Background: Tumour deposits (TDs) are a poor prognostic marker in colorectal cancer, but their significance after neoadjuvant chemoradiotherapy is less certain because this group of patients is excluded in most studies. Post-treatment TD might even be a sign of tumour response. No previous reviews have assessed outcomes in this group.
Materials and methods: A systematic review and meta-analysis was undertaken according to Preferred Reporting for Systematic Reviews and Meta-Analyses guidelines to determine the relevance of post-treatment TD. Inclusion criteria were studies assessing TD in patients who had undergone pre-operative treatment with radiotherapy and/or chemotherapy and reporting prevalence and survival outcomes. Studies that did not include histological review of cases were excluded.
Results: Eight studies and 1283 patients were included in the review. Prevalence of TDs varied from 11.8% to 44.2% (mean 23.7%), similar to untreated patients. The presence of TDs after chemoradiotherapy was associated with invasion depth, lymph node involvement, perineural invasion and synchronous metastases. The pooled hazard ratio for 5-year adverse disease-free survival was 2.3 (95% confidence interval [CI]: 1.8-2.9), and that for overall survival was 2.5 (95% CI: 1.9-3.3). One study showed a survival benefit with adjuvant therapy in the TD-positive group.
Conclusions: In analogy with untreated patients, the presence of TDs in patients with rectal cancer after neoadjuvant treatment is associated with advanced disease and a poor outcome.
Keywords: Neoadjuvant therapy; Prognosis; Radiotherapy; Rectal cancer; Tumour deposits.
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