Impact and relationship of anterior commissure and time-dose factor on the local control of T1N0 glottic cancer treated by 6 MV photons

Abstract

BackgroundTo evaluate prognostic factors that may influence local control (LC) of T1N0 glottic cancer treated by primary radiotherapy (RT) with 6 MV photons.MethodsWe 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.ResultsThe 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).ConclusionsThe 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.

Value of open horizontal glottectomy in the treatment for T1b glottic cancer with anterior commissure involvement

“…Smee et al in 356 T1 glottic cancers treated by XRT enlisted no involvement of AC, normal cord movement, no ventricular involvement to be significant prognostic factors for cancer specific survival. Tong et al in the recent analysis concluded that the negative impact of AC involvement could be overcome by delivering a higher tumor biologically effective dose using a fraction size of >2.0 Gy.…”

Comparison between 4‐MV and 6‐MV radiotherapy in T1N0 glottic cancer

“…The primary endpoint of this analysis is LC. Previous studies have reported nontreatment and treatment factors that may influence LC, including T‐substage, smoking status, dose per fraction, field size, anterior commissure involvement, photon energy, and treatment time . The results from our study showed that none of the patient, tumor, and radiotherapy parameters was adversely associated with LC.…”

“…Previous studies have reported nontreatment and treatment factors that may influence LC, including T-substage, smoking status, dose per fraction, field size, anterior commissure involvement, photon energy, and treatment time. 9,[12][13][14][15][16] The results from our study showed that none of the patient, tumor, and radiotherapy parameters was adversely associated with LC. The majority of the local recurrence was amenable to successful salvage surgery, with an ultimate 5-year LC rate of 96.8%.…”

“…Many radiotherapy centers have decommissioned cobalt machines, and linear accelerators generating 2‐ to 4‐MV and 6‐MV photons have increasingly become the treatment for T1 glottic carcinoma. Several authors have reported satisfactory LC rate in patients treated with 6‐MV photon radiotherapy . However, there are limited clinical data comparing 4‐MV and 6‐MV photons.…”

“…Several authors have reported satisfactory LC rate in patients treated with 6-MV photon radiotherapy. 4,8,9 However, there are limited clinical data comparing 4-MV and 6-MV photons. This study aims to report the outcomes of a retrospective consecutive cohort study of patients with T1N0M0 glottic carcinoma treated with 4-MV or 6-MV radiotherapy.…”