Radiotherapy techniques in the treatment of breast cancer; primary focus on 2D planning.

1. Radiotherapy Techniques in
CA breast
by Dr Animesh Agrawal
Moderator Dr Shagun Misra

2. Treatment Planning
Objectives
• Adequate tumor coverage
• Uniform dose distribution throughout target volume
• Minimize doses to normal tissue

3. Steps in Planning
• Positioning
• Immobilization
• Simulation
• Target Volume
• Treatment Planning
• Dose & Fractionation
• Set Up Verification
• Sequelae Of Radiotherapy

4. Primary goal
• Reproducibility and patient comfort
• Minimize positioning errors
Importance of efficient setup
• Make patient feel more secure & less apprehensive.
• Help stabilize relationship between external skin marks &
internal structures.
• May help the planning process itself.
• Can reduce time for daily set up
Setup & Immobilization

5. Treatment Position
• Most important aspect of positioning - patient comfort &
reproducibility.
• Supine
• Prone
• Older techniques
- Lateral
- Erect

6. Positioning devices
• Breast board
• Wing board

7. Breast Board
• An inclined plane
with multiple angle
positions.
• Anterior chest wall
slopes downward
from mid chest to
neck.
• Inclination is limited to a 10 – 15° angle for 70 cm, and 17.5 –
20° for larger bore CT scanners.
• Has a wedge to prevent the patient from sliding down.

8. • Several adjustable parts to
allow for the manipulation of
patients’ arms, wrists, head &
elevation.
• Makes chest wall surface
horizontal.
Advantages of breast board
• Takes the arms out of the way of lateral beams.
• Thermoplastic breast support can be added for immobilization
of large pendulous breast.
• Constructed of carbon fibre which has lower attenuation levels
permitting maximum beam penetration.

9. Wing board
Pros & cons
• Simpler positioning device
• Can be used in narrow bore gantry
• Chest wall slope cannot be corrected
• Need other techniques for reducing
OAR doses and field matching.
Wing boards are also suitable devices for
patient setup while treating the breast/CW.
They allow the patient to raise both arms
above the head with comfortable resting
platforms for the elbows.

10. Other treatment positions
• Requires patient to climb onto a prone board, lie on the
stomach & rest the arms over the head.
• The i/l breast gravitates through a hole in the breast board &
c/l breast is pushed away against an angled platform to avoid
the radiation beams

11. Prone breast board
System includes:
• Prone board
• Face cushion
• 15 Degree Contralateral Wedge
• Handles

12. Advantages

13. Prone vs Supine: Pros and Cons
A systematic review of methods to immobilise breast tissue during adjuvant breast irradiation
Sheffield Hallam University Research Archive

14. Immobilization devices
• Thermoplastic shells
• Adhesive tape
• Vac lock
• Alpha cradle
• Wireless bra
• Breast ring
• Breast cup
• Stocking
• Vacuum
• L-shaped breast plate

15. For large pendulous breast:
• These patients if treated supine may require a breast support,
either with a thermoplastic shell, or breast cup which can be used
to bring the lateral and inferior part of the breast anteriorly away
from the heart, lung and abdomen.

16. Ring device
The ring consisted of a hollow PVC tube wrapped around the base
of the breast and supported by a Velcro strap

17. Simulation
• CT acquired superiorly from neck to diaphragm.
• Slice thickness should be sufficient (usually 5 mm) but
dependent on agreed local CT protocols.
- Inverse planning?
- Motion management
• Three reference tattoos are placed on the central slice and in
right & left sides to facilitate setup.
• CT based planning is the standard.
• Scar & drain sites identified with
wires/markers.
• Field borders marked with radiopaque wires.
• Radiopaque wires are also placed encircling
breast tissue.

18. Supine:
• Most common and preferred setup.
• Arm(s) abducted, externally rotated & head turned to the C/L side.
• Breast tilt boards with armrests used for positioning.
• Immobilization devices (e.g., Alpha cradle, plastic moulds) can be
used.

19. Arm Position
• Arm elevation required to facilitate tangential fields across the
chest wall without irradiating the arm.
• The preferred arm position is bilateral arms to be abducted 90
degrees or greater & externally rotated.
• Advantages of raising both arms vs only the I/L arm
- Patient is more comfortable and relaxed
- More symmetrical and easily reproducible with lesser chances of rotation
of the torso
- Better matching of the previously irradiated field if c/l breast requires
radiation in future.
• Factors deciding the angle of arm elevation
- Ability to elevate without discomfort.
- No/Minimal skin folds in the Supraclavicular region.
- Ability to move the patient through the CT aperture.

20. Position of head
• Rigid head holder or a neck rest can be used to stabilize &
position head.
• Chin should be elevated to minimize neck skin folds within the
SCF field.

21. Treatment Planning
• Conventional planning
• Three-Dimensional Conformal RT
• Intensity-Modulated Radiation Therapy

22. Treatment volumes
After BCS After Mastectomy
• Whole breast + Lumpectomy
cavity boost + Regional
nodes
OR
• Partial Breast + Regional
Nodes
• Chest wall
• Mastectomy scar
• Regional nodes

23. 2D Planning

24. Conventional planning
• Setup & immobilization
• Technique
• Field borders
• Simulation
• Setting the tangential beams
• Beam modification
• Setting additional fields (SCF, PAB, IMN)
• Field matching

25. Positioning
• Breast board.
• Supine with anterior chest wall
parallel to couch.
• Arms overhead.
• 2 field: Patient looks straight up.
• 3 field technique: Turn the head
to the opposite side to be treated.

26. Technique for EBRT
• Two tangential fields are used.
• Additional fields may be required for SCF, IMC & boosting
the axilla.

27. Field borders For tangential fields
• Cranial border: 2nd ICS (angle of Louis) or
head of clavicle, depending on SCF
treatment.
• Medial border: at or 1cm away from
midline.
• Lateral border: 2cm beyond all palpable
breast tissue – mid axillary line.
• Lower border: 2cm below inframammary
fold (of opposite breast if post MRM).
• Borders can be modified in order to
- Cover entire breast tissue.
- Include nodal volumes and scars.
DO NOT MISS THE TARGET.

28. SSD technique
• Lead wire placed on lateral border
• Field opened at 0⁰ rotation on chest wall and central axis placed
along medial border of marked field
• Gantry rotated , until on fluoroscopy, central axis & lead wire
intersect – angle of gantry at that point is noted – medial
tangent angle.
• Lateral tangential angle is 180 °opposite to medial tangent
• Simulation film is taken.
Deciding angle of gantry for tangents

30. SSD: 80cm
A
B C

32. Gantry 00
Gantry 900
SAD
SSDSAD - SSD

33. • POP contour of the breast is made at this point
and transferred onto paper.

34. • The length of the field is set from the upper margin
marked clinically to the lower margin marked
clinically. The width of the field is taken such that
anteriorly around 1.5 cm margin is given from the
surface of skin for breathing movements.
• The isocentre is derived.

36. Junction of 1/3rd
with 2/3rd
A
B C

37. • Check whether the entire breast
is covered in portal.
• Margin of 1.5 - 2cms beyond the
breast for respiratory excursion.
• Whether there is 1 to 3 cm of
lung visible on the simulation
film in the field anterior to the
posterior field edge.
- At least 1cm of lung?
• Whether the lead wire coincides
with the posterior edge of the
portal.

38. Beam Modification Devices in
Breast Radiotherapy
Blocks
Wedges
Compensators
Bolus
WBRT uses tangential field technique; however,
dose distribution is complicated because of
• Irregularities in the chest-wall contour.
• Varying thickness of the underlying lung.

39. • To prevent excess volume of lung irradiated, the divergence
of the deep margins is matched.
- Angle the central axes slightly more than 180⁰
- Half beam block technique
Matching Divergence of Photon Beam

41. Half Beam Block technique.
• By moving one of the
independent jaws to midline, a
half beam block can be created.
• This forms a non-divergent field
edge centrally.
• The half beam block is easier to
set up (less movements of the
couch/gantry).

42. • Wedges Are Used As Compensators In Breast Radiotherapy.
• Dose uniformity within the breast tissue can be improved
• Preferred in the lateral tangential field than the medial
• However, wedges can compensate only along one axis.
• Compensators can be used to allow better dose distribution.
• Bolus increases dose to skin & scar after mastectomy
• In PMRT 3-5mm bolus is used over the chest wall every other
day or every day for 2 weeks (20 Gy total dose) and then as
needed to ensure that a brisk radiation dermatitis develops
• Cosmetic results may be inferior.
• Universal wax bolus is used.

43. Wedges alter dose distribution
only in the transverse direction
and not in the sagittal direction
of the tangential fields.
Higher dose to the apex without
wedges

44. • If a wedge with an
inadequate angle is
used, the correction
isn’t adequate.
• Ideal correction; only
small hotspot.
• Too high a wedge
angle will result in
cold spots.

45. Alignment of the Tangential Beam with
the Chest Wall Contour
• Rotating Collimators
• Breast Board
• MLC shaping

46. Sloping surface of chest wall
Due to the obliquity of the anterior chest wall, the tangential fields
would include a disproportionate amount of lung cranio-caudally.
Collimator of the tangential beam may be rotated to resolve this.

47. • The need for collimation can be eliminated if the upper torso
is elevated so as to make the chest wall horizontal.
• This can be done by Breast board.

49. Selection of appropriate energy
• Beam energy of 4 to 6 MV are preferred (>6 MV would
underdose superficial tissue).
• However a large tangential field separation will cause significant
dose inhomogeneity, necessitating higher energy beams.
- Often combined with lower energy beams as part of a
forward optimized plan (along with field-in-field technique)
to obtain desirable distributions.
• Dynamic multileaf collimators (MLCs) may also be utilized to
reduce dose inhomogeneity.

50. Doses to Heart & Lung By Tangential Fields
• The amount of lung included in the irradiated volume is
greatly influenced by the portals used.
• Various parameters are used to determine he amount of lung
& heart in tangential field.

51. Central lung distance (CLD)
• Predictor of percentage of
ipsilateral lung volume treated
by tangential fields.
CLD
% of lung
irradiated
1.5 cm 6%
2.5 cm 16%
3.5 cm 26%
• Upto 2-3cm of underlying lung may be safely included in the
tangential portals.
• Radiation pneumonitis risk <2% with CLD < 3cm, rising upto
10% with CLD 4-4.5 cm.

52. • CLD: Perpendicular distance from the posterior tangential field
edge to the posterior part of the anterior chest wall at the center
of the field
• MLD: Maximum perpendicular distance from the posterior
tangential field edge to the posterior part of the anterior chest
wall.
Central lung distance marked on the digitally
reconstructed radiograph (a) and on the central
axial slice (b).

53. Dose to heart can be minimized by
• Median tangential breast port
• Cardiac block & electron field
• Breath hold
• Gating
Maximum Heart Distance: maximum perpendicular distance
from the posterior tangential field edge to the heart border.

54. Dose to the Contralateral Breast
• Radiation dose to the contralateral breast is of concern due to
potential carcinogenic effect of radiation.
• This risk appears to be minimal with modern techniques;
however ALARA principle is to be followed.
• Techniques used:
- Lead blocks (2.5cm thickness) over contralateral breast while
treating the Medial tangent.
- Wedges should be used, whenever possible, on the lateral tangent
rather than the medial.
- Half beam blocks/independent jaws to block out posterior half of
them beam also help reduce the dose to opposite breast.

55. Dose of radiation
• Whole breast radiotherapy/chest wall irradiation
• Conventional Dose: 50 Gy / 25# given in 5 weeks
• Hypofractionated dose schedule
- 40 – 42.4 Gy in 15-16 daily fractions given in 3 weeks
• Boost irradiation to Tumour bed
- 10 - 16 Gy in in 5-8 fractions given over 1 - 1.5 weeks.
• Regional Nodal irradiation
- Same dose as to Whole breast/Chest wall
• APBI
- Brachytherapy: 34Gy/10# treating 2#/day, over 5 days
- EBRT: 38Gy/10# treating 2#/day, over 5 days

56. Irradiation of Regional Lymphatics
• Supraclavicular Lymph Nodes
• Axillary Lymph Nodes
• Posterior Axillary Boost
• Internal Mammary Lymph Nodes

57. SCF field
• Single anterior field is used.
Field borders
• Cranial: Thyrocricoid groove.
• Medial: At or 1cm across midline
extending upward along medial border
of SCM to thyrocricoid groove.
• Lateral: Just medial to the humeral
head, insertion of deltoid muscle
• Caudal: Matched with cranial border of
tangents (usually just below clavicle
head).
• Field is angled approximately 10 to 15 degrees laterally to spare
the cervical spine.
• Dose is calculated at a depth of ~3 cm.

58. • The level III of the axilla and the upper IMN have been
contoured and projected on the DRR.
• These contours can be used to determine depth of dose
prescription.
Humeral head
shielding

59. Matching SCF & chest wall fields
• A hot spot caused by divergence of the tangential & the SCF
field at the junction.
• This may result in severe match line fibrosis or even rib
fractures.
• The divergence of fields can be eliminated by
- Angling the foot of the treatment couch away from the radiation
- Collimator rotation
- Hanging block
- Half beam block

60. Angulation: Angling the foot of the treatment couch away from the
radiation source direct the tangential beams inferiorly so that the
superior edges of these beams line up perfectly with the inferior
border of the supraclavicular field.
Matching SCF & chest wall fields

61. Matching SCF & chest wall fields
Hanging block technique:
Superior edge of tangential beam
made vertical by vertical hanging
block.
Half beam block technique:
Blocking the SCF field’s inferior
half, eliminating its inferior
divergence. Simultaneously,
cranial half of the tangents is also
half-blocked.

62. • Single isocenter is set at the match between the supraclavicular
and tangential fields.
Mono - Isocentric matching technique

63. Typical dose distribution after planning with a
mono-isocentric technique.

64. • Level I & part of level II nodes included in tangents.
• Level III nodes are covered in SCF field.
Modifications
• Modifications in the tangential & axillary field can be done for
better coverage of axillary nodes.
• Depending on the dose distribution and patient’s anatomy, a
posterior axillary boost may be considered
Axillary Nodal Irradiation

65. Modification in tangential field: High tangents
Field border:
• Cranial edge: 2 cm below humeral head
• Deep edge: 2 cm lung from chest wall interface
Covers 80% of level I/II node.

66. • Usually the lateral border of SCF
field is just medial to the humeral
head.
• When the axilla is treated
supraclavicular field is extended
laterally
- To cover at least two-thirds of
the humeral head.
- Insertion of deltoid or up to
surgical head of humerus
Modification in SCF field

67. Field borders
• Medial: Allow 1.5-2cm of
lung on portal film.
• Caudal: Inferior border of
SCF field.
• Lateral: Just blocks fall off
post axillary fold.
• Cranial: Splits the clavicle.
Posterior Axillary Boost
• Superolateral: Shields or splits humeral head
• Centre: at acromial process of scapula

68. • The posterior axillary boost was traditionally employed to
supplement axillary dose.
• This was done in patients with ↑ axilla separation, as the
axillary plane would receive only 70-80% of the prescribed
dose.
• The remainder of the dose (i.e. 20-30% of the prescription
dose) would be prescribed through a posterior field to achieve
a more desirable distribution.
• Mostly a feature of the low energy Co-60 based era. Only
rarely required during modern day accelerator based therapy.
Posterior Axillary Boost

69. Indications of RT to Internal Mammary nodes
• Positive axillary lymph nodes with central & medial lesions.
• Stage III disease.
• Positive sentinel lymph nodes in IM chain.
• Positive SLN axilla with drainage to IM on lymphoscintigraphy.
Internal Mammary Nodal Irradiation

70. IMN Irradiation
Techniques used:
• Wide or deep tangents
• Direct anterior field matched to tangential fields
- Direct anterior / Oblique
- Photon / Electron / Mixed photon-electron

71. Wide Tangents
• The nodes in the first three
intercostal spaces are thought to
be most clinically significant.
• The medial border of the
tangential field is moved 3 to 5
cm across the midline to cover
the internal mammary nodes in
the first three intercostal spaces
• To minimize lung and cardiac
exposure, block can be used

72. Normal tangential fields
Wide tangents

73. Separate IMC field
• Medial: Midline
• Lateral: 5-6cm from midline
• Superior: Inferior border of SCF (or lower border of clavicle)
• Inferior: At xiphoid (or higher if 1st three ICS covered)
• Depth: 4-5 cm

74. • The match between an anterior IMN field and the medial
tangent can be a problem if there is a significant amount of
breast tissue beneath the match line.
Separate IMC field: Issues
A significant cold region exists if the IM
and tangential match-line overlies a
large amount of breast tissue.
As long as the breast tissue beneath
the match line is thin, the cold area
is negligible.

75. Oblique incidence of IMC portal
match the orientation of the adjacent
medial tangential portal; this results
in a more homogeneous dose
distribution at the junction of the
two fields.
• Isodose presentation of optimal
matching of an obliquely incident
electron beam to the tangential
beams. The target volume is
enclosed by the 90% isodose line.
Separate IMC field: Oblique Beams

76. • Using photons only to treat the IMN causes a large dose to
be delivered to the OARs, irrespective of the planning
technique and beam orientations employed.
• Using electrons to treat the IMN allows much lower doses to
the lungs and heart given the sharp dose fall offs.
• However, because of that fall off it is often difficult to
achieve desirable coverage of IMN with electrons.
- Especially so because of the decreasing depth of the IMN chain as
one moves in the caudal direction.
• Using electrons for IMN creates a problem of matching of
photon and electron fields.
Photon – Electron Combination

77. • Isodoses of a combined plan.
• Representation of such a plan
on patient surface.

78. A: IMN covered together with
the chest wall by extending
the tangents 3 cm across the
midline.
B: IMN covered by a separate
5-cm-wide anteroposterior
field.
C: IMN covered by a separate
field angled laterally 50 less
than the medial tangential
field. The cost of doing this is
increasing the lung dose.
D: Chest wall and IMN
covered by anterior electron
field. The depth of
penetration is shaped by a
custom bolus placed on the
chest wall.

79. Problems with IMN treatment
• Dose to heart/lungs
- Irrespective of the technique used, there is at least some compromise
in terms of the dose delivered to the lung and/or heart.
• Field matching
- If a separate IMN field is used, the issue of matching arises. Match
line fibrosis/hot spots or cold spots with geometric miss are both
risks of such a plan.
• Clinical benefit?
- Given the uncertain clinical benefits with IMN irradiation, it is
uncommon to irradiate these nodes.

80. CT Based planning
Set user origin
Mark the Inter
field separation

83. Low Energy (Cobalt)
High Energy (6MV)

84. Boost to Tumor Site after WBRT in BCS
• Rationale: Local recurrences tend to be primarily in and around
the primary tumor site – boost ↓ risk of marginal recurrence.
• More advantageous when margins unknown & in women less
than 40 years. Benefit in elderly uncertain; may omit.
• Given by either EBRT or Brachytherapy.
• EBRT: Photon, Electrons
• Brachytherapy: Interstitial catheters, mammosite

85. Localization of lumpectomy cavity
• Various techniques of localizing the tumour bed include
• CT scan
• MRI
• USG
• Pre op MMG
• Surgical scar/ pT size

86. Localization of lumpectomy cavity
• The combination of surgical clips with a treatment planning
CT with pre-treatment imaging is most ideal.
• CT of biopsy cavity or postsurgical changes, in
combination with clinical information including
mammography, scar location, operative reports, and patient
input, provide accurate information regarding placement of
the field and energy of the electron boost.

87. Boost: Electrons
• The accelerator head points straight down onto the target
volume.
• Electron beam boost preferred because of
- Relative ease in setup
- Low dose to whole breast
- Good cosmetic results
- Lower cost
- Decreased time demands on the physician
• Lumpectomy cavity + 2cm margin in all directions =
approximate size of boost field.

88. • The margins of this field are marked on the skin with the
centre of the scar as the centre of field

89. Photon Boost
Mini tangential fields
used to boost target
volume

90. Interstitial boost
• 1 - 3 planes of needles
may be needed to cover
the PTV depending upon
size.
• Needles are implanted (typically following the Paris rules).
• In most cases inserted in a mediolateral direction.
• In very medially or laterally located tumor sites, needles should
be implanted in a craniocaudal direction .to enable separate target
area from skin points.

91. • Beam matching can be difficult
• Dosimetry performed only on in the midplane of the target
volume.
• Dose distribution can be inhomogenous away from the
central axis (superoinferiorly), especially in large breasts.
• Doses to the OARs (Heart and lung) cannot be determined
accurately.
• Shielding of heart while treating the left breast, won’t
ensure whether a part of the target volume is being missed.
Disadvantages of 2D Planning

92. Conformal Radiotherapy
• Standard opposed tangential fields with appropriate use of
wedges and field-in-field technique to optimize dose
homogeneity remains the most commonly employed method
for RT to whole breast/chest wall.
• 3D-CRT may improve dose to target volume & reduction in
dose to normal tissues & critical organs
• Better cosmetic results
• Less dose to heart and lung

93. Conformal Radiotherapy
• Setup and Immobilization
• Image acquisition
• Delineation of target
- Whole Breast + Lumpectomy cavity
- Chest Wall
- Axilla, SCF and IMN: As indicated
• Delineation of OARs
- Lungs
- Heart
- Left Anterior Descending artery
- Brachial plexus
• Planning: Forward; 3D-CRT (Role of inverse planning?)
• Treatment

94. Forward IMRT

95. Accelerated Partial Breast Irradiation
• Interstitial brachytherapy using catheters
• Intracavitary brachytherapy: Mammosite
• 3DCRT/IMRT
• Intra-operative electrons (ELIOT) or orthovoltage X rays
(TARGIT)

98. Thank you