Practical radiation oncology | 2019
Biological Indices Evaluation of Various Treatment Techniques for Left-Sided Breast Treatment.
Abstract
PURPOSE\nTo compare dose to organs at risk (OAR) and biological evaluation using normal tissue complication probability (NTCP) for left-sided breast radiation therapy in four techniques; supine free breathing (SFB), supine deep inspiration breath hold (SDIBH), prone free breathing (PFB) and prone deep inspiration breath hold (PDIBH).\n\n\nMETHODS AND MATERIALS\nTwenty-five left-sided breast cancer patients suitable for this study underwent a CT scan using four techniques e.g. SFB, SDIBH, PFB and PDIBH. One radiation oncologist contoured the planning target volume (PTV) and OAR (cardiac components). Dose-volume histograms (DVH s) and normal tissue complication probabilities (NTCP) for the heart, left ventricle (LV), left anterior descending artery (LAD) and left lung were calculated for all four techniques.\n\n\nRESULTS\nThe mean heart dose in PDIBH is 0.77 Gy which is statistically significantly lower than in SFB (1.88 Gy, P < 0.0001), SDIBH (0.97 Gy, P< 0.001) and PFB (0.85 Gy, P< 0.001). The mean left lung dose in PFB is 0.69 Gy and in PDIBH is 0.88 Gy. PFB and PDIBH have statistically significantly lower dose as compared to SFB (6.09 Gy, P < 0.0001) and SDIBH (5.41 Gy, P < 0.0001). The mean NTCP in SFB for the heart, LV, and LAD is 0.27%, 0.62%, and 4.23% respectively, and it is negligible for other techniques.\n\n\nCONCLUSION\nIt is found that PDIBH has dosimetrically lower mean dose for the heart and LV, as compared to other three techniques. Also, SDIBH, PFB and PDIBH have statistically significantly lower NTCP for the heart, LV and LAD as compared to SFB. NTCP for the left lung is statistically significantly lower for prone techniques as compared to supine techniques. It is concluded therefore that PDIBH provides the added benefit of sparing the heart than SDIBH while keeping the benefit of sparing the lung in prone technique.