Carbon Ion Radiotherapy: An Evidence-Based Review and Summary Recommendations of Clinical Outcomes for Skull-Base Chordomas and Chondrosarcomas

Introduction: Curative intent definitive treatment for chordoma and chondrosarcoma includes surgery, radiotherapy, or a combination. In those patients with high-volume tumors, unresectable, or recurrent disease, carbon ion radiotherapy (CIRT) has been used to reduce both relapse and treatment sequelae. Because of the limited number of heavy particle institutions worldwide, however, there is difficultly in accumulating data and providing consensus guidance for its clinical use.

Methods: We performed a systematic and evidence-based review of clinical outcomes of patients with skull base chordoma and chondrosarcoma treated with CIRT. A literature review was performed using a MEDLINE search of all articles to the present. A total of 227 studies were identified as appropriate for review and 24 were ultimately included for review.

Results: While maximal safe surgery remains the primary treatment, because of the high likelihood of residual tumor, adjuvant particle therapy is used to improve local control. Based on the quality of the present literature, the strength of the following recommendation for CIRT is an option because of quality of the data and limited availability as illustrated in [Table 1]. Based on this evidence, CIRT should be considered for those with the following:

• Unresectable or subtotally removed chordoma or chondrosarcoma,

o Strongly consider for high volume residual disease (>25 mL).

• Recurrent following prior surgery.

• Recurrent following prior irradiation.

• Tumors not encroaching or directly abutting the brainstem or optic apparatus.

Data from ongoing phase II and III prospective, randomized studies are still needed to further refine the magnitude of benefit and patient selection radioresistant tumors. While other prior systematic reviews exist, this is the first to not only summarize the quality of evidence but also provide a multi-institutional, recommendation based on the available evidence, which is valuable for treatment decision-making and resource allocation because of the limited availability and access to CIRT.

Conclusions: CIRT is an advanced treatment technique which may provide not only dosimetric benefits over conventional photon therapy but also biologic intensification to overcome mechanisms of radioresistance. Ongoing research is needed to define the magnitude of benefit, patient selection, and cost-effectiveness for CIRT compared to other forms of radiotherapy.

Table 1

 

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

Publication History

Article published online:
05 February 2024