Hypofractionated whole breast radiotherapy: current perspectives

Figures & data

Table 1 Characteristics and outcomes of randomized hypofractionation trials

	Dose comparisons (Gy/fraction/wk)	Mastectomy (%)	Grade 3 (%)	Node positive (%)	10 years local control (%)	10 years cosmesis (% with good/excellent or “no event”)
RMH/GOC^Citation11
Control	50/25/5	0	Unknown	32.7	87.0	28.8
Arm 1	39/13/5				85.2	42
Arm 2	42.9/13/5				90.4	25.6
START A^Citation13
Control	50/25/5	15	28.1	28.8	92.6	72.9
Arm 1	39/13/5				91.2	78.4
Arm 2	41.6/13/5				93.7	71.8
START B^Citation13
Control	50/25/5	8	23	22.3	94.5	68.8
Arm 1	40/15/3				95.7	73.8
Canadian^Citation12
Control	50/25/5	0	19	0	93.0	71.3
Arm 1	42.5/16/3.5				94.0	69.8

Abbreviations: START, Standardization of Breast Radiotherapy Trial; wk, week.

Table 2 BED of different hypofractionated regimes compared to standard at different α/β (time factor not included)

Trial	Dose (Gy/fr)	Weeks	α/β=1	α/β=2	α/β=3.4	α/β=5
Control^Citation12,Citation13,Citation30	50/25	5	150	100	79.4	70
Canadian^Citation12	42.5/16	3.5	155.4	99	75.7	65.1
START A^Citation13	39/13	5	156	97.5	73.4	62.4
START A^Citation13	41.6/13	5	174.7	108.2	80.7	68.2
START B^Citation13	40/15	3	146.7	93.4	71.4	61.4
RAPID^Citation30,Citation31	38.5/10 (BID)	1	186.7	112.6	82.1	68.1

Notes: BED = nd[1 + d/α/β]; n = number of fractions, d = dose per fraction,²⁸ BID =2 fr/d separated by >6 hours.

Abbreviations: BED, biologically equivalent dose; START, Standardization of Breast Radiotherapy Trial.

Table 3 EQD2 of reported hypofractionation regimes compared to standard at different α/β

Trial	Dose (Gy/fr)	Weeks	α/β=1	α/β=2	α/β=3.4	α/β=5
Control^Citation12,Citation13,Citation30	50/25	5	50	50	50	50
Canadian^Citation12	42.5/16	3.5	51.8	49.5	47.7	46.5
START A^Citation13	39/13	5	52	48.8	46.2	44.6
START A^Citation13	41.6/13	5	58.2	54.1	50.8	48.7
START B^Citation13	40/15	3	48.5	46.6	44.9	43.9
RAPID^Citation30,Citation31	38.5/10 (BID)	1	62.2	56.3	51.7	48.6

Notes: EQD2 = BED/[1 + 2/α/β]²⁸; BID = 2 fr/d separated by >6 hours.

Abbreviations: EQD2, equivalent dose in 2 Gy/fr; START, Standardization of Breast Radiotherapy Trial; BED, biologically equivalent dose.

Figure 1 Recommended breast dose/fractionation prescribing algorithm for patients treated with breast-conserving surgery and whole breast radiation therapy.

Note: *Patients with large breast size that precludes achieving max dose of <107%, current smoker, implant for augmentation or reconstruction, postoperative infection, or significant postoperative breast edema.

Table 4 BED and EQD2 of different fractionation used in regional nodal radiation compared to standard

Dose (Gy/fr)	α/β=1		α/β=2		α/β=3.4		α/β=5
	BED	EQD2	BED	EQD2	BED	EQD2	BED	EQD2
50/25	150	50	100	50	79.4	50	70	50
40/15^Citation13	146.7	48.5	93.4	46.6	71.4	44.9	61.4	43.9
40/16^Citation3	140	46.7	90	45	69.4	43.7	60	42.8
37.5/16^Citation3	125.4	41.7	81.4	40.7	63.4	39.9	55.1	39.3
45/25^Citation3	126	42	85.5	42.8	68.9	43.4	61.2	43.7
45/15^Citation62	180	60	112.5	56.2	84.7	53.3	72	51.4
54/30^Citation62	151.2	50.4	102.6	51.3	82.6	52	73.4	52.5
Boost doses
10/4^Citation3	35	11.7	22.5	11.2	17.3	10.9	15	10.7
10/5^Citation46	30	10	20	10	15.9	10	14	10
16/8^Citation45	48	16	32	16	5.4	16	22.4	16

Notes: BED = nd[1 + d/α/β]; n = number of fractions, d = dose per fraction.²⁸ EQD2 = BED/[1 + 2/α/β].²⁸

Abbreviations: BED, biologically equivalent dose; EQD2, equivalent dose in 2 Gy/fr.

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