Radiotherapy after mastectomy is designed to prevent locoregional recurrence. However, the question of which breast cancer patients should receive radiotherapy after a mastectomy is not settled. This is an important question since using radiation can potentially improve prognosis. However, the side effects associated with radiation treatment (which include a higher rate of complications from breast reconstruction surgery) should be avoided, if possible.

Radiation treatment is designed to prevent locoregional recurrence

Radiation treatment is designed to prevent locoregional recurrence (recurrence in the breast, chest wall, or lymph nodes). This is an important goal since successful prevention has a survival benefit. It is not true that since radiation is not a systemic treatment and prevents only locoregional recurrence, any such recurrence will likely be caught in time and treated in any event. Even for small early stage tumors treated with lumpectomy, it has been shown that approximately one in four local recurrences eventually will lead to stage IV disease and death. Radiation treatment also appears to help prevent a late recurrence (five years or longer after the initial breast cancer diagnosis).

Circumstances under which radiation might be beneficial after mastectomy

As noted above, there is disagreement concerning which breast cancer patients should receive radiotherapy after mastectomy. Therefore, we have divided this section into two parts: (1) tumor characteristics upon which there is broad agreement that radiation treatment is called for; and (2) other tumor characteristics that have also been identified by researchers as benefitting from radiation treatment.

Circumstances under which radiation is always recommended after mastectomy

According to published guidelines, breast cancer patients with high-risk tumors should receive radiation treatment. High risk is defined as stage T3-T4 (tumor size more than 5.0 cm or tumor of any size growing into the chest wall or skin) and/or N2-N3 ( at least 4 axillary lymph node metastases, lymph node metastases attached to each other or to other structures, or internal mammary lymph node metastases). Up to half of women who are candidates for post-mastectomy radiation treatment under these guidelines do not receive it.

Circumstances under which radiation might be beneficial for other tumors

The controversy regarding post-mastectomy radiation centers around when it is appropriate for stage T1-T2 (invasive breast cancer up to 5 cm in diameter) and N1 (1 to 3 positive lymph nodes) tumors. Below we summarize circumstances under which omitting radiation appears to lead to higher rates of locoregional recurrence for such tumors, based on research published since 2010:

  • Negative estrogen receptor (ER-), negative progesterone receptor (PR-) or both (ER-/PR-). This includes mixed receptor (ER+/PR- or ER-/PR+) and triple negative (ER-/PR-/HER2-) disease.
  • Ki-67 >20%. Ki-67 is a measure of proliferation.
  • Lymphovascular invasion (invasion of the cancer cells into the blood vessels or lymphatic channels).
  • Extracapsular extension of at least one lymph node metastasis (the cancer cells are not only inside the lymph node, they also extend outside of it).
  • Mammographic dense breasts.
  • Presence of at least one close (< 2 mm) or positive surgical margin. A surgical margin is considered to be positive if the pathologist finds cancer cells right up to the edge of the removed tissue.
  • Young age (under 40 years).
There is some evidence that patients with more than one of the attributes listed above have significantly increased risk of isolated locoregional failure compared to those with only one of the factors.

Below are links to recent studies on this topic. For a more complete list of studies, please click on mastectomy.