PQA 10 - PQA 10 Head & Neck Cancer and Health Services Research/Global Oncology Poster Q&A
3603 - The Use of a Low Dose Elective Volume in Head and Neck Stereotactic Body Radiation Therapy (SBRT): Initial Report of Outcomes of a Novel Planning Approach
K. Amarell1, K. Brito1, J. E. Arpi-Palacios2, N. Karasik3, E. J. Murray4, A. Dorfmeyer1, L. M. Zickefoose5, M. Dylong1, C. Chaney2, C. Hymes1, P. Xia5, S. A. Koyfman5, J. A. Miller4, N. M. Woody5, and S. R. Campbell4; 1Cleveland Clinic Foundation, Cleveland, OH, 2Cleveland Clinic Foundation, cleveland, OH, 3Department of Hematology/Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH, 4Cleveland Clinic, Cleveland, OH, 5Department of Radiation Oncology, Taussig Cancer Institute, Cleveland Clinic, Cleveland, OH
Purpose/Objective(s): Stereotactic body radiation therapy (SBRT) is increasingly being used in the upfront setting and more commonly in the re-irradiation setting for head and neck cancers. Typically, SBRT planning involves targeting the gross tumor volume with narrow expanded planning margins without any elective or nodal secondary volumes. At our institution, we piloted adding a lower dose elective volume treated simultaneously for tumors thought to be at high risk for adjacent soft tissue, perineural or nodal spread beyond the radiographically visible tumor. In this initial report, we describe the safety, feasibility, and patterns of failure in patient treated in this fashion. Materials/
Methods: An IRB approved database was queried for patients treated with five fraction SBRT to the head and neck either in the upfront or recurrent setting with a minimum dose of 30 Gy. Each SBRT plan was reviewed by K.A. and patients were included only if a lower dose elective volume was confirmed to be included in the plan. Images at the time of recurrence were reviewed, correlated with the SBRT plan and coded as in the SBRT high dose volume, in the SBRT low dose volume, or out of field. Survival and follow up was calculated from the date of completion of SBRT. Late toxicity (>90 days post SBRT) was graded according to CTCAE V5.0. Results: From 2012-2023, 35 of 116 patients treated with SBRT had a simultaneous low dose elective volume treated concurrently. Median follow up of these patients was 4.7 months (IQR 3.1 – 9.6). Of eight patients still alive, median follow up was 27.1 months (IQR 4.6 – 66.4). Primary tumor sites included oropharynx (11), oral cavity (6), skin (5), salivary gland (4), larynx (3), nasopharynx (2), thyroid (1), sinonasal (1), paranasal sinus (1), and unknown (1). Primary disease was treated in 4 (11.4%) pts while 32 pts (88.6%) were treated for recurrent disease. High dose SBRT volumes included 30 Gy (1), 35 Gy (8), and 40 Gy (20) in 5 fractions. Low dose volumes included doses of 20 Gy (2), 25 Gy (5), 30 Gy (26) and 35 Gy (3) in 5 fractions. There were 14 (40%) loco-regional recurrences. Of these, 5 recurred within the high dose field only, 2 recurred in the high dose field and out of field simultaneously, and 5 recurred out of field only. There were no recurrences within the low dose field. Late effects were modest with one grade 3 dysphagia, three grade 3 aspiration pneumonias, and one grade 2 aspiration pneumonia. Conclusion: The use of a low dose elective volume in patients undergoing head and neck SBRT is feasible. Further study is needed to ascertain whether it is effective at reducing adjacent recurrences.