Dose-response relationship for fractionated irradiation in the treatment of spinal meningeal melanocytomas: a review of the literature

Complete resection (CTR) of meningeal melanocytomas results in better outcome than incomplete resection (ITR). After ITR, outcome is improved by radiotherapy. CTR is less frequent with spinal melanocytomas than with cerebral melanocytomas. This study of 49 spinal melanocytoma patients was performed to define an appropriate radiation dose after ITR. All reported spinal melanocytoma cases were reviewed for extent of surgery, radiotherapy (total dose, dose per fraction), and outcome. CTR was compared to ITR for local control (LC) and overall survival (OS). ITR alone was compared to ITR plus radiotherapy (ITR + RT). In the ITR + RT group, doses of 50-52.2 Gy (1.8-2.0 Gy per fraction) were compared to doses <50 Gy (30-45 Gy). The 5-year LC was 78% after CTR alone vs. 22% after ITR alone (P < 0.001). Five year OS was 83 and 40% (P = 0.011) respectively. ITR + RT was superior to ITR for LC (59% vs. 22%, P = 0.029) and OS (85% vs. 40%, P = 0.10). In the ITR + RT group, 50-52.2 Gy resulted in better LC than 30-45 Gy (100% vs. 33%; P = 0.042), but not in significantly better OS (100% vs. 77%, P = 0.33). CTR was associated with better significantly outcome than ITR. After ITR, the outcome was significantly improved by radiotherapy, 50-52.2 Gy was significantly superior to 30-45 Gy. To reduce the risk of radiation myelopathy, 50.4 Gy (1.8 Gy per fraction) appears appropriate for most patients. The recurrence rates after CTR would mandate the use of post-operative radiotherapy in all spinal meningeal melanocytoma cases. Our results should be confirmed in a larger series of patients when available.