Pelvic MRI (PMRI)
is an important pre-radiotherapy (RT) evaluation procedure in patients with
intermediate- and high-risk prostate cancer. We conducted a retrospective study
to evaluate an influence of PMRI to delineation of RT clinical target volume
(CTV).
Medical records of
prostate cancer patients treated with intensity-modulated RT (IMRT) in single
institution in 2009-2015 were retrieved and examined retrospectively. Initial
risk group affiliation was defined using NCCN criteria. PMRI reports of
patients with intermediate and high-risk prostate cancer were reviewed and risk
group affiliation was re-defined in regards of T- and N-stage. CTVs for IMRT
treatment plans were contoured. Accounting to information obtained from PMRI.
Extra-capsular extension (ECE) and seminal vesicles invasion (SVI) were
included to high-dose CTV. Regional pelvic lymph nodes (RPLN) were planned to
treat in all high-risk pts. RPLN considered pathological by PMRI were included
to separate CTV to receive RT dose higher than unaffected RPLN stations.
Between 2009 and
2013, 169 patients with intermediate and high-risk prostate cancer underwent
PMRI at around 1 month before commencing IMRT. Initially, 89 patients were
affiliated to intermediate-risk and 80 to high-risk group. In general,
PTV-changes based on PMRI data required in 66 patients (39%). Thirty seven of
89 intermediate-risk patients (42%) were switched to high-risk group,
necessitating irradiation of RPLN. ECE and SVI were included to high-dose CTV
in 64 (38%) and 29 patients (17%) respectively. RPLN were thought pathological
in 10 patients (6%), which justified contouring of a separate CTV for dose
escalation.
In our retrospective
series, PMRI-scans had a significant impact on RT target coverage decision in
patients with intermediate and high-risk prostate cancer. However, a true value
of this impact should be defined a large scale prospective clinical trial.
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