# Robotic Radiosurgery for Sacral Chordoma: Preserving Function in a Clinical Conundrum Scenario

## TL;DR

Robotic radiosurgery using CyberKnife® effectively treated a rare sacral tumor with minimal side effects and preserved the patient's quality of life.

## Contribution

Demonstrates the safe and effective use of CyberKnife® robotic radiosurgery for sacral chordoma with real-time motion management.

## Key findings

- The patient experienced a 90% reduction in pain after treatment.
- Substantial tumor regression was observed with minimal toxicity.
- Intra-fractional movements were within acceptable ranges during treatment delivery.

## Abstract

Sacral chordoma is a rare and locally aggressive neoplasm that presents significant treatment challenges due to its anatomical location and tendency toward local invasion. Although complete surgical resection remains the gold standard for a potential cure, the high surgical morbidity necessitates alternative, less invasive treatment approaches. Robotic radiosurgery using the CyberKnife® system has emerged as a promising option, particularly for patients who refuse surgery or are unsuitable surgical candidates. Furthermore, the precise delivery of high-dose radiation is crucial, as even minor sacral movements can affect dose distribution and treatment outcomes. We present the case of a 27-year-old male with a confirmed diagnosis of sacral chordoma who experienced progressive tumor growth. Given the high morbidity associated with surgical resection in the sacral region and the patient’s preference for avoiding surgery, a multidisciplinary team opted for stereotactic radiosurgery (SRS) using CyberKnife®. Robotic radiosurgery with real-time image guidance accounted for minor sacral movements during treatment delivery. The patient received 600-700 centigray (cGy) with a simultaneous integrated boost of radiation every other day, culminating in a total dose of 3,000 and 3,500 cGy to the planning target volume 30 and planning target volume 35, respectively, defined as the sacral mass with and without subclinical extension plus an appropriate margin. The quantitative analysis of intra-fractional patient movements recorded during treatment delivery revealed a range of displacements: 0.0-1.0 mm along the x-axis, 0.0- 1.5 millimeters (mm) along the y-axis, and 0.0- 1.0 mm along the z-axis. Rotational deviations were also assessed, with roll ranging from 0.0° to 0.8°, pitch from 0.0° to 0.4°, and jaw rotation from 0.0° to 0.7°. Following the completion of treatment on July 24, 2023, the patient reported a 90% reduction in pain. Subsequent clinical and radiological evaluations demonstrated substantial lesion regression with minimal toxicity, preserving the patient’s quality of life. This case reinforces the expanding body of evidence supporting advanced SRS for managing complex tumors. The successful application of CyberKnife® in this sacral chordoma case, along with robust motion management strategies, highlights its potential as a safe and effective alternative when conventional surgery is not feasible.