When can women with early-stage breast cancer avoid radiation therapy after lumpectomy?

Emerging research may allow more women with early-stage breast cancer to safely avoid radiation therapy.

Women diagnosed with early-stage breast cancer can often choose to have a lumpectomy, which removes only cancerous tissue and a thin margin of surrounding healthy cells instead of the entire breast. Current cancer guidelines for most women under 65 recommend undergoing a lumpectomy with radiation therapy, which targets wandering cancer cells that could otherwise cause breast cancer to come back or spread to other parts of the body. .

A new study presented at the 2022 annual meeting of the American Society of Clinical Oncology may eventually expand an option to skip radiation therapy to some women as young as 55. expert.

Lower risk of breast cancer recurrence

Landmark research from 2004, supplemented by later studies, helped cancer experts develop guidelines defining which women with early-stage breast cancer could safely omit radiation after lumpectomy.

Generally, this option is offered to women 65 or older who have small tumors with non-aggressive cells that have not spread to the lymph nodes. Medically, this is described as a T1N0 tumor, grade 1-2. Tumors must be positive for estrogen receptors, which means that the hormone estrogen helps fuel their growth. They must also have an adequate margin of normal tissue surrounding the cut tumor to ensure that all of the cancer has been removed. Women who decide to skip radiation therapy are instead given a drug known as hormone therapy for five years. This prevents cancer cells from using hormones like estrogen to grow and spread.

“This has long been the standard of care for women aged 65 or over. Now the debate is whether we can also omit radiotherapy for a larger group of breast cancer patients. For example, can we take this approach in patients under the age of 65, if the patients are chosen carefully?” says Dr. Nadine Tung, director of the breast cancer risk and prevention and medical oncology program at Beth Israel Deaconess Medical Center.

What does the new evidence suggest?

The new evidence suggests that younger women with tumor characteristics similar to those described above may also be able to forego radiotherapy without increasing their risk of recurrence. Instead, they would undergo endocrine therapy for five years.

The study involved 500 women aged 55 and older with early-stage breast cancers similar to established criteria for skipping radiation therapy during treatment. It also allowed women to enroll if the margin of normal breast tissue removed was very thin (only 1 millimeter or more). The analysis used an additional test on tumor cells removed during lumpectomy to confirm that they were growing slowly.

Over an average follow-up of five years, the study found that the rate of breast cancer recurrence in the same breast was 2.3% in women who skipped radiation therapy after a lumpectomy and took inhibitors instead endocrine – the same rate expected with the use of radiation therapy, which was impressive, says Dr. Tung. “Most recurrences will occur within five years. If reproducible, the results could suggest a new set of criteria for avoiding radiation.”

Promising results, but daunting obstacles remain

The results of the study are considered preliminary and further in-depth research is needed to confirm its findings. An additional hurdle makes it difficult to translate these trial results into clinical practice: the reliability of the test used in the study to demonstrate that cancers grew slowly – called Ki67 – varies, and many hospitals do not use it routinely. . to evaluate breast tumours.

“It will be useful to evaluate the results of other radiation-omitting studies to be sure that we have identified other patients with invasive breast cancer for whom radiation can be safely omitted,” said the Dr. Tung. “Some of these studies use molecular tests to assess characteristics of breast cancer, and we are also awaiting the results of these trials.”

Questions to ask your cancer team

For women diagnosed with early-stage breast cancer who want to know if radiation therapy is needed after lumpectomy surgery, Dr. Tung suggests asking your oncology team these questions:

  • Does my type of tumor meet the criteria to avoid radiation therapy? If not why ? “I think a lot of radiation oncologists don’t usually get asked that question,” says Dr. Tung.
  • What are the chances that my tumor will recur whether or not I receive radiation? If you have a choice, it’s important to understand the difference in your chances of recurrence or recovery, says Dr. Tung.
  • Would I need to take medicine instead of having radiation? If so, how long and what are the possible side effects?
  • What are the possible side effects if I undergo radiotherapy? “Radiation therapy can cause redness, like a burning on the breast,” she explains, “and the treated breast may shrink a little over time. Ask about short-term and long-term side effects.”
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