What are tumor deposits and what do they mean for patient outcome?

This study examined whether there is a link between tumor deposits and tumor stage, treatment response rates and patient survival in patients with rectal cancer.

After surgical removal of rectal tumors and the surrounding tissue, doctors analyze the samples to help determine the severity of the cancer. One characteristics they look for are tumor deposits. These are irregular clusters of tumor cells that are not associated with lymphoid tissue (parts of the body needed to generate an immune response) and are not attached to the main tumor. The significance of these tumor deposits in rectal cancer, especially after chemoradiation therapy, has not been extensively researched.

The authors reviewed patient records for 205 patients with rectal cancer who underwent surgical resection (surgical removal of part of the rectum). Tissue samples were analyzed to determine the tumor grade, depth of the invasion through the intestinal layers and if tumor deposits were present.

Tumor deposits were detected in 25% of patients. The average main tumor size was significantly bigger for patients with tumor deposits (3.5 cm) than patients without tumor deposits (2 cm). 27% of patients with tumor deposits had grade III tumors (the tumor has grown to the outer layer of the rectum) compared to only 10% of patients without tumor deposits. 73% patients with tumor deposits had stage 3 or stage 4 cancer (the tumor has spread to lymph nodes or distant sites) compared to only 29% of patients with no tumor deposits.

At the end of the study 42% of patients with tumor deposits had died from rectal cancer compared to 24% of patients with no tumor deposits. A statistical analysis showed, however, that tumor deposits were not predictors of cancer-specific mortality, but advanced cancer stage was: the risk of death was 4.17 times higher for patients with stage 4 cancer.

Patients were sub-grouped based on whether they received neoadjuvant therapy (chemoradiation before surgery). Overall 54% of patients (110 patients) received neoadjuvant therapy. Of those 110 patients, 21% had tumor deposits. A higher percentage of patients with tumor deposits had local recurrence of the tumor (19%) than patients who did not (10%). A higher percentage of patients with tumor deposits had a recurrence of cancer at distant sites (metastatic recurrence), 51% compared to 30% of patients without tumor deposits.

The authors concluded that the tumor characteristics of patients with tumor deposits suggests that they might have more aggressive tumors. Overall, tumor deposits appear to predict worse patient outcome.