New ASTRO Guidelines for APBI in Early-Stage Breast Cancer

Kristin Jenkins

November 23, 2016

More women with early-stage breast cancer, including younger patients and those with ductal carcinoma in situ (DCIS), may be suitable for accelerated partial-breast irradiation (APBI) after lumpectomy, according to a new guideline issued by the American Society for Radiation Oncology (ASTRO).

The guideline, which is an update of the 2009 ASTRO consensus statement for APBI, is based on more recent evidence showing that in the right patients, targeted treatment with APBI is as good as whole-breast irradiation (WBI) for prolonging survival and controlling local recurrence in early-stage breast cancer.

The updated consensus statement also makes recommendations for the use of intraoperative radiation therapy (IORT) in "suitable" women with invasive breast cancer.

"APBI has been tested in a limited number of trials with more than 1000 patients over the past 10 years," Jay R. Harris, MD, chair of the guideline task force, and colleagues say in an executive summary of the guideline, published November 17 in Practical Radiation Oncology.

"In light of new literature, the suitability criteria for APBI have now been updated," they say. "It is hoped that this update will provide ongoing direction for radiation oncologists and other specialists participating in the care of breast cancer patients."

The updated consensus statement, which has been endorsed by the Society of Surgical Oncology, recommends lowering the minimum age of women considered "suitable" for APBI to 50 years from the previously recommended age of 60 years.

Patients 40 years of age and older who meet all other suitability requirements, including patients with low-risk DCIS, may also be considered "cautionary" candidates for APBI.

The original guideline didn't recommend any patients with DCIS for APBI, which offers shorter treatment time, less damage to healthy surrounding tissue, and less risk for adverse effects involving the heart and lungs.

The current criteria on margin status, as described in the 2009 statement, stays the same.

"As trials mature and evidence accumulates, we can understand more comprehensively who benefits from accelerated radiation treatment following lumpectomy," Dr Harris commented in a statement released by ASTRO. Dr Harris is distinguished professor of radiation oncology at the Dana-Farber Cancer Institute, Harvard Medical School, in Boston, Massachusetts.

"We are finding that the pool of suitable candidates for this emerging treatment is larger than first anticipated," he explained. "Carefully selected patients may achieve similar tumor control following shorter, targeted schedules of radiation as they would with weeks of radiation to the whole breast."

Dr Harris told Medscape Medical News that these guidelines precede the release of results from two large randomized controlled trials comparing APBI with conventional WBI.

"These trials will provide Level I evidence, which we don't have now," he said. "ASTRO thought it would be helpful to provide guidance in the meanwhile and these updated guidelines identify patients who are reasonably treated with APBI."

Until now, WBI, usually with external-beam radiation, has been recommended for patients younger than 60 years of age with early-stage breast cancer. WBI reduces risk for recurrence or metastases after breast-conserving surgery.

Since APBI was introduced in the late 1990s, it has been used in more than 75,000 women in the United States.

"The expert panel believes that local recurrence will be low in 'suitable' patients treated with APBI," Dr Harris commented.

Addresses Two Questions

The updated consensus statement on APBI addresses two key questions.

The first, a holdover from the 2009 consensus statement, asks which patients might be considered for APBI outside of a clinical trial. The second question asks which patients may be considered for IORT.

The guideline recommends that patients be considered for APBI outside of clinical trial settings on the basis of age, DCIS status, and status of surgical margins.

In addition to now considering patients 50 years of age and older suitable for APBI, patients age 40 to 49 years who meet other pathologic suitability criteria are considered cautionary. This group replaces patients 50 to 59 years of age in the original recommendation.

Patients younger than 40 years (rather than those younger than 50 years as recommended in 2009) are considered unsuitable for APBI. Those who don't meet the pathologic criteria are also considered unsuitable.

For the first time, patients with low-risk DCIS are also considered suitable for APBI. Low-risk DCIS is defined as screen-detected disease, low to intermediate nuclear grade, a tumor size of 2.5 cm or less, and surgical resection with margins negative at 3 mm or greater.

The current standards for surgical margins, which remain unchanged, state that margins negative by 2 mm or greater are considered suitable for APBI, and margins close or less than 2 mm are considered "cautionary." Positive margins are not suitable for APBI.

New Recommendations on IORT

The update also has new recommendations on the use of IORT, which are based on results from two large, phase 3 clinical trials comparing WBI with IORT: the Intraoperative Radiotherapy with Electrons (ELIOT) trial and the Targeted Intraoperative Radiotherapy (TARGIT) trial.

Both trials show that the risk for ipsilateral breast tumor recurrence (IBTR) is higher in patients treated with IORT than those treated with WBI. What's more, this increased risk for IBTR persists over time.

IORT uses an electron beam or low-energy x-rays to deliver partial-breast irradiation during surgery and provides an alternative to brachytherapy and external-beam radiation therapy.

In ELIOT, the 5-year IBTR risk was 4.4% (35/651) after electron-beam IORT vs 0.4% (4/654) after WBI, with a median follow-up of 5.8 years.

In TARGIT, the 5-year IBTR risk was 3.3% (23/3375) in the low-energy x-ray IORT group compared with 1.3% (11/3375) in the WBI group, with an overall median follow-up of 2.4 years.

The update recommends that physicians counsel patients about these risks and provide routine long-term follow-up for at least 10 years to screen all patients treated with IORT for tumor recurrence.

It is also recommended that the use of electron-beam IORT be restricted to patients considered suitable for partial-breast irradiation.

Low-energy x-ray IORT should be used only in patients enrolled in a prospective registry or in a clinical trial, according to the guideline. Further, its use should be restricted to women with invasive cancer who are considered "otherwise suitable for partial breast irradiation."

No funding was declared. Task force member Benjamin D. Smith, MD, reported a relationship with Varian Medical Systems, and fellow task force member Julia White, MD, declared relationships with the Komen Foundation, IntraOp Medical, and Qfix.

Pract Radiat Oncol. Published online November 17, 2016. Full text

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