Need for High Radiation Dose (≥70 Gy) in Early Postoperative Irradiation After Radical Prostatectomy: A Single-Institution Analysis of 334 High-Risk, Node-Negative Patients

Cesare Cozzarini,Milan, Italy   IJROBP 2009;75:966

 

To determine the clinical benefit of high-dose early adjuvant radiotherapy (EART) in high-risk prostate cancer (hrCaP) patients submitted to radical retropubic prostatectomy plus pelvic lymphadenectomy.

Patients and Methods

The clinical outcome of 334 hrCaP (pT3-4 and/or positive resection margins) node-negative patients submitted to radical retropubic prostatectomy plus pelvic lymphadenectomy before 2004 was analyzed according to the EART dose delivered to the prostatic bed, <70.2 Gy (lower dose, median 66.6 Gy, n = 153) or ≥70.2 Gy (median 70.2 Gy, n = 181).

From April 1993 (first patient of this series), the dose of EART to the prostatic bed was gradually increased from 55.8 Gy to the present standard of 72 Gy.

For the purposes of this analysis, the 334 cases were divided into two groups: those irradiated at doses <70.2 Gy (lower dose, LD) and the remaining 181, whose prostatic bed received an EART dose ≥70.2 Gy (higher dose, HD)

 

 

The two groups were comparable except for a significant difference in terms of median follow-up (10 vs. 7 years, respectively) owing to the gradual increase of EART doses over time. Nevertheless, median time to prostate-specific antigen (PSA) failure was almost identical, 38 and 36 months, respectively. At univariate analysis, both 5-year biochemical relapse-free survival (bRFS) and disease-free survival (DFS) were significantly higher (83% vs. 71%] and 94% vs. 88%], respectively) in the HD group. Multivariate analysis confirmed EART dose ≥70 Gy to be independently related to both bRFS (hazard ratio 2.5, p = 0.04) and DFS (hazard ratio 3.6, p = 0.004). Similar results were obtained after the exclusion of patients receiving any androgen deprivation. After grouping the hormone-naïve patients by postoperative PSA level the statistically significant impact of high-dose EART on both 5-year bRFS and DFS was maintained only for those with undetectable values, possibly owing to micrometastatic disease outside the irradiated area in case of detectable postoperative PSA values.

Conclusion

This series provides strong support for the use of EART doses ≥70 Gy after radical retropubic prostatectomy in hrCaP patients with undetectable postoperative PSA levels.