A Balloon Catheter for Partial Breast Intracavitary Brachytherapy

Abstract & Commentary

Synopsis: Breast brachytherapy has been practiced for nearly 100 years, but its modern day use is limited to a few diehard radiation oncologists who have organized phase I/II trials in their own institutions. Based on promising early data from patients treated with a newly FDA-approved breast brachytherapy device, and on forthcoming RTOG toxicity data to be presented this fall, it appears that breast brachytherapy may become more popular in the near future. This study from William Beaumont Hospital published their experience with a dozen patients treated with the new applicator. They presented clinical observations and described dosimetry characteristics and considerations that will prove useful when deciding whether to offer this modality to our patients.

Source: Edmundson GK, et al. Int J Radiat Oncol Biol Phys. 2002;52:1132-1139.

While breast brachytherapy has been practiced and written about for nearly a century, external beam radiotherapy following lumpectomy remains the standard. Though Janeway reported on interstitial radiotherapy for operable breast cancer in lieu of mastectomy in 1917, very few physicians have adopted the procedure. Today’s typical technique of inserting needles into the breast tissue surrounding a resection cavity varies little from the way brachytherapy was performed in Janeway’s time. The main improvements have been computerization and image guidance. In spite of the fairly static nature of the basic technology, favorable data on adjuvant interstitial brachytherapy as a sole modality following breast-conserving surgery have begun to emerge as the technique has been revisited. This has attracted interest in the radiation oncology community. Most recently, new data from implementation of an innovative intracavitary applicator look promising.1-3 If ongoing interstitial brachytherapy studies indicate that breast brachytherapy is efficacious in selected patients, then the new intracavitary applicator may supplant the older interstitial needles as the instrument of choice.

Edmundson and associates conducted a phase I trial testing safety, reliability, and dosimetric characteristics from June 2000 through May 2001 involving 12 patients in 9 hospitals. All 12 patients had T1N0 lesions with negative surgical margins, and all were implanted with a silicone balloon catheter at the time of their breast resection. The prescribed dose to the resection bed at 1 cm from the surface of the balloon was 3.4 Gy b.i.d ´ 10 = 34 Gy in 5 days. Treatments were commenced after the final pathology report was ready, usually postoperative day 2-3. Treatment was administered by attaching the balloon catheter to a standard high-dose rate brachytherapy unit containing an iridium-192 source. Eight patients were treated per protocol. Problems causing removal of the device in 4 patients included air pockets adjacent to the balloon, balloon asymmetry, and balloon puncture. At the conclusion of the therapy, the balloon was removed by the radiation oncologist after it was deflated. One patient developed moist changes from treatment, and the rest did well.

Edmundson et al concluded that, in comparison to historical controls, the new system provided better coverage of the target volume, ie, the resection cavity, and was more reproducible than interstitial brachytherapy. Critical issues discussed were the mandatory > 5 mm distance between the balloon and the skin surface, and the size limit of < 5 cm for the resection cavity. The former is necessary to prevent untoward reactions on the skin, and the latter maintains the overall treatment time to a reasonable length while keeping exposure to the heart and lungs low. Strict adherence to RTOG 95-17 protocol guidelines was emphasized several times throughout the paper. The main thrust of those guidelines is the careful monitoring of dosimetry parameters, most easily accomplished with image guidance.

Comment by Edward J. Kaplan, MD

If partial breast irradiation is shown to be efficacious in certain circumstances, then breast brachytherapy might enjoy some of the rising popularity that prostate brachytherapy has commanded over the last 10 years. This would be particularly true given the short learning curve that seems to be associated with the new balloon catheter system. Most radiation oncologists have never attempted breast brachytherapy, and a simple, effective tool would certainly make us more prone to trying it. Although the device has been approved for use by the FDA, the American Brachytherapy Society (ABS) still considers it to be investigational. In fact, it is so new that the just-published ABS guidelines for breast brachytherapy omit the intracavitary brachytherapy approach altogether.4

There are a host of potential advantages of a 5-day intracavitary brachytherapy program as the sole adjuvant radiotherapeutic treatment following lumpectomy. These include conformation of the radiation to the resection cavity rather than treatment of the entire breast, improvement of patient quality of life based on a shorter treatment schedule, simplification of treatment, elimination of logistical issues involving integration of chemotherapy and radiotherapy, increased willingness of women to undergo breast conservation because of the more convenient schedule, and the possibility of treating second primary ipsilateral breast tumors without fear of overlapping previously irradiated tissue.

Exclusion criteria were mentioned by Edmundson et al. These included resection cavities larger than 6 cm, T3-4 lesions, multifocality, positive margins, more than 4 involved lymph nodes, and intraductal histology. It appears that these are an initial set of empiric guidelines since no rationale was offered.

There has never been a randomized trial comparing external beam RT to brachytherapy alone in breast cancer. RTOG 95-17 is a phase I/II trial that was closed in March 2000 after accruing 99 patients who received interstitial breast brachytherapy as a sole modality post lumpectomy. Forty-five patients were treated with low- dose rate therapy, and 34 received the same HDR schedule used by the William Beaumont group. Toxicity data are scheduled to be presented at the upcoming ASTRO meeting in October 2002. It is anticipated that RTOG 95-17 will be followed by a phase III trial.

Aside from the question whether or not irradiation of most of the breast can be omitted in any cases following lumpectomy, there are other interesting points associated with use of an intracavitary system. For example, it is not known exactly how much margin around the resection cavity is actually being treated since inflation of the balloon causes some amount of breast compression. Will the device eliminate postoperative seromas, and can it cause seeding of the incision line? Breast tissue tolerance to brachytherapy using this entirely new system is not known, and fat necrosis along with telangiectasias or worse may be important. Should the system be used as an up-front boost rather than as sole therapy in some or all cases?

One would hope that a system like that described by Edmundson et al can be shown to offer clinical benefit to our patients, given its easy deployment and use. As always, careful planning and measurements are essential to success. I am sure we will be hearing and reading much more about this technique in the months and years ahead.

Dr. Kaplan is Acting Chairman, Department of Radiation Oncology, Cleveland Clinic Florida, Ft. Lauderdale, FL. He is also Medical Director, Boca Raton Radiation Therapy Regional Center, Deerfield Beach, FL.

References

1. Kuske R, et al. Proc ASTRO. October 1998.

2. Vicini FA, et al. Miami Breast Cancer Conference abstract. 2002.

3. Keisch ME, et al. 2001; RSNA abstract

4. Nag S, et al. Oncology. 2001;15:195-202.