Optimization of radiotherapy for patients with cranial chordoma. A review of dose-response ratios for photon techniques.
BACKGROUND
Cranial chordomas arise adjacent to critical neural tissues within the notochordal remnants in the clivus, frequently compromising adequate surgical removal of the primary tumor and making difficult the delivery of an adequate dose of radiotherapy. The optimal dose and fractionation have not been established.


METHODS
The results of radiation combined with surgery, radiation alone, and surgery alone were compared based on the cases of 159 patients reported in the literature. An analysis of the optimal biologically equivalent doses (BED) was performed using the linear-quadratic formula on 47 patients.


RESULTS
Past techniques using conventional photon irradiation have shown no dose-response relationship. Survival is improved for patients undergoing surgery followed by radiotherapy.


CONCLUSIONS
Combined surgery and postoperative radiation is preferable to radiotherapy or surgery alone for management of cranial chordoma. Newer radiotherapeutic approaches will allow increased dose delivery to the target volume without an anticipated increase in radiation morbidity. It is believed that this will increase tumor control. Recent results of studies using charged particle therapy in cranial chordoma suggest that this may be an alternative way to optimize radiotherapy.
Tai
P T
PT
Allan Blair Memorial Clinic, Saskatchewan Cancer Foundation, Canada.
Craighead
P
P
Bagdon
F
F
D001932:Brain Neoplasms / Q000401:mortality / Q000532:radiotherapy*; D002817:Chordoma / Q000401:mortality / Q000532:radiotherapy*; D003131:Combined Modality Therapy; D004307:Dose-Response Relationship, Radiation; D006801:Humans; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D015996:Survival Rate