Comparison of the Outcomes of Various Radiation Treatment Modalities for Prostate Cancer

Abstract

To evaluate biochemical control rates (BCR) and identify prognostic factors for patients (pts) with localized prostate cancer treated with conventional-dose 3-D conformal radiotherapy (3D-CRT), high-dose intensity-modulated radiotherapy (IMRT), or permanent transperineal brachytherapy (BRT). 684 pts. who received RT at Mayo Clinic Arizona between May of 1993 and July of 2004 are included in this analysis. Of these patients, 270 received 3D-CRT, 145 received IMRT, and 269 received BRT (225 pts with BRT alone & 44 pts with external beam RT (XRT) +BRT as a boost). The distribution of T-stages included: T-1:221 pts, T-2:432 pts, & T-3:31 pts. Pre-treatment PSA levels ranged from 0.5–197 (median:7) and Gleason Scores ranged from 2–10 (median:6). Adjuvant androgen deprivation therapy was administered to 175 (26%) of the 684 pts. The 3D-CRT pts received a median dose of 68.4 Gy (range:66–71 Gy) and the IMRT pts received a median dose of 75.6 Gy (range, 70.2–77.4 Gy). The BRT pts who received I-125 alone or Pd-103 alone had a prescribed dose of 144 Gy or 120 Gy, respectively. Pts who received combined XRT and BRT boost had 45 Gy XRT followed 110 Gy with I-125 or 90 Gy with Pd-103. Univariate analysis was performed with the log-rank test and multivariate analysis with the Cox Proportional Hazards Model. Biochemical failure was defined a rise in PSA of 2.0 above the nadir. Follow up ranged from 3–121 months (median: 55 mo). The 4-year biochemical control rates (BCR) were 82% for 3-DCRT, 91% for IMRT, 95% for BRT alone, and 94% for XRT+BRT (p < 0.0001). On univariate analysis, the following factors were found to be significantly associated with BCR's: T-stage (p < 0.0001), Gleason Score (p < 0.0001), pre-RT PSA levels (p < 0.0001), Memorial Sloan Kettering Cancer Center Risk Group (p < 0.0001), and perineural tumor invasion (p = 0.0003). The use of adjuvant androgen deprivation therapy was not associated with BCR's (p = 0.5). Multivariate analysis was performed excluding the risk grouping because it contains elements of T-stage, PSA level, and Gleason Score & would confound the analysis. The multivariate analysis revealed the following factors to be associated with biochemical control: pre-treatment PSA level (p = 0.003), Gleason Score (p = 0.0006), perineural invasion (p = 0.008), and treatment modality (p < 0.0001). If one excluded the pts treated with 3-DCRT from the multivariate analysis, the effect of treatment modality on biochemical control became non-significant (p = 0.08). The 4-year overall survival of the entire group was 97%. Biochemical control rates are associated with Gleason Score, pre-RT PSA level, and perineural involvement. These factors can be used to create an excellent method of predicting treatment outcome and stratifying patients. In addition, higher-dose RT modalities such as brachytherapy or high-dose IMRT appear superior to conventional-dose 3-DCRT.