Techniques of tumour bed boost irradiation in breast conserving therapy: Current evidence and suggested guidelines

Figures & data

Table I.  Dose fractionations used in various prospective randomized studies of boost versus no boost.

Trial	Number of patients	EBRT (dose/ fraction)	Boost (dose/ fraction)	LR (%)	Median Follow-up (year)
Bartelink et al. [11]	2 657	46–50Gy/25 fr	–	10.2	10
	2 661	50 Gy/25 fr	16 Gy/8 fr	6.2
Romestaing et al. [24]	503	47–50 Gy/20 fr	−10 Gy/4 fr	4.5	3.3
	521	50 Gy/20 fr		3.6
Teissier et al. [25]	327	48–50 Gy/25 fr	–	6.8	6.1
	337	50 Gy/25 fr	10 Gy/5 fr	4.3
Polgar et al. [26], [27]	103	49–50 Gy/25 fr	–	15.5	5.3
	104	50 Gy/25 fr	12–16Gy/3–8 fr	6.7
Graham et al. [28]*	674	50 Gy/25 fr	–	NR	NR
	674	45 Gy/25 fr	–	NR
Nagykalnai et al. [29]	55	50 Gy/25 fr	–	10.7	3.8
	56	50 Gy/25 fr	10 Gy HDR/20 Gy LDR	5.4

*The results haven't been reported as yet. Only early quality of life results have been reported.

EBRT: external beam radiation therapy; LR: Local recurrence; fr: fractions; HDR: High dose rate; LDR: Low dose rate; NR: recorded.

Table II.  Histopathological analysis for microscopic tumour foci.

Author	No. of pts/Specimens	No MCF*	MCF in index quadrant/tumor bed	MCF elsewhere in ipsilateral breast
Holland et al. [29]	282	37%	20%	43%
Vicini et al. [30]	441	36%	55%	9%
Vaidya et al. [31]	30	37%	50%	13%

*MCF: Multicentric tumour foci; pts: patients; Tumor: tumour.

Table III.  Comparison of various techniques of boost delineation.

Technique	Advantages	Disadvantages
Surgical Scar	Feasible. No additional costs. Non invasive.	Depends on placement of scar. Highly subjective.
Clips & Fluoroscopy.	Feasible. Inexpensive.	Mobility of clips in the lumpectomy cavity. Variable position and numbers.
Ultrasonography	Can be used intra as well as post-operatively. Images are compatible with RT planning systems. Is relatively inexpensive. Non-invasive. Reproducible images. Tumour bed is directly visualised.	Ineffective for identifying tumour bed. Definition hampered by healing process. Poor definition 6–8 weeks post-operatively.
Clips & Computerised Tomography	Accuracy same as that of clips and fluoroscopy. Can be planned in treatment position. Excellent definition of breast tissues.	Glandular tissues not well defined. Clips necessary for definition. Varies with window settings.
Magnetic resonance imaging	Accurate localisation of target volume. Accurate localisation of organs at risk.	Costly, limited resources. Image distortion during co- registration with TPS. Difficulty in scanning in treatment position.

Table IV.  Comparison of electron beam and interstitial brachytherapy boost.

	Electron Beam			Brachytherapy
Author	No. of pts.	10 yr DFS	IBTR	No. of pts.	10 yr DFS	LR*
Mansfield et al. [23]	416	78%	18%	654	76%	12%
Perez et al. [71]	490	79%	6%	129	80%	7%
Touboul et al. [72]	160	85%	15%	169	86%	8%
Bartelink et al. [9]	1 653	–	4.7%*	225	–	2.5%^#
Polgar et al. [27]	52	94%^#	–	52	91.4%*	–

*LR: local (ipsilateral breast) recurrence; ^#5 year survival.

DFS: Disease free survival; IBTR: Ipsilateral breast tumour recurrence.

Table V.  Controversies and suggested guidelines in tumour bed boost in breast cancer.

Controversy	Suggested Guidelines	Level of Evidence
To boost or not to boost	To give boost to all patients; maximum absolute risk in younger patients	I
Boost dose	15–20 Gy	I
Positive margins	Boost dose escalation.	III
Boost fractionation	Electrons: 2–2.5 Gy per fraction HDR: 3–4 Gy per fraction	III
Concomitant/Simultaneous integrated boost	Investigational	III
Technique of Boost delivery	Electrons or brachytherapy	I
Boost delineation	Electrons – CT with surgical clips Brachytherapy – Ultrasound	III
Margins to tumour bed	Electrons – 1–2 cm High dose rate brachytherapy – 1 cm	III

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