Abstract
<b><i>Introduction:</i></b> Adjuvant chemotherapy (AC) after radical surgery following preoperative chemoradiotherapy (CRT) for locally advanced rectal cancer (LARC) is now the standard of care. The identification of risk factors for the discontinuation of AC is important for further improvements in survival. We herein examined the prognostic impact of chemotherapy compliance and its relationship with the prognostic nutritional index (PNI) before surgery. <b><i>Methods:</i></b> A total of 335 stage II–III LARC patients who underwent preoperative CRT between 2003 and 2022 at the University of Tokyo Hospital were retrospectively reviewed. We excluded patients with recurrence during AC and those who had not received AC. The relationship between AC and long-term outcomes and that between PNI values and the duration of AC were examined. <b><i>Results:</i></b> Thirty-one patients discontinued AC and 62 continued AC. Recurrence-free survival (RFS) was significantly shorter in patients who discontinued AC (<i>p</i> = 0.0056). The discontinuation of AC was identified as an independent risk factor for RFS (hazard ratio [HR]: 2.24, <i>p</i> = 0.0233). Twenty-one patients were classified as having low PNI (less than 40), which correlated with an older age, low body mass index, and incomplete AC. Low PNI was an independent risk factor for a shorter duration of AC (HR: 2.53, <i>p</i> = 0.0123). <b><i>Conclusion:</i></b> The discontinuation of AC was related to poor RFS in patients with LARC undergoing preoperative CRT. Furthermore, a low PNI value was identified as a risk factor for a shorter duration of AC.