Updated: 18 July 2005
Radiation Therapy Complementing Partial Mastectomy
If the primary tumour has been treated by partial mastectomy, the breast itself is treated by a tangential pair of fields to encompass the anatomic extent of the breast. Partial breast irradiation is considered investigational at present, and is not preformed outside of a clinical trial.Treatment takes from three to six weeks and is optimally started four to eight weeks following the surgery, unless adjuvant chemotherapy is given, in which case this precedes the radiation treatment. If there is disease close (within 2 mm) or focally involving the margins of the partial mastectomy specimen, then a re-excision should be considered, and when not possible, a boost dose is given to the tumour cavity (see resection margins). The location of the boost is determined by metal clips placed by the surgeon at the time of the partial mastectomy. Women under the age of 50 are offered a boost even when the margins are clear in light of level I evidence supporting a significant reduction in local relapse with a boost in this setting. The lymph node drainage may also be irradiated when indicated (see item (3) below).
Experience with a 3 week course of radiation fractionation over the past decade has shown that patients with large breasts and those with significant post-operative induration, edema, erythema, hematoma or infection have an inferior cosmetic outcome. These women will be offered extended fractionation with smaller daily doses over five to six weeks, in an effort to reduce normal tissue side effects from the radiation.
Radiation Therapy to the Regional Lymph Nodes
There are a number of situations where postoperative radiation therapy is recommended following modified radical mastectomy or to extend radiotherapy to the regional nodes in conjunction with treatment to the intact breast.
1. Where there is tumour present at the surgical or pathological margins after mastectomy, particularly if any of the following apply: age under 50, LVI positive, grade 3, or T2 tumour,
2. T3 or T4 primary tumours,
3. Where the axillary nodes are involved, individualization of patient treatment is necessary. Indications for the use of regional radiotherapy include the presence of cancer in multiple or bulky lymph nodes or the presence of extranodal or extensive fatty involvement by cancer in the axilla.
4. For T1-2, N0, margin negative tumours in the following two settings:
a) grade 3 and LVI positive,
b) grade 3 and T2 tumour (ie greater than 2 cm) and no systemic therapy is used.
Postoperative radiation therapy under the first three circumstances will markedly reduce but not eliminate the risk of local recurrence. In the fourth circumstance, there is an unacceptably high rate of local-regional relapse without RT. There is also new evidence that it may have an effect on overall survival in combination with systemic therapy post mastectomy. It is started approximately four weeks following surgery or integrated with chemotherapy depending upon the agents prescribed. It usually takes three to five weeks of daily treatments. The locoregional volume includes some or all of the following: chest wall, internal mammary, supraclavicular and axillary node drainage areas, depending on individual circumstances. Good but not perfect shoulder movement is required to raise the ipsilateral arm out of the treatment fields. The extent of the scar either medially or laterally and the placement of the drainage tubes can at times confound this treatment and lead to unnecessarily large volumes of normal tissues, particularly lung, being included in the treatment volume (See Modified Radical Mastectomy). Ideally scars and drain sites should not extend beyond the midline medially, beyond the anterior axillary line laterally, or inferior to the inframammary fold caudally. A trial is currently being done assessing the role of regional radiation with systemic therapy after breast conserving surgery.
Follow this link for information about side effects of radiation therapy.