SAN FRANCISCOPatients with lower PSA values after radiation therapy are more likely to be alive and free from distant metastasis 10 years later than those with higher values, according to study results presented at the 43rd Annual Meeting of the American Society for Therapeutic Radiology and Oncology (ASTRO abstract 203).
PSA doubling time was also shown to be predictive of later death from prostate cancer, said Gerald Hanks, MD, who recently retired as director of the Department of Radiation Oncology, Fox Chase Cancer Center. Dr. Hanks, a coauthor of this study, reported the results on behalf of study statistician Alexandra Hanlon, PhD.
"This is the first report that demonstrates a very strong predictive power of postradiation PSA nadir for determining distant failure and death due to prostate cancer. These results shed light on clinical progression as a function of PSA nadir and PSA doubling time," Dr. Hanks said.
The researchers followed 615 men who were treated at Fox Chase with three-dimensional conformal radiation therapy for prostate cancer between April 1989 and December 1995. The median dose was 73 Gy (range, 64 to 82 Gy).
After a median follow-up period of 64 months, 186 of the patients had experienced biochemical relapse (using the ASTRO definition of three increases in PSA), 40 had developed distant metastasis, and 18 had died of their prostate cancer. Of the 186 biochemical failure patients, 48 received androgen-deprivation therapy.
Multivariate analysis revealed that several factors were extremely predictive of improved freedom from distant metastasis: lower post-treatment PSA nadir (P < .0001), longer interval to nadir from start of treatment (P = .0002), favorable tumor grade (P = .005), androgen-deprivation therapy after PSA failure (P = .001), and stage T1/T2A tumors (P < .01). Pretreatment PSA level, however, was not predictive of freedom from distant metastasis.The 10-year incidence of freedom from distant metastasis was 96% for patients with post-treatment PSA nadirs of less than 1 ng/mL vs 89% and 49% for patients with values of 1.1 to 2 ng/mL and greater than 2 ng/mL, respectively (P < .0001).