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Brachytherapy for Breast Cancer
There are already effective treatments for breast cancer. Many ask why a new treatment is needed. The answer is that despite 7 randomized trials comparing mastectomy to lumpectomy plus radiation, and all of the trials without exception showing that these two treatments are absolutely equal in terms of cancer cure, recurrence rates, etc., it is estimated that less than 50% of women in the United States receive breast-conserving treatment. The main obstacle for most of these women is the inconvenience of 6-7 weeks of external beam radiation. Patients who live a long distance from a radiation oncology center, who depend on others for transportation, are frail, or elderly may prefer an accelerated 5-day brachytherapy treatment as opposed to traditional external beam radiation treatments.
Brachytherapy, therefore, will allow for breast conservation in a group of women who at this point are treated with mastectomy. An additional advantage is that the cosmetic outcome appears to be superior with brachytherapy, especially for large breasted women, because less of the breast is irradiated. Skin dose, lung dose, and dose to the lymphatic drainage area under the arm is less as well.
History of Breast Brachytherapy
Robert Kuske M.D. pioneered modern breast brachytherapy in 1991 at the Ochsner Clinic In New Orleans, though this treatment was first done as far back as 1929. Dr. Kuske had a breast cancer patient insisting on a treatment that allowed her to keep her breast, and was shorter than the standard 6-7 weeks of external beam radiation. He performed a wide-volume flexible catheter implant surrounding the lumpectomy cavity then treated her with HDR brachytherapy. Success with this first patient led to multiple single institution phase II studies, and ultimately to a large National Cancer Institute sponsored multi-institutional study headed by the RTOG (Radiation Therapy Oncology Group), one of the United States major cancer trial organizations.
Treatment Rationale
When mastectomy specimens are fixed and analyzed slice by slice, the distribution of breast cancer cells within the breast can be determined. Researchers have shown that cancer spreads outward from the epicenter. The chance of finding cancer decreases as the distance from the primary cancer increases. The vast majority of true recurrences after Breast Conservation Therapy occur within and surrounding the original tumor site. Very few patients have recurrences in a different part of the breast. The question arises whether this low recurrence rate in other parts of the breast is attributable to treating the whole breast with external beams, or if it was radiation going to the lumpectomy cavity that gave the benefit?
If whole breast radiation were essential, then one would expect the rate of recurrence away from the lumpectomy cavity to increase dramatically in studies where women underwent lumpectomy alone, without any radiotherapy. This, however, is not the case.
Researchers clearly show that recurrences away from the lumpectomy cavity are only a couple of percent. This low failure rate is the same whether or not whole breast radiation is given. On the other hand, recurrences very near the lumpectomy cavity are very high, around 40%, when no radiation is given.
Thus, the primary benefit of whole breast radiation is not that it sterilizes other parts of the breast, but that it eradicates microscopic cancer near the original tumor. In other words, it appears to be more important to irradiate the lumpectomy cavity and immediate adjacent tissue, rather than radiating the entirety of the breast.
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