Background: This study investigated the effects of preoperative chemoradiotherapy (PCRT) and the prognoses of patients with mucinous rectal cancer compared with those with nonmucinous cancer.
Methods: We retrospectively reviewed the medical records of 368 patients who underwent curative resection after PCRT, between 2000 and 2006, for midrectal to lower-rectal adenocarcinoma. Mucinous cancers were present in 23 patients (6.3%) and nonmucinous cancers in 345. In each patient, clinical stage before chemoradiotherapy was compared with pathologic stage to evaluate the extent of downstaging. Survival and multivariate analyses were performed using clinicopathologic variables. The median follow-up period was 42 months (range, 4-105 months).
Results: There was no difference in clinical stage between the groups. Although 58 patients (16.8%) in the nonmucinous group achieved pathologic complete responses (pCR), no mucinous group patient showed such a response. T-downstaging was more frequently observed in the nonmucinous than in the mucinous group (189 vs 7 [54.9% vs 30.4%], P = .03), but N-downstaging was similar in the 2 groups. The 5-year overall survival rate (OS) was significantly lower in the mucinous than in the nonmucinous group (64.8% vs 79.8%, P = .049). Multivariate analysis revealed that mucinous histotype was an independent (negative) prognostic factor for survival (hazard ratio, 2.36; 95% confidence interval, 1.05-5.3; P = .04).
Conclusions: Patients with mucinous rectal cancer experienced a lower rate of T-downstaging after PCRT and had a poorer prognosis than did patients with nonmucinous cancer.