Posterior Neck Coverage in Patients Receiving Regional Nodal Irradiation for Breast Cancer
International Journal of Radiation Oncology, Biology, Physics
Purpose/Objective(s): Patterns-of-failure studies suggest the posterior neck (PN) may harbor microscopic disease in patients with locally advanced breast cancer. We compared target coverage, lung dose, and toxic effects in patients treated with either an anterior oblique field (AO) or opposed oblique fields (OO) to address the superior axillary and supraclavicular nodal (SCV) regions. Materials/Methods: We identified 119 consecutively treated patients who received regional nodal irradiation, including a “third field,” to address the superior axillary and supraclavicular nodal regions with a monoisocentric technique in our institution. Coverage of the axillary clinical target volume (CTV), SCV CTV and PN CTV was determined based on the delivered treatment plan. Wilcoxon rank-sum test and Fisher’s exact test were used to compare coverage of the axillary, SCV, and PN CTVs, lung dosimetry, and toxic effects (graded by the Common Terminology Criteria for Adverse Events v4.0) between patients receiving an AO or OO. Results: There were 29 patients in the AO group and 80 in the OO group. All patients in the AO group received conventionally fractionated radiation versus 61% in the OO group. Modestly hypofractionated plans were delivered to 39% of the OO group. The body mass index and anterior-posterior separation at the matchline (measured at the center of the carotid artery) were similar in both groups. The median volume (%) of the SCV CTV receiving at least 90% of the prescription dose (V90%) was 91% (85, 99) in the AO group and 93% (91, 95) in the OO group (P = 0.2). The median V90% of the PN CTV was 30% (12, 49) in the AO group and 100% (100, 100) in the OO group (P<0.001). The median V90% in the axillary levels I, II and III CTVs were 98%, 95% and 90%, respectively, in the AO group and all 100% in the OO group (P<0.001). Maximum dose and heterogeneity in the SCV CTV were similar in both groups. Including only patients who received conventionally fractionated plans, the mean lung dose (cGy) was 1216 in the AO group and 1328 in the OO group (P = 0045). The lung V5 Gy, V10 Gy and V20 Gy were similar in both groups. Ipsilateral upper extremity lymphedema (all grade 1) was 3.4% in the AO group and 2.5% in the OO group (p>0.9). Moist desquamation in the neck was 0% in the AO group and 1.2% in the OO group (p>0.9). Pneumonitis (all grade 1) was 0% in the AO group and 1.2% in the OO group (p>0.9). Conclusion: Compared to a single anterior field, opposed oblique fields provide superior axillary and posterior neck coverage without increasing toxicity.
Oyeniyi JF, Quinn TJ, Dilworth JT. Posterior neck coverage in patients receiving regional nodal irradiation for breast cancer. Int J Radiat Oncol Biol Phys. 2023 Oct;117(2 Suppl.):e196-e197. doi:10.1016/j.ijrobp.2023.06.1067