Comparison of different calculation indexes with dose volume histogram parameters for evaluation of radiation treatment plans in gynecologic malignancies

We aimed to investigate the accordance of Critical Organ Scoring Index (COSI), Conformity Index (CI) and Normal Tissue Complication Probability (NTCP) parameters with Dose Volume Histograms (DVH) used for evaluation of 3 different pelvic radiotherapy plans.

Ten gynecologic carcinoma patients who underwent adjuvant radiotherapy were enrolled in this study. Treatment plans were created with conformal treatment planning (3DCRT) and intensity modulated radiation therapy (IMRT) to a total dose of 50.4 Gy in 28 fractions. Initially, volume related dose evaluation was done via DVH. Subsequently, HI, CI, COSI and NTCP for selected normal tissues were calculated for each plan and compared with DVH parameters. Finally, a graphical demonstration was evaluated to see if the results were in accordance with DVH.

CI results were statistically significant in favor of IMRT (p<0.001). Rectum V40Gy decreased with 9IMRT compared to 3DCRT and 7IMRT (p=0.013 and p=0.013). V40Gy for bladder was also lower with 9IMRT compared with 3DCRT and 7IMRT (p=0.005 and p=0.012). COSI calculations revealed better small intestine protection in IMRT plans similar with DVH (p=0.005 and p=0.022). Femoral heads were better protected with IMRT plans were better compared to 3DCRT in NTCP calculations (p=0.002). Normal tissue protection was worst with 3DCRT via both DVH and COSI evaluations (p=0.001 and p<0.001 respectively).

Using the indexes in this study to decide the most appropriate plan among multiple treatment plans in gynecologic cancer patients will be timesaving and easier in comparison with evaluating the DVH of every alternative plan.