New risk classification system proposed for prostate cancer

By Afsaneh Gray, medwireNews Reporter

US researchers have put forward a risk stratification system for patients with intermediate-risk prostate cancer undergoing dose-escalated external-beam radiation therapy (EBRT).

"We have shown that intermediate-risk PCa [prostate cancer] is a heterogeneous disease that can be stratified into favorable and unfavorable risk groups that have markedly different prognoses based on clinical and pathologic factors that are not currently included in most risk-stratification systems," they comment in European Urology.

Their study included 1204 patients with intermediate-risk prostate cancer - defined according to National Comprehensive Cancer Network criteria - who were treated with dose-escalated EBRT between 1992 and 2007, and then followed up for a median period of 71 months. All patients had complete biopsy information.

The researchers classified patients as having unfavorable intermediate risk if they had any of the following factors: primary Gleason pattern of 4; percentage of positive biopsy cores (PPBC) 50% or greater; or multiple intermediate-risk factors (clinical stage T2b-c, prostate specific antigen (PSA) 10-20, or Gleason score 7). All other patients were classified as having favorable intermediate risk.

All three factors were independent predictors of distant metastasis, with hazard ratios (HRs) of 3.26, 2.72, and 2.20 for primary Gleason pattern of 4, PPBC of 50% or above, and multiple intermediate-risk factors, respectively.

Prostate-cancer-specific mortality was independently predicted by primary Gleason pattern 4 (HR=5.23), and PPBC of 50% or greater (HR=4.08), but not by multiple intermediate-risk factors (HR=1.74).

Lead researcher Michael Zelefsky (Memorial Sloan-Kettering Cancer Center, New York) and colleagues found that patients with unfavorable intermediate-risk prostate cancer had a 2.4-fold increase in PSA recurrence, a 4.3-fold increase in distant metastasis, and a 7.4-fold increase in prostate-cancer-specific mortality. This was despite the fact that they were nearly twice as likely to receive androgen-deprivation therapy as those with favorable intermediate-risk prostate cancer.

"Given this clinical heterogeneity, a uniform treatment paradigm is unlikely to be the optimal approach for intermediate-risk PCa," they suggest, and add that this is particularly important for determining which patients are suitable for treatment with androgen-deprivation therapy.

The researchers did find that androgen-deprivation therapy resulted in significantly lower rates of distant metastasis and prostate-cancer-specific mortality in patients with unfavorable intermediate-risk, but not favorable intermediate-risk, cancer; however, they caution that these results are not statistically certain.

Nonetheless, they suggest that "omitting short-term ADT [androgen-deprivation therapy] may be a reasonable option for patients with FIR [favorable intermediate-risk] disease undergoing dose-escalated EBRT, especially in older men or those with cardiac comorbidities."

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