INTRODUCTIONPreoperative, long-course chemoradiotherapy is recommended for rectal cancers involving or threatening the mesorectal resection margin, but tumor response is variable. Some highly radiosensitive cancers completely regress, leading to reduced local recurrence and improved survival. This study was designed to evaluate the influence of anemia during chemoradiotherapy on tumor response, local and distant recurrence, and overall survival.METHODSMean hemoglobins during chemoradiotherapy of consecutive patients with rectal cancer undergoing chemoradiotherapy and surgery were calculated and ranked. Anemia was defined as lowest quartile for males and females. Tumor response was histologically quantified using rectal cancer regression grade.RESULTSOf 100 patients, 5 females and 20 males were anemic. Nonanemic patients achieved better tumor response (54 percent regression Grade 1) than anemic patients (28 percent, P = 0.028). There were more locally advanced cancers in anemic (48 percent T4) compared with nonanemic patients (21 percent T4), but radiologic T stage did not influence tumor response (50 percent T3 vs. 43 percent T4 regression Grade 1, P = 0.53) or overall survival. Mesorectal margin positivity was less in nonanemic (15 percent) compared with anemic patients (36 percent, P = 0.021). At median follow-up of 39 months, nonanemic patients (7 percent) suffered less local recurrence than anemic patients did (38 percent, P = 0.003). Overall survival at two years was improved in nonanemic (91 percent) compared with anemic patients (64 percent, P = 0.021), but was similar for T3 and T4 patients.CONCLUSIONSPatients with normal hemoglobin during chemoradiotherapy achieved better tumor response, less local recurrence, and improved overall survival compared with anemic patients, independent of radiologic T stage. Correcting anemia before chemoradiotherapy might improve tumor response and oncologic outcomes.