Use of lymphoscintigraphy in radiation treatment of primary breast cancer in the context of lymphedema risk reduction

Purpose: The goal of this study was to determine the feasibility of SPECT/CT scintigraphic method for mapping lymphatic drainage for radiation therapy of breast cancer. Materials and methods: Thirty-six patients were enrolled in a SPECT/CT lymphoscintigraphy study. ^99mTc sulfur colloid (1 mCi) was injected intradermally in the ipsilateral arm. After 5-8 h post-injection, the SPECT/CT scans were taken and analyzed on a GE eNTRGRA system. The SPECT/CT images were co-registered in the treatment planning system (TPS). The original treatment plan was recreated for nodal dosimetry. Intensity modulated radiation therapy (IMRT) planning was performed for reducing lymph node dose for reducing arm lymphedema. Results: The number of lymph nodes varied from 0 to 10 with a mean value of 3.4 ± 5.4 nodes. The location of nodes varied in the axillary, supraclavicular, and breast regions depending upon the surgical procedure and the extent of the disease. The prescribed radiation dose to the breast varied from 45 to 50.4 Gy depending on the disease pattern in 32 evaluated patients having CT data. The dose to lymph nodes varied from 0 to 61.8 Gy depending upon the location and the radiation technique used. SPECT/CT study in conjunction with IMRT plan showed that it is possible to decrease nodal dose and thereby potentially reduce the risk of developing arm lymphedema. Conclusions: The SPECT/CT device provides a novel method to map the lymph nodes in the radiation treatment fields that could be used to tailor the radiation dose.