Risk of radiculopathy caused by second course of spine stereotactic body radiotherapy

Abstract

Objective Stereotactic body radiotherapy is used to treat spinal metastases; however, 10% of patients experience local failure. We aimed to clarify the outcomes of the second course of stereotactic body radiotherapy for spinal metastases with a uniform fractionation schedule at our institution. Methods Data of patients treated with a second salvage stereotactic body radiotherapy course at the same spinal level or adjacent level from July 2018 to December 2020 were retrospectively reviewed. The initial prescribed dose was 24 Gy in two fractions, and the second dose 30 or 35 Gy in five fractions. The spinal cord dose constraint at the second course was 15.5 Gy at the maximum point dose. The endpoints were local failure and adverse effects. Local failure was defined as tumor progression using imaging. Results We assessed 19 lesions in 17 patients, with radioresistant lesions in 14 (74%) cases, the second stereotactic body radiotherapy to the same/adjacent spinal level in 13/6 cases, the median interval between stereotactic body radiotherapy of 23 (range, 6–52) months, and lesions compressing the cord in 5 (26%) cases. The median follow-up period was 19 months. The 12- and 18-month local failure rates were 0% and 8%, respectively. Radiation-induced myelopathy, radiculopathy and vertebral compression fractures were observed in 0 (0%), 4 (21%) and 2 (11%) lesions, respectively. Three patients with radiculopathy experienced almost complete upper or lower limb paralysis. Conclusions The second course of salvage stereotactic body radiotherapy for spinal metastases achieved good local control with a reduced risk of myelopathy. However, a high occurrence rate of radiation-induced radiculopathy has been confirmed.

Phase II Clinical Trial of Second Course of Stereotactic Body Radiotherapy for Spinal Metastases

“…Herein, we discussed the optimal dose–fraction schedules for SBRT2 based on published studies. Two retrospective studies of SBRT2 in spinal metastases have reported [ 13 , 18 ] delivering 30 Gy in four fractions (median dose) [ 18 ] and 30 or 35 Gy in five fractions [ 13 ]. The latter revealed the absence of LF within 1 year or RM in 19 lesions [ 13 ].…”

“…The prescribed SBRT2 dose was 30 Gy delivered in five fractions on the basis of a previous retrospective case series [ 13 , 18 ]. The objective was to guarantee that 95% of the PTV received the prescribed dose, while ensuring that the normal tissues adhered to dose constraints.…”

“…For patients with LF, after the initial SBRT course (SBRT1), a second SBRT course (SBRT2) can be considered [ 12 ]. Nonetheless, the risk of plexopathy was recently reported to be clinically relevant, occurring in more than 20% of patients treated with salvage SBRT2 for spinal metastases [ 13 ]. To mitigate the risk of plexopathy even with the use of SBRT2, we hypothesized that reducing the dose to the brachial or lumbosacral plexuses would be beneficial, as the aforementioned study did not apply dose constraints to those nerves [ 13 ].…”

“…Nonetheless, the risk of plexopathy was recently reported to be clinically relevant, occurring in more than 20% of patients treated with salvage SBRT2 for spinal metastases [ 13 ]. To mitigate the risk of plexopathy even with the use of SBRT2, we hypothesized that reducing the dose to the brachial or lumbosacral plexuses would be beneficial, as the aforementioned study did not apply dose constraints to those nerves [ 13 ]. To establish a safe re-irradiation protocol for spinal metastases, we conducted the current clinical trial of SBRT2 with dose constraints on the brachial or lumbosacral plexuses.…”

Incidence and Prognostic Factors of Painful Vertebral Compression Fracture Caused by Spine Stereotactic Body Radiotherapy

“…The SBRT technique has been discussed in great detail in previous publications [15,16] and is briefly summarized here. The clinical target volume included the gross tumor and the immediately adjacent bony anatomic compartments at risk of microscopic disease extension, as described by the contouring guidelines for spine SBRT [17,18].…”