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probably favored LDR-B, as patients in this group were
younger and more likely to have private insurance and/or
intermediate risk. To further adjust for this bias, we
artificially increased GS from 7 to 8–10 for DE-EBRT
patients, and found that the benefit of LDR-B boost
remained until 80% of patients receiving DE-EBRT were
increased from GS 7 to 8–10. Although we attempted to
control for variables known to affect survival with MVA
using Cox proportional hazards models and propensity
score matching, we cannot adjust for unknown variables.
Third, although the study included patients receiving
neoadjuvant AS, the AS duration was not evaluated or
controlled for because of data collection limitations.
Therefore, it is possible that men in the EBRT only cohort
were not treated adequately according to current stan-
dards. A recent population-based analysis has suggested
that 25% of men receiving radiation for high-risk disease
do not receive AS
[34] .Fourth, patients in the DE-EBRT
cohort were not excluded according to the presence or
absence of whole-pelvis radiation (WPRT) because of
NCDB coding limitations. Therefore, it is possible that men
with high-risk disease received EBRT only and did not
receive WPRT and a conformal boost, which could
represent undertreatment of these men. However, the
role of WPRT remains indeterminate for unfavorable PCa
[35,36]. Finally, we could only assess OS and not cancer-
specific survival or cancer-specific outcomes, but we
performed a subset analysis for younger healthy men to
attempt to better approximate PCSM. Any analysis of
observational data with a treatment outcome of OS alone
should be viewed with caution
[37] .5.
Conclusions
Our study revealed a decline in LDR-B boost use between
2004 and 2012 for men with unfavorable PCa and better
survival compared to DE-EBRT alone. In accordance with
these data, the improvement in biochemical failure from
ongoing trials such as ASCENDE-RT will probably translate
into better OS outcomes with additional follow-up. Long-
term follow-up for randomized trials is needed before
definitive conclusions can be drawn regarding the benefit of
LDR-B for these men.
Author contributions:
Sameer K. Nath had full access to all the data in the
study and takes responsibility for the integrity of the data and the
accuracy of the data analysis.
Study concept and design:
Johnson, Yu, Nath.
Acquisition of data:
Johnson, Lester-Coll, Yu, Nath.
Analysis and interpretation of data:
Johnson, Lester-Coll, Kelly, Kann, Yu,
Nath.
Drafting of the manuscript:
Johnson, Lester-Coll, Nath.
Critical revision of the manuscript for important intellectual content:
Johnson, Lester-Coll, Kelly, Kann, Yu, Nath.
Statistical analysis:
Johnson, Lester-Coll, Kelly, Kann, Yu, Nath.
Obtaining funding:
None.
Administrative, technical, or material support:
None.
Supervision:
Yu, Nath.
Other:
None.
Financial disclosures:
Sameer K. Nath certifies that all conflicts of
interest, including specific financial interests and relationships and
affiliations relevant to the subject matter or materials discussed in the
manuscript (eg, employment/affiliation, grants or funding, consultan-
cies, honoraria, stock ownership or options, expert testimony, royalties,
or patents filed, received, or pending), are the following: James B. Yu has
received research funding from 21st Century Oncology. Nataniel H.
Lester-Coll has received an honorarium from Elekta AB. The remaining
authors have nothing to disclose.
Funding/Support and role of the sponsor:
None.
Appendix A. Supplementary data
Supplementary data associated with this article can be
found, in the online version, at
http://dx.doi.org/10.1016/j. eururo.2017.06.020.
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