Prognostic value of tumor regression evaluated after first course of radiotherapy for anal canal cancer

Conclusion: The amount of tumor regression before EBRT or brachytherapy boost is a strong prognostic factor of disease control without colostomy. When regression is ≤80% in patients with an initial T3-T4 lesion, the use of conservative RT should be carefully evaluated because of the very poor disease-free and colostomy-free survival.