This document compares 2D and 3D treatment planning for cervical cancer patients. It found that using only bony landmarks in 2D planning led to inadequate coverage of the clinical target volume (CTV) in 29 out of 30 patients, with a median CTV coverage of only 95.35%. 3D planning based on computed tomography contouring of the CTV and organs at risk provided much better CTV coverage of 99.55% on average. The study recommends using 3D CT-based planning over conventional 2D planning to improve treatment accuracy for cervical cancer patients.

1. 2D vs. 3D EXTERNAL
BEAM PLANNING IN
CERVICAL CANCER
ANOMALIES IN TREATMENT VOLUME

2. Objective
To estimate inadequacies in target volume
coverage when using conventional planning
based on bony landmarks.

3. EXTERNAL BEAM
RADIOTHERAPY
• (EBRT) plays an important role in the management of patients with
carcinoma cervix.
• Whole pelvis is treated including clinically and radiologically apparent
tumour, uterine corpus, upper part of vagina, parametrium, and the
draining lymph nodes.
• The central disease can further be boosted by intracavitary
brachytherapy.

4. EBRT CONT’D
• 2D planning is based on bony landmarks delivered by (AP-PA) parallel
opposed fields & opposed laterals (conventional four field planning).
• May provide good coverage to the target volume.
• Has few disadvantages.

5. 3D CT BASED PLANNING
• Preferred EBRT technique for cervical carcinomas.
• The conformal four field box technique with parallel opposed AP-PA
fields and two lateral opposed fields (3D Planning).
• CTV and OAR are delineated prior to placement of beams.

6. 2 Dimensional 3 Dimensional

7. METHODOLOGY
• 30 patients of locally advanced uterine cervix cancer FIGO stage III A-III
B registered at Cancer Care Kenya were planned during the period
January – August 2014.
• Radical radiation of 50Gy delivered in 25 fractions over 5 weeks.
• With concurrent chemotherapy.
• Central disease is boosted by intracavitary brachytherapy.

8. METHODOLOGY
CONT’D • The clinically and the radiologically visualized primary tumour, was
included in the clinical target volume (CTV).
• CTV was delineated from the bifurcation of aorta.
• Bladder and Rectum (OAR) were delineated as per their extent.

10. METHODOLOGY
CONT’D • Placement of beams on the Digitally Reconstructed
Radiograph (DRR).
• Two Parallel opposed and two Lateral opposed fields
(Four Field Box Technique).

12. METHODOLOGY
CONT’D • Conventional four field plan generated using the standard bony
landmarks.
• AP-PA Sup:L4-L5 junction,Inf. Under ischial tuberosity
• RL-LL Post: S2-S3 junction, Ant.:Include symphisis
• The target volume delineated previously was then projected onto the
DRR.
• The volume of the target receiving at least 95% of the prescribed
dose was calculated (V95). V95 for 2D was subtracted from the V95
for 3D .

15. RESULTS
PATIENT
2D PLAN 3D PLAN
Bladder Rectum CTV V95 Bladder Rectum CTV V95
(Gy) (Gy) (Gy) % (Gy) (Gy) (Gy) %
PATIENT A 49.662 46.087 49.135 93.8 50.151 42.306 50.073 98.8
PATIENT B 43.010 41.160 49.873 99.7 42.942 41,182 50.380 99.9
PATIENT C 29.215 31.943 34.965 91.7 28.018 31.983 36.074 100.0
PATIENT D 45.974 44.827 45.165 81.0 44.552 39.104 49.788 98.9
PATIENT E 49.393 41.193 49.575 98.9 46.676 42.628 49.899 99.3
PATIENT F 47.061 48.076 48.996 99.8 48.717 39.604 49.648 99.8

16. RESULTS CONT’D
• Mean V95 for 2D plans 93.67 %
• Mean V95 for 3D plans 99.50 %
• In only 1 patient (3.33%) out of 30 was the whole of the target
volume encompassed by the conventional four field marked on bony
landmarks.

17. 2D planning encompassed whole CTV Same for 3D

18. Doses to OAR for 2D and
3D
• Mean dose to bladder and
rectum 44.053 Gy & 42.214Gy
respectively.
• Median dose to bladder and
rectum 49.975Gy & 47.810 Gy
respectively.
• Mean dose to bladder and
rectum 40.509 Gy & 39.468 Gy
respectively.
• Median dose to bladder and
rectum 45.885 Gy & 44.895 Gy
respectively.

19. RESULTS CONT’D
• The areas of miss were at the anterior and posterior border of the lateral
fields and the superior borders of the anterior-posterior fields.
• The median miss at the anterior and posterior borders was 3.135cm, and
the maximum was 3.17cm
• The median miss at the superior borders was 1.365cm, and the maximum
was 1.75cm
• The median V95 for conventional fields marked with bony landmarks was
only 95.35% as compared to 99.55% for target delineation based on CT
contouring.

20. Conclusion and
Recommendation
• Target volume miss in 29 out of 30 cases thus study shows
inadequate CTV coverage with conventional Four field
technique.
• Increase in dose to OAR with conventional planning.
• 3D CT-based treatment planning for advanced cases of
uterine cervix carcinoma is recommended.