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Post-treatment PSA Nadir Predicts Prostate Cancer Outcome

Post-treatment PSA Nadir Predicts Prostate Cancer Outcome

SAN FRANCISCO—Patients 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).

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