[Effectiveness and toxicity of reirradiation (Re-RT) for metastatic spinal cord compression (MSCC)].

Background and Purpose: Radiation myelopathy is a serious late toxicity after radiotherapy (RT) of metastatic spinal cord compression (MSCC). The risk of myelopathy depends on the equivalent dose in 2-Gy fractions (EQD2). Many radiation oncologists are concerned about spinal Re-RT, because it may result in a high cumulative EQD2. This study investigates effectiveness and feasibility of Re-RT for in-field recurrence of MSCC.
Patients and Methods: 74 patients, irradiated between 01/1995 and 12/2003 for MSCC, were reirradiated for in-field recurrence of MSCC (Table 1). Primary RT was performed with 1 x 8 Gy (n = 34), 5 x 4 Gy (n = 28), 10 x 3 Gy (n = 4), 15 x 2.5 Gy (n = 4), or 20 x 2 Gy (n = 4). Recurrence occurred after median 6 months (2-40 months). Re-RT was performed with 1 x 8 Gy (n = 35), 5 x 3 Gy (n = 16), 5 x 4 Gy (n = 13), 10 x 2 Gy (n = 4), 12 x 2 Gy (n = 3), or 17 x 1.8 Gy (n = 3). Cumulative EQD2 (alpha/beta = 2 Gy) was 39-40 Gy (n = 21), 49-50 Gy (n = 41), 56-60 Gy (n = 6), or > 60 Gy (n = 6). Follow-up after Re-RT was median 9 months (2-52 months).
Results: Re-RT led to an improvement of motor function in 29/74 patients (39%; Figures 1 to 3). On multivariate analysis, outcome was significantly influenced by type of primary tumor (p = 0.013) and by the time of developing motor deficits before Re-RT (p = 0.037), but not by radiation schedule (p = 0.560), by ambulatory status before Re-RT (p = 0.471), by cumulative EQD2 (p = 0.795), nor by the interval between primary RT and Re-RT (p = 0.420; Table 2). Radiation myelopathy was not observed in the whole series.
Conclusion: Re-RT is an effective treatment for an in-field recurrence of MSCC. After a cumulative EQD2 < or = 50 Gy, radiation myelopathy appears unlikely.