title: Relationship between sentinel lymph nodes and postoperative tangential fields in early breast cancer, evaluated using SPECT/CT.
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.
authors.affiliation: Department of Radiation Oncology, Hiroshima Prefectural Hospital, 1-5-54 Ujinakanda Minami-ku, Hiroshima 734-8530, Japan k-wadasaki@hph.pref.hiroshima.jp.
authors.forename: Koichi
authors.initials: K
authors.lastname: Wadasaki
authors.affiliation: Department of Radiation Oncology, Hiroshima Prefectural Hospital, 1-5-54 Ujinakanda Minami-ku, Hiroshima 734-8530, Japan.
authors.forename: Ikuno
authors.initials: I
authors.lastname: Nishibuchi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D001940:Breast / Q000528:radiation effects; D001943:Breast Neoplasms / Q000532:radiotherapy* / Q000601:surgery*; D005260:Female; D006801:Humans; D008198:Lymph Nodes / Q000473:pathology; D008327:Mammography; D015412:Mastectomy, Segmental; D008875:Middle Aged; D011857:Radiographic Image Interpretation, Computer-Assisted; D011868:Radioisotopes; D011878:Radiotherapy; D015203:Reproducibility of Results; D000071036:Sentinel Lymph Node / Q000473:pathology*; D000072098:Single Photon Emission Computed Tomography Computed Tomography
chemical_list: D011868:Radioisotopes
keywords: SPECT/CT; breast cancer; sentinel lymph node; whole-breast irradiation