Feasibility of intensity-modulated radiation therapy in the treatment of advanced cervical chordoma.
OBJECTIVE
Postoperative radiation is often given in cases of cervical chordoma because of the high incidence of local recurrence. The tumor mass usually surrounds the spinal cord and infiltrates vertebral bone. A combined technique using protons or electrons to boost the initial photon fields is generally applied. We evaluated the use of dynamic intensity-modulated radiation therapy as an alternative technique for treating advanced cervical chordoma.


METHODS
A female patient with incomplete resection of a vertebral chordoma surrounding C2-C3 was irradiated with a total dose of 58 Gy (ICRU point) in 2 Gy daily fractions for 29 days between December 2001 and January 2002. Beam arrangement consisted of seven 6 MV non-opposed coplanar fields. Pretreatment quality assurance included checking of the absolute dose at reference points and 2D dose map analysis. Treatment was delivered with a 120-leaf collimator in sliding window mode. To verify the daily setup, portal images at 0 degrees and 90 degrees were compared with the simulation images before treatment delivery (manual matching) and after treatment delivery (automatic anatomy matching).


CONCLUSIONS
The mean dose to the planning target volume (PTV) was 57.6 +/- 2.1 Gy covering 95% of the PTV per 95% isodose. The minimum dose to the PTV (D99) was 53.6 Gy in the overlapping area between the PTV and the spinal cord planning organ at risk volume (PRV). The maximum dose to the spinal cord was 42.2 Gy and to the spinal cord PRV (8 mm margin) 53.7 Gy. The mean dose to the parotid glands was 37.4 Gy (homolateral gland) and 19.5 Gy (contralateral gland). Average deviation in setup was -1.1 +/- 2.5 mm (anterior-posterior), 2.4 +/- 1.3 mm (latero-lateral), 0.7 +/- 0.9 mm (craniocaudal) and -0.43 +/- 1 degree (rotation).


CONCLUSIONS
In the treatment of chordomas surrounding the spinal cord, intensity-modulated radiotherapy can provide high dose homogeneity and PTV coverage. Frequent digital portal image-based setup control is able to reduce random positioning errors for head and neck cancer patients immobilized with conventional thermoplastic masks.
Gabriele
Pietro
P
Department of Radiation Oncology, Institute for Cancer Research and Treatment, Ordine Mauriziano, Turin, Italy.
Macias
Victor
V
Stasi
Michele
M
Chauvie
Stéphane
S
Munoz
Fernando
F
Delmastro
Elena
E
Scielzo
Giuseppe
G
D002817:Chordoma / Q000175:diagnosis / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008875:Middle Aged; D010306:Parotid Gland / Q000528:radiation effects; D017785:Photons / Q000627:therapeutic use; D061766:Proton Therapy; D011832:Radiation Injuries / Q000517:prevention & control; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D013120:Spinal Cord Neoplasms / Q000175:diagnosis / Q000532:radiotherapy*; D011522:Protons
D011522:Protons