Malnutrition in rectal cancer patients receiving preoperative chemoradiotherapy is common and associated with treatment tolerability and anastomotic leakage.

Purpose: This study assessed the incidence of malnutrition caused by preoperative chemoradiotherapy (CRT) in rectal cancer patients, which is seemingly underestimated; however, malnutrition affects treatment tolerability, postoperative complications, including anastomotic leakage (AL), and oncological outcomes.

Methods: Between January 2008 and December 2014, 54 consecutive patients with T3-4, N0-2, M0-1 resectable rectal cancer received CRT comprising 45 Gy radiotherapy and S-1 alone or with irinotecan for 5 weeks and then underwent curative surgery with diverting or permanent stomas 6-8 weeks after CRT. We assessed malnutrition after completion of CRT (5-6 weeks after CRT start date) and at surgery (11-14 weeks after CRT start date), defining weight loss as ≥5 % of pre-CRT weight; this definition differs from commonly used criteria for adverse events. We evaluated the incidence of malnutrition associated with CRT and influence of malnutrition on treatment tolerability, AL, and disease-free survival (DFS). We also assessed the influence of CRT on the rate of postoperative complications by comparing the study group with 61 patients who had undergone excision with diverting or permanent stomas alone.

Results: Malnutrition was observed in 51 % of patients after CRT and in 29 % at surgery. Malnutrition after CRT was associated with treatment tolerability, and malnutrition at surgery was significantly associated with AL, which significantly influenced DFS in stage 1-3 patients.

Conclusion: Malnutrition caused by CRT is common and is associated with treatment tolerability and AL. Nutritional assessment and support seem indispensable for the rectal cancer patients receiving CRT.