2580 - Comparison of Single Dose Radiation Therapy and Stereotactic Body Radiation Therapy in Patients with Spinal Metastases
Presenter(s)
B. Cuevas1, D. Rodriguez1, T. Gonzalez1, S. Lobaugh2, Z. Zhang2, Y. Yamada3, M. Bilsky4, and J. Haseltine3; 1Weill Cornell/Rockefeller/Sloan Kettering Tri-Institutional MD-PhD Program, New York, NY, 2Department of Epidemiology and Biostatistics, Memorial Sloan Kettering Cancer Center, New York, NY, 3Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 4Memorial Sloan Kettering Cancer Center, New York, NY
Purpose/Objective(s): Single-dose radiation therapy (SDRT; 24Gy x 1fx) has been shown to provide superior local control to stereotactic body radiation therapy (SBRT; 27Gy x 3fx) in treatment of oligometastatic lesions, as previously reported in a phase 3 randomized trial (RCT). We performed a secondary analysis focusing on spinal metastases to evaluate local control (LC), metastatic progression, and survival.
Materials/Methods: This secondary analysis included spine oligometastases from a prospective RCT. Local recurrence (LR) was defined to be cancer recurrence in the irradiated spinal lesion. Distant metastasis (DM) was defined as the development of new distant metastases outside the irradiated lesions. Event free survival (EFS) is defined as survival without LR or DM. Cumulative incidence of LR and DM were analyzed using a competing risks framework and Gray’s test was used to compare treatment groups. Overall survival (OS) and event free survival (EFS) were estimated using the Kaplan-Meier method and compared using log-rank tests. The primary objective is to compare cumulative incidences of LR and DM between treatment arms, while secondary endpoints include comparing OS and EFS between groups.
Results: There were 73 patients with 82 spinal metastases. The median follow-up time for all patients was 84 months. 12-month LR [95% CI] was 15% [5.9%, 27%] for SDRT and 14% [4.9%, 27%] for SBRT, and 24-month LR was 29% [16%, 44%] for SDRT and 19% [8.2%, 33%] for SBRT (overall p=0.4). 12-month DM [95% CI] was 40% [24%, 56%] for SDRT and 39% [23%, 56%] for SBRT, and 24-month DM was 58% [39%, 72%] for SDRT and 64% [44%, 78%] for SBRT (overall p=0.7). Median OS [95% CI] was 43 months [27, 104] for SDRT and 39 months [30, 59] for SBRT. 12-month OS [95% CI] was 100% [100%, 100%] in both groups and 24-month OS [95% CI] was 80% [68%, 94%] for SDRT and 67% [53%, 84%] for SBRT (overall p=0.6). Median EFS [95% CI] was similar between groups (13 [7.3, 35] vs. 14 months [10, 27] for SDRT and SBRT, respectively). 12-month EFS [95% CI] was 57% [43%, 76%] for SDRT and 61% [46%, 80%] for SBRT, and 24-month EFS was 37% [24%, 57%] for SDRT and 36% [23%, 57%] for SBRT (overall p=0.8).
Conclusion: This secondary analysis of an RCT found similar cumulative incidences of LR for SDRT and SBRT used in treatment of spine oligometastases. Of note, these LR cumulative incidences are higher than expected based on prior publications, and there may be other factors such as tumor histology contributing to this finding. The published per-protocol analysis found improvement in DM in the SDRT group, and the current report found that SDRT had a lower cumulative incidence of distant metastases than SBRT after approximately 1 year, but no significant difference overall. EFS reporting is newly included in the present analysis; a statistically significant difference between SDRT and SBRT was not observed.