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"Ten-Year Follow-Up of Radiation Therapy
Oncology Group Protocol 92-02: A Phase III Trial of the Duration of
Elective Androgen Deprivation in Locally Advanced Prostate Cancer",
Horowitz, JCO, to be published, May 20, 2008.
(May 2008)
This article is the
radiation therapy counterpart of the SWOG 8794 study (reviewed above)
with a comparable duration of follow-up of a median 11.3 years. RTOG
92-01 had as its purpose "To determine whether adding 2 years of
androgen-deprivatioon therapy (ADT) improved outcome for patients
electively treated with ADT before and during radiation therapy." Long
term ADT (LTAD+RT) with an LHRH agonist was assigned to 758 men and
short term ADT (STAD+RT) to 763. Radiation therapy consisted of 44-46 Gy
to the pelvis followed by conedown to the prostate for a total dose of
65-70 Gy. The characteristics of eligible men in the two arms were
nearly identical: median age, 70; PSA <30, 67%; PSA >30
33%; clinical stage, T2c, 45%; T3, 50-52%; T4, 3-5%; Nx, 87-86%; N0
9-11%; and Gleason score was <6 in 38%; 7, in 36-39%, and 8-10
in 14%.
The 10-year study
results comparing STAD+RT versus LTAD+RT are as follows:
· Local
progression
(LP): 22.2%, STAD; 12.3%, LTAD; P = <.0001.
LP was defined as clinical
evidence of local recurrence (by any method) during the ten-year
follow-up or persistent disease.
· Distant
failure
(DF): 22.8% (STAD); 14.8% (LTAD); P < .0001
DF was defined as clinical evidence of
metastatic disease by any method.
· Biochemical
failure
(BF): 68.1% (STAD); 51.9% (LTAD). P < .0001.
BF was defined as the earliest of the following: three
consecutive rises after a post treatment PSA nadir; receiving additional
ADT; or PSA greater than 4 ng/mL. Similar to what was seen in SWOG 8794
long term ADT prolonged freedom from PSA relapse. The median time to
biochemical failure for the STAD group was at ~2 1/2 years versus ~ 7
years for men in the LTAD arm. For a subset of men with Gleason score
8-10 PSA failure occurred at a median of ~ 1 3/4 years (STAD), compared
to ~5 years (LTAD).
· Disease
free survival
(DFS): 13.2% (STAD); 22.5%, LTAD; P < .0001.
DFS was defined as avoidance of LP, DF, BF, or
death. The converse of DFS specifies men who did have LP, Distant
Failure, BF, or who died, and expressed in this manner the percentages
were 86.8% for STAD and 77.5%, LTAD.
· Disease
specific survival
(DSS): 83.9% (STAD); 88.7% (LTAD); P = .0042
DSS was defined as avoidance of death due to prostate
cancer or treatment toxicity, or from unknown causes in association with
metastases. P = .0042
· Overall
survival
for the two arms at ten years was not significantly different,
51.6 % for STAD compared to 53.9% for LTAD, P = .36. However, in the
small subset of men with Gleason score 8-10 (~24 men in each arm) the
10-year overall survival was 31.9% (STAD) compared to 45.1% (LTAD), P =
0061.
What observations arise
from this important long term study? Despite a much shorter biochemical
progression-free interval for the STAD arm, and despite the impressive P
values for the comparisons, the absolute differences at 10 years between
the two study arms were relative minimal and the 10-year outcomes were
quite favorable: DSS at 10-years was 88.7% v. 83.9% and freedom from
distant metastases 77.2% v. 85.2% favoring those whose ADT totaled 24
months after primary treatment.
BOTTOM LINE:
Similar to the results in the SWOG study, the course of prostate cancer
can be long for men after treatment of locally advanced disease. And as
with many studies of outcome for primary treatment of prostate cancer in
older men, the major cause of death is not from cancer, but from "other
causes."
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