Session Item

Tuesday
May 10
08:30 - 09:10
Auditorium 15
Toxicity vs tumour control: What makes a good pelvic radiotherapy plan?
Peter Hoskin, United Kingdom
4000
Teaching lecture
Interdisciplinary
16:40 - 16:50
Dosimetric comparison of SBRT and HDR brachytherapy in patients from randomized study.
OC-0041

Abstract

Dosimetric comparison of SBRT and HDR brachytherapy in patients from randomized study.
Authors:

S. Nonikov1, N. Ilin1, Y. Melnik1, R. Novikov1, Y. Merezhko1, S. Kanaev1

1N.N. Petrov National Research Cancer Center, Department of radiotehrapy, Saint Petersburg, Russian Federation

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Purpose or Objective

Background: There has been an increasing interest in stereotactic body therapy (SBRT) and high dose rate brachytherapy (HDRB) in treatment of low-intermediate risk prostate cancer. In order to compare efficacy and safety of both methods in 2018 we initiated single center prospective randomized trial.

The aim of this study was to compare dosimetric plans of patients that received HDRB with those that were randomized to SBRT.

Material and Methods

Between 01.06.2018 and 01.07.2019, 139 men with low-intermediate risk prostate cancer were randomized between HDRB or SBRT. Sixty-nine patients received TRUS guided HDRB in 2 fractions of 13 Gy (BED-251.3; α/β-1.5), among them 10 men received HDRB with the low dose tunnel for urethra (D10 ur<90%). Another 70 men were treated by SBRT in 5 fractions of 7.25Gy (BED-211.5; α/β-1.5). For comparison of dosimetric plans we used the following parameters: V100 pr – the percentage of prostate that received 100% of prescription does and D90 pr – minimum dose that covers 90% of prostate; D2cc rec - the maximum dose for 2cc of the rectal wall; D10 ur – the dose that covered 10% of the urethra volume.

Results

All plans were characterized by excellent coverage of the target (prostate). V100 and D90 for prostate were as follows: for SBRT - 91% (87.3-94.7%) and 100.1% (99.9-100.3%); for HDRB – 94.3% (92.1-96.5%) and 104.7% (102.3-107.1%). SBRT demonstrated uniform dose distribution with nearly equivalent dose to the prostate and urethra (D10ur- 101%; 100.3-101.7%) and high dose to the rectum (D2cc – 91%; 86.7-95.3%) and bladder (D2cc 100.9%; 99.6-102.2%). HDRB give the opportunity for significant reduction of the dose to the anterior rectal wall (D2cc - 55.3%; 48.4-62.2%) with moderate dose to the bladder (D2cc – 69%; 61.6-76.4%) and urethra (D10 – 108.3%; 105.5-111.1%). HDRB with “tunnel for urethra” was performed only in low risk patients with negative periurethral biopsy cores. This technique gives the opportunity to reduce dose to the urethra (D10 – 89.4%; 86.5-92.3%) and to the bladder (D2cc - 56%; 49.1-62.94%) with moderate underdose of the prostate (central and transitional zones). 

Conclusion

Our data indicate that both HDRB and SBRT characterized by excellent target (prostate) coverage. Important advantage of HDRB against SBRT is significant (from 91% to 55.3%) reduction of the dose to the rectum. HDRBT with “tunnel to urethra” reduce the dose to the urethra and bladder neck with underdose of the central and transitional zones of prostate.