Candidate dosimetric predictors of long-term swallowing dysfunction after oropharyngeal intensity-modulated radiotherapy.
OBJECTIVE
To investigate long-term swallowing function in oropharyngeal cancer patients treated with intensity-modulated radiotherapy (IMRT), and to identify novel dose-limiting criteria predictive for dysphagia.


METHODS
Thirty-one patients with Stage IV oropharyngeal squamous carcinoma enrolled on a Phase II trial were prospectively evaluated by modified barium swallow studies at baseline, and 6, 12, and 24 months post-IMRT treatment. Candidate dysphagia-associated organs at risk were retrospectively contoured into original treatment plans. Twenty-one (68%) cases were base of tongue and 10 (32%) were tonsil. Stage distribution was T1 (12 patients), T2 (10), T3 (4), T4 (2), and TX (3), and N2 (24), N3 (5), and NX (2). Median age was 52.8 years (range, 42-78 years). Thirteen patients (42%) received concurrent chemotherapy during IMRT. Thirteen (42%) were former smokers. Mean dose to glottic larynx for the cohort was limited to 18 Gy (range, 6-39 Gy) by matching IMRT to conventional low-neck fields.


RESULTS
Dose-volume constraints (V30 < 65% and V35 < 35% for anterior oral cavity and V55 < 80% and V65 < 30% for high superior pharyngeal constrictors) predictive for objective swallowing dysfunction were identified by univariate and multivariate analyses. Aspiration and feeding tube dependence were observed in only 1 patient at 24 months.


CONCLUSIONS
In the context of glottic laryngeal shielding, we describe candidate oral cavity and superior pharyngeal constrictor organs at risk and dose-volume constraints associated with preserved long-term swallowing function; these constraints are currently undergoing prospective validation. Strict protection of the glottic larynx via beam-split IMRT techniques promises to make chronic aspiration an uncommon outcome.
Schwartz
David L
DL
Department of Radiation Oncology, University of Texas M. D. Anderson Cancer Center, Houston, TX 77030-4009, USA. docdls@mdanderson.org
Hutcheson
Katherine
K
Barringer
Denise
D
Tucker
Susan L
SL
Kies
Merrill
M
Holsinger
F Christopher
FC
Ang
K Kian
KK
Morrison
William H
WH
Rosenthal
David I
DI
Garden
Adam S
AS
Dong
Lei
L
Lewin
Jan S
JS
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D003131:Combined Modality Therapy / Q000379:methods; D003679:Deglutition / Q000502:physiology / Q000528:radiation effects*; D003680:Deglutition Disorders / Q000209:etiology*; D005260:Female; D006801:Humans; D007821:Laryngeal Muscles / Q000000981:diagnostic imaging / Q000528:radiation effects; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects*; D009959:Oropharyngeal Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D009960:Oropharynx / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000528:radiation effects; D011446:Prospective Studies; D011832:Radiation Injuries / Q000517:prevention & control; D011835:Radiation Protection; D011859:Radiography; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods; D014062:Tongue Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy; D014067:Tonsillar Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy; D047368:Tumor Burden