Impact of initial tumor volume on radiotherapy outcome in patients with T2 glottic cancer

BACKGROUND: The aim of this study was to quantify the impact of initial tumor volume (TV) on radiotherapy (RT) outcome in patients with T2 glottic cancer. MATERIALS AND METHODS: Initial TV was calculated for 115 consecutive patients with T2 glottic cancer who had been treated with definitive RT alone at a single institution. RESULTS: The results showed strong correlations of TV with 3-year local tumor control (LTC) and disease-free survival (DFS). For TV ≤ 0.7 cm(3), 3-year LTC was 83 %; for TV 0.7–3.6 cm(3) this was 70 % and for TV 3.6–17 cm(3) 44 %. Analysis of total dose vs. initial TV showed that larger T2 glottic tumors with a TV of around 5 cm(3) (2–2.5 cm in diameter with 10(10) cancer cells) need an extra 6.5 Gy to achieve similar 3-year LTC rates as for small tumors with a TV of 0.5 cm(3) (~ 1 cm in diameter with 10(9) cancer cells). CONCLUSION: Although classification of tumors according to TV cannot replace TNM staging in daily practice, it could represent a valuable numerical supplement for planning the optimal dose fractionation scheme for individual patients.