title: Impact and relationship of anterior commissure and time-dose factor on the local control of T1N0 glottic cancer treated by 6 MV photons.
abstract: BACKGROUND
  To evaluate prognostic factors that may influence local control (LC) of T1N0 glottic cancer treated by primary radiotherapy (RT) with 6 MV photons.
  
  
  METHODS
  We retrospectively reviewed the medical records of 433 consecutive patients with T1N0 glottic cancer treated between 1983 and 2005 by RT in our institution. All patients were treated with 6 MV photons. One hundred and seventy seven (41%) patients received 52.5 Gy in 23 fractions with 2.5 Gy/fraction, and 256 (59%) patients received 66 Gy in 33 fractions with 2 Gy/fraction.
  
  
  RESULTS
  The median follow-up time was 10.5 years. The 10-year LC rates were 91% and 87% for T1a and T1b respectively. Multivariate analysis showed LC rate was adversely affected by poorly differentiated histology (Hazard Ratio [HR]: 7.5, p = 0.035); involvement of anterior commissure (HR: 2.34, p = 0.011); fraction size of 2.0 Gy (HR: 2.17, p = 0.035) and tumor biologically effective dose (BED) < 65 Gy15 (HR: 3.38, p = 0.017).
  
  
  CONCLUSIONS
  The negative impact of anterior commissure involvement could be overcome by delivering a higher tumor BED through using fraction size of > 2.0 Gy. We recommend that fraction size > 2.0 Gy should be utilized, for radiation schedules with five daily fractions each week.
authors: Department of Clinical Oncology, Queen Elizabeth Hospital, 30 Gascoigne Road, Kowloon, Hong Kong. chichungtong@hkcr.org
authors: Chi-Chung
authors: CC
authors: Tong
authors: Kwok-Hung
authors: KH
authors: Au
authors: Roger K C
authors: RK
authors: Ngan
authors: Sin-Ming
authors: SM
authors: Chow
authors: Foon-Yiu
authors: FY
authors: Cheung
authors: Yiu-Tung
authors: YT
authors: Fu
authors: Joseph S K
authors: JS
authors: Au
authors: Stephen C K
authors: SC
authors: Law
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