How Much Radiation Do Breast Cancer Patients Need?

April 12, 2021

Radiation therapy is one of the pillars of breast cancer treatment and may be used at any stage of the disease. It is primarily used in one of two ways: to decrease the chance of the cancer recurring following surgery, or to palliate symptoms of metastatic disease.

What is radiation therapy?

Radiation consists of beams of high-energy X-rays that injure the DNA of tumor cells and cause them to die.

How is radiation used to treat breast cancer?

Patients with early breast cancers that have been removed by lumpectomy or mastectomy often receive radiation to kill remaining cancer cells and prevent a cancer recurrence. Radiotherapy may also be used to treat breast tumors that can’t be surgically removed, or to ease the symptoms of cancers that have metastasized (spread to other parts of the body).

Careful planning for radiation treatment is carried out by team that consists of:

  • a radiation oncologist — a physician who specializes in treating cancer with radiation
  • a medical physicist, who calculates the appropriate radiation dosage and how it will be delivered
  • and radiation therapists, who operate the equipment and administer the treatments.

Many patients who have been treated with surgery for early breast cancer receive radiation afterward to prevent any cancer cells left behind from causing a recurrence. Removal of just the tumor — called a lumpectomy — combined with radiation therapy is called breast conservation therapy. It is extremely effective in preventing recurrences. While most patients in this situation are treated with radiation, some who have a very low risk of recurrence may not need radiation.

Until the past few years, the standard course of radiotherapy for patients having breast conservation treatment was five or six weeks of daily radiation sessions (five days a week) to deliver the optimal amount of radiation. However, clinical trials showed that a “hypofractionated” schedule in which radiation is delivered daily for three to four weeks was just as effective in preventing recurrences. The shorter regimen is less inconvenient and disruptive to the lives of patients, “and this has become standard practice for almost all our patients undergoing breast conservation,” says Jennifer Bellon, MD, director of Breast Radiation Oncology at Dana-Farber.

For women who choose or are advised to have a mastectomy — removal of the breast and reconstructive procedures — there is still uncertainty about the safety of the shorter course of radiation, particularly in the setting of reconstruction. Two Dana-Farber radiation oncologists, Julia Wong, MD, and Rinaa Punglia, MD, are leading a trial comparing the long-term effects of the standard course of radiation therapy with the shorter hypofractionated schedule in patients having mastectomy and immediate reconstruction.