Dedifferentiated chondrosarcoma of the pelvis: clinical outcomes and current treatment.

Background: Dedifferentiated chondrosarcomas (CS) are a high-grade variant of CS that confers a 5-year survival of around 10-24%. Dedifferentiated CS arising from the pelvis confers an even worse prognosis.

Questions: (1) What is the prognosis of patients with dedifferentiated CS of the pelvis? (2) Do wide margins or type of surgical intervention influence outcome? (3) Does the use of adjuvant therapy affect outcome?

Methods: Patients were retrospectively reviewed from a prospectively collated musculoskeletal oncology database from 1995 to 2016. Thirty-one cases of dedifferentiated CS arising from the pelvis were included. Wide margins were defined as greater than 4 mm. The mean age was 55.6 years (range 33 to 76 years) and there were 19 males (61.3%) and 12 females (38.7%).

Results: The disease presented at a locally or systemically advanced stage in 13 patients (41.9%). Eighteen patients (58.1%) underwent surgery with curative intent. Overall survival at 12 months was 15.4% for patients treated with palliative intent and 50% for those treated with surgery. In the surgical group, there were higher rates of disease-free survival in patients who underwent hindquarter amputation and those who received wide surgical margins (p = 0.047 and p = 0.019, respectively). Those who underwent hindquarter amputation were more likely to achieve wide margins (p = 0.05). Time to recurrent disease (local or systemic) was always less than 24 months. No hindquarter amputation for recurrent disease resulted in disease-free survival. No patient who received adjuvant therapy for palliative or recurrent disease had disease control.

Conclusions: Pelvic dedifferentiated CS often presents at an advanced local or systemic stage and confers a poor prognosis. Achieving wide surgical margins (> 4 mm) provided the highest rate of long-term disease-free survival. Failing to achieve wide margins results in rapid disease recurrence, conferring deleterious consequences.