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6.10 Radiation Therapy

Updated Frbruary 2021

6.10.1 Contraindications to Radiation Therapy

Radiation Therapy may be relatively or absolutely contraindicated in the following circumstances:

  1. Pregnancy
  2. Connective tissue disorders (systemic lupus erythematosus, scleroderma, etc.) with significant vasculitis. The use of radiation may not be contraindicated with all connective tissue disorders. 
  3. Significant pre-existing lung disease  if the diffusing capacity is severely reduced
  4. Prior radiation therapy to the same part
  5. Pacemaker in the radiotherapy field

6.10.2 Radiotherapy Planning and Prescription

Radiation Therapy Planning for Breast only radiotherapy:

  1. Indications: Patients with DCIS or node-negative (low-moderate risk) invasive breast cancer, treated with breast-conserving surgery, patients with locally recurrent node-negative disease who have not previously had radiotherapy (RT).
  2. Clinical Target Volume: For whole breast RT, the entire ipsilateral breast tissue should be included in the field. The lower axilla may be included if the patient has high-risk features, particularly if an axillary node dissection has not been done.  For external-beam PBI, a tumor bed to CTV expansion of 1 cm is recommended for cases with clear margins (> 2 mm) and cases with close or positive anterior margins (at skin) and/or posterior margins (at pectoralis fascia) that cannot be rendered negative with further surgery. For other cases with a boost indication, a tumor bed to CTV expansion of 1.5 cm is recommended.
  3. Dose: Fractionation:
    1. Standard whole breast RT prescription is 40 Gy in 15 daily fractions.
    2. Some patients may be eligible for whole breast short-course RT (refer to section 6.3.1.2) using 26 Gy in 5 daily fractions over 1 week.
    3. Certain patients are at risk for inferior cosmetic outcome. Extended fractionation could be considered for patients with very large breast size, and those with significant post-operative induration, edema, erythema, hematoma or infection. Patients with indications for extended fractionation could consider 50 Gy in 25 daily fractions or 50.4 Gy in 28 daily fractions.
    4. Patients eligible for partial breast RT (refer to section 6.3.1.2) can be treated using standard external beam radiotherapy (EBRT) dose of 40 Gy in 15 fractions, 26 Gy in 5 fractions, or with brachytherapy seed implants.
    5. If a boost is used, an additional dose of 10 Gy in 4 or 5 fractions or 16 Gy in 8 fractions is recommended.
  4. Technique: For whole breast RT, ordinarily a tangential pair of fields to encompass the anatomic extent of the breast is used.  Patients may be positioned in the supine or prone position.  Forward or inverse-planned tangential IMRT (sometimes referred to as multi-leaf collimator compensation) to improve dose homogeneity is recommended. For partial breast radiotherapy, EBRT using short tangents, 3D conformal radiotherapy, IMRT, or brachytherapy using seed implants can be used. 
  5. Overall treatment time: For EBRT, patients should be treated daily, Monday to Friday, for an interval of one to six weeks depending on the treatment recommended by the radiation oncologist.  If a 5-fraction course is used, no more than 3 days between fractions is recommended.  Breast brachytherapy is a one-day out-patient surgical procedure.
  6. Boost technique: The location of the boost may be guided by the presence of clips placed at the time of surgery or the post-operative seroma as contoured on the RT-planning CT scan.  Boost may be treated with a direct electron field or conformal/mini-tangent photon fields.
Radiation Therapy Planning for Breast/Chest wall + nodal radiotherapy:

  1. Indications: Patients with node-positive or high-risk node-negative invasive breast cancer
  2. Clinical Target Volume: Entire chest wall or ipsilateral breast and regional nodes. The regional nodal volume should include the supraclavicular and level 3 axillary nodes medial to the coracoid process. The axillary contents lateral to the coracoid process should be included if fewer than 10 nodes were recovered, or if there are bulky or N2-3 disease or significant extranodal spread in the fat of the axilla.  Treatment of the ipsilateral internal mammary chain (IMC) nodal region including the first three inter-costal spaces should be considered when the supraclavicular or axillary nodes are to be treated, and for those with inner quadrant or central tumours.  Studies demonstrating a survival impact from regional RT consistently included the IMC lymph node region in the treatment volume. Doing so increases the lung volume treated and for left-sided breast cancer, cardiac exposure.
  3. Dose: Fractionation:
    1. Standard whole breast dose is 40Gy in 15 daily fractions, chest wall dose is 40 Gy in 15 fractions, nodal dose is 37.5-40 Gy/15 fractions.
    2. After breast conserving surgery, extended fractionation should be considered for patients with very large breast size, and those with significant post-operative induration, edema, erythema, hematoma or infection. Recommended extended fractionation dose: 50 Gy in 25 daily fractions or 50.4 Gy in 28 daily fractions to the breast and 45 Gy in 25 fractions to the supraclavicular nodal region.
    3. After mastectomy, patients with significant postoperative infection, very large chest wall separation, and those undergoing reconstruction could also be considered for extended fractionation. Recommended extended fractionation dose: 50Gy in 25 daily fractions or 50.4 Gy in 28 daily fractions to the chest wall and 45 Gy in 25 fractions to the supraclavicular nodal region.
    4. For those with close or positive margins post-mastectomy, a higher chest wall dose (e.g. 42.5 Gy in 16 fractions) may be used, or a boost dose of 10Gy in 4 or 5 fractions or 16Gy in 8 fractions may be considered, if the anatomic area requiring the boost dose can be accurately delineated.
    5. For patients post-breast conserving surgery with close or positive margins, or young age, supplemental boost is recommended as described above in the T1T2 N0 Post "Breast Conserving Surgery" section.
  4. Technique: Ordinarily a mono-isocentric 4-field technique to encompass the anatomic extent of the breast/chest wall and regional nodes will be used. Forward or inverse-planned tangential IMRT (sometimes referred to as multi-leaf collimator (MLC) compensation) to improve dose homogeneity is recommended. Inclusion of the IMC nodes may be achieved using a modified-wide tangent pair in addition to the nodal fields. Specialized techniques, such as multi-field IMRT and Deep Inspiration Breath Hold techniques may be necessary to minimize dose to normal tissues in certain patients.
  5. Overall treatment time: Patients should be treated daily, Monday to Friday, for an interval of three to six weeks.
  6. Boost technique post-BCS: The location of the boost may be guided by the presence of clips placed at the time of surgery or the post-operative seroma as contoured on the RT-planning CT scan. Boost may be treated with a direct electron field or conformal/mini-tangent photon fields.

6.10.3 Side Effects of Radiation Therapy

Updated: February 2021

Side effects of curative intent, adjuvant radiation therapy are directly proportional to the volume of the irradiated tissues. Since radiation therapy (except whole body radiation) is essentially a localized treatment, the side effects depend also on the anatomic location irradiated. The severity of side effects is directly related to the dose of radiation delivered and the time over which it is delivered.

  1. Skin - Mild to moderate erythema generally develops through the course of treatment but for the 5-fraction course of breast radiotherapy, the skin reaction is expected to occur after the completion of radiotherapy.   The skin reaction can continue to progress for eight to fourteen days following treatment after which it will subside quickly.  Dry desquamation or moist desquamation may occur in the axilla or in the inframammary fold, particularly in large breasted women.  Commonly, there may be late changes in the appearance or texture of the skin or soft tissue within the radiotherapy field, e.g. hyperpigmentation (tanned appearance), telangiectasias, or fibrosis.                                                                                                                    For acute skin reaction we recommend that patients use a water-based moisturizer regularly on the irradiated areas.  A steroid cream may be used over small areas where the reaction is particularly itchy, but without moist desquamation. Saline soaks may be used over areas of moist desquamation.  Read more about the care of radiation skin reactions here.
  2. Esophagitis - Patients undergoing nodal radiotherapy may experience mild esophagitis, typically described by patients as mild difficulty swallowing or a feeling of a "lump in the throat.  Medication is occasionally required for symptom relief. 
  3. Fatigue - A variable amount of generalized tiredness may begin after the first one to two weeks of treatment and last for several months thereafter. The cause is not known. Resting appropriately, reducing stress, and doing moderate exercise (e.g. a daily walk) can also improve fatigue.
  4. Lung - Some part of the lung is always irradiated in patients undergoing breast/chest wall/nodal radiotherapy. The amount of irradiated lung is the least in the "breast only" tangent pair technique and is maximal when nodal areas are irradiated.  Subacute pneumonitis is uncommon. Patients with subacute pneumonitis will typically present with dry cough or shortness of breath, often with accompanying radiologic changes, 6 weeks to 6 months after the completion of radiotherapy. Patients who are symptomatic may need treatment with steroids (prednisone 30-50 mg daily for two weeks and then very slowly tapered over the next few weeks). Late radiologic changes of radiation fibrosis are common but symptoms from this are rare.
  5. Heart - Symptomatic cardiac toxicity with current techniques is rare, but patients treated with left-sided regional radiation, especially those treated using older techniques, have a slightly increased risk of coronary artery disease. There is also a small risk of acute or subacute pericarditis.
  6. Musculoskeletal - Occasionally, radiotherapy may cause mild pain or discomfort in the breast/chest wall or shoulder. Radiotherapy to the breast/chest wall is associated with a 1% risk of a rib fracture. Radiotherapy to the axilla increases the risk of lymphedema in the ipsilateral arm. There is also a very small risk of brachial plexopathy secondary to radiotherapy to the axilla.
  7. Second Malignancy – There is a very small risk of second malignancy after radiotherapy. These tumours are typically soft-tissue sarcomas or lung cancer, and usually will occur 7-10 years after radiotherapy.
  8. Radiation Recall – Radiation recall is a rare phenomenon where patients who have received radiation therapy and subsequently need certain types of chemotherapy (for example Adriamycin) may have a "recall" of the radiation reaction

SOURCE: 6.10 Radiation Therapy ( )
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