Cancer prevalance and incidence is increasing with aging of populations and age is a critical factor in decision-making for anti-cancer treatment. However it is believed that chronological age is not enough to guide management in elderly cancer patients. Multidisciplinary evaluation and comprehensive geriatric assessment has gained importance regarding the treatment selection especially for definitive anti-cancer therapy recently. We here aimed to analyse the effect of the comprehensive geriatric assessment parameters on radiotherapy toxicity and tolerability in a series of geriatric cancer patients in Turkey.