The standard treatment for locally advanced rectal cancer is preoperative chemoradiation and total mesorectal excision.
After surgery, tumors are classified according to the depth of tumor invasion, nodal involvement, and tumor regression grade.
These staging systems do not provide information about the distribution of residual cancer cells within the bowel wall.
Dr Marjun Duldulao and colleagues commented determined the distribution of residual cancer cells in each layer of the bowel wall in rectal cancer specimens.
The research team assessed that it was a secondary analysis of data from a prospective phase II study.
The researchers performed the study in a multi-institutional setting.
The team of doctors included 153 patients with stage II or stage III rectal cancer.
Patients were treated with chemoradiation and surgery.
|42 of 153 patients had complete response in the bowel wall|
|Diseases of the Colon & Rectum|
The doctors examined that the surgical specimen tumor tissue was analyzed, and the distribution of residual cancer cells in each layer of the bowel wall was determined.
Statistical analysis was used to examine the correlation of residual cancer cells in each layer of the bowel wall with the clinical/pathologic stage, and tumor regression grade.
The research team reported that 42 of 153 patients had complete response in the bowel wall.
Of the remaining 111 patients who had residual cancer cells, 5 were ypTis, 12 were ypT1, 41 were ypT2, 50 were ypT3, and 3 were ypT4.
Of the 94 patients with ypT2-4 tumors, 12 had cancer cells in the mucosa, and 53 had cancer cells in the submucosa, and 92 had cancer cells in the muscularis propria.
The doctors noted that pretreatment cT correlated with the distribution of residual cancer cells.
Tumor regression grade was not associated with the distribution of residual cancer cells after chemoradiation.
The researchers assessed that patients received different chemotherapy regimens.
Dr Marjun's team concluded, "Residual cancer cells in rectal cancer specimens after chemoradiation are preferentially located close to the invasive front."
"This should be considered when designing strategies to diagnose complete pathologic response and when investigating the mechanisms of tumor resistance to chemoradiation."