title: Hypothyroidism after 3-dimensional conformal radiotherapy and intensity-modulated radiotherapy for head and neck cancers: prospective data from 2 randomized controlled trials.
abstract: BACKGROUND
  The purpose of this study was to determine the incidence of hypothyroidism after chemoradiation in head and neck squamous cell cancer (HNSCC).
  
  
  METHODS
  One hundred twenty-two patients treated with 3-dimensional conformal radiotherapy (3DCRT; 70 Gy/35#) or intensity-modulated radiation therapy (IMRT; 66 Gy/30#) in 2 identical simultaneous randomized trials were studied. Thyroid function was assessed at baseline and every 3 to 6 monthly thereafter. Development of subclinical (thyroid-stimulating hormone [TSH] >4.67 μIU/mL) or biochemical (T4 <4.5 μg/dL) hypothyroidism was noted. Multivariate analyses were done to determine the factors associated with hypothyroidism.
  
  
  RESULTS
  At a median of 41 months, 55.1% of the patients developed hypothyroidism (39.3% subclinical, 15.7% biochemical). The IMRT arm had higher subclinical hypothyroidism (51.1% vs 27.3%; p = .021) peaking around 1 year postradiotherapy in both arms. Younger age, hypopharynx/larynx primary, node positivity, higher dose/fraction (IMRT arm), and D100 were statistically significant factors for developing hypothyroidism.
  
  
  CONCLUSIONS
  Postradiotherapy hypothyroidism peaks at 1 year. Higher dose per fraction possibly led to greater incidence of hypothyroidism in the IMRT cohort.
authors.affiliation: Department of Radiation Oncology, Tata Memorial Centre, Mumbai, India.
authors.forename: Vedang
authors.initials: V
authors.lastname: Murthy
authors.forename: Kushal
authors.initials: K
authors.lastname: Narang
authors.forename: Sarbani
authors.initials: S
authors.lastname: Ghosh-Laskar
authors.forename: Tejpal
authors.initials: T
authors.lastname: Gupta
authors.forename: Ashwini
authors.initials: A
authors.lastname: Budrukkar
authors.forename: Jai Prakash
authors.initials: JP
authors.lastname: Agrawal
mesh_terms: D000328:Adult; D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D018572:Disease-Free Survival; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006258:Head and Neck Neoplasms / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007037:Hypothyroidism / Q000453:epidemiology* / Q000209:etiology* / Q000503:physiopathology; D015994:Incidence; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D011379:Prognosis; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000009:adverse effects* / Q000379:methods; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects* / Q000379:methods; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D012720:Severity of Illness Index; D013223:Statistics as Topic; D016019:Survival Analysis; D013960:Thyroid Function Tests; D016896:Treatment Outcome
keywords: 3-dimensional conformal radiotherapy (3DCRT); head and neck cancers; hypothyroidism; intensity-modulated radiation therapy (IMRT); randomized