The MammoSite Radiation Therapy System (RTS) is a widely used method of partial breast irradiation that works by delivering radiation from inside the breast directly to the tissue where cancer is most likely to recur. The device is implanted in the lumpectomy cavity during or shortly after breast-conserving surgery. The balloon is inflated with a sterile solution of contrast media in saline, and its position is confirmed radiographically using computed tomography. A high-dose rate source of iridium-192 is then centrally positioned within the applicator by a remote afterloader. This system is used to deliver 34 Gy in 10 fractions over five days. Thus, balloon brachytherapy uses a single radioactive source that delivers radiation to a spherical or elliptical target volume. Like interstitial brachytherapy, it
An updated literature search identified several reports from uncontrolled phase II trials of interstitial and balloon brachytherapy to deliver accelerated partial-breast irradiation. However, there were no published reports from controlled studies comparing long-term rates of in-breast recurrence after whole-breast versus accelerated partial-breast radiotherapy. Several review articles discuss the promising results reported from phase I and II clinical trials and emphasize the importance of phase III clinical trials in determining the role of accelerated partial breast irradiation in the treatment of breast cancer.
At a panel discussion held during the October 2004 meeting of the American Society of Therapeutic Radiology and Oncology (ASTRO), investigators announced the opening of a randomized trial comparing whole-breast and accelerated partial-breast irradiation in November 2004. This trial is funded by the U.S. National Cancer Institute and conducted jointly by two cooperative groups (The National Surgical Adjuvant Breast and Bowel Project [NSABP] and the Radiation Therapy Oncology Group [RTOG]). Investigators plan to randomize 3,000 patients over 30 months to whole breast or partial breast irradiation after lumpectomy with tumor-free margins verified by histologic examination. Eligible patients for the trial include patients with Stage 0, I or II breast cancer resected with a lumpectomy. Additionally, the tumor must be less than or equal to 3.0 cm, and there must be no more than three positive axillary nodes. The patients will be stratified according to disease stage, menopausal status, hormone receptor status and intention to receive chemotherapy, and then randomized to either whole breast irradiation or partial breast irradiation. For those randomized to the experimental arm, physicians and patients will be free to choose one of three methods to deliver accelerated partial breast irradiation (e.g., conventional interstitial brachytherapy, balloon brachytherapy using the Mammosite™ device, or 3-D conformal external-beam radiotherapy). The trial’s primary objective is a randomized comparison of in-breast tumor control (i.e., recurrence rates) for whole breast versus partial breast irradiation. Nonrandomized comparison of outcomes from the three alternatives for partial breast irradiation is a secondary objective. Further details and study sites for the clinical trial are located on the National Cancer Institute Web site.
The American College of Breast Surgeons (ACBS) has determined that partial breast irradiation is an accepted technique for early breast cancer with negative nodes and has established guidelines for its application. Both the American Society of Breast Surgeons (ASBS) and the American Brachytherapy Society (ABS) have issued position statements on partial breast irradiation, advocating it as an accepted technique for women with small tumors and negative axillary nodes. The 2002 updated report from the ABS consists of a literature review of data on local recurrences of breast cancer after APBI using brachytherapy. The authors concluded that the majority of breast cancers recur at the site of the tumor bed. While the ABS recommendations are based on these data, the same observations served as the impetus to further study long-term outcomes in the randomized intergroup (NSABP/RTOG) trial. The consensus statement from the ASBS is unreferenced.
In their updated guideline, the National Comprehensive Cancer Network (NCCN) recommends radiation therapy to the whole breast with boost for patients with clinical stages I, II, and T2N1M0 breast cancer undergoing lumpectomy (additional radiation and chemotherapy are also discussed). In a footnote, they amplify as follows: “Whole breast irradiation with boost (by photons, brachytherapy or electron beam) to tumor bed. Boost to tumor bed is especially encouraged in those 50 years of age or younger. Partial breast irradiation should be performed only as part of a high quality prospective clinical trial.”
Results from patients participating in the NCI-sponsored trial, Phase III Randomized Study of Adjuvant Whole Breast Versus Partial Breast Irradiation in Women With Ductal Carcinoma In Situ or Stage I or II Breast Cancer [NSABP-B-39, NCT00103181, RTOG-0413, SWOG-NSABP-B-39] are still pending.
In July 2009, 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, 2009 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.
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.
Nevertheless, with these statements, PBI can not be considered mediclaly necessary.
Adam Dickler The MammoSite® breast brachytherapy device: targeted delivery of breast brachytherapy Future Oncology, Dec 2005, Vol. 1, No. 6, Pages 799-804
Douglas W. Arthur, MD and Frank A. Vicini, MD MammoSite RTS: The Reporting of Initial Experiences and How to Interpret Annals of Surgical Oncology 11:723-724 (2004)
MammoSite and accelerated partial breast irradiation: Rethinking one-size-fits-all breast irradiation after lumpectomy.Brachytherapy. 2005;4(3):183-5.
Benitez P, Streeter O, Vicini F et al. Preliminary results and evaluation of MammoSite balloon brachytherapy for partial breast irradiation for pure ductal carcinoma in situ: a phase II clinical study. Am J Surg 2006 Oct;192(4):427-33
National Cancer Institute. Radiation therapy in treating women who have undergone surgery for ductal carcinoma in situ or Stage I or Stage II breast cancer.
Arthur DW, Vicini FA, Kuske R et al. Accelerated partial breast irradiation: an updated report from the American Brachytherapy Society. Brachytherapy 2002; 1(4):184-90.
The American Society of Breast Surgeons. Official Statement. Consensus Statement for Accelerated Partial Breast Irradiation.
National Comprehensive Cancer Network. Breast Cancer. Clinical Practice Guidelines in Oncology, v2.2006. Available at www.nccn.org/professionals/physician_gls/PDF/breast.pdf
Prosnitz LR, Horton J, Wallner PE.Accelerated partial breast irradiation: caution and concern from an ASTRO task force.Int J Radiat Oncol Biol Phys. 2009 Jul 15;74(4):981-4.
Smith BD, Arthur DW, Buchholz TA, Haffty BG, Hahn CA, Hardenbergh PH, Julian TB, Marks LB, Todor DA, Vicini FA, Whelan TJ, White J, Wo JY, Harris JR.
Accelerated partial breast irradiation consensus statement from the American Society for Radiation Oncology (ASTRO).Int J Radiat Oncol Biol Phys. 2009 Jul 15;74(4):987-1001.