PSA levels, post-radiation biopsies, and disease progression
Posted Sep 28 2008 5:40pm
Zapatero et al. have recently conducted an interesting analysis of the relationship between post-radiation PSA levels, post-treatment biopsies, and subsequent disease progression. Their results appear to demonstrate that control of PSA by three-dimensional conformal radiation therapy (3DCRT) can be an adequate surrogate for local disease control, as assessed by post-treatment biopsies.
Differentiation between therapeutic success and failure after radiotherapy (RT) for prostate cancer is still a significant clinical challenge. The goal of this study was to investigate the relationship between post-treatment biopsy results, prostate-specific antigen (PSA) levels, and clinical outcomes in patients treated with 3DCRT in a dose-escalation study.
The study included 160 Spanish patients with clinical stage T1c to T3b diseae treated between 1995 and 2005 who consented to and underwent a transrectal ultrasound (TRUS)-guided prostate biopsy 24-36 months after RT. The median follow-up was 78 months (range 27-171 months). The median radiation dose was 74 Gy (range 66.0-84.1 Gy). Risk-adapted short-term androgen deprivation (STAD) and long-term androgen deprivation (LTAD) were given to 25 and 106 patients, respectively. Right and left systematic biopsies were carried out by the same urologist and were examined by a genitourinary pathologist. Biochemical disease-free survival (bDFS) was assessed according to American Society for Therapeutic Radiology and Oncology (ASTRO) 1997 and Phoenix definition criteria as well as histologic control using post-treatment prostate biopsies.
Twenty-one percent of patients (34/160) had positive post-treatment biopsies (PPBs). The 5-year bDFS according to the Phoenix definition was as follows:
87 percent for the full series of all 160 patients
65 percent for the 34 patients with PPBs
92 percent for the 126 patients who had negative port-treatment biopsies (NPBs)
Multivariate analysis showed that biopsy status at 24-36 months was an independent predictor of bDFS (p < 0.0005) and of clinical failure-free survival (p = 0.043). The authors concluded that the results of their study show a strong correlation between a PPB and the 5-year probability of bDFS.