Brachytherapy in the Treatment of Breast Cancer

Dr. Subir Nag et al are to be congratulated for their excellent, thorough analysis and presentation of the use and role of brachytherapy in the treatment of patients with breast cancer.

Brachytherapy: Long Time Coming

In 1896, Gocht[1] used x-rays in the treatment of breast cancer, 1 year after Roentgen’s first report on his discovery. Radium was also used to treat early and advanced breast cancer very soon after its discovery. In 1924, Koenig[2] reported a 5-year survival of 21% for stage I breast cancer and 17% for stage II disease in patients treated with radium only.

In 1929, Keynes[3] suggested that it might be possible to cure breast cancer by means of irradiation. He described techniques in which radium needles were implanted into the breast tumor, axilla, and occasionally, the internal mammary node region. He chose this modality on the basis of previous experiences in which he had used preoperative irradiation and noted complete disappearance of the tumor when examined microscopically in about one-third of cases.

McKittrick[4] agreed with Keynes that interstitial irradiation was of use for tumors that occupied no more than
one-quarter of the breast. He consid-ered interstitial irradiation to be of no value in operable patients because of sequelae (pain, fibrosis, and late deformity).

The sequelae of brachytherapy led to its limited use until the mid-1900s. At that time, the Europeans, especially the French—who had continued to use radium in combination with orthovoltage therapy—began to use radium and other radioactive sources to give a boost dose to the tumor or tumor bed. On the basis of work by European investigators, such as Pierquin,[5,6] the use of brachytherapy as a boost for breast cancer was given credence.

In the recent past, a few investigators opposed its use. In addition, the availability of the electron beam made boosting of the tumor site more practical. As a result of these issues, brachytherapy, even as a local boost, has been used only at a few centers in the United States.[7]

Necessity for Guidelines on Brachytherapy

Since most radiation oncologists do not have extensive experience in breast brachytherapy, it made good practical sense for the American Brachytherapy Society (ABS) to develop guidelines for the clinical use of this strategy. The result has been a well-prepared and well-written document.

There are multiple methods for the use of brachytherapy in the treatment of breast cancer. Among these techniques are:

As the Sole Method of Treatment: In the past, this method was used for patients with advanced disease. However, Dr. Kuske has begun to show favorable results in patients with early-stage disease.[8,9]

As a Low-Dose-Rate Boost Following External-Beam Irradiation: Although this method has been used in the United States, the majority of cases have been treated in France.[5,6]

As a Boost Before External-Beam Irradiation: This is performed at the time of surgical excision of the lump.[7,10,11] We have treated over 600 patients using brachytherapy at the time of lumpectomy. We have noted excellent local control, survival, and cosmetic results.[12]

As a Mold to Treat Postmastectomy Recurrence on the Chest Wall: The use of this method today would be very rare because of the availability of the electron beam.

As a Low- or High-Dose Boost: This can be done with or without external-beam irradiation.[13,14]

In the conservative treatment of the breast, the local tumor is excised with a 1- to 2-cm margin of normal tissue. As mentioned above, an implant can be performed at the time of lumpectomy.[10-12] However, the most common approach has been to have the patient start on external-beam therapy to the whole breast 1 to 2 weeks later. The adjacent nodes are treated, depending on the location of the primary and status of the axillary nodes. The tumor bed is then boosted with electrons or an interstitial implant (photons are rarely used, because they are associated with sequelae). The interstitial therapy can be administered at a high or low dose rate.

The ABS panel discusses the indications, use, and evaluation of breast implants as the sole treatment modality following lumpectomy, as a boost following whole-breast irradiation, and as a treatment of local recurrences. As pointed out by the ABS, the use of brachytherapy as the sole method of treatment to the tumor bed is being investigated in a randomized trial. At present, this is not the recommended method of treatment, except in a randomized trial setting. This is particularly true for patients with stage II disease, since a higher percentage of their recurrences can occur outside of the tumor site.

Treat the Whole Breast or Tumor Site?

For more than 100 years, the treatment of early breast cancer has been based on the concept that the whole breast needs to be treated. This has been supported by the fact that the whole breast is at risk for recurrent disease. However, the majority of recurrences have occurred in the region of the original tumor. As a result, a school of thought has arisen suggesting that it should be possible to achieve a cure in the breast even if only the tumor site in the breast is treated.[8, 9,13,14]

Conclusions

In summary, up until now, no real standards have been developed for the use of brachytherapy in the breast. This paper establishes guidelines that are sorely needed in the brachytherapy community. Dr. Nag and the panel address important issues such as the clinical target volume, optimal volume, type of interstitial implants, use of templates, high dose rate, and dosimetry. Their work has resulted in a well-done reference article.