Long-Term Outcomes of Grade I–II Skull Base Chondrosarcoma: An Insight into the Role of Surgery and Radiotherapy

Introduction: Skull base chondrosarcoma is a rare skull base malignancy. In cases of incomplete resection, planned upfront postoperative radiotherapy is frequently offered; however, a substantial portion of chondrosarcomas exhibit a relatively benign natural history and thus could be managed with watchful waiting. Thus, the role of radiotherapy needs to be clarified.

Methods: Data on patients who had skull base chondrosarcoma and were treated at our institution was retrospectively reviewed to see the clinical outcomes per post-surgical treatment strategy: watchful waiting (group A, 18 patients) and planned upfront radiotherapy (group B, 14 patients). We excluded patients who were referred after multiple recurrences to focus on the effect of the first intervention with or without radiotherapy. We also excluded high-grade (III) chondrosarcoma, which represent a minority of cases and exhibit a substantially more aggressive clinical course.

Results: Thirty-two patients (16 grade I and 16 grade II; mean follow-up period, 103.1 months) were included. Gross total resection (GTR) was achieved in nine in initial surgery; eight (88.9%) of them did not undergo upfront radiotherapy, and thus there were more patients with GTR in group A than in group B (44 vs. 7%, p = 0.0443). No other significant difference was observed between the two groups. In group A, 13 did not have a recurrence over a mean of 80.0 months. Five (27.8%) had a recurrence at a mean of 34.7 months, which were treated with salvage radiotherapy (n = 3), resection (n = 1), and both (n = 1). Over a mean of 126.6 months after salvage therapy, no one experienced further recurrence or debilitating complications except for 1 who had an extensive remnant tumor. In group B, patients received radiotherapy at a mean of 6.5 months. One (7.1%) recurrence was observed at 139.0 months. The 10-year progression-free rates were 61.1% in group A and 100% in group B (p = 0.0913; [Fig. 1]). No significant benefit in tumor control was observed with grade I (versus II) tumor (p = 0.8340, [Fig. 2]), whereas GTR was negatively associated with tumor control (p = 0.0295, [Fig. 3]). At the last follow-up, favorable tumor control without debilitating functional decline was achieved in all but one extensive case as described above (94 vs. 100%, p = 1.000). Overall, radiotherapy was performed in 18 patients: proton (12), gamma knife ± photon radiotherapy (5), and detail not available (1); among them, radiation-induced complications were observed in 7 (38.9%): hypopituitarism (3), cranial nerve dysfunction (3), hearing loss (2), temporal lobe edema (2), and nearby perforator occlusion (1).

Conclusion: GTR alone does not seem to warrant long-term tumor control, whereas radiotherapy may prevent early tumor recurrence. However, radiotherapy cannot exclude the risk of late recurrence, and thus long-term follow-up is warranted. Given that recurrent low/intermediate grade chondrosarcoma is manageable with a single or combined treatment without causing debilitating functional decline, a strategy employing watchful waiting with salvage radiotherapy is also feasible and helps avoid radiation-induced complications so long as sufficient surgical tumor reduction is achieved and close surveillance can be provided.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
12 February 2021