What’s new in prostate cancer screening and prevention?

Zdroj:
Cleveland Clinic Journal of Medicine

Prostate cancer is extremely common but causes death in only a minority of men in whom it develops, facts that raise issues regarding screening and treatment morbidity. Two large trials of screening with prostate-specific antigen (PSA) measurements came to seemingly opposite conclusions. Furthermore, a large trial of selenium and vitamin E found that these agents have no value as preventive agents.

- Rather than relying on PSA screening alone, we should stratify the risk of prostate cancer on the basis of race, age, PSA level, family history, findings on digital rectal examination, whether the patient has ever undergone a prostate biopsy, and whether the patient is taking finasteride (Proscar). A simple online tool is available to do this.

-We used to think the cutoff PSA level that had high sensitivity and specificity for finding cancer was 4 ng/mL. However, in the PCPT, 6.6% of men with PSA levels below 0.5 ng/mL were found to have cancer, and 12.5% of those cancers were high-grade. Of those with PSA levels of 3.1 to 4.0 ng/mL, 26.9% had cancer, and 25.0% of the cancers were high-grade. These data demonstrate that there is no PSA level below which risk of cancer is zero, and that there is no PSA cutoff with sufficient sensitivity and specificity to be clinically useful.




-The PCPT risk calculator (http://deb.uthscsa.edu/URORiskCalc/Pages/uroriskcalc.jsp)
 is a wonderful tool that came out of that study. It uses seven variables—race, age, PSA level, family history of prostate cancer, findings on digital rectal examination, whether the patient has ever undergone a prostate biopsy, and whether the patient is taking finasteride—and calculates the patient’s risk of harboring prostate cancer and, more important, the risk of having high-grade prostate cancer. This tool allows estimation of individual risk and helps identify who is at risk of cancer that may require therapy.

-Men with a higher body mass index have lower PSA levels.

-New markers under study

• A number of new biological markers probably will improve our ability to detect prostate cancer, although they are not yet ready for widespread use.

• Urinary PCA3. Prostate cancer gene 3 (PCA3) codes for a messenger RNA that is highly overexpressed in the urine of men with prostate cancer. Urine is collected after prostate massage. Marks et al14 reported that PCA3 scores predicted biopsy outcomes in men with serum PSA levels of 2.5 ng/mL or higher.

• Serum EPCA-2 (early prostate cancer antigen 2) is another candidate marker undergoing study.

• Gene fusions, specifically of TRMPSS2 and the ETS gene family, are detectable in high levels in the urine of some men with prostate cancer, and appear to be very promising markers for detection.

• Metabolomics is a technique that uses mass spectroscopy to detect the metabolic signature of cancer. Sreekumar et al15 identified sarcosine as a potential marker of prostate cancer using this technique.

Genetic tests: Not yet

Some data suggest that we can use genetic tests to screen for prostate cancer, but the tests are not yet as good as we would like.



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