Multiple Myeloma Spinal Lesion Care: Management of a Primary Bone Malignancy Rather Than a Spinal Metastasis.

Objective: Multiple myeloma (MM) is too often wrongly categorized as a spinal metastasis (SpM), although it is distinguishable from SpM in many aspects, such as its earlier natural history at the time of diagnosis, its increased overall survival (OS), and its response to therapeutic modalities. The characterization of these 2 different spine lesions remains a main challenge.

Methods: This study compares 2 consecutive prospective oncologic populations of patients with spine lesions: 361 patients treated for MM spine lesions and 660 patients treated for SpM between January 2014 and 2017.

Results: The mean time between the tumor/MM diagnosis and spine lesions was respectively 0.3 (standard deviation [SD] 4.1) and 35.1 months (SD 21.2) for the MM and SpM groups. The median OS for the MM group was 59.6 months (SD 6.0) versus 13.5 months (SD 1.3) for the SpM group (P < 0.0001). Regardless of Eastern Cooperative Oncology Group (ECOG) performance status, patients with MM always have a significantly better median OS than do patients with SpM: ECOG 0, 75.3 versus 38.7 months; ECOG 1, 74.3 versus 24.7 months; ECOG 2, 34.6 versus 8.1 months; ECOG 3, 13.5 versus 3.2 months and ECOG 4, 7.3 versus 1.3 months (P < 0.0001). The patients with MM had more diffuse spinal involvement (mean, 7.8 lesions; SD 4.7) than did patients with SpM (mean, 3.9; SD 3.5) (P < 0.0001).

Conclusions: MM must be considered as a primary bone tumor, not as SpM. The strategic position of the spine in the natural course of cancer (i.e., nurturing cradle of birth for MM vs. systemic metastases spreading for SpM) explains the differences in OS and outcome.