Clinical delivery of intensity modulated conformal radiotherapy for relapsed or second-primary head and neck cancer using a multileaf collimator with dynamic control.
OBJECTIVE
Concave dose distributions generated by intensity modulated radiotherapy (IMRT) were applied to re-irradiate three patients with pharyngeal cancer.


METHODS
Conventional radiotherapy for oropharyngeal (patients 1 and 3) or nasopharyngeal (patient 2) cancers was followed by relapsing or new tumors in the nasopharynx (patients 1 and 2) and hypopharynx (patient 3). Six non-opposed coplanar intensity modulated beams were generated by combining non-modulated beamparts with intensities (weights) obtained by minimizing a biophysical objective function. Beamparts were delivered by a dynamic MLC (Elekta Oncology Systems, Crawley, UK) forced in step and shoot mode.


CONCLUSIONS
Median PTV-doses (and ranges) for the three patients were 73 (65-78), 67 (59-72) and 63 (48-68) Gy. Maximum point doses to brain stem and spinal cord were, respectively, 67 Gy (60% of volume below 30 Gy) and 32 Gy (97% below 10 Gy) for patient 1; 60 Gy (69% below 30 Gy) and 34 Gy (92% below 10 Gy) for patient 2 and 21 Gy (96% below 10 Gy) at spinal cord for patient 3. Maximum point doses to the mandible were 69 Gy for patient 1 and 64 Gy for patient 2 with, respectively, 66 and 92% of the volume below 20 Gy. A treatment session, using the dynamic MLC, was finished within a 15-min time slot.
Division of Radiotherapy, University Hospital Gent (U.Z.G.), Belgium.
W
W
De Neve
W
W
De Gersem
S
S
Derycke
G
G
De Meerleer
M
M
Moerman
M T
MT
Bate
B
B
Van Duyse
L
L
Vakaet
Y
Y
De Deene
B
B
Mersseman
C
C
De Wagter
C
C
De Waeter
D000328:Adult; D001933:Brain Stem / Q000528:radiation effects; D002277:Carcinoma / Q000473:pathology / Q000532:radiotherapy; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy; D019583:Dose Fractionation, Radiation; D004867:Equipment Design; D005500:Follow-Up Studies; D006801:Humans; D007012:Hypopharyngeal Neoplasms / Q000532:radiotherapy; D008334:Mandible / Q000528:radiation effects; D009303:Nasopharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy; D009364:Neoplasm Recurrence, Local / Q000473:pathology / Q000532:radiotherapy*; D009367:Neoplasm Staging; D016609:Neoplasms, Second Primary / Q000473:pathology / Q000532:radiotherapy*; D009959:Oropharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy; D010610:Pharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000295:instrumentation / Q000379:methods*; D013116:Spinal Cord / Q000528:radiation effects; D013997:Time Factors; D016896:Treatment Outcome