Clinical Epidemiology of Low-Grade and Dedifferentiated Osteosarcoma in Norway during 1975 and 2009

Table 3

Patients with local recurrence and/or metastasis at diagnosis or during follow-up among 54 low-grade or dedifferentiated osteosarcoma (OS) patients.

	Low-grade OS (%)	Dedifferentiated OS (%)	All patients (%)
Local recurrence
No	33 (79)	6 (50)	39 (72)
Yes	9 (21)	6 (50)	15 (28)
Median/mean in months	27/31	26/94	27/57
Range in months	7–62	15–255	7–255
Metastasis
No	40 (95)	4 (33)	44 (81)
Yes	2 (5)	8 (67)	10 (19)
Median/mean in months	59/59	33/78	33/74
Range in months	0–117	0–263	0–263

Five with parosteal OS (POS), nine with low-grade central OS (LGCOS), and one with secondary low-grade OS. None of the six patients with high-grade malignancy at time of diagnosis experienced local recurrence during follow-up. Metastasis at diagnosis or during follow-up. Three patients had primary metastatic disease: one with low-grade OS and two with dedifferentiated OS. Five with POS and five with LGCOS. Five patients with metastatic relapse during follow-up had previously experienced a local recurrence.