title: The prognostic role of comorbidity in salivary gland carcinoma.
abstract: BACKGROUND
  Patients with head and neck cancer are prone to develop significant comorbidity mainly because of the high incidence of tobacco and alcohol abuse, both of which are etiologic and prognostic factors. However, to the authors' knowledge little is known regarding the prognostic relevance of comorbidity in patients with salivary gland cancer.
  
  
  METHODS
  A retrospective cohort of 666 patients with salivary gland cancer was identified within the Dutch Head and Neck Oncology Cooperative Group database. For multivariate analysis, a Cox proportional hazards model was used to study the effect of comorbidity on overall survival and disease-specific survival.
  
  
  RESULTS
  According to the Adult Comorbidity Evaluation-27 (ACE-27) index, 394 patients (64%) had grade 0 comorbidity, 119 patients (19%) had grade 1 comorbidity, 71 patients (12%) had grade 2 comorbidity, and 29 patients (5%) had grade 3 comorbidity. In multivariate analysis for overall survival, the ACE-27 comorbidity grade was a strong independent prognostic variable. The hazards ratio (HR) of death, including all causes, was 1.5 (95% confidence interval [CI], 1.1-2.1) for patients with ACE-27 grade 1 comorbidity versus grade 0 comorbidity (P < .007). The HR was 1.7 (95% CI, 1.2-2.5) for grade 2 comorbidity (P = .003) and 2.7 (95% CI, 1.5-4.7) for grade 3 comorbidity versus grade 0 comorbidity (P = .001). In the current analysis, ACE-27 comorbidity grade was not an independent prognostic factor for disease-free survival.
  
  
  CONCLUSIONS
  To the authors' knowledge, this is the first study concerning the prevalence and relevance of the prognostic comorbidity variable ACE-27 grade in patients with salivary gland cancer. Overall survival, but not disease-free survival, was correlated strongly with ACE-27 grade. Compared with other studies that investigated the effect of comorbidity on patients with head and neck cancer, patients with salivary gland cancer had less comorbidity. Their comorbid status appeared to be reasonably comparable to that of patients with other nonsmoking- and nonalcohol-related cancers.
authors.affiliation: Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands. c.h.j.terhaard@umcu.nl
authors.forename: Chris H J
authors.initials: CH
authors.lastname: Terhaard
authors.forename: Marc P
authors.initials: MP
authors.lastname: van der Schroeff
authors.forename: Kim
authors.initials: K
authors.lastname: van Schie
authors.forename: Simone E J
authors.initials: SE
authors.lastname: Eerenstein
authors.forename: Herman
authors.initials: H
authors.lastname: Lubsen
authors.forename: Johannes H A M
authors.initials: JH
authors.lastname: Kaanders
authors.forename: Ludwig E
authors.initials: LE
authors.lastname: Smeele
authors.forename: Fred R
authors.initials: FR
authors.lastname: Burlage
authors.forename: Piet L
authors.initials: PL
authors.lastname: van Den Ende
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Baatenburg de Jong
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000437:Alcoholism / Q000150:complications; D002648:Child; D015897:Comorbidity; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012468:Salivary Gland Neoplasms / Q000150:complications*; D012907:Smoking / Q000009:adverse effects; D015996:Survival Rate