EVIDENCE OF INCREASED FAILURE IN THE TREATMENT OF PROSTATE CARCINOMA PATIENTS WHO HAVE PERINEURAL INVASION TREATED WITH 3-DIMENSIONAL CONFORMAL RADIATION-THERAPY

BACKGROUND. The detection of perineural invasion (PNI) in the diagnost ic transrectal biopsy of the prostate is associated with a 93% frequen cy of extracapsular disease extension in patients treated by prostatec tomy for adenocarcinoma of the prostate. Extracapsular extension is as sociated with an inferior outcome compared with that of patients who h ave organ-confined disease. This study examined the association of PNI and treatment failure in a consecutive series of patients treated wit h three-dimensional conformal radiation therapy (3DCRT) alone. METHODS , The authors report actuarial biochemical no evidence of disease (bNE D) survival rates for 484 consecutive patients with clinically localiz ed prostate carcinoma diagnosed by transrectal needle biopsy who compl eted 3DCRT alone between May 1989 and December 1994. The median follow -up time was 28 months (range, 2-75 months), and the median dose to th e center of the prostate was 7368 centigray (cGy) (range, 6316-8074 cG y). Patients were subdivided into 2 groups according to pretreatment p rostate specific antigen (PSA) levels (< 20 ng/mL vs. greater than or equal to 20 ng/mL). Pathology records were reviewed for the presence o r absence of PM. bNED failure was defined as a PSA level greater than or equal to 1.5 ng/mL, and rising on 2 consecutive occasions. bNED sur vival rates were calculated using Kaplan-Meier methodology and compari sons of survival curves were accomplished using the log rank test. RES ULTS, The 3-year bNED survival for all 484 patients was 77%. The prese nce of PNI predicted decreased bNED survival in all patients. This det rimental effect, however, was confined to patients with pretreatment P SA values < 20 ng/mL. The bNED survival rates for patients with pretre atment PSA < 20 ng/mL demonstrated a highly significant decrease if PN I was present versus when it was absent (65% vs. 88% at 3 years, 39% v s. 65% at 5 years; P = 0.0009 for overall curve comparison). For patie nts with pretreat ment PSA < 20 ng/mL, multivariate analysis of progno stic variables demonstrated a significant association between bNED sur vival and PNI (P = 0.002), palpation stage (P = 0.02), and pretreatmen t PSA (P = 0.006). Gleason score, age, and dose were not independent p redictors of bNED survival in this group of patients. CONCLUSIONS, To the authors' knowledge, this is the first report demonstrating that PN I detected on diagnostic transrectal biopsy is a significant predictor of decreased bNED survival in patients treated with radiotherapy. The subgroup of patients affected are those with pretreatment PSA < 20 ng /mL. This result suggests that such patients may benefit from more agg ressive treatment, particularly the use of larger planning target volu mes or adjuvant therapies. (C) 1997 American Cancer Society.