Study: SPECT/CT reduces lymphedema in breast cancer patients

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Integrating SPECT with the CT scans utilized for breast cancer radiotherapy planning may offer patients substantial protection against lymphedema, an incurable, chronic swelling of tissue that results from damage to lymph nodes sustained during breast cancer radiation, according to a study presented at CTRC-AACR's San Antonio Breast Cancer Symposium last week.

The SPECT/CT scan pinpoints the precise locations of the lymph nodes that are critical for removing fluid from the arm, allowing physicians to block them, as much as possible, from x-ray beams delivered to the chest, according to the study.

"In an effort to deliver therapeutic doses of radiation to the breast, lymph nodes under the arm are innocent bystanders that often are irrevocably harmed. Minimizing harm to these nodes during breast cancer treatment is the most effective way we have seen to reduce women's risk of developing lymphedema," said the study's lead investigator Andrea L. Cheville, MD, a consultant in physical medicine and rehabilitation at Mayo Clinic in Rochester, Minn.

The study included 30 women with early-stage, low-risk breast cancer who had completed surgery to remove tumors and were scheduled for radiotherapy to the affected breast. These patients either had no lymph nodes that had cancer, or had only micrometastasis to lymph nodes. Thus, radiation to the lymph nodes in the armpit was not warranted in these patients.

The technique the researchers developed to shield lymph nodes from radiation involved merging SPECT scans with the CT images utilized in radiation treatment planning.

The critical lymph nodes are under the armpit - ones that drain the arm. "While a person can have as many as 62 lymph nodes under the arm, only a few are responsible for that function. We can use this information to personalize the fields of radiation such that the tumor bed in the breast is therapeutically treated while the lymph nodes that drain the arm are maximally blocked from radiation and thereby spared," Cheville said.

Using the SPECT/CT images, the researchers identified all of the critical lymph nodes in the patients. They found that 65 percent of these nodes would have been located within the standard radiation treatment fields if they were not blocked. They also found that among the 25 patients with at least one critical lymph node within the radiation treatment field, at least some blocking was possible for all of them.

The researchers calculated that the number of lymph nodes receiving a moderate dose of radiation was reduced from 26 percent to 4 percent with blocking.

Cheville said that the technique of locating critical lymph nodes and blocking them from radiation may prove most useful for patients who require surgical removal of the lymph nodes in the armpit but do not require radiation targeting any remaining nodes. These patients' risk of developing lymphedema may be as high as 50 percent without blocking, and measures that preserve the function of their lymphatic systems may be critical to their long-term quality of life, she added.