EURURO Vol. 71 No. 4

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3.1. FST with docetaxel
FST included taxane chemotherapy, androgen signaling–
directed therapy, and immunotherapy . Overall,
there was low prevalence of cabazitaxel and enzalutamide
as FST. Docetaxel was by far the most common FST in the AA
arm (48%, 261/546) and in the P arm (50%, 272/542). The
median duration of docetaxel therapy following AA was
3.0 mo (interquartile range [IQR] 0.95–5.7; ). The
reason most commonly reported for discontinuation of
docetaxel as FST was PSA progression, although more than
one reason was reported for 39 patients. Toxicity appeared
to be a fairly infrequent reason for docetaxel discontinua-
tion, even though these patients had advanced disease and
previous medical therapy for mCRPC.
A total of 100 AA patients who received docetaxel as FST
had post-trial baseline and post-baseline PSA values
available. Among these 100 patients the median duration
of docetaxel therapy was 4.2 mo (IQR: 2.8–6.4). However,
data on the median number of docetaxel courses adminis-
tered were not available. The rate of post-treatment PSA
decline 50% was 40% (40/100), including the 27 patients
with a confirmed response (PSA response rate 27%; ).
TTPP was estimated based on 29 events and 71 censored
patients. The median TTPP for these 100 patients was
7.6 mo (95% CI 5.0 to not estimable; Supplementary .
The major reasons for censoring were the proportion of
patients who did not have PSA progression and those who
had PSA progression but did not have complete PSA data
available because of retrospective data collection.
3.2. Treatment patterns by age subgroup
The treatment patterns by age subgroup are shown in
and Supplementary . In the overall ITT
population, 15% (114/738) of younger patients received no
subsequent therapy, compared with 38% (132/350) of older
patients (Supplementary . The proportion of
patients who died without receiving subsequent therapy
followed the same pattern (Supplementary ).
Moreover, 43% (79/185) of older patients with progression
on AA did not receive subsequent therapy for mCRPC
following discontinuation of the protocol-specified study
drug. Docetaxel was the most common FST among older and
younger patients in each treatment arm. More than half of
younger patients from both treatment arms received
docetaxel as FST: 55% (197/361) in the AA arm and 56%
(210/377) in the P arm. By contrast, 35% (64/185) and 38%
(62/165) of older patients from the AA and P arms,
respectively, received docetaxel as FST. Similar trends were
observed when treatment patterns were assessed according
to the mCRPC drugs used in any sequence (Supplementary
). For both younger and older patients in the P arm,
the subsequent therapy most commonly used was doc-
etaxel and AA. Cabazitaxel was more commonly used as
subsequent therapy among younger compared to older
patients.
4. Discussion
This post hoc analysis characterized subsequent therapy
and treatment patterns among patients with mCRPC who
progressed on AA. Patients were commonly treated with
subsequent therapy, although older patients were almost
three times more likely not to receive any subsequent
therapy in comparison younger patients. Docetaxel was the
FST for a large majority of patients, irrespective of age
group.
The observed post-treatment PSA declines 50%support
an antitumor effect of docetaxel as FST in some patients
who progressed with AA. Although 27% of patients had a
confirmed PSA response, the data overall on PSA decline
Table 2 – Subsequent therapy for metastatic castration-resistant
prostate cancer following discontinuation of protocol-specified
study drug
AA P
Patients 546 542
Any subsequent therapy 365 (67.0) 435 (80.3)
Two or more subsequent therapies 194 (36.0) 243 (45.0)
Three or more subsequent therapies 83 (15.2) 121 (22.3)
No subsequent therapy 139 (25.4) 107 (19.7)
Protocol-specified treatment ongoing 42 (7.7) 0
AA = abiraterone acetate plus prednisone; P = placebo plus prednisone.
Data are presented as n (%).
Table 3 – First subsequent therapy for metastatic castration-
resistant prostate cancer
AA P
Patients 546 542
Taxane chemotherapy
Docetaxel 261 (48.0) 272 (50.2)
Cabazitaxel 4 (<1) 3 (<1)
Androgen synthesis inhibitor
Abiraterone acetate 13 (2.4) 80 (14.8)
Ketoconazole 36 (6.6) 56 (10.3)
Androgen receptor antagonist (enzalutamide) 20 (3.7) 4 (<1)
Immunotherapy (sipuleucel-T) 31 (5.7) 20 (3.7)
AA = abiraterone acetate plus prednisone; P = placebo plus prednisone.
Data are presented as n (%).
Table 4 – Treatment duration and discontinuation reasons for
261 patients who received FST with docetaxel
Median duration of docetaxel as FST, mo (IQR) 3.02 (0.95–5.72)
Reason for discontinuation per investigator, n (%)
Clinical progression 38 (15)
Radiographic progression 36 (14)
Prostate-specific antigen progression 75 (29)
Adverse event 41 (16)
Therapy ongoing 11 (4)
Other 73 (28)
FST = first subsequent therapy; IQR = interquartile range.
a Start and end dates for docetaxel therapy were known for 235 patients.
Among 100 patients for whom baseline and at least one post-baseline
prostate-specific antigen values were available, the median duration was
4.17 mo (IQR 2.79–6.37).
b During first subsequent therapy with docetaxel. Reasons were based on
investigator judgment without specific criteria; more than one reason was
selected for 39 patients.
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