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Updated ASTRO guideline expands pool of accelerated partial breast irradiation candidates
The American Society for Radiation Oncology updated its guideline on the treatment of early-stage breast cancer, recommending accelerated partial breast irradiation for a wider range of women.
This update is based on data published over the past 8 years.
“As trials mature and evidence accumulates, we can understand more comprehensively who benefits from accelerated radiation treatment following lumpectomy, and we are finding that the pool of suitable candidates for this emerging treatment is larger than first anticipated,” Jay R. Harris, MD, distinguished professor of radiation oncology at Dana-Farber Cancer Institute and Harvard Medical School, said in a press release. “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.”
Patients with early-stage breast cancer often receive whole-breast irradiation (WBI) following breast-conserving surgery to decrease the risk for recurrence or metastasis. Accelerated partial breast irradiation — a localized alternative to WBI that delivers radiation directly to the tissue at risk — reduces treatment time. It also has been shown to limit adverse side effects, particularly to the heart and lungs, in the more than 75,000 women who have been treated since it was introduced to the United States in the late 1990s.
Harris and an eight-member task force of radiation oncologists, medical oncologists and experts in intraoperative radiation therapy (IORT) updated the 2009 ASTRO consensus statement for accelerated partial breast irradiation (APBI).
ASTRO’s new guideline, based on 44 articles retrieved from PubMed, recommended the consideration of the following factors for the use of APBI outside of clinical trials:
- Patients aged years 50 or older should be considered suitable (expanded from 60 years or older); patients aged 40 to 49 years who meet other pathologic suitability criteria should be considered cautionary (expanded from age 50 to 59 years); and patients aged younger than 40 years or those who do not meet the pathologic criteria should be considered unsuitable (expanded from age younger than 50 years).
- Patients with low-risk ductal carcinoma in situ (DCIS) should be considered suitable if they meet all aspects of low risk status, including screen-detected disease, low to intermediate nuclear grade, tumor size less than 2.5 centimeters and surgical resection with margins negative at greater than 3 millimeters. The 2009 guideline did not place any DCIS patients in the suitable group.
- Adhere to standard guidelines that suggest patients are suitable if surgical margins are negative by greater than 2 millimeters; cautionary if margins are close or less than 2 millimeters; and not suitable if margins are positive.
ASTRO’s guideline also addresses the use of IORT for early-stage breast cancer, drawing on two large, phase 3 clinical trials comparing WBI with IORT. Partial breast irradiation can be administered through brachytherapy, external beam RT and IORT, a single-dose radiation treatment commonly delivered at the time of surgery using either an electron beam or low-energy X-rays.
ASTRO now recommends:
- Based on clinical trials, physicians should counsel patients that the risk for ipsilateral breast tumor recurrence may be higher with IORT than with WBI.
- Electron beam IORT should be restricted to patients with invasive cancer who are considered suitable for APBI, based on data from a trial with a 5.8-year median follow-up.
- Low-energy X-ray IORT should be used only in the context of a prospective registry or clinical trial and restricted to women with invasive cancer who are considered otherwise suitable for partial breast irradiation.
- All patients treated with IORT should undergo routine long-term follow-up for at least 10 years to screen for tumor recurrence.
Harris told HemOnc Today that the new recommendations should help decrease the risk for ipsilateral breast tumor recurrence in “suitable” patients treated with APBI.
“There are two large randomized controlled trials comparing APBI with conventional whole-breast radiotherapy that have completed accrual but have not reported results,” Harris added. “These trials will provide level-one evidence, which we don’t have now. ASTRO thought it would be helpful to provide guidance in the meantime. These updated guidelines identify patients who are reasonably treated with APBI.” – by Chuck Gormley
For more information:
Jay R. Harris, MD, can be reached at hay_harris@dfci.harvard.edu.
Disclosure: Harris reports no relevant financial disclosures. Please see the full guidelines for a list of all other authors’ relevant financial disclosures.
Perspective
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The new 2016 update of the accelerated partial breast irradiation (APBI) ASTRO Consensus Statement reflects this rapidly evolving field in radiation oncology with three major changes:
1. The minimum age for patients deemed “suitable” for APBI has been lowered from 60 years to 50 years, whereas the maximum age of patients considered “unsuitable” has been lowered to 40 years;
2. Patients with pure low-risk ductal carcinoma in situ (DCIS) per RTOG 9804 criteria are now included in the “suitable” group; and, 3. Electron beam intraoperative radiation therapy (IORT) is considered a “suitable” APBI option for women with invasive cancer, but patients must be counseled on a higher risk for ipsilateral breast tumor recurrence than with whole-breast irradiation (WBI).
Interestingly, the task force was largely in 100% agreement with the above changes, but the quality of the evidence supporting these changes were rated as moderate or had no evidence rating. Additionally, the majority of these recommendations were rated as weak, reflecting the need for longer follow-up and the eagerly anticipated publication of the NSABP B39/RTOG 0413 and RAPID trials.
Although the task group discusses the low absolute risk for recurrence in select favorable patients with DCIS who may be observed without radiation (APBI or WBI), a corresponding favorable group of patients with invasive cancer treated with breast conserving surgery alone is not identified. Observation also appears to be a viable option in select patients with low-risk DCIS or invasive breast cancer, many of whom would also fit in in the “suitable” group for APBI.
Of note, the margin criteria are unchanged for “suitable” patients, requiring 2mm for invasive cancer and 3mm for DCIS despite the recent guidelines from Society of Surgical Oncology, ASCO and ASTRO advocating no tumor at ink for invasive and 2-mm or larger margins for DCIS. Although most published APBI trials required at least 2-mm margins, it is unclear whether specific margin distances are necessary in light of the jointly endorsed margin guidelines. Further, when DCIS is found along with invasive cancer, are patients suitable for APBI if invasive cancer margins are negative, but have close (< 2 mm) DCIS margins?
Perhaps, the most significant change is the inclusion of IORT. Electron beam IORT is endorsed for appropriately counseled patients given the ELIOT trial’s longer median follow-up. Although the task group advocates offering low-energy X-ray IORT as part of a prospective registry or clinical trial, we recognize that many centers may be offering patients this treatment off-trial given the results of the TARGIT study. However, the 2016 APBI update may help curb practices and encourage physicians to use low-energy X-ray IORT cautiously until longer follow-up is available.
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