TECHNICAL ISSUES IN BREAST RADIOTHERAPY Dr Bharti Devnani

Moderator:- Dr Manoj Kumar Sharma

RADIOTHERAPY BY CONVENTIONAL METHOD

IMMOBILIZATION METHODS FOR IMPLEMENTATION

BREAST BOARD

Several adjustable features to allow for the manipulation of patients arms, wrists, head and shoulders.

To make chest wall surface horizontal, brings arms out of the way of lateral beams.

Arm abducted at 90 & hand holds handle of arm rest.⁰

Face turned towards opposite side.

Thermoplastic breast support can be added.

Constructed of carbon fiber which has lower attenuation levels

permitting maximum beam penetration.

VAC-LOCK

Breast ring with valecro Alpha cradle

FIELD BORDERS

FOR TANGENTIAL FIELDS Upper border – 2nd ICS (angle of Louis) when

supra clavicular field used. When SCF not irradiated – head of clavicle

Medial border – at or 1cm away from midline

Lateral border – 2-3cm beyond all palpable breast tissue – mid axillary line

Lower border – 2cm below inframammary fold

Anterior -2cm margin of light, above the highest point of breast.

A pectoralis major muscle

B axillary lymph nodes: levels I

C axillary lymph nodes: levels II

D axillary lymph nodes: levels III

E supraclavicular lymph nodes

F internal mammary lymph nodes

HOW TO IMPLEMENT IT?

Deciding angle of rotation of gantry for tangential fields:

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 pt. noted – medial tangent angle

CENTRAL LUNG DISTANCE

Perpendicular distance from post. tangential field edge to post part of ant. chest wall at centre of field

Best predictor of %age of ipsilateral lung vol. treated by tangential fields

CLD (cm) % of lung irradiated

1.5 cm 6%

2.5 cm 16%

3.5 cm 26%

IMPORTANCE OF BEAM MODIFICATION DEVICES (WEDGES)

Higher dose to

the apex without wedges

BOLUS

Increases dose to skin & scar after

mastectomy

Cosmetic results may be inferior

Universal wax bolus used

IRRADIATION OF REGIONAL LYMPHATICS

SCF IRRADIATION

SCF

Single anterior field is used.Field borders – Upper border : thyrocricoid groove

Medial border : at or 1cm across midline extending upward following medial border of SCM ms to thyrocricoid groove

Lateral border: insertion of deltoid muscle

Lower border : matched with upper order of tangential fields

A pectoralis major muscle

B axillary lymph nodes: levels I

C axillary lymph nodes: levels II

D axillary lymph nodes: levels III

E supraclavicular lymph nodes

F internal mammary lymph nodes

SUPRACLAVICULAR-AXILLARY FIELD

Humeral head shielding:–

• If arm angled >90⁰: Ax nodes overlap head

of humerus anteriorly.

• Larger the angle – less the head of humerus

spared in s.c port

MATCHING SUPRACLAV & CHEST WALL FIELDS

AngulationBy inferior angulation of the tangential fields.

Half beam block technique Blocking the supraclav field’s inferior half, eliminating its divergence inferiorly .

Hanging block technique

Superior edge of tangential beam

made vertical by vertical

hanging block.

Single isocentre technique:

• Isocentre placed at the

junction

of tangential and

supraclavicular field

• Inferior portion of field

blocked for supraclavicular

treatment and superior

portion blocked for tangential

field

IMN IRRADIATION

1. Extension of tangential fields– by extending medial border – 3cm across midline or by using imaging techniques

2. Separate field – • Medial border – midline , matching with

tangential field border• Lateral border – 5-6cm from midline• Superior border – abuts inferior border of

supraclav field or at 1st ICS (superior border of head of clavicle) if only IMNs are to be treated

• Inferior border – at xiphoid or higher if 1st three ICS covered

More normal tissue is being irradaited. (lung, heart and contralateral breast)

Anterior field Oblique field

MATCHING THE TANGENTIAL BEAMS WITH INTERNAL MAMMARY FIELD

ISSUES WITH DIRECT ANTERIOR FIELD (LARGE BREASTED WOMEN)

Cold region:- large amount of breast tissue over the

matchline

POSTERIOR AXILLARY BOOST

Medial border – To allow 1.5-2cm of lung on the portal film

Inferior border – at same level of inferior border of s.c field

Lateral border – just blocks fall off across post axillary fold

Superior border – splits the clavicle

Superolaterally – shields or splits humeral head

Centre – at acromial process of scapula

ELECTRON BOOST

BOOST-ELECTRONS

Appropriate energy selected to allow 85 -90% isodose line to encompass target volume & decrease dose to the lung.

Clinical set up - post lumpectomy volume or scar on skin +3 cm in all directions.

Energy – 9-16 MeV

Dose – 10-20Gy

TREATMENT IN PRONE POSITION

Plexiglas plateform with

rounded opening

TREATMENT IN LATERAL DECUBITUS POSITION

Carbon epoxy disposer

Opposite breast retracted upwards & outwards from the

field by elastic straps

• Useful for voluminous breast• For patients who are heavy smoker and previous history of lung or cardiac disease

• For deep seated tumor

Disadvantage – For nodal RT treatment position has to be changed

TREATMENT OF BILATERAL BREAST CANCER WITH CONVENTIONAL TECHNIQUE

ROLE OF IMRT IN BREAST CANCER

Reduces the hotspots specially in the superior and inframammary portions of the breast.

Increases homogenity

Manifests clinically into decrease in moist desqumation in these areas.

IMRT BREAST: WHY?

(1) Better dose homogeneity for whole breast RT

(2) Better coverage of tumor cavity(3) Feasibility of SIB(4) Decrease dose to the critical organs(5) Left sided tumors- decrease heart dose

FORWARD PLAN IMRT

ROLE OF 4D-CRT

RTOG GUIDELINES

DURING CT SIMULATION

Post-BCS

Post-Mastectomy

REGIONAL NODAL CONTOURING

Breast-superior

Breast-inferior

SCF begins

Axillary level III begins

Axillary level II begins

Axillary level I begins

Axillary level I ends

IMC begins

IMC ends

THANK YOU

INTERSTICIAL BOOST

When the CTV extends

deeper than 28 mm under the

epidermal surface, implants

have a higher ballistic

selectivity in terms of the

volume of the irradiated

breast tissue and dose to the

skin blood vessels than

electron beam boosts.

LOCALIZATION OF LUMPECTOMY CAVITY

Pre-op clinical finding , pictures Imaging- mammogram,usg,MRI Per-op finding HPR Surgical clips Post op imaging with USG,CT or MRI

Use of marker clips to localise the

boost target volume and

simulate entrance points of guide

needle at the skin of the

breast

Use of mammography in defining the boost target localisation in breast conserving treatment

A. Defining the implantation isocentre and definitive needle entrance and exit points at the skin for a breast implant. Reconstruction boost target isocentre from mammography, by simulator, or CT. The indicated entrance points are too close to the target volume (A)

B. Inclination of the implantation equator plane away from the target to avoid an overlap of the boost PTV and needle exit points at the skin

(C). Indication of new entrance and exit points, further away from the boost CTV, to avoid skin teleangiectases .

(D)Occurrence of severe teleangiectasic ‘stars’ at skin entrance or exit points if rules for implementation are not followed

Why this planning so important.With a delivered dose of 50 Gy , chances of late teleangiectases may occur in 30% of cases Vessels may have already received 20–40 Gy from the breastirradiation.Therefore, there is usually only a small dose amount left in skin vessel tolerance for teleangiectases

ANAESTHESIA Breast implants can easily be carried out under

L.A. and premedication with 2.5–5 mg midazolam given 15–30 min before the implantation.(GA, <0.5%)

The patient is placed in supine position with the homolateral arm in 90° abduction.

After the design of implant geometry and localisation of entrance and exit points of the needles, the skin is infiltrated at each point with 0.5–1 ml 1% lidocaine.

Retroareolar region is painful (1-5 ml extra infiltrate in that area)

DESIGN OF THE IMPLANT GEOMETRY

Needles are implanted parallel and equidistance from each other (Paris system).

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.

In some rare cases, the upper outer quadrant has to be implanted with needles orientated in a 45° angle to avoid overlap of source positions and skin

2 planes of needles are usually needed to cover the PTV.

A single plane may be sufficient in case of a target thickness of less than 12 mm.

Three planes are required in a large breast where the targeted breast tissue between pectoral fascia and skin is thicker than 30 mm.

Five to nine needles spaced 15–20 mm are usually required.

Reference needle is first implanted at the posterior (deepest) side into the centre of the PTV.

For definitive positioning, the needle should pass about 5 mm behind the internal scar.

The other needles of the posterior plane are then implanted parallel to the first one.

For definitive positioning, the needle should pass about 5 mm behind the internal scar.

The other needles of the posterior plane are then implanted parallel to the first one.