Study of the application of the deformed dose summation (DDS) method in brachytherapy for advanced cervical cancer and analysis of regional dosing in recurrent cervical cancer
This study evaluated the cumulative brachytherapy (BT) dose in cervical cancer using different methods and explored using deformed dose summation (DDS) techniques for assessing doses to targets and organs at risk (OAR). A total of 41 patients with cervical cancer who underwent BT were retrospectively analyzed, the cumulative dose, measured as the equivalent dose in 2 Gy fractions, was calculated using dose-volume histogram (DVH) superposition and DDS methods. The dice similarity coefficient (DSC), Jaccard coefficient (JC), and mean distance to agreement (MDA) were utilized to evaluate the deformable image registration (DIR) accuracy. Furthermore, the difference between the target and OAR doses obtained through the two methods was calculated and compared. The Spearman method was employed to analyze dose differences and geometric correlations, comparing the dose in the relapsing area with that in the post-fusion high-risk clinical target volume (HR-CTV) in patients experiencing relapse to identify potential associations. In evaluating deformable registration, the registration outcomes for both the bladder and rectum were deemed satisfactory. The DSC, JC, and MDA values for the bladder and rectum were calculated as follows: 0.89 ± 0.07, 0.81 ± 0.09, 2.14 ± 1.44 mm and 0.80 ± 0.08, 0.67 ± 0.10, 2.28 ± 1.80 mm, respectively. Compared to DVH superposition, DDS techniques reduced the average cumulative doses of the D2cc and D0.1 cc of bladder by 11.4 % and 8.2 %, respectively; and the doses of the D2cc and D0.1 cc of rectum to be decreased by 9.7 % and 14.1 %, respectively. Additionally, the D90 of HR-CTV and Intermediate risk CTV (IR-CTV) were reduced by 6.60 ± 3.70 Gy and 4.55 ± 2.70 Gy, respectively. No significant correlation was observed between DSC, JC, and MDA and the dose difference. No correlation was observed between the relapsing regional dose and the dose parameters related to the HRCTV following fusion. Calculating the cumulative dose using DVH parameters is a conservative approach that may limit target dose enhancement. During planning, DIR can guide clinicians in selecting the target dose and visually display the cumulative dose distribution in the cervical target area.