A recently published Italian study has reported on whether perineural invasion (PNI) has prognostic value in patients undergoing radical prostatectomy for organ-confined prostate cancer, and on its possible correlation with other recognized prognostic factors.
Between January 2000 and December 2007, Masieri et al. carried out a careful prospectively designed study and collected data from 251 consecutive patients who had pathologically localized (organ-confined) prostate cancer after radical prostatectomy. Data from 239 of these patients was usable for analysis. The authors defined PNI as adenocarcinoma observed within the perineural space adjacent to a nerve.
The results of their study showed that:
- Intraprostatic PNI occurred in a total of 157/239 patients (65.7 percent).
- PNI was more commonly observed in men with pathologic stage T2b/c (149/204 patients or 73 percent)) than in men with pathologic stage T2a (8/35 patients or 26 percent).
- PNI was also more common in men with a Gleason score of 7 to 10 (73/93 patients or 78.5 percent) than in men with a Gleason score of 2 to 6 (84/146 patients or 57 percent).
- Average (mean) follow-up was 65.4 months (range, 24 to 118 months).
- 11/239 patients (4.6 percent) had biochemical recurrence after surgery and 7 of these 11 patients (63.6 percent) showed PNI.
- 228/239 patients (95.4 percent) were free from biochemical progression after surgery and 150 of these 228 patients (65.7 percent) had PNI.
- The actuarial biochemical progression-free survival rate for all patients was 96.9 percent at 60 months and 93.5 percent at 84 months, respectively.
- Stratification based on the presence or absence of PNI did not allow for identification of different prognostic groups.
The authors conclude that, at least in their series of patients, men with pathological stage T2 disease and PNI were found to present with a higher pT2 stage and Gleason score than men without PNI, but that the biochemical progression-free outcomes among these patients were similar to the outcomes of patients without PNI at a follow up of between 2 and 12 years.
This study appears to suggest that the prognostic impact of PNI on risk for progressive prostate cancer is actually much lower than has been assumed in the past. It may well be that as men have increasingly been diagnosed earlier in the progression of their disease, that perineural invasion is a less significant prognostic factor for men with truly localized disease than it has been thought to be for men known to have extraprostatic extension of their disease. In other words, PNI in men with pathological T3/4 disease may have greater prognostic significance than it does in men with pathological T2 disease.