Use of preoperative tattooing to increase lymph nodes (LNs) retrieved in patients with locally advanced rectal cancer who receive preoperative chemoradiotherapy (CRT): A randomized controlled trial

561 Background: Retrieval of 12 or more LNs has been recommended for accurate staging of colorectal cancer. Patients with 12 or more LNs revealed better survival than those with less than 12 LNs. Preoperative tattooing has been reported to improve LNs retrieval in colorectal cancer. Preoperative CRT had been reported to decrease the number of LNs in rectal cancer. We conducted a randomized controlled study to validate whether preoperative tattooing increases the number of LNs in patients who receive preoperative CRT. Methods: Fifty patients with cStage II or III rectal cancer were randomly assigned to a group in which tattooing was performed at the time of colonoscopy one day before surgery (T group) or a group without tattooing (C group). Submucosal injection of India ink was performed into two sites at the lower tumor margin. All patients had received 40/45 Gy of radiotherapy in 20/25 fractions with concurrent oral UFT or S-1 chemotherapy. Mesorectal excision was performed 6 to 8 weeks after completion of CRT. Results: There were no significant differences in characteristics between the groups. The numbers of retrieved LNs (mean±SD) in T group and C group were 14±7 and 8±6, respectively (p < 0.01). The number of patients with 12 or more LNs was greater in T group (56%) than in C group (20%) (p < 0.01). The numbers of metastatic LNs were similar in both groups (0.5±1.2 and 0.5±1.4, respectively p = 0.92). In patients with poor histologic tumor regression (TRG grade 3 to 5), the number of LNs was significantly greater in T group (17±9) than in C group (6±5; p < 0.01). However, in patients with good histologic response (TRG grade 1 or 2), the numbers of LNs in T group and C group were 11±5 and 9±6, respectively (p = 0.31). In T group, the numbers of LNs and metastatic LNs were significantly greater only in patients with poor histologic regression. Conclusions: Preoperative tattooing increases the number of retrieved LNs. In patients with poor histologic response following CRT, tattooing significantly increases the numbers of LNs. However, tattooing does not increase the numbers of retrieved LNs and metastatic LNs in patients with good histologic response. Clinical trial information: 11R-004.