2180 - Outcomes Following Stereotactic Body Radiotherapy (SBRT) for Melanoma Spine Metastases

03:00pm - 04:00pm ET

Poster Hall - Exhibit Hall A

Screen: 15

POSTER

Presenter(s)

Maleeha Qazi, MD, PhD - University of Toronto, Toronto, ON

M. Qazi¹, M. Jeeva¹, M. O. Butler², C. J. Tsai¹, A. Y. Sun¹, L. A. Dawson¹, D. Shultz¹, and P. Wong¹; ¹Department of Radiation Oncology, Princess Margaret Cancer Centre, University of Toronto, Toronto, ON, Canada, ²Department of Medical Oncology and Hematology, Princess Margaret Cancer Centre, Toronto, ON, Canada

Purpose/Objective(s): Immunotherapy (IO) and targeted therapies improve survival in metastatic melanoma, though management of spine metastases remains a challenge. Stereotactic body radiotherapy (SBRT) has been shown to provide higher local control (LC) and pain response than conventional external beam radiotherapy. This study reports outcomes of SBRT for melanoma spine metastases.

Materials/Methods: In this single-centre retrospective study, patients with melanoma spine metastases treated with SBRT between 2007–2025 were identified. Chart review was completed to extract patient demographics, treatment course, toxicities, and disease outcomes. Pre- and post-treatment imaging as well as radiation treatment plan was reviewed for each treated spine segment to assess for radiographic response and vertebral compression fractures (VCF). The primary endpoint was local control (LC) and secondary endpoint was toxic effects.

Results: 43 patients (median age 62, IQR 50.8-70.1) with 77 spine segments were reviewed. Primary melanoma sites were cutaneous (n=22, 51.2%), uveal (n=13, 30.2%), mucosal (n=3, 7.05), and unknown (n=5, 11.6%). The median time from diagnosis to developing spine metastases was 27 months (IQR 8.5-58.6). At the time of SBRT, 14 patients (32.5%) had oligometastatic disease (1-5 lesions in <3 sites) and of those only 4 patients (9.3%) had spine only metastasis. 47 (61%) spine metastases were limited to a single spine segment, while 16 (20.8%) and 14 (18.2%) spine metastases were in two or more than two consecutive spine segments, respectively. 14 (18.2%) spine segments had received previous radiation (most common dose 20 Gy in 5 fractions).

The treatment indication for SBRT was local control (n=34, 44.2%), pain (n=29, 37.7%) or post-operative (n=14, 18.2%). The median number of treated spine metastases per patient was 2. For single or two consecutive spine segments, 24 Gy in 2 fractions (BED₂ 168 Gy, n=46 segments) was the most common regimen. In re-irradiation setting, 30 Gy in 4 fractions (BED₂ 142.5 Gy) or 30 Gy in 5 fractions (BED₂ 120 Gy) were the most common regimens. At the time of SBRT, 23 patients (53.5%) were on concurrent systemic treatments (17 on 1^st line, 2 on 2^nd line, and 4 on 3^rd line treatment).

The median clinical follow-up was 8.4 months (IQR 5.5-23.2) and 70 (90.9%) of the 77 segments had post-SBRT imaging. LC at 3 months, 6 months and 12 months was 90.0%, 82.9% and 81.4%, respectively. There were 7 segments (10%) that developed iatrogenic VCF, of which 4 (57.1%) were treated with percutaneous cement-augmentation and the remaining 3 (42.9%) were managed conservatively. Following SBRT, the median time to next systemic therapy was 4.8 months (IQR 3.5-19.3) in oligometastatic patients and 1.5 months (IQR 1.1-5.0) in polymetastatic patients.

Conclusion: SBRT for melanoma spine metastases provides good local control with VCF rates similar to those reported in the literature. Future analysis will focus on assessment of pain response and rate of radiation myelopathy/plexopathy.