procedure. Results: Variables found to be independently and significantly associated to the presence of cancer included age, digital rectal examination, trnsition zone volume, PSA density, and the presence of hypoechogenic nodules during transrectal ultrasound. Such variables were therefore used to develop the nomogram. The goodness-of-fit of the nomogram was 84%. Validation with an external sample showed a 73% concordance index. Conclusion: A nomogram having a satisfactory predictive ability and fit that allows for predicting the prostate biopsy result with a high accuracy rate was developed(AU)

[A preliminar mathematical model for patients with a previous negative prostate biopsy]. / Desarrollo de un Modelo Matemático preliminar para la detección de cancer de próstata en los pacientes con biopsias prostáticas de repetición.

INTRODUCTION AND OBJECTIVES: It is usual to identify patients with a negative prostate biopsy who are still at risk of prostate cancer. We try to analyse if the classical variables used in the prostate cancer screening are useful for those patients with a previous negative prostate biopsy, and if there is a possibility for making a nomogram witch would help us in the decision to repeat the biopsy. MATERIAL AND METHODS: We studied 179 patients with at least 1 initial negative biopsy. At each biopsy session we recorded: Patient age, serum prostate specific antigen (PSA), free PSA/total PSA, PSA slope, digital rectal examination, prostate volume, PSA density, cancer suspicion in previous transrectal ultrasounds findings, number of negative cores previously obtained, history of precarcinomatous lesions and time between biopsies. Through Logistic regression analysis we determined the association of each variable a positive biopsy. A nomogram was constructed using all variables and discrimination was calculated as the concordance index. RESULTS: Overall 46% of patients had cancer at the repeated biopsy session. In the univariate analysis: Age, digital rectal examination, prostate volume, PSA density, cancer suspicion in ultrasounds findings, and precarcinomatous lesions were associated with repeat positive biopsy for cancer (all p <0.05). In the multivariate study, age, digital rectal examination, prostate volume and history of precarcinomatous lesions were associated with repeat positive biopsy. A nomogram was constructed that had a concordance index of 0.80.