Many men diagnosed with prostate cancer harbor tumors that have very little or no risk to harm their life and immediate treatment can be safely delayed. Therefore, active surveillance is the preferred management for men with low risk cancer and endorsed by various guidelines.
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Despite wide acceptance of active surveillance as a viable option for men with low risk cancer, the details regarding follow-up and triggers for intervention are not standardized. Prostate biopsy remains the most accepted criteria to trigger treatment for men on active surveillance. Most published reports examining men on active surveillance, advocate confirmatory prostate biopsy within one year of initiating active surveillance based on studies suggesting 23-38% of men with low risk prostate cancer may harbor high grade tumors detected on second biopsy. However, prostate biopsy is associated with known risks, including infectious complications, hematuria, hematospermia, and pain. In addition, serial biopsies for men on active surveillance may be associated with an increasing risk of infectious complications with each additional biopsy. Therefore, a risk-adapted approach to guide active surveillance follow-up based on patient, pathologic and imaging characteristics can reduce the number of prostate biopsies.
During the past decade, multiparametric MRI has emerged as a promising tool to diagnose prostate cancer by helping guide prostate biopsies. Most studies report improvement in the detection rate of higher Gleason grade cancer using MRI-targeted biopsy techniques compared to systematic biopsy. Therefore, it is reasonable to hypothesize that MRI data can be used to improve risk stratification for men considering active surveillance. Specifically, we evaluated if combining MRI data and pathologic characteristics may select men with a low risk of reclassification to higher Gleason grade; thereby sparing these men unnecessary biopsy.
We included 392 men with Gleason score 6 prostate cancer on initial biopsy undergoing confirmatory biopsy prior to enrollment into active surveillance. Of note, all men being considered for active surveillance at our institution are recommended to undergo confirmatory biopsy. We assessed the impact of initial biopsy pathologic parameters (percent positive cores, percent cancer in positive cores, and total tumor length), prostate-specific antigen density, and MRI identification of a dominant lesion prior to confirmatory biopsy on high-grade cancer (Gleason grade ≥7) on confirmatory biopsy.
Overall, all predictors were significantly associated with high-grade cancer on confirmatory biopsy on univariate analysis. However, only prostate-specific antigen density and total tumor length on initial biopsy were significantly associated with reclassification. A decision analytic model using this model to select patients for confirmatory biopsy would provide a higher net benefit than performing confirmatory biopsy in all patients, across a wide range of threshold probabilities.
Our study demonstrated an 11% rate of reclassification to higher Gleason grade cancer among men on active surveillance. We demonstrated that clinical and pathologic characteristics can be used to select patients that have an increased risk of reclassification and using this risk-adaptive strategy provides a higher net benefit that performing confirmatory biopsies in all patients. Furthermore, we showed MRI can help detect higher Gleason grade cancer; however, the usefulness of MRI was mitigated by incorporating other diagnostic characteristics in the decision to perform a confirmatory biopsy. However, a validation study using a prospective cohort with standardized MRI acquisition and reporting protocol may help clarify whether MRI has a predictive role in the context of our multivariable model. Finally, while the multivariable analysis did not demonstrate MRI to be predictive of results on confirmatory biopsy, MRI may still be useful in this population, both as a baseline study as well as a guide for targeted biopsy to monitor men on active surveillance.
Written By: Behfar Ehdaie, MD MPH
J Urol. 2015 Jul 17. pii: S0022-5347(15)04410-9. doi: 10.1016/j.juro.2015.07.078. [Epub ahead of print]
Satasivam P1, Poon BY2, Ehdaie B1, Vickers AJ2, Eastham JA3.
1 Department of Surgery, Urology Service, Memorial Sloan Kettering Cancer Center, New York, New York.
2 Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, New York.
3 Department of Surgery, Urology Service, Memorial Sloan Kettering Cancer Center, New York, New York.