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Preoperative Partial Breast Irradiation for Early-Stage Breast Cancer

The current standard of care for early-stage breast cancer is to first surgically remove the tumor, then deliver postoperative radiation therapy. This protocol entails irradiating the entire surgical cavity, plus a margin around the cavity, which is a much larger area than just the tumor. Inevitably, this unnecessarily exposes surrounding organs and tissues to high doses of radiation.

Asal Rahimi, M.D., Associate Professor of Radiation Oncology, thinks that reversing the standard order of therapies and delivering radiation before surgery could lessen the amount of unnecessary tissue exposure to radiation. Dr. Rahimi is investigating this strategy in a new phase I clinical trial (NCT04040569) that tests preoperative partial breast irradiation for early-stage breast cancer. The idea is that treating with radiation before surgery would allow radiation oncologists to irradiate only the tumor, not the entire surgical cavity

“If we were able to deliver the radiation up front, we could treat the tumor, with some margin around it, and we would irradiate magnitudes of volume less than if we treated in the postoperative setting,” Dr. Rahimi explains.

Treating less tissue would mean dramatically reducing the radiation dose to surrounding organs, and treating a smaller volume would mean that radiation could potentially be delivered in fewer fractions. Both could alleviate the toxicity associated with radiation therapy

Plan of pre-operative single fraction of radiationto primary breast tumor

Plan of pre-operative single fraction of radiation to primary breast tumor

What’s more, performing surgery after treating with radiation would remove most of the irradiated tissue from the body, which could further minimize adverse effects after treatment.

One of the greatest advantages of delivering radiation before surgery is that more patients could be offered partial-breast, rather than whole-breast, irradiation. During surgical resection, surgeons perform a variety of oncoplastic techniques that rearrange the tissue to ensure a good cosmetic outcome after surgery. Unfortunately, rearranging the tissue can make partialbreast irradiation very difficult. Instead, those patients are usually offered whole-breast irradiation, which exposes more tissue to radiation. Delivering radiation preoperatively, before oncoplastic rearrangement, would eliminate this problem.

“If we were to treat with radiation first, before surgery, then the surgeons could still do all the oncoplastic rearrangements they want to do to ensure the best cosmetic outcome, and the patient would still be able to receive the partial-breast irradiation,” Dr. Rahimi says.

The clinical trial might also benefit research into the biological mechanisms and effects of radiation therapy for breast cancer. Because tumor tissue will be removed after irradiation, this tissue will be available for researchers to study the pathological response to radiation. This biological research might yield insights that could lead to future advances in treatment for breast cancer.

The current phase I dose escalation study will determine the radiation dose required to elicit a high pathologic response rate and ablate the tumor without causing excessive toxicity. If the trial is successful, the next step would be a phase II clinical trial to evaluate the efficacy of the preoperative protocol.

If implemented into clinical practice, this innovative treatment approach could ultimately reduce the toxicity associated with radiation therapy and improve the overall quality of life for patients with early-stage breast cancer.