From Medscape Medical News
ASTRO Provides Guidance on Use of Partial-Breast Irradiation
July 21, 2009 — Catching up with what is happening in clinical practice and citing the "markedly increased" use of accelerated partial-breast irradiation (APBI), the American Society for Therapeutic Radiology and Oncology (ASTRO) has issued its first-ever consensus statement on this therapeutic approach to breast cancer.
The statement was published in the July 15 issue of the International Journal of Radiation Oncology Biology Physics.
The statement, which comes from an ASTRO task force and is not as authoritative as a set of guidelines, includes a strong focus on patient selection.
Conservative patient-selection criteria for APBI should be followed.
"Conservative patient-selection criteria for APBI should be followed," write the consensus-statement authors, led by Benjamin Smith, MD, from Wilford Hall Medical Center at the Lackland Air Force Base in Texas.
Patients are "suitable" for APBI if all of a long list of criteria are met, according to consensus statement.
The ASTRO criteria for suitable patients include age 60 years or older, a tumor size of 2 cm or less, tumor stage T1, negative margins of at least 2 mm, pathologically negative nodes, positive estrogen-receptor status, an absence of lymphovascular space invasion, and no multicentricity. Patients with ductal carcinoma in situ (DCIS) are excluded.
The ASTRO criteria for patient selection are more conservative than those published by the American Society of Breast Surgeons, which indicated that APBI can be used for women 45 years and older and is for either invasive or DCIS disease with tumors of 3 cm or less.
The reason for the conservative patient-selection emphasis from ASTRO is that there is "increasing evidence that whole-breast irradiation improves long-term overall survival," say the consensus-statement authors.
To date, there is not a similar body of evidence for APBI.
Nevertheless, American clinicians have increasingly embraced the partial-breast approach, suggest a trio of editorialists in an essay accompanying the ASTRO statement.
"Despite the paucity of Phase III data, APBI has increased rapidly in popularity in the United States in the past 10 years," write the editorialists, led by Leonard R. Prosnitz, MD, from Duke University Medical Center in Durham, North Carolina.
Dr. Prosnitz told Medscape Oncology that he hopes that clinicians are receptive to the new guidance from ASTRO.
Consensus statements tend to have a quasi-legal sound to them, making it a little risky from a medical-legal standpoint to deviate very much.
He also suggested that clinicians probably will be. "Consensus statements tend to have a quasi-legal sound to them, making it a little risky from a medical-legal standpoint to deviate very much," he said.
The consensus statement is especially valuable until the results of the "definitive trial" comparing whole-breast- and partial-breast-radiation approaches are available, which won't be for "many years," write the editorialists.
That definitive study comprises both the Radiation Therapy Oncology Group (RTOG) 0413 and the National Surgical Adjuvant Breast Project (NSABP) B-39 trials, which are collectively comparing APBI with whole-breast irradiation in a randomized design.
Patient Selection: Suitable, Cautionary, and Unsuitable
As Dr. Prosnitz and his fellow editorialists note, there is lack of phase 3 data for APBI.
Indeed, a recent meta-analysis comparing outcomes from APBI and whole-breast radiation involved only 3 trials and 1140 patients, as reported by Medscape Oncology.
This relative lack of data led the ASTRO consensus-statement authors to repeatedly use quotation marks around the 3 patient selection groups, observe the editorialists.
The 3 groups are "suitable" (see above for the inclusion criteria), "cautionary," and "unsuitable."
A patient belongs in the cautionary group if any 1 of the following criteria are met: age younger than 60 years, T2 primary disease, pure DCIS of less than 3 cm, close margins (<2 mm), focal lymphvascular space invasion, multifocal or multicentric disease, invasive lobular carcinoma, or estrogen-receptor negativity. "Any of these criteria should invoke caution and concern when considering APBI," write the consensus statement authors.
Finally, unsuitable patients are those who meet any of the following: use of neoadjuvant chemotherapy, tumor size of more than 3 cm, positive margins, any positive lymph nodes, no axillary surgery, extensive lymphvascular space invasion, multicentricity, DCIS of more than 3 cm, or the presence of a BRCA1 or 2 mutation. "If any of these factors are present, the Task Force recommends against the use of APBI outside of a prospective clinical trial," the authors write.
What's Driving the Use of Partial-Breast Techniques?
"Accelerated partial-breast irradiation is a new technology that provides faster, more convenient treatment after breast-conserving surgery," write Dr. Smith and colleagues in the consensus statement.
One APBI device was singled out by the ASTRO task force as influencing the uptake of the partial-breast approach outside of clinical trials." To date more than 32,000 women in the United States have been treated with the MammoSite breast brachytherapy catheter," write the authors.
It is probably the most widely used technique used off-protocol in the [United States].
Editorialist Dr. Prosnitz acknowledged the influence of the marketing of APBI by individual breast cancer clinics and by the makers of MammoSite (Hologic, Inc.).
"They have been aggressive marketers of their device, which is the only specific device marketed for APBI. It is probably the most widely used technique used off-protocol in the [United States]," he told Medscape Oncology.
However, he also noted that MammoSite's brachytherapy was not the most used technique in the RTOG/NSABP study; external-beam radiation was, he said.
In addition to those 2 techniques, APBI can also be carried out using interstitial brachytherapy and intraoperative electron beam.
Which technique is best? The task force's answer to that is that "there are insufficient clinical and dosimetric data to determine the optimal technique."
There are several theoretical disadvantages to APBI.
The biggest worry about APBI is that it will miss other cancer in the breast, suggest the consensus-statement authors. "There are several theoretical disadvantages to APBI, principally the possibility that occult foci of cancer exist elsewhere in the breast and will not be treated."
Also, the long-term safety of the approach is not established, write the editorialists, who also point out that a number of whole-breast radiation schemes "shorten the course of radiotherapy without compromising outcome or increasing normal-tissue toxicity."
Four of the ASTRO consensus statement authors have disclosed relevant financial relationships, having served as consultants to SenoRx.
Int J Radiat Oncol Biol. Phys. 2009;74:981-984 and 987-1001. Abstract, Abstract
Authors and Disclosures
Nick Mulcahy is a senior journalist for Medscape Hematology-Oncology. Before joining Medscape, Nick was a freelance medical news writer for 15 years, working for companies such as the International Medical News Group, MedPage Today, HealthDay, McMahon Publishing, and Advanstar. He is also the former managing editor of breastcancer.org. He can be contacted at firstname.lastname@example.org.
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