Effects of chemoradiotherapy on lymph nodes in patients with rectal adenocarcinoma: evaluation of numbers and sizes of retrieved lymph nodes inside and outside the radiation field.

BACKGROUND Preoperative chemoradiotherapy (CRT) decreases the number of retrieved lymph nodes (LNs) in rectal cancer. LNs inside the irradiation field are affected by CRT, whereas those outside the irradiation field are affected only by concurrent chemotherapy. PATIENTS AND METHODS The study cohort comprised of 210 patients with clinical stage II/III rectal adenocarcinoma. One hundred and eight received surgery alone (S group), and 102 received preoperative CRT (40 or 45 Gy) with concurrent oral UFT or S-1 uracil/tegafur or S-1 (CRT group). RESULTS The number of LNs inside the irradiation field was significantly smaller in the CRT group (4 ± 4) than in the S group (6 ± 6, p<0.01), but the number of LNs outside the irradiation field did not differ (5 ± 4 in both groups). The longest diameters of LNs in the S group were significantly smaller than those of the CRT group both inside and outside the irradiation fields (p<0.01). CONCLUSION The effects of CRT on LNs in patients with rectal adenocarcinoma differed inside and outside the radiation field.