Abstract
Single-photon emission computed tomography/computed tomography (SPECT/CT) demonstrates the precise location of the sentinel lymph nodes (SLNs) in patients with breast cancer. We evaluated the relationship between SLNs and postoperative tangential fields by using SPECT/CT images. Subjects included 72 patients with early breast cancer who underwent SPECT/CT of the SLNs and received whole-breast irradiation with tangential fields after partial mastectomy. The SLN locations evaluated by using SPECT/CT images were entered into the treatment-planning CT image with a 5-mm-diameter sphere. A 15-mm-diameter sphere including the 5-mm treatment margin around the SLNs was defined as PTV-SLN. The PTV-SLN doses with tangential irradiation were evaluated and expressed as the percentage of the prescribed dose. In 69 patients, SLNs were detected by using SPECT/CT; 68 SLNs were located at axillary lymph node Level I, and one was located at Level II. A total of 62 SLNs (90%) were determined to be located inside the tangential fields on the digitally reconstructed radiography (DRR) images. The median doses of SLN center, mean PTV-SLN dose, and PTV-SLN D95 (the minimum dose delivered to 95% of the volume) were 94.1% (range, 15.3–101.9%), 93.7% (range, 29.3–104.0%) and 84.8% (range, 6.8–99.8%). The D95 for the SLNs with treatment margins were ≤90% of the prescribed doses in more than half of the cases. Modification of the individual treatment fields seemed to be necessary to ensure coverage of the SLNs in whole-breast irradiation.
Highlights
The sentinel lymph nodes (SLNs) are those that first receive lymphatic drainages from the breast tissue
We evaluated the relationship between SLNs and postoperative tangential fields by using SPECT/CT images
Several randomized studies have shown the non-inferiority of SLN biopsy alone compared with axillary lymph node dissection for SLN-negative patients with breast cancer [1, 6]
Summary
The sentinel lymph nodes (SLNs) are those that first receive lymphatic drainages from the breast tissue. Two randomized studies showed that in certain groups of patients with early breast cancer, axillary lymph node dissection was not required, regardless of the SLN biopsy results [2, 3]. Another purpose of SLN biopsy is to guide systemic therapy decisions. We retrospectively reviewed the SPECT/CT images of the SLNs of patients with early breast cancer who received whole-breast irradiation after partial mastectomy and evaluated the relationship between the SLNs and tangential radiation fields by entering the SLN locations into the treatment-planning CT images
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