Neoadjuvant therapy for rectal cancer down-stages the tumor but reduces lymph node harvest significantly

The impact of neoadjuvant therapy (NAT) for rectal cancer on lymph node yield is not well known. This study evaluates the impact of NAT on tumor regression and lymph node harvest.

The subjects were 40 patients with rectal cancer; 20 receiving high-dose, long-course neoadjuvant therapy, and 20 age- and sex-matched controls who did not receive neoadjuvant therapy. Tumor regression (TRG) was graded from 1 to 5 as: TRG1, no residual tumor cells; TRG2, occasional residual tumor cells with marked fibrosis; TRG3, marked fibrosis with scattered tumor cells or groups; TRG4, abundant cancer cells with little fibrosis; TRG5, no tumor regression. We also evaluated the number of lymph nodes retrieved from excised specimens, the size of the largest node, and the extent of lymph node involvement by the tumor.

Tumor regression was seen in all patients; as TRG1 in 6 (30%), TRG2 in 2 (10%), TRG3 in 3 (15%), and TRG4 in 9 (45%). The median nodal harvest was 4 (range (0-12) in the NAT group vs 9 (range 1-19) in the control (P = 0.001). The median size of the largest lymph node was 5 mm (range 2-12 mm) in the NAT group vs 9 mm (range 4-15 mm) in the control group (P = 0.004). Tumor-positive nodes were identified in 4 of 17 of the NAT group patients and in 9 of the 20 controls (P = 0.308).

Although NAT down-stages rectal cancer, it results in a significantly low yield of lymph nodes, which are also significantly smaller than those in nonirradiated controls. Therefore, surgeons and histopathologists must ensure adequate sampling and accurate staging is done for patients with irradiated rectal cancer.