Computed Tomography-based Three-dimensional Image-guided Brachytherapy for Cancer of the Cervix Uteri

Objective: To clarify the treatment results of three-dimensional (3D) image-guided brachytherapy (IGBT) for cancer of the cervix uteri in Hong Kong. Methods: Between January 2014 and June 2016, 52 patients underwent computed tomography (CT)-based 3D IGBT, in which three patients had interstitial needles inserted. Contouring was done with dose volume parameters recorded, as recommended by the GEC-ESTRO guidelines. Recorded parameters included HRCTV D90 mean dose (dose delivered to 90% of the high-risk clinical target volume), HRCTV V100 (percentage of HRCTV receiving 100% of the prescribed dose), and D-2cc (minimum dose in the most exposed 2 cm(3) volume) of rectum, sigmoid colon, and bladder. One-way analysis of variance with Bonferroni's multiple comparison post-hoc tests for normally distributed data or Dunn's multiple comparisons test were used to assess any statistically significant differences. Results: The HRCTV D90 mean doses in 2014, 2015, and 2016 were 75.1 Gy, 77.8 Gy and 82.1 Gy, respectively. The corresponding HRCTV V100 values were 88.7%, 91.6%, and 94.4%, respectively. The HRCTV D90 value in 2016 was found to be significantly higher than that in 2014. The D-2cc value of sigmoid colon in 2016 was significantly lower than that in 2014 or 2015. The D-2cc value of bladder in 2016 was significantly higher than that in 2015 but still within acceptable limits. None of the patients developed grade 3 to 4 acute radiation toxicities. There was one patient with persistent disease in the cervix after radiotherapy, three patients with distant failure, and one patient with both local and distant failure. Conclusion: The CT-based 3D IGBT treatment for cancer of the cervix uteri with interstitial needle insertion is feasible in the local setting. There is potential to give higher dosages to the HRCTV by the 3D IGBT technique, while the doses to organs at risk can still be limited to acceptable levels.