title: Treatment planning constraints to avoid xerostomia in head-and-neck radiotherapy: an independent test of QUANTEC criteria using a prospectively collected dataset.
abstract: OBJECTIVE
  The severe reduction of salivary function (xerostomia) is a common complication after radiation therapy for head-and-neck cancer. Consequently, guidelines to ensure adequate function based on parotid gland tolerance dose-volume parameters have been suggested by the QUANTEC group and by Ortholan et al. We perform a validation test of these guidelines against a prospectively collected dataset and compared with a previously published dataset.
  
  
  METHODS
  Whole-mouth stimulated salivary flow data from 66 head-and-neck cancer patients treated with radiotherapy at the British Columbia Cancer Agency (BCCA) were measured, and treatment planning data were abstracted. Flow measurements were collected from 50 patients at 3 months, and 60 patients at 12-month follow-up. Previously published data from a second institution, Washington University in St. Louis (WUSTL), were used for comparison. A logistic model was used to describe the incidence of Grade 4 xerostomia as a function of the mean dose of the spared parotid gland. The rate of correctly predicting the lack of xerostomia (negative predictive value [NPV]) was computed for both the QUANTEC constraints and Ortholan et al. recommendation to constrain the total volume of both glands receiving more than 40 Gy to less than 33%.
  
  
  RESULTS
  Both datasets showed a rate of xerostomia of less than 20% when the mean dose to the least-irradiated parotid gland is kept to less than 20 Gy. Logistic model parameters for the incidence of xerostomia at 12 months after therapy, based on the least-irradiated gland, were D(50) = 32.4 Gy and and γ = 0.97. NPVs for QUANTEC guideline were 94% (BCCA data), and 90% (WUSTL data). For Ortholan et al. guideline NPVs were 85% (BCCA) and 86% (WUSTL).
  
  
  CONCLUSIONS
  These data confirm that the QUANTEC guideline effectively avoids xerostomia, and this is somewhat more effective than constraints on the volume receiving more than 40 Gy.
authors.affiliation: Department of Medical Physics, Vancouver Cancer Centre, British Columbia Cancer Agency, Vancouver, BC, Canada. vmoiseenko@bccancer.bc.ca
authors.forename: Vitali
authors.initials: V
authors.lastname: Moiseenko
authors.forename: Jonn
authors.initials: J
authors.lastname: Wu
authors.forename: Allan
authors.initials: A
authors.lastname: Hovan
authors.forename: Ziad
authors.initials: Z
authors.lastname: Saleh
authors.forename: Aditya
authors.initials: A
authors.lastname: Apte
authors.forename: Joseph O
authors.initials: JO
authors.lastname: Deasy
authors.forename: Stephen
authors.initials: S
authors.lastname: Harrow
authors.forename: Carman
authors.initials: C
authors.lastname: Rabuka
authors.forename: Adam
authors.initials: A
authors.lastname: Muggli
authors.forename: Anna
authors.initials: A
authors.lastname: Thompson
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001955:British Columbia; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D010306:Parotid Gland / Q000528:radiation effects*; D017410:Practice Guidelines as Topic; D011446:Prospective Studies; D011829:Radiation Dosage; D011836:Radiation Tolerance; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000379:methods; D014987:Xerostomia / Q000453:epidemiology / Q000517:prevention & control*; D055815:Young Adult