Volumetric Modulated Arc Therapy (VMAT): A modern radiotherapy technique - A single institutional experience

Objective: To evaluate VMAT plans for conformity and homogeneity of radiation dose to the target in order to share our experience as a pioneering institute to use VMAT technology in Pakistan.

Methods: Since December 2014 to January 2018, 530 patients of various anatomical sites were treated by VMAT technique at Neurospinal Cancer Care Institute (NCCI) Karachi Pakistan. ERGO++ planning system (Version 1.7.2) was used to develop VMAT plans with single or multiple arcs by the rotation of couch and gantry. The plans were evaluated by calculating Conformity Index (CI) and Homogeneity Index (HI) and critical organ (OARs) doses of individual tumor sites.

Results: The average CI of various sites was 1.4 (range: 1.0–2.0) and average HI of various sites was 1.20 (range: 1.07–1.374), respective critical organ doses were adequately achieved.

Conclusions: VMAT treatment planning technique showed good conformal and homogeneous target coverage with sparing of organs at risk and reduced treatment delivery time. With these features, safety of VMAT technique may allow its routine clinical use, though it is still under investigation in many areas.

Abbreviations Used:
CI: Conformity Index, HI: Homogeneity Index, GI: Gradient Index, SIB: Simultaneous Integrated Boost, SRS: Stereotactic Radiosurgery, SBRT: Stereotactic Body Radiotherapy, VMAT: Volumetric Modulated Arc Therapy, MLCs: Multi-leaf Collimators, MU: Monitor Units, DAM: Dynamic Arc module, TV: Target Volume, MD: Maximum Dose, PD: Prescription Dose, RTOG: Radiation Therapy Oncology Group, Linac: Linear accelerator.