Dosimetric analysis and comparison of reduced longitudinal cranial margins of VMAT-IMRT of rectal cancer

Radiation Oncology

Table 2 Absolute dose parameters of organs at risk for different cranial PTVs of rectal cancer

Structure	Parameter	PTV0	PTV-1	p-value	PTV-2	p-value	PTV-3	p-value
		Dose (Gy)
Rectum	Median	50.5	50.4	0.170	49.9	0.220	49.6	0.185
Rectum	Max	53.4	53.2	0.110	53.3	0.687	53.3	0.624
Sigmoid colon	Median	38.8	37.4	0.362	33.1	0.126	29.8	0.093
Sigmoid colon	Max	51.9	52.0	0.575	51.7	0.444	52.0	0.221
Femoral head	Median	23.4	23.6	0.646	23.9	0.241	23.8	0.646
Femoral head	Max	37.9	38.2	0.441	38.8	0.203	38.6	0.114
Bladder	Median	28.0	27.8	0.153	27.0	0.110	25.7	0.013
Bladder	Max	52.5	52.5	0.575	52.7	0.314	52.7	0.221
Bone	Median	27.6	26.6	0.007	24.9	0.005	21.9	0.005
Bone	Max	53.8	53.8	0.959	53.7	0.594	53.8	0.959
Small bowel loops	Median	2.7	1.1	0.005	0.6	0.005	0.4	0.005
Small bowel loops	Max	45.5	45.5	0.508	42.8	0.441	41.1	0.445
Peritoneal space	Median	20.9	15.5	0.005	9.9	0.005	5.0	0.005
	Max	53.6	53.6	0.721	53.8	0.386	53.4	0.214
	65 cc	50.9	50.4	0.475	48.5	0.083	46.1	0.007
	100 cc	49.3	48.5	0.153	46.2	0.028	44.4	0.005
	180 cc	46.2	44.2	0.038	42.8	0.009	41.6	0.005
	830 cc	18.0	14.9	0.012	9.6	0.012	7.5	0.012

Bold values: statistic significant to PTV0. PTV-1 = PTV minus 1 cm on cranial site. p-value = PTV1,2,3 vs. PTV0

ISSN: 1748-717X