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Brachytherapy in the Treatment of Breast Cancer

Brachytherapy in the Treatment of Breast Cancer

The article by Nag and colleagues of the American Brachytherapy Society is a well-intentioned effort to establish guidelines for the use of temporary implants in the treatment of breast cancer. Unfortunately, it attempts a multitude of tasks all at once: to define the role of brachytherapy (temporary iridium-192 implants), establish guidelines for its performance, and establish standards of treatment. It mixes the use of brachytherapy boost treatment (largely abandoned by radiation oncologists in the United States) after whole-breast external-beam treatment with breast implants used alone after primary-site excision (an investigational procedure). It even mixes in brachytherapy for recurrences—a setting for which few data exist, as the authors acknowledge.

Role of Brachytherapy

As the authors have carefully outlined, the effectiveness of brachytherapy as boost treatment has been well established. Recent results from the European Organization for Research and Treatment of Cancer trial support the use of a boost as well,[1] but it has been very difficult to determine any clinical difference in outcome with regard to either tumor control or cosmesis between the use of iridium-192 implants or external-beam electrons as boost treatment.

A Radiation Therapy Oncology Group study attempted to randomize this treatment but was closed before accrual was completed due to slow accrual. In this country, the Patterns of Care Process Survey showed that the use of brachytherapy for this purpose has been largely abandoned in patients with early breast cancer, with only 0.3% (2 of 609 patients) receiving this type of boost.[2]

As a sole treatment after excision of a breast primary, brachytherapy is still investigational, and as such, is defined in the investigational protocols for such studies. Guidelines at this time in the general literature are thus premature; they tend to lend support for such an application outside of such protocols, which should not be encouraged until we have long-term results in a large number of carefully defined patients.

Finally, as the authors have acknowledged, there is very little evidence to support the use of brachytherapy as treatment for recurrences, and therefore, such treatment should not be performed outside of carefully defined studies.

Guidelines and Standards

With the above caveats, guidelines, appropriateness criteria, and standards are certainly valuable for any radiation treatment, as the American College of Radiology (ACR) has long recognized. Several publications already exist, and others in progress cover much of what these authors are attempting to establish (eg, the ACR standards for diagnosis and management of invasive breast carcinoma, performance of high-dose-rate and low-dose-rate brachytherapy, and performance of brachytherapy physics with manually loaded sources[3]; and ACR appropriateness criteria for breast cancer treatment).[4] In the present publication, Nag et al have tried to bring some of these recommendations together for breast cancer treatment per se, for all of the roles indicated above.

Given that these recommendations were "generally" made with a consensus category 2, there is little high-level evidence (ie, randomized studies) to support these guidelines. It should also be noted that "generally" is not defined under the list of definitions for consensus categories 1 through 3; that is, it was not made clear whether the panel was in agreement 50% of the time or 90% of the time. Even when there is major disagreement among panel members (consensus category 3), recommendations are still provided, as in the section entitled "General Considerations Regarding Technique," which recommended potentially modifying the margins on the clinical target volume, depending on tumor size and extent of surgical resection.

This group could do a service to the radiation oncology community by developing better terminology for the calculation planes rather than using truly anatomic terms (coronal and sagittal), and then trying to qualify them by indicating that they may not be "coronal" or "sagittal" in a strict anatomic sense. In fact, these planes will almost never correspond to the anatomic planes. For instance, the word, "transverse," has geometric meaning. In this case, perhaps the words "parallel" and "longitudinal" (which also have geometric meaning) would have been more suitable.

Overall, there is no clear statement in the authors’ recommendations as to whether or not there are differences in the guidelines for an implant as a boost vs an implant as a sole treatment. The only relevant statements appear in the sections entitled "Physics/Dosimetry Considerations" (regarding skin dose) and "Dose of Sole-Modality Brachytherapy."

The "Patient Selection Criteria" section is not well substantiated and often appears either arbitrary or incomplete. For example, there was obvious and considerable controversy within the panel regarding treatment for patients with positive axillary lymph nodes, and yet a hedged recommendation from some panel members was still given—with no discussion of rationale. On the other hand, tumor characteristics that might influence one’s decision, such as the presence of lymphatic vascular invasion, extensive intraductal carcinoma, or high tumor grade, were not mentioned at all.

The meaning of "technically unsuitable for brachytherapy" (under "Special Circumstances") was also not explained. In addition, in the section "Benefits of Brachytherapy Boost," the authors did not substantiate their suggestion that a higher dose may be required in younger patients. Finally, in the same section, the authors attribute the poor cosmetic results of boost brachytherapy to older studies with poor attention to technical details, but then cite references as recent as 1999 and 2000.

Conclusions

Guidelines and standards are important, but their value is greater when the treatments themselves are used frequently and are well established. Since breast implant boosts have gone out of favor and breast implants as a sole treatment have not yet become an established proven treatment, it would certainly be wise to revisit this latter topic in a few years, when more long-term data are available.

References

1. Collette L, Fourquet A, Horiot JC, et al: Impact of a boost dose of 16 Gy on local control in patients with early breast cancer: The EORTC "boost versus no boost" trial (abstract). Radiother Oncol 56:S46, 2000.

2. Shank B, Moughan J, Owen J, et al: The 1993-94 patterns of care process survey for breast irradiation after breast-conserving surgery ¾ Comparison with the 1992 standard for breast conservation treatment. Int J Radiat Oncol Biol Phys 48(5):1291-1299, 2000.

3. American College of Radiology: Standards 1999-2000, pp 185-188, 289-292, 293-296, 391-409. Reston, Va, American College of Radiology, 1999. Available at: www.acr.org. Accessed January 12, 2001.

4. American College of Radiology. Appropriateness Criteria. Available at: www.acr.org. Accessed January 12, 2001.

 
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