Qu A, et al. J Gynecol Oncol. 2018 Aug;30(1):e9. https://doi.org/10.3802/jgo.2019.30.e9

E15143 Background: To evaluate the efficacy of 125I radioactive seed implantation for locally recurrent rectal cancer (LRRC), and analyze the associated prognostic factors, the relationship between the efficacy and dosimetry. Methods: From September 2003 to December 2011, 36 patients with locally recurrent rectal cancer received 125I seeds implantation under CT guidance in our center. Each patients underwent three-dimentional treatment planning pre-implantation and dosimetric verification post-implantation. The median activity of seed was 0.7 mCi (0.4 to 0.8 mCi), and the median number of seeds was 74 (33 to 137). Double variates correlation analysis for gross tumor volume (GTV), D90, D100, V100, V150 and volume covered with the prescription dose, homogeneity index (HI), external index (EI) and conformity index (CI). The Logistic regression analysis between the overall survival, local control and the dosimetry was performed with the SPSS 22.0. Overall survival of the patients was calculated and prognostic factors were evaluated. Results: The D90 was 118.6±25.1Gy, the V100 was 90.0±0.3%. The mean CI, HI and EI was 1.48±0.36, 0.32±0.08, and 0.58±0.37. The D90 and CI decreased with the increasing of the GTV volume. The median overall survival was 16.2 months (95%CI 13.5-18.9 months). The median local control time was 10.0 months (95%CI 6.2-13.8 months). Analysis using the Cox proportional hazards model suggested that V100 is correlated to the overall survival time (p = 0.026), D90 is correlated to the local control time (p = 0.017). D90 > 140Gy and V100 > 90% is beneficial to improve the tumor control and patient survival. CI and EI is not related to the overall survival and local control, but related to the normal tissue sparing. Conclusions: CT-guided radioactive seed implantation provides a safe and effective method to control local tumor growth and prolong the survival of patients with locally recurrent rectal cancer without additional complications. V100 and D90 may predict a favorable tumor control and patients survival, whereas CI and EI is closely related to the normal structure side effects. CT image-guidance and satisfactory seeds implant is the key technique components for better clinical efficacy.