A Dosimetric Evaluation and Comparison of Point A and Volume Based HDR Intracavitary Brachytherapy

This study aims to compare two different plans, point A based 3-dimensional intracavitary brachytherapy (3D-ICBT) plan and volume-based 3D-ICBT plan in cervical carcinoma with the help of dosimetric parameters. Methods: 30 patients with large tumor volume who received CT image-based point A treatment planning method were replanned to volume-based planning using a treatment planning system for this study. The patient was given a 7 Gy per fraction total 21Gy in 3 fractions is considered for this study. The dose to organ at risk (OARs), bladder, rectum and intermediate clinical target volume (IR-CTV) was compared between both point A based plan and volume based (volume optimization) treatment plan. Results: The total mean doses of IR-CTV D90 and D80 is 15.64 Gy and 19.03 Gy respectively for volume optimization plan and 12.82 Gy and 16.14 Gy for point A based plan. The doses of intermediate CTV for volume optimization show significantly higher than point A based plan (p<0.001). And bladder dose for 0.2cc and 2cc is 18.64 Gy and 15.72 Gy respectively for volume optimization and 25.12 Gy and 19.87 Gy respectively for point A based plan. Similarly, 0.2cc and 2cc rectum dose for volume optimization is 17.82 Gy, 14.63 Gy respectively and 21.05 Gy and 16.48 Gy for point A based plan. So, the OARs doses show significantly lower than point A based plan in large volume lesion(p<0.001). Conclusion: This study demonstrates that volume optimization-based plan can reduce organ at risk (OAR) doses and also get better tumor coverage than point A based plan in large volume lesion.