To explore the incidence and influential factors of acute hematologic toxicity in elderly rectal cancer patients treated with pelvic radiotherapy.

Fifty elderly patients aged 75 and older with rectal cancer, who were treated with pelvic radiotherapy at our hospital, were retrospectively analyzed. 111 non-elderly patients under 75 years of age, who were treated with pelvic radiotherapy in the same period, were selected as a control group. The relationship between clinical characteristics and incidence of grade 3~4 hematologic toxicity were analyzed by using chi-square test and multinomial logistic regression.

In the elderly patient group, the incidence of grade 0, grade 1~2, grade 3~4 hematologic toxicity were 6.0%, 78.0%, and 16.0%, respectively. In the non-elderly patient group, the incidence of grade 0, grade 1~2, grade 3~4 hematologic toxicity were 24.3%, 68.5%, and 7.2%, respectively. The incidence of grade 3~4 hematologic toxicity in elderly patients was higher than that in non-elderly patients (P=0.009). Multivariate analysis showed that the body mass index was significantly correlated with the incidence of grade 3~4 hematologic toxicity in elderly patients (P=0.038).

Acute hematologic toxicity induced by pelvic radiotherapy was well tolerated in elderly patients with rectal cancer. High body mass index may be associated with severe hematologic toxicity in elderly patients.