Table 2.

Planning target volumes, dose, and constraints in randomized controlled trials of accelerated partial breast irradiation (APBI)

	GEC-ESTRO	ELIOT	TARGIT-A	IMPORT LOW	OCOG-RAPID	NSABP-B39/RTOG 0413	University of Florence
Study dose/fractionation	PBI: 32 Gy/8# BID or 30.3 Gy/7# BID (HDR multi-catheter BT) OR 50 Gy, 0.6–0.8 Gy/h PDR multi-catheter BT WBI: 50–50.4 Gy/25–28# + 10 Gy/5# tumor bed boost	PBI: 21 Gy/1# WBI: 50 Gy/25# + 10 Gy/5# tumor bed boost	PBI: 20 Gy/1# WBI: varied	PBI: 40 Gy/15# daily or 36 Gy/15# to whole breast and 40 Gy/15# to partial breast or WBI: 40 Gy/15#	PBI: 38.5 Gy/10# BID WBI: 42.5 Gy/16# or 50 Gy/25# ± 10 Gy/4–5# tumor bed boost	PBI: 34 Gy/10# BID (BT) or 38.5 Gy/10# BID (3D-CRT) WBI: 50–50.4 Gy/25–28# ± 10–16 Gy tumor bed boost	PBI: 30 Gy/5# non-consecutive days (over 2 weeks) WBI: 50Gy/25# + 10 Gy/5# tumor bed boost
Partial breast irradiation modality	HDR multi-catheter BT or PDR	Intraoperative (electrons)	Intrabeam intraoperative device (kV X-rays)	Forward planned field-in-field IMRT	3D-CRT (87%) IMRT (10%)	3D-CRT (73%) or HDR multi-catheter (6%) or single entry (e.g., Mammosite or SAVI) (21%) BT	IMRT
Partial breast planning volume	Tumor bed + at least 2 cm margin (defined individually for each patient based on width of pathologically clear surgical margin and radiation safety margin)	CTV based on tumor size and site	Tumor bed	Visualized surgical cavity + 1.5 cm (CTV) + 1 cm (PTV) *CTV edited to 5 mm from skin surface and pectoralis fascia posteriorly *PTV edited to 5 mm from skin surface	Visualized surgical cavity + 1 cm (CTV) + 1 cm (PTV) *CTV excludes 5 mm from skin, chest wall and pectoralis muscle *PTV edited from skin and chest wall to create a PTVeval	3DCRT: Visualized surgical cavity + 1.5 cm (CTV) + 1 cm (PTV) *CTV excludes 5 mm from skin, chest wall and pectoralis muscle *PTV edited from skin and chest wall to create a PTVeval Multicatheter BT/Mammosite: excision cavity/balloon + 1.5/1 cm = CTV=PTV = PTVeval * edited from skin and chest wall to create a PTVeval	Visualized surgical cavity + 1 cm (CTV) + 1 cm (PTV) *CTV excludes 3 mm from skin surface *PTV extends only 4 mm into lung, and excludes 3 mm from skin
Target dose constraints	100% prescribed dose to ≥ 90% target volume	Dose prescribed to 90% isodose line	20 Gy to tumor bed surface, attenuating to 5–7 Gy at 1 cm depth	≥ 95% CTV should be covered by 95% isodose line	95–107% prescription dose to PTVeval	3DCRT: ≥ 90% PTVeval be covered by 90% isodose Multicatheter BT/Mammosite: ≥ 90% PTVeval be covered by ≥ 90% isodose	100% PTV covered by 95% prescribed dose;
Homogeneity constraints	V100%/V150% < 0.35	-	-	Dose to 2 cc < 105–107%	Maximum dose to PTV ≤ 107%	3DCRT: Maximum dose to PTV ≤ 120% Multicatheter BT: V150% ≤ 70 cc, V200% ≤ 20 cc, 1-V150/V100 ≥ 0.75 Mammosite: V150% ≤ 50 cc, V200% ≤ 10 cc	Maximum dose to PTV < 105%; minimum dose to PTV = 93%;
Ipsilateral breast volume constraints	Maximum skin dose < 70% of prescription dose	-	-	-	< 25% (35% acceptable) to be covered by > 95% isodose; < 50% (up to 60% acceptable) to be covered by 50% isodose; 0% to receive > 107%	3DCRT: < 35% to be covered by 100% isodose; < 60% to be covered by ≥ 50% isodose Multicatheter BT: skin dose ≤ prescription dose, < 60% to be covered by ≥ 50% isodose Mammosite: maximum skin dose ≤ 145% prescription dose, < 60% to be covered by ≥ 50% isodose	≤ 50% uninvolved breast to receive > 50% of prescribed dose

BT brachytherapy, HDR high-dose rate, PDR pulsed-dose rate, IMRT intensity-modulated radiation therapy, 3D-CRT 3D conformal radiation therapy, kV kilovoltage, PBI partial breast irradiation, # = fractions, WBI whole breast irradiation, CTV clinical target volume, PTV planning target volume, PTVeval planning target volume for dose volume evaluation