One of the main reasons that PNI is not an independent predictor of recurrence after radical prostatectomy is its close link to pathologic stage. Some have argued, however, that PNI may be more useful in predicting risk in patients treated with radiation therapy since precise pathologic staging is not available.

In the October issue of the Journal of Radiation Oncology - Biology - Physics, Beard, and colleagues from Dana Farber presented their contemporary experience with 517 consecutive patients treated with external beam radiotherapy for low and intermediate-risk prostate cancer. The presence or absence of PNI was evaluated by a urologic pathologist and compared to prostate cancer-specific mortality.

After a median follow-up of nearly 5 years, 16% (84/517) of patients had died, of which 18% (15/84) died of prostate cancer. Interestingly, the only predictor of cancer-specific mortality in multivariate analysis was the presence of PNI (p = 0.012), with an estimated 8-year cancer-specific mortality of 14% compared with 5% in patients without perineural invasion. (p = 0.0008).

Not uncommonly, patients with low and intermediate risk prostate cancer are pathologically upstaged after radical prostatectomy. Unfortunately, currently few clinical or pathologic criteria exist to sub-stratify patient risk if these patients are treated with a non-extirpative modality such as external beam radiotherapy or brachytherapy. Parameters commonly used include the percent of positive biopsies and the PSA velocity before diagnosis (if greater or less than 2 ng/ml/year).

The data from this small study show that the presence of perineural invasion on biopsy may predict prostate cancer-related death, perhaps suggesting that these patients may not be optimal brachytherapy candidates and may consider a short course of androgen deprivation therapy when treated with radiotherapy.

Clair Beard, Delray Schultz, Marian Loffredo, Kerri Cote, Andrew A. Renshaw, Mark D. Hurwitz and Anthony V. D'Amico

Int J Radiat Oncol Biol Phys.66(2):403-7. 2006 Oct 1

Written by Ricardo Sånchez-Ortiz, MD, a Contributing Editor with UroToday.

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