Dosimetric comparison between CT-guided free-hand intracavity/interstitial adaptive brachytherapy and conventional point-A brachytherapy in the treatment of cervical cancer

Objective To analyze the dosimetric differences between CT-guided free-hand intracavity/interstitial brachytherapyimage-guided adaptive brachytherapy (IGABT)] and conventional point-A plan (CP) in the treatment of cervical cancer. Methods Twenty-six cervical cancer patients who received four cycles of IGABT in Sun Yat-sen University Cancer Center were enrolled in this study. Two sets of CT images were obtained before and after applicator adjustment to aid in the design of CP and IGABT plans. The high-risk clinical target volume (HRCTV), point A, and organs at risk (bladder, rectum, and sigmoid colon) were defined on CT images. CP and IGABT plans were designed on CT images. Parameter differences between CP and IGABT plans were analyzed with paired t-test and Wilcoxon test. Results According to the coverage index (CI) of CP, plans were divided into two groups:in group A (CI≥0.90), 20 CP and corresponding IGABT plans were included, and 84 CP and corresponding IGABT plans in group B (CI<0.90). The mean volume of HRCTV and mean tumor diameter in group A were significantly smaller than those in group B (46.7 cm³ vs. 62.1 cm³, P<0.001 and 3.1 cm vs. 4.4 cm, P<0.001). Compared with CP, IGABT significantly improved the value of D90% in all plans and group B, whereas lowered the bladder dose. IGABT also reduced the dose of sigmoid colon in group A. IGABT significantly improved conformal index and dose homogeneity index. Conclusions IGABT can significantly improve the target coverage, conformal index and dose homogeneity index, protect organs at risk. Compared with CP, IGABT has advantages in the treatment of patients with bulky tumor.