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.
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 ¡Ý10 Gy, and 26 % in the STD versus 4 % in the MOD plans received a mean of ¡Ý40 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.
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.