Carotid-sparing intensity-modulated radiotherapy for early-stage squamous cell carcinoma of the true vocal cord.
OBJECTIVE
To compare radiation doses to carotid arteries among various radiotherapy techniques for treatment of early-stage squamous cell carcinoma (SCC) of the true vocal cords.


METHODS
Five patients were simulated using computed tomography (CT). Clinical and planning target volumes (PTV) were created for bilateral and unilateral stage T1 vocal cord cancers. Planning risk volumes for the carotid arteries and spinal cord were delineated. For each patient, three treatment plans were designed for bilateral and unilateral target volumes: opposed laterals (LATS), three-dimensional conformal radiotherapy (3DCRT), and intensity-modulated radiotherapy (IMRT), for a total of 30 plans. More than 95% of the PTV received the prescription dose (63Gy at 2.25 Gy per treatment).


RESULTS
Carotid dose was lowest with IMRT. With a bilateral vocal cord target, the median carotid dose was 10Gy with IMRT vs. 25 Gy with 3DCRT and 38 Gy with LATS (p < 0.05); with a unilateral target, the median carotid dose was 4 Gy with IMRT vs. 19 Gy with 3DCRT and 39 Gy with LATS (p < 0.05). The dosimetric tradeoff with IMRT is a small area of high dose in the PTV. The worst heterogeneity results were at a maximum point dose of 80 Gy (127%) in a unilateral target that was close to the carotid.


CONCLUSIONS
There is no question that IMRT can reduce the dose to the carotid arteries in patients with early-stage vocal cord cancer. The question is whether the potential advantage of reducing the carotid dose outweighs the risk of tumor recurrence due to contouring errors and organ motion and the risk of complications from dose heterogeneity.
Chera
Bhishamjit S
BS
Department of Radiation Oncology, University of Florida College of Medicine, Gainesville, Florida, USA.
Amdur
Robert J
RJ
Morris
Christopher G
CG
Mendenhall
William M
WM
D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D002339:Carotid Arteries / Q000528:radiation effects*; D005260:Female; D006801:Humans; D007822:Laryngeal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D009367:Neoplasm Staging; D011832:Radiation Injuries / Q000473:pathology / Q000517:prevention & control*; D011859:Radiography; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D014827:Vocal Cords / Q000000981:diagnostic imaging