Kidney-sparing radiotherapy by multiple-field three-dimensional technique in the postoperative management of patients with gastric cancer: comparison with standard two-field conformal technique.

AIMS AND BACKGROUND: The opposed two-field technique is the standard approach for delivering adjuvant radiotherapy to patients with resected gastric cancer. Since a considerable radiation dose may reach both kidneys with this beam arrangement, with a potential risk of late effects, we investigated whether the CT-based multiple-field (M-F) approach was superior in terms of sparing critical organs at risk. METHODS: From March 2001 to March 2004, 19 patients with radically resected gastric cancer entered the study. They were treated with adjuvant chemoradiotherapy according to the INT 0116 protocol. For each patient dose-volume histograms were calculated and the volume values of both kidneys and liver receiving 25 Gy (V25), 30 Gy (V30) and 40 Gy (V40) individually estimated with the M-F and two-field techniques were compared in detail. RESULTS: Right kidney median V25, V30 and V40 values for the two-field and M-F techniques were 1.50%, 0%, 0% and 0%, 0% and 0%, respectively (P < 0.005, P < 0.01, P < 0.05). Left kidney median V25, V30 and V40 values for the M-F and two-field technique were 16%, 9.80%, 0.90% and 33.20%, 30.20%, 21.40% (P < 0.001, P < 0.0005, P < 0.0005). Liver median V25, V30 and V40 values for the M-F and two-field techniques were 51.30%, 22.30%, 8.90% and 13.30%, 11.60%, 8.10%, respectively (P < 0.0001, P < 0.0005 and P = 0.18). CONCLUSIONS: Our comparison revealed that with the multiple-field technique the right kidney may be largely spared from irradiation; with respect to the two-field technique, the left kidney may receive a significantly reduced dose; however, the liver receives an increased dose that warrants careful long-term monitoring of hepatic function.