Tumor deposits in rectal adenocarcinoma after neoadjuvant chemoradiation are associated with poor prognosis

Although tumor deposits have been associated with poor prognosis in colorectal carcinoma, the prevalence and clinical significance of tumor deposits in rectal adenocarcinoma following neoadjuvant chemoradiation are relatively unexplored. The aims of this study are to assess the clinical significance of tumor deposits in rectal adenocarcinoma patients, including those receiving neoadjuvant therapy. Pathology slides and medical records from 205 consecutive patients who underwent resection for rectal adenocarcinoma between 1990 and 2010 at a single tertiary care center were reviewed. Patients with tumor deposits had higher tumor grade (P=0.006) and worse tumor stage (P<0.001) at presentation than patients without tumor deposits. Among 110 patients who underwent neoadjuvant chemoradiation, tumor deposits were associated with higher rates of lymph node involvement (P=0.035) and distant metastases (P=0.006), and decreased survival (P=0.027). These patients had a trend toward lower treatment response scores (P=0.285) and higher local recurrence (P=0.092). Of 52 patients with tumor deposits, those who underwent neoadjuvant chemoradiation had significantly worse pretreatment stage by endoscopic ultrasound (P<0.001) but interestingly had significantly lower rates of lymphovascular invasion on resection (P<0.001) compared with those who had not received neoadjuvant chemoradiation. Despite treatment with neoadjuvant chemoradiation, tumor deposits were present in over one-fifth of rectal adenocarcinoma patients. Overall, the outcome of patients with tumor deposits in treated and untreated patients were similar, however the association of tumor deposits with deeply invasive tumors and less tumor regression when comparing with treated patients without tumor deposits raises the possibility that these tumors could have a more aggressive biology, possibly explaining the association of tumor deposits with higher rates of recurrence and lower survival after neoadjuvant chemoradiation. Overall, tumor deposits appear to be a poor prognostic marker among rectal adenocarcinoma patients following neoadjuvant chemoradiation and may identify a subset of patients who require aggressive adjuvant therapy to prevent recurrence.