Transcript Document

Comparison of Rectal Dose Volume Histograms for Definitive
Prostate Radiotherapy Among Stereotactic Radiotherapy,
IMRT, and 3D-CRT Techniques
Author(s): Berit Madsen, MD; Huong Pham, MD; R. Alex Hsi, MD; Joseph Presser, MSc, DABR; Laura Esagui, CMD, Nancy Collins, CMD; Edward Lawrence, MSc; Guobin Song, MD,
PhD; Kasra Badiozamani, MD; Michael Hunter, MD; Eric Taylor, MD, Section of Radiation Oncology, Virginia Mason Medical Center, Seattle, WA
I ABSTRACT
II METHODS
PURPOSE
3D-CRT
IMRT
STEREOTACTIC RT
To compare rectal dose volume histograms (DVH) among stereotactic
radiotherapy, intensity modulated radiation therapy (IMRT), and 3Dconformal radiotherapy (3D-CRT) for prostate cancer.
III FINDINGS
Stereotactic Localization
Stereotactic Localization
External Beam Radiation Therapy
Mean Rectal DVH of Stereotactic RT/IMRT/3D-CRT
60
3D-CRT
53.77
(2 7 .9 9 )
42.33
(2 0 .2 7 )
50
METHODS/MATERIALS
Radiotherapy plans for 28 patients treated with stereotactic radiotherapy, IMRT, and
3D-CRT techniques were reviewed. There were 10 stereotactic plans, 9 IMRT plans,
and 9 3D-CRT plans. The planning systems utilized were Northwest Medical
Physics/pReference for the stereotactic plans and ADAC/Pinnacle for IMRT and 3DCRT plans. Fused MRI and CT were used for target delineation with IMRT and
stereotactic radiotherapy. CT alone was utilized for 3D-CRT. For patients treated with
IMRT and stereotactic radiotherapy, fiducial markers were placed within the gland and
utilized for daily target localization with electronic portal imaging. Patients treated with
3D-CRT were localized with skin marks. The CTV was expanded by 0.4 cm for
stereotactic radiotherapy plans and 0.5 cm for IMRT plans based on accuracy of the
localization technique and on previous data related to intrafractional stability. CTV
expansion was 1-1.5 cm for the 3D-CRT plans. Stereotactic radiotherapy was
delivered with 6 non-coplanar fields and custom stereotactic cones on the 2100 CD
Varian linac with patients lying in a flex-prone position. IMRT was delivered with 7
coplanar beams, and 3D-CRT with 6 coplanar beams. Treatment was delivered with
either 0.5 cm or 1 cm MLC on a Varian 2100 CD or 21 EX linac for IMRT and 3D-CRT
in supine position without other immobilization. The dose to the prostate was 33.5
Gy/6 fractions for stereotactic radiotherapy plans, and 75-78 Gy/35-42 fractions for
IMRT and 3D-CRT plans. The rectal volume was contoured as a solid organ from anal
canal to the level of the sacro-iliac joint in all plans and reported in cubic centimeters.
3 Implanted Gold Markers
•
3 Implanted Gold Markers
•
Daily Portal Imaging
•
Daily Portal Imaging
IMRT
3D-CRT
50%
4.29 ± 3.15
6.04 ± 3.93
11.5 ± 6.83
18.16 ± 11.5
0.1 ± 0.13
1.95 ± 1.12
5.99 ± 2.92
23.24 ± 10.52
42.33 ± 20.27
2.56 ± 2.29
14.16 ± 4.59
21.09 ± 8.65
39.97 ± 19.81
53.77 ± 27.99
2 1. 0 9
Stereotactic RT
Conformal Blocking Around
Prostate for 3-D Plan
18 . 16
(8 .6 5 )
(11.5 0 )
14 . 16
11. 5 0
(4 .5 9 )
(6 .8 3 )
10
6 . 0 4(3 .9 3 )
4 . 2 9 (3 .15 )
(2 .9 2 )
1. 9 5
0
30
50
80
% Reference Dose
90
(1.12 )
2 . 5 6 (2 .2 9 )
0 . 9 0 (1.18 )
0 . 11 (0 .13 )
100
MRI/CT Fusion
Gold markers used
for registration
•
•
7 coplanar fields
35-40 control points
CTV-PTV 5 mm expansion
5 mm MLC
•
•
•
6 coplanar fields
CTV-PTV expansion 10-15 mm
5 mm MLC
3D Conformal Isodose Plan
Beam Arrangements &
Stereotactic Cones
30%
0.9 ± 1.18
20
(10 .5 2 )
5.99
Rectal DVH Expressed in Cubic Centimeters
Stereotactic
MRI/CT Fusion
(19 .8 1)
30
Gold markers used
for registration
There were notable differences in the rectal DVH among the three treatment
techniques (see table). IMRT produced the most rectal sparing at the high dose levels
but below the 80% level, stereotactic radiotherapy produced better sparing. 3D-CRT
plans provided the least rectal sparing at all dose levels.
80%
•
No Immobilization
Skin Marks for localization
23.24
Flex-prone Position
•
90%
•
Volume (cc's)
•
•
100%
39.97
40
RESULTS
Dose %
( ) = s.d.
IMRT
IMRT Isodose Plan
IV CONCLUSIONS
• Stereotactic RT & IMRT plans
result in minimal rectal volume
exposed to high dose radiation
• Stereotactic RT results in least
rectal volume exposed to
moderate and lower doses of
radiation
•
CONCLUSION
•
In our experience, IMRT and stereotactic radiotherapy plans resulted in minimal rectal
volumes exposed to high dose radiation compared to 3D-CRT plans. Additionally,
stereotactic radiotherapy resulted in significantly less rectal volume exposed to the lower
radiation dose levels than IMRT or 3D-CRT plans which could be advantageous in
hypofractionated treatment regimens. This analysis helps substantiate the use of this
unique stereotactic technique for our phase I/II clinical trial of hypofractionated radiation
therapy for prostate cancer.
•
6 stationary non-coplanar fields
CTV-PTV 4 mm expansion
Precision conformal blocks are
cast within stereotactic cones
3-D conformal dose distribution
as seen on a CT image
Intensity Modulated (IMRT)
dose distribution
i
Isodose Plan
Rectum
CTV
Madsen B, Hsi RA, Pham H, Presser J, Esagui L, et al. Intrafractional
Stability of the Prostate Using a Stereotactic Radiotherapy Technique. Int
J Radiat Oncol Biol Phys 2003;57:1285-1291.