Abstract
Purpose: Radiation therapy is the treatment of choice for early glottic squamous cell cancer in many institutions over the world. Despite a relatively homogenous clinical model of T1 glottic tumors for the fractionation studies, the relationships between dose-time parameters remain unclear. To analyze the influence of fractionation parameters and hemoglobin level on tumor cure, this study has been performed. Materials and Methods: This is a retrospective review of 235 patients with T1N0M0 glottic cancer treated by radiation therapy alone given in a conventional schedule with 5 fractions each week. The individual total dose, dose per fraction, and overall treatment time ( OTT) ranged from 51–70 Gy, 1.5–3.0 Gy, and 24–79 days, respectively. The median follow-up was 48 months. Patient data—total dose, dose per fraction, OTT, and hemoglobin level (Hb) measured before the radiation treatment—were fitted by the mixed LQ/log-logistic model. Results: The 5-year local relapse-free survival rate was 84%. All parameters included in the mixed LQ/log-logistic model improved the fit significantly. The dose–response curve for 235 patients with T1 glottic cancer was well defined and steep, and showed significant decrease in tumor control probability ( TCP) when total doses were below 61 Gy. The 10-day prolongation of OTT, from 45 to 55 days, decreased the TCP by 13%. The dose of 0.35 Gy/day, compensated repopulation during the 1 day of prolongation, which indicates a potential doubling time (T pot) for glottic T1 tumor clonogens of 5.5 days. The drop of Hb level of 1 g/dl (from 13.8 g/dl to 12.8 g/dl) gave a 6% decrease of TCP, provided that OTT was 45 days. Conclusion: The significant correlation between the total dose, overall treatment time, hemoglobin concentration, and tumor control probability has been found for T1 glottic cancer.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have