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Primary Radiation Treatment of the Breast


Medical editor Bjørn Naume MD
Oncologist
Oslo University Hospital
Norway

General

Primary radiation treatment is often given in combination with other tumor-directed treatment such as chemotherapy, surgery, or endocrine treatment. Dose and target volume are adapted individually.

Sometimes when the tumor is large and the effect of chemotherapy is not satisfactory, surgery is difficult to perform. In such cases, radiation treatment can be performed without prior surgery.

Primary radiation treatment may be an alternative in the event that the patient cannot undergo surgery for medical reasons. Treatment in these cases are individualized and a radiation dose of 60 Gy to the tumor area is striven for.

Indications

  •   Locally advanced/invasive, inoperable breast cancer T3-4N0-3, T1-2N2-3 
  •   Inoperable inflammatory breast cancer
  •   The patient does not want surgical treatment

Goal

  • To reduce tumor volume as preparation for surgical treatment.

Definitions

Target Volume

Target volume definitions from ICRU
(International Commission on Radiation Units and Measurements)

GTV (= Gross Tumor Volume)

Tumor volume

Palpable or visible/identifiable area of malignant growth. Proven lymph nodes may be reported as  GTV-N, other metastases as GTV-M.

CTV (= Clinical Target Volume)

Clinical target volume

Tissue volume containing GTV and/or subclinical microscopic malignant disease.

ITV (= Internal Target Volume)

Target volume

Volume containing CTV and an internal margin taking into account internal movements and changes in  CTV.  This is the volume that should receive an optimal dose.

PTV (= Planning Target Volume)

Planning volume

Geometric volume containing ITV and one Set-up margin taking into account variations for patient movement, patient positioning, and field modeling.

Planning contour: Beams-Eye-View projection of PTV.

 IM (= Inner margin) and SM (= Setup margin)

IM and SM cannot be summed linearly. Total margin must be given specifically for different tumor localizations.
 

GTV

Gross tumor volume is not applicable for postoperative radiation.

CTV breast

Includes breast and the axillary process of the breast.

Limits

  • Ventrally: 5 mm under skin layer
  • Dorsally: fascia covering the pectoral muscle, possibly anterior surface of ribs in deeply located tumors.

CTV boost

With CT as reference, this volume includes the tumor bed defined as the operative cavity and the visible postoperative reaction, with additional 5-10 mm surrounding tissue, or alternatively as visible operation cavity and possibly staples with about 2 cm surrounding tissue. The scar is not part of the target.

CTV parasternal lymph nodes

Routine radiation is no longer necessary. The method should be considered for:

  • large, medially or centrally localized tumors
  • positive parasternal sentinel lymph node

Limits

  • Medially: lateral border of sternum 
  • Laterally: 2 cm laterally to the medial limit
  • Dorsally: pleura
  • Ventrally: anterior edge of ribs
  • Cranially: immediately caudally to the sternoclavicular joint
  • Caudally: cranial border of ribs IV (often equals 1 cm below carina)

CTV periclavicular lymph nodes

Limits

  • Medially: 1.5 cm from trachea
  • Caudally/laterally: border to the axilla
  • Cranially: equals 1 cm caudal to vocal cords or the lower part of C6
  • Caudally: lower part of the sternoclavicular joint
  • Anteriorly: 5 mm deep to the skin
  • Dorsally: anterior to the transverse process in upper part, the ribs more caudally.

CTV axilla

  • Level I lateral to pectoralis minor muscle 
  • Level II posterior to pectoralis minor muscle 
  • Level III medial to pectoralis minor muscle. Lateral to the supra/infraclavicular region.

CTV thoracic wall

  • Includes the area underlying the breast as well as the operation scar. The outer 5 mm of the skin is not included in the clinical target volume. Over the scar itself and 20 mm to the sides of the scar, the clinical target volume includes the surface of the skin when the distance from the tumor to the skin is short (use of bolus). In the depth the target volume reaches the anterior rib surface. The medial border mimics the edge of the remaining breast. If this is not possible to identify, the medial border should be 25 mm lateral to the lateral edge of the sternum.

ITV=CTV

PTV

  • Margins set to 5-7 mm, toward the heart 0 mm. Minimum dose in PTV should be 90% over the target dose.

Preparation

  • Review of operation protocol, histology results, receptor status, and indication for radiation therapy as well as adjuvant treatment.
  • The patient is examined and informed by the physician and nurse in an outpatient setting.
  • Routine blood tests and X-ray of thorax are taken. Other necessary examinations if necessary (for example ultrasound and cytology of actual tumors/skin changes etc., bone scintigraphy, ultrasound of liver).
  • Patient lies in the supine position with arm support/holder. Breast board. Wing board.
  • Drawing of target volume is CT-based and will be the basis for the treatment planning.
  • Conventional simulation is rarely used, and only when the CT-based treatment planning are not possible to perform (most often due to reduce mobility of shoulder/arm). The target area is defined by the superficial anatomical structures and by means of X-ray.

NBCG recommends that all women having curative irradiation for breast cancer should have fT4, TSH, and anti-TPO taken prior to the irradiation.

Organs at risk

  • Heart
  • Lungs
  • Spinal cord 
  • Contralateral breast
  • Brachial plexus 

Implementation

The treatment is given in the form of daily 2 Gy fractions (Monday to Friday, a total of 5 fractions per week). Usually, 25 or more fractions are given toward the thoracic wall and other macroscopic tumors.

The treatment will last about 5-7 weeks.

The total dose is usually 50 Gy or higher (up to 60 Gy) toward the macroscopic tumor.


Follow-up

During radiation treatment

  • Routine follow-up by nurses during the course of radiation.
  • The patient will have a consultation with a doctor toward the end of the treatment. The patient is offered a consultation during treatment as needed.

After concluding radiation treatment

  • In preoperative/primary radiation treatment, the first follow-up check is usually at the regional hospital after 4-6 weeks. This includes evaluation by oncologist of the radiation effect, as well as by surgeon of operative result.
  • Further follow-up depends on the treatment plan. The first followed-up is preferably at a regional hospital. Thereafter, follow-up continues at the referring hospital.  
  • A yearly check and mammogram is recommended for the following ten years.

Side Effects of Radiation therapy

Acute

  • Skin reactions in the form of redness, heat, soreness, and edema. Some may develop more serious radiation dermatitis with peeling skin and formation of ulcerations.
  • Soreness while swallowing (after radiation treatment toward regional lymph nodes of the neck).
  • Nausea, often low-grade and manageable.

Delayed

  • Lasting skin changes in the form of scarring/fibrosis, pigment changes, and telangiectasia.
  • Lung fibrosis to a varying degree.
  • Lymph edema in the arm of the treated side.
  • Reduced movement in the shoulder of the involved side.
  • Weakness of the skeletal structure, especially in the ribs/clavicle of the treated side.
  • Small increase in risk for secondary cancer.
  • Previously, an increased risk for cardiovascular disease was observed especially when irradiating toward the left thorax, but with today’s radiation treatment technique, the risk is small.

 

 


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