title: The addition of SPECT/CT lymphoscintigraphy to breast cancer radiation planning spares lymph nodes critical for arm drainage.
abstract: BACKGROUND
  This prospective cohort study was designed to determine whether the amount of radiation delivered to the nonpathological lymph nodes (LNs) that drain the arm can be significantly reduced by integrating single-photon emission computed tomography (SPECT)/computed tomography (CT) scans into radiation treatment planning.
  
  
  METHODS
  SPECT-CT scans were acquired for the 28 patients with stage I or II breast cancer and fused with the routinely obtained radiation oncology planning CT scans. Arm-draining LNs were contoured with 0.5-cm margins automatically using a threshold of 50% maximum intensity. Two treatment plans were generated: 1 per routine clinical practice (standard; STD) and the second (modified; MOD) with treatment fields modified to minimize dose to the arm-draining LNs visible on SPECT/CT images without interfering with the dosage delivered to target tissues. Participants were treated per the MOD plans. Arm volumes were measured prior to radiation and thereafter at least three subsequent 6-month intervals.
  
  
  RESULTS
  Sixty-eight level I-III arm-draining LNs were identified, 57% of which were inside the STD plan fields but could be blocked in the MOD plan fields. Sixty-five percent of arm-draining LNs in the STD versus 16% in the MOD plans received a mean of ≥10 Gy, and 26% in the STD versus 4% in the MOD plans received a mean of ≥40 Gy. Mean LN radiation exposure was 23.6 Gy (standard deviation 18.2) with the STD and 7.7 Gy (standard deviation 11.3) with the MOD plans (P<.001). No participant developed lymphedema.
  
  
  CONCLUSIONS
  The integration of SPECT/CT scans into breast cancer radiation treatment planning reduces unnecessary arm-draining LN radiation exposure and may lessen the risk of lymphedema.
authors: Department of Physical Medicine and Rehabilitation, Mayo Clinic, Rochester, MN 55905, USA. Cheville.andrea@mayo.edu
authors: Andrea L
authors: AL
authors: Cheville
authors: Debra H
authors: DH
authors: Brinkmann
authors: Shelly B
authors: SB
authors: Ward
authors: Jolanta
authors: J
authors: Durski
authors: Nadia N
authors: NN
authors: Laack
authors: Elizabeth
authors: E
authors: Yan
authors: Paula J
authors: PJ
authors: Schomberg
authors: Yolanda I
authors: YI
authors: Garces
authors: Vera J
authors: VJ
authors: Suman
authors: Ivy A
authors: IA
authors: Petersen
mesh_terms: D000328:Adult; D000368:Aged; D001132:Arm / Q000000981:diagnostic imaging*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D005260:Female; D006801:Humans; D008196:Lymph / Q000502:physiology; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000528:radiation effects; D008209:Lymphedema / Q000209:etiology / Q000517:prevention & control*; D061305:Lymphoscintigraphy / Q000379:methods*; D008875:Middle Aged; D059351:Organ Sparing Treatments / Q000379:methods*; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D011446:Prospective Studies; D011832:Radiation Injuries / Q000517:prevention & control; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods*