Diagnóstico precoz del cáncer de próstata en pacientes con sintomatología prostática mediante tacto rectal, antígeno específico prostático, ecografía tumorrectal y densidad-psa

Situación epidemiológica del cáncer de próstata en España

Prostate cancer is the third most frequent neoplasms in Spanish men and the third cause of cancer death. Incidence grows up with the increase of age. 90% of cases are diagnostic in people over 65 years old. Etiology is quite unknown and has been associated with environmental exposure, life style, family sign and genetic factors. In 2002 mortality rate was 21.5/ 100.000 (situated among the lowest in Europe), with more than 5.000 deaths. Trend of mortality has grown up until 1998, from this year it has decreased due to improve on diagnostic and treatment. In order to study prostate cancer incidence we find a difficulty due to shortage of population cancer register. Estimations have found incidence rates of 45.33/100.000 which are among the lowest in Europe. Annual incidence of prostatic cancer has grown up in all Spanish registers, not only improve in register systems explains it, but also the development of diagnosis tests with a higher survival from the beginning of 90s (86% the first year after diagnosis and 65,5% five years after diagnosis), similar to other European countries. Blow up the cancer register system is necessary to know the incidence and prevalence, to assess survival and effectiveness of screening programs and to improve the knowledge of risk factors.

[Diagnostic algorithm based on a multivariate model to reduce the percentage of negative prostatic biopsies in patients with changed PSA or suspicious rectal palpation]

OBJECTIVES

To determine what tests have a better diagnosis utility in patient with suspected prostate cancer due to PSA equal or greater than 4 ng/ml or abnormal digital rectal examination in order to reduce the number of negative prostate biopsies.

MATERIAL AND METHODS

We carried out a ultrasound-guided sextant transrectal biopsy in a series of 400 patient with prostate-specific antigen (PSA) levels equal or greater than 4 ng/ml or abnormal digital rectal examination. All patients had also transrectal rectal ultrasonography to value the echographic prostatic characteristics and the prostatic volume, and a free PSA determination.

RESULTS

The free/total PSA ratio (PSAl) and the PSA density (DPSA) were the most powerful predictors of prostate cancer, both with a 66% sensitivity and a 70% specificity (at a 0.15 cutoff), followed by the total PSA (PSAt), the digital rectal examination and the hypoechogenic prostatic nodules. We constructed a logistic multivariate model with these data. The outcome variable of logistic model was the probability of having prostate cancer. The significant predictive variables of the model were the PSAl, the DPSA, the digital rectal examination and the presence and extension of hypoechogenic prostatic. This model had a 81% sensitivity and 79% specificity at a 0.24 probability cutoff. We considered a 0.1 probability cutoff to reduce the number of false negative. With this strategy the sensitivity was 94% and the specificity 54%. If we had applied this model to the patient of our series then, we would be able to avoid prostate biopsy in 164 cases (the 41% of the patient), leaving only 7 cases without diagnosis of prostate cancer.

CONCLUSIONS

The most effective combination parameters were the digital rectal examination, PSAl, presence and extension of prostatic hypoechogenic zones and DPSA. This combination allows us to diminish the percentage of negative prostate biopsy in patient with prostate-specific antigen (PSA) levels equal or greater than 4 ng/ml or abnormal digital rectal examination without significantly descending the number of detected prostate cancers.