Implementation of high-dose-rate brachytherapy as monotherapy for over-sized prostatic gland
MO-0302
Abstract
Implementation of high-dose-rate brachytherapy as monotherapy for over-sized prostatic gland
Authors: Yiannis Roussakis1, George Antorkas1, Anna Antoniou2, Constantina Cloconi3, Efstratios Karagiannis3,4, Konstantinos Ferentinos3,5, Christakis Damianou2, Iosif Strouthos3,5
1German Oncology Center, Medical Physics, Limassol, Cyprus; 2Cyprus University of Technology, Electrical Engineering, Computer Engineering and Informatics, Limassol, Cyprus; 3German Oncology Center, Radiation Oncology, Limassol, Cyprus; 4European University Cyprus, Medical School, Limassol, Cyprus; 5European University Cyprus, Medical School, Nicosia, Cyprus
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Purpose or Objective
Prostatic
gland enlargement can be considered a contraindication for high-dose-rate (HDR)
brachytherapy (BT). The current study aims to dosimetrically compare prostate HDR
BT plans as a function of prostate
volume (greater/less than 55 cubic centimetres (cc)), while at the same time
evaluating gastrointestinal and genitourinary toxicity through patient reported
outcomes (PRO).
Material and Methods
Fifty-three
patients
previously treated for prostate cancer with HDR brachytherapy as monotherapy (2
x 14 Gy) between January 2018 to February 2021 were retrospectively selected.
Several dose volume histogram (DVH) statistics for prostate, urethra, rectum,
and bladder have been calculated for each plan (two implants per case) and
analysed in correlation to prostate volume. Additionally, PRO information was
recorded using two validated questionnaires (a. RTOG/EORTC: Radiation
Oncology Therapy Group/ European Organization for Research and Treatment of
Cancer; b. IPSS: International Prostate System Score), with a baseline before
treatment and repeats every 3 months following completion of treatment.
Results
The
median prostate gland volume for the entire cohort (n = 53), <55cc cohort (n
= 37), ≥55cc cohort (n = 16) was 48.7cc, 34.5cc and 78.8cc, respectively. Median
follow up was 9 months. No statistically significant differences (p>0.05)
were observed in DVH parameters D90%, D100%, V200% for
prostate; D0.1cc for urethra; and D0.1cc for rectum. While
the dosimetric constraints were met for all plans, significant correlations against
prostate volume were observed (p<0.05) in the following DVH parameters were exposed:
prostate V150%; D1cc for urethra; D10%, D2cc
for bladder; and D1cc, D2cc, D10% for
rectum. Analysis of PRO measures gathered through the questionnaires to date,
does not reveal any significant differences in toxicity between the two groups.
Conclusion
HDR
BT plans created for prostate glands below and above 55cc met all dosimetric objectives
and constraints. Significant correlations of certain DVH parameters against
prostate volume do not seem to correlate with any clinically measurable
toxicity differences between the two cohorts.