Optimal radiotherapy technique selection for left-sided breast cancer remains challenging. This study compared volumetric-modulated arc therapy (VMAT), VMAT+IMRT (VMAT+IMRT) and IMRT+VMAT (IMRT+VMAT) using an innovative integrated scoring system and risk factor (RF) assessment.

Retrospectively analysed 41 patients with left-sided breast cancer. Treatment plans were evaluated using an integrated scoring system considering tumour coverage and organs at risk (OARs) sparing. RF analysis assessed potential adverse effects on the heart and lungs. Correlation analysis explored relationships between integrated scores and risk factors.

VMAT showed the best overall integrated score (1·0931 ± 0·1707), followed by IMRT+VMAT (1·2011 ± 0·2440) and VMAT+IMRT (1·2264 ± 0·2499). VMAT had the highest percentage of Excellent OAR plans (14·6%), while VMAT+IMRT and IMRT+VMAT showed better PTV coverage (53·7% and 51·2% Excellent, respectively). RF analysis revealed: VMAT (heart RF: 0·341, lung RF: 0·671), VMAT+IMRT (heart RF: 0·294, lung RF: 0·750) and IMRT+VMAT (heart RF: 0·533, lung RF: 0·546). Correlation analysis showed strong positive correlations between integrated scores and lung RF for VMAT (r = 0·671) and VMAT+IMRT (r = 0·750), with IMRT+VMAT showing moderate correlations for lung (r = 0·546) and heart (r = 0·533) RFs.

VMAT demonstrated the best balance between PTV coverage and OAR sparing, hybrid techniques improved target coverage but increased risk to OAR. The RF analysis highlighted varying impacts on heart and lung across techniques. This analysis provides valuable insights for technique selection, potentially improving treatment outcomes and reducing complications in left-sided breast cancer radiotherapy.

A comprehensive analysing method has been required since long in the field of radiotherapy. The basic purpose of all techniques has been to deliver the prescribed dose safely to the target volume containing tumour and as well as to reduce dose to organs at risk (OARs). The detailed comparison between different treatment techniques is very difficult and inexplicit as well. The gradual improvement in imaging software has made easy to users to assess spatial arrangement of tumour, critical organs and isodose lines in the form of a single 3D representation that can be observed from all angles. The conformity index (CI) alone cannot provide practical information about treatment plans as it is a single isodose line quantity.

The aim of this study was to develop a new method to assess the degree of damage numerically for OARs along with CI assessment for the target.

The radiotherapy plans of 30 patients of different sites, diagnosed as cancer, were selected for this study irrespective of gender. Out of 30 cases, 8 plans were of head and neck, 2 were of glyoblastoma (GBM), 10 were of pelvis, 5 were of left breast and other 5 were of oesophagus cancer. The mean age was 42 years ranging from 31 to 72 years. Patient’s consents were taken before starting the treatment and carried out this research. Risk factor (RF) for OARs depends on volume of irradiation (VVOI), total volume of the organ (VTVO) and tolerance dose (DTDO). All radiotherapy plans (Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT)) were generated using eclipse planning system, version 11.0 (Varian Medical System, Palo Alto, California, USA).

The formula developed to assess degree of damage of OARs including CI of the target is risk factor conformity index (RFC) = CI + RF. In head and neck cases, for right parotid, the maximum value of RF is 1·50 and minimum value is observed as 0·97. Optic nerve, brainstem and spinal cord are completely safe as their RF values are found to be 0 on RF scale.

RFC is a comprehensive evaluation tool encompassing a wider range of clinically relevant parameters, isodose volumes and tolerance dose of OARs. It is an advance analysing method to check both the qualitative and quantitative nature of a conformal plan, and at the same time, it assesses the degree of damage of OARs.

If RF ≥ 1, then OAR will be completely damaged as a result of irradiation.

If RF = 0, then OAR will remain safe totally during the course of irradiation.