Table 1.

Dosimetric objectives and constraints

5-Fraction SBRT dose escalation
	PTV_Low	zPTV_High*
Target	([iGTV + TVI] + 3 mm)	([iGTV + TVI] + 3 mm)–GI PRV
Total dose, cGy	3300	5000
Objective	>98% coverage	1. ≥98% coverage of iGTV to 4000 cGy
		2. ≥95% coverage of TVI to 4000 cGy
		3. ≥90%–95% coverage of iGTV to 5000 cGy†
15-Fraction IMRT dose escalation
	PTV_Low	zPTV_High*
Target	(iGTV + CA/SMA‡) + 10 mm	iGTV–GI PRV
Expansion	CTV + 5 mm	None
Total dose	3750 cGy	6750 cGy
Objective	>98% coverage	1. ≥98% coverage of iGTV to 4500 cGy
		2. ≥90%–95% coverage of iGTV to 6750 cGy†
Organ at Risk	15-fraction (IMRT) constraint	5-fraction (SBRT) constraint
Spinal cord	Dmax <30 Gy	V20 <1 cm3
Liver	700 cm3 <24 Gy	V12 <50%
	Mean <24 Gy
Kidneys (left and right)	V20 <33%	V12 <75%
iStomach	Dmax < 45 Gy	V40 <0.5 cm3
		V35 <1 cm3
		V30 <2 cm3
iDuodenum	Dmax <45 Gy	V40 <0.5 cm3
		V35 <1 cm3
		V30 <3 cm3
iBowel (small)	Dmax <45 Gy	V40 <0.5 cm3
		V35 <1 cm3
		V30 <2 cm3
iBowel (large)	Dmax <50 Gy	V35 <1 cm3
Bile duct	Dmax <70 Gy	Max 55 Gy
Spleen	Mean <6 Gy	Mean <2 Gy
Heart	V40 < 10%, V50 <1 cm3, Max 55 Gy	Max 30 Gy

Abbreviations: CA = celiac axis; CTV = clinical target volume; Dmax = maximum dose; GI PRV = gastrointestinal planning organ-at-risk volume; iGTV = internal gross tumor volume; IMRT = intensity modulated radiation therapy; PTV = planning target volume; SBRT = stereotactic body radiation therapy; SMA = superior mesenteric artery; TVI = tumor–vessel interface.

^*Modified planning target volume is indicated by prefix “z” and is not to be used for plan evaluation.

^†Represents an ideal target objective and may not be attainable in all cases.

^‡Areas at high clinical risk of microscopic disease.