Comparison of conventional and three-dimensional conformal CT planning techniques for preoperative chemoradiotherapy for locally advanced rectal cancer.
OBJECTIVE
We assessed the impact of three-dimensional (3D) conformal planning vs conventional planning of preoperative chemoradiotherapy (CRT) for locally advanced rectal cancer (LARC) on small bowel and bladder sparing and in optimising coverage of tumour target volume.


METHODS
Conformal and conventional plans were created for 50 consecutive patients. The conformal plan delineated a gross tumour volume (GTV), a clinical target volume (CTV) 1 to cover potential subclinical disease spread, a CTV2 to outline the mesorectum and lymph node areas at risk, and a planning target volume (PTV) to cover set-up error and organ movement. The conventional plan was created using digitally reconstructed radiographs (DRRs). Patients were treated with a dose of 45 Gy in 25 fractions with concurrent chemotherapy over 5 weeks. Dose-volume histograms (DVHs) were created and compared for GTV, PTV, small bowel and bladder. The GTV was covered by the conventional plan in all patients.


RESULTS
Significant differences were shown for median PTV coverage with conformal planning compared with conventional planning: 99.2% vs 94.2% (range 95.9-100% vs 75.5-100%); p<0.05. The median volume of irradiated small bowel was significantly lower for CT plans at all DVH levels. Median bladder doses did not differ significantly.


CONCLUSIONS
3D conformal CT planning is superior to conventional planning in terms of coverage of the tumour volume. It significantly reduces the volume of small bowel irradiated with no decrease in the rate of R0 resection compared with published data, and at the present time should be considered as the standard of care for rectal cancer planning.
Mount Vernon Cancer Centre, Northwood, Middlesex, UK. cariecorner@yahoo.com
C
C
Corner
F
F
Khimji
Y
Y
Tsang
M
M
Harrison
R
R
Glynne-Jones
R
R
Hughes
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001003:Anal Canal / Q000528:radiation effects; D003131:Combined Modality Therapy / Q000379:methods; D005260:Female; D006801:Humans; D007421:Intestine, Small / Q000000981:diagnostic imaging / Q000473:pathology / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden; D001743:Urinary Bladder / Q000000981:diagnostic imaging / Q000528:radiation effects
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