Skull base chordoma is a rare, locally aggressive tumor, accounting for about 0.1%–0.2% of all intracranial tumors. It originates from embryonic notochord remnants. Although it grows slowly, its location at the skull base, surrounded by many critical nerves, blood vessels, and the brainstem, makes treatment extremely challenging. Even after surgical resection followed by postoperative radiotherapy, the 5-year recurrence rate remains around 50%.

In my clinic, I often see patients with recurrent chordoma, and I have long been asking myself one question: How can we delay recurrence? I have reviewed a large number of studies and frequently examined clinical data on proton and heavy-ion therapy, but the results are generally unsatisfactory. The key issue lies in this: when the tumor is large or adjacent to critical structures such as the brainstem, optic nerve, or cavernous sinus, the radiation dose—whether using proton, heavy-ion, or conventional radiotherapy—cannot be too high, as excessive doses may cause fatal damage to the patient.

Long-term tumor control is closely related to both the extent of surgical resection and the high-dose irradiation achieved through postoperative radiotherapy. Since 2008, I have been using CyberKnife high-precision irradiation to treat chordoma, and one of my patients has remained recurrence-free for 17 years. Another patient, a middle school teacher, underwent three courses of CyberKnife therapy and has also been recurrence-free for 15 years.

About ten years ago, I began to adopt a two-stage CyberKnife treatment strategy for residual chordoma after surgery and achieved remarkably good results. In the first stage, I administer 5.5–6 Gy × 4 sessions, and six months later, a second stage with 5–6 Gy × 4 sessions. By adjusting the isodose curve, this approach allows the tumor to receive a very high dose—significantly higher than conventional radiotherapy, proton, or heavy-ion therapy—while maintaining a sufficiently wide treatment field.

A published study once emphasized that accurately identifying the tumor boundaries before surgery is crucial for chordoma treatment. As a neurosurgeon, I have a deep understanding of the tumor's preoperative extent, which I always consider when planning CyberKnife therapy. By combining preoperative tumor range with the postoperative residual area, I design a more rational and precise treatment plan—one that delivers an extremely high dose inside the tumor and a tolerable dose to the brainstem.

Recently, two of my patients returned for follow-up. Both had large tumors at the time of CyberKnife treatment. After two-stage CyberKnife therapy and six years of follow-up, their tumors had shrunk by 90%, with no signs of recurrence.

These exploratory CyberKnife treatments have provided me with valuable clinical experience and, more importantly, have allowed my patients to enjoy high-quality lives.