Cancer-induced spiculation on computed tomography: a significant preoperative prognostic factor for colorectal cancer Abstract Purpose Cancer-induced spiculation (CIS) on computed tomography, which is reticular or linear opacification of the pericolorectal fat tissues around the cancer site, is generally regarded as cancer infiltration into T3 or T4, but its clinicopathological significance is unknown. This study examines the correlation between CIS and clinicopathological findings to establish its prognostic value. Methods The subjects of this retrospective study were 335 patients with colorectal cancer (CRC), who underwent curative surgery between January, 2010 and December, 2011, at the National Defense Medical College Hospital in Saitama Prefecture, Japan. Results The level of interobserver agreement in the evaluation of CIS was substantial (83%; kappa value, 0.65). The presence of CIS was specific for T3/T4 disease (positive predictive value, 88.3%), and was significantly associated with tumor size and venous invasion. The 5-year relapse-free survival rate was significantly lower in patients with CIS than in those without CIS (68.6% and 84.0%, respectively, p = 0.001). Subgroup analysis revealed remarkable prognostic differences in patients with stage III and T3 disease. Multivariate analysis revealed that CIS was a significant independent prognostic factor. Conclusions CIS was a significant preoperative prognostic factor and could be useful in the selection of preoperative therapy for patients with CRC.