For the first time, we have shown that it is possible to reduce RIIS in a statistically significant manner, compared to standard of care, via optimized RT planning using a predictive model. This has implications in increasing the efficacy of immunotherapy by preserving the existing tumor reactive T cells in the immune system to enhance anti-tumor activity, and in reducing hospitalizations and improving survival.

Aim: Deep inspiratory breath hold (DIBH) during left-breast irradiation helps to minimise cardiac irradiation by physically separating the heart from the left breast. The dose to organs-at-risk in intensity-modulated radiotherapy (IMRT) and opposed tangent three-dimensional conformal radiotherapy (3DCRT) during DIBH in patients with left-sided breast cancer was compared.Materials and methods: A total of 20 consecutive patients with left-sided breast cancer had a computed tomography scan utilising DIBH. Mean volumes of the heart, left anterior descending coronary artery, total lung and right breast receiving 5-95% of the prescription dose were calculated.Results: Target volume homogeneity was improved with IMRT and average mean dose to target was higher for 3DCRT (51.03 Gy) compared with IMRT (50.47 Gy, p < 0.01). The average mean dose to the heart was lower with 3DCRT (87 versus 77 cGy, p < 0.01). The average mean dose to the contralateral breast was also lower with 3DCRT (19 versus 17 cGy, p < 0.01). Less monitor units (MUs) were required with 3DCRT with an average difference of 225 MU/fraction (p < 0.01).Findings: Under DIBH, absolute differences between 3DCRT and IMRT were minimal. 3DCRT under DIBH provided excellent dosimetric results in most patients with left-sided breast cancer without the need for IMRT.

Patients who have received radiation therapy to the whole left breast in the treatment of breast cancer are at increased risk for ischemic heart disease because of iatrogenic cardiac irradiation. Deep inspiratory breath hold (DIBH) during treatment helps to minimize cardiac irradiation by physically separating the heart from the left breast. The purpose of this study is to compare the dose to organs at risk in intensity modulated radiation therapy (IMRT) and 3-dimensional conformal radiation therapy (3D-CRT) during DIBH for patients with left sided breast cancer. Ten patients with left sided breast cancer had a computed tomography scan utilizing DIBH after breast conserving surgery. Optimization of the IMRT plan was performed using 6 noncoplanar tangential beams. The 3D-CRT plan was optimized using standard tangents. The prescription dose for both IMRT and 3D-CRT was 50 Gy at 2.0 Gy per fraction. At least 95% of the breast PTV received at least 95% of the whole breast prescribed dose of 50 Gy for both IMRT and 3D plans. Mean volumes of the heart, left anterior descending coronary artery (LAD), total lung, and right breast receiving 5% to 95% (in 5% increments) of the prescription dose were calculated. The volume of heart, LAD, total lung, and right breast receiving 5% to 95% of the prescription dose did not differ between the IMRT or 3D-CRT plans. The mean dose to the heart trended lower with 3D-CRT (92 cGy vs 81 cGy, p = 0.09), but did not reach statistical significance. The mean dose delivered to the contralateral breast was lower with 3D-CRT (15 cGy vs 13 cGy, p = 0.02). IMRT demonstrated improved dose homogeneity in the target volume (p = 0.01), and mean dose to target was higher for 3D-CRT (50.88 Gy) compared to IMRT (50.49 Gy, p < 0.01). Less monitor units were delivered per fraction in the 3D-CRT plan with an average difference of 173 MU per session (p < 0.01). When administered under DIBH, 3D-CRT is equivalent to IMRT in sparing organs at risk during the treatment of left sided breast cancer. 3D-CRT should be considered an alternative approach to IMRT that provides a clinically equivalent treatment for patients with left-sided breast cancer while sparing organs at risk with increased ease of implementation.

Purpose/Objective(s)Intensity-modulated radiation therapy (IMRT) with multiple non-coplanar static beams delivers conformal dose distribution to planned target volume (PTV) and minimizes dose to organs at risk (OAR), but may have long treatment time with a large number of beams. RapidArc (RA) technology based on volumetric modulated arc therapy (VMAT) may offer considerably shorter treatment time and highly conformal dose distributions delivered with a dynamic rotation of the gantry with beam intensity modulation every 2o throughout the gantry rotation. Non-coplanar partial arcs (NCPA) may deliver beams to the target through the cephalic portion of the brain and avoid OAR. Ring gantry-based Helical TomoTherapy (HT) delivers conformal and highly homogeneous dose distribution inside the tumor volume, while sparing the OAR. In this study, we evaluate RA capabilities using coplanar and non-coplanar arcs and do a dosimetric comparison with IMRT and HT.Materials/MethodsThree brain tumor patients with target volumes of 26.7, 193.4, and 425.2 cc who had completed IMRT were replanned for HT using 0.287 pitch and RA using single 360o arc (SA), double 720o arc (DA), and combinations of SA with 1 and 3 NCPA. Couch rotations were 90o for 1NCPA and 90o, 30o, and 330o for 3NCPA. Partial arcs ranged from 0o-30o to 150o-179.9o. At least 95% of the PTV was required to receive the prescribed dose. IMRT plans used 6-8 non-coplanar beams. Similar dose constrains and PTV coverage criteria were used in all plans.ResultsFor the smallest tumor, PTV coverage D99% was the highest for RA plans (96.4%), followed by HT (94.2%) and IMRT (93.8%). Multiple-arc RA plans were more homogeneous ((D5%-D95%)/D95% ˜3.5%) compared to IMRT (5.9%), RA-SA (6.2%), and HT (7.2%). Conformity was the same for 95% isodose, but higher for RA-NCPA plans at 50% isodose. Average and max dose to most OAR like brainstem, optic chiasm, pituitary and optic nerves were lower with RA. For the larger tumors, HT had the highest PTV dose homogeneity (˜2%) and coverage (99.3%), followed by RA-NCPA (98.6%), RA-DA and SA (97.9%) and IMRT (96.6%). Conformity was similar at 95% and higher with RA-NCPA and IMRT at 50% isodose. Most OAR sparing was similar for HT, RA and IMRT. For all three tumors, average dose to brain was the highest with HT, and dose to lenses and retina was higher but well below the allowed limits with RA.ConclusionsWe compared RapidArc VMAT using multiple coplanar and non-coplanar arcs with static beam IMRT and Helical TomoTherapy for brain tumor treatment. For the smallest tumor (26.7 cc), multiple-arc RA showed advantages over IMRT and HT in PTV coverage, dose homogeneity, and OAR sparing. For the larger brain tumors both HT and RA-NCPA offered high quality of PTV coverage and dose homogeneity. Purpose/Objective(s)Intensity-modulated radiation therapy (IMRT) with multiple non-coplanar static beams delivers conformal dose distribution to planned target volume (PTV) and minimizes dose to organs at risk (OAR), but may have long treatment time with a large number of beams. RapidArc (RA) technology based on volumetric modulated arc therapy (VMAT) may offer considerably shorter treatment time and highly conformal dose distributions delivered with a dynamic rotation of the gantry with beam intensity modulation every 2o throughout the gantry rotation. Non-coplanar partial arcs (NCPA) may deliver beams to the target through the cephalic portion of the brain and avoid OAR. Ring gantry-based Helical TomoTherapy (HT) delivers conformal and highly homogeneous dose distribution inside the tumor volume, while sparing the OAR. In this study, we evaluate RA capabilities using coplanar and non-coplanar arcs and do a dosimetric comparison with IMRT and HT. Intensity-modulated radiation therapy (IMRT) with multiple non-coplanar static beams delivers conformal dose distribution to planned target volume (PTV) and minimizes dose to organs at risk (OAR), but may have long treatment time with a large number of beams. RapidArc (RA) technology based on volumetric modulated arc therapy (VMAT) may offer considerably shorter treatment time and highly conformal dose distributions delivered with a dynamic rotation of the gantry with beam intensity modulation every 2o throughout the gantry rotation. Non-coplanar partial arcs (NCPA) may deliver beams to the target through the cephalic portion of the brain and avoid OAR. Ring gantry-based Helical TomoTherapy (HT) delivers conformal and highly homogeneous dose distribution inside the tumor volume, while sparing the OAR. In this study, we evaluate RA capabilities using coplanar and non-coplanar arcs and do a dosimetric comparison with IMRT and HT. Materials/MethodsThree brain tumor patients with target volumes of 26.7, 193.4, and 425.2 cc who had completed IMRT were replanned for HT using 0.287 pitch and RA using single 360o arc (SA), double 720o arc (DA), and combinations of SA with 1 and 3 NCPA. Couch rotations were 90o for 1NCPA and 90o, 30o, and 330o for 3NCPA. Partial arcs ranged from 0o-30o to 150o-179.9o. At least 95% of the PTV was required to receive the prescribed dose. IMRT plans used 6-8 non-coplanar beams. Similar dose constrains and PTV coverage criteria were used in all plans. Three brain tumor patients with target volumes of 26.7, 193.4, and 425.2 cc who had completed IMRT were replanned for HT using 0.287 pitch and RA using single 360o arc (SA), double 720o arc (DA), and combinations of SA with 1 and 3 NCPA. Couch rotations were 90o for 1NCPA and 90o, 30o, and 330o for 3NCPA. Partial arcs ranged from 0o-30o to 150o-179.9o. At least 95% of the PTV was required to receive the prescribed dose. IMRT plans used 6-8 non-coplanar beams. Similar dose constrains and PTV coverage criteria were used in all plans. ResultsFor the smallest tumor, PTV coverage D99% was the highest for RA plans (96.4%), followed by HT (94.2%) and IMRT (93.8%). Multiple-arc RA plans were more homogeneous ((D5%-D95%)/D95% ˜3.5%) compared to IMRT (5.9%), RA-SA (6.2%), and HT (7.2%). Conformity was the same for 95% isodose, but higher for RA-NCPA plans at 50% isodose. Average and max dose to most OAR like brainstem, optic chiasm, pituitary and optic nerves were lower with RA. For the larger tumors, HT had the highest PTV dose homogeneity (˜2%) and coverage (99.3%), followed by RA-NCPA (98.6%), RA-DA and SA (97.9%) and IMRT (96.6%). Conformity was similar at 95% and higher with RA-NCPA and IMRT at 50% isodose. Most OAR sparing was similar for HT, RA and IMRT. For all three tumors, average dose to brain was the highest with HT, and dose to lenses and retina was higher but well below the allowed limits with RA. For the smallest tumor, PTV coverage D99% was the highest for RA plans (96.4%), followed by HT (94.2%) and IMRT (93.8%). Multiple-arc RA plans were more homogeneous ((D5%-D95%)/D95% ˜3.5%) compared to IMRT (5.9%), RA-SA (6.2%), and HT (7.2%). Conformity was the same for 95% isodose, but higher for RA-NCPA plans at 50% isodose. Average and max dose to most OAR like brainstem, optic chiasm, pituitary and optic nerves were lower with RA. For the larger tumors, HT had the highest PTV dose homogeneity (˜2%) and coverage (99.3%), followed by RA-NCPA (98.6%), RA-DA and SA (97.9%) and IMRT (96.6%). Conformity was similar at 95% and higher with RA-NCPA and IMRT at 50% isodose. Most OAR sparing was similar for HT, RA and IMRT. For all three tumors, average dose to brain was the highest with HT, and dose to lenses and retina was higher but well below the allowed limits with RA. ConclusionsWe compared RapidArc VMAT using multiple coplanar and non-coplanar arcs with static beam IMRT and Helical TomoTherapy for brain tumor treatment. For the smallest tumor (26.7 cc), multiple-arc RA showed advantages over IMRT and HT in PTV coverage, dose homogeneity, and OAR sparing. For the larger brain tumors both HT and RA-NCPA offered high quality of PTV coverage and dose homogeneity. We compared RapidArc VMAT using multiple coplanar and non-coplanar arcs with static beam IMRT and Helical TomoTherapy for brain tumor treatment. For the smallest tumor (26.7 cc), multiple-arc RA showed advantages over IMRT and HT in PTV coverage, dose homogeneity, and OAR sparing. For the larger brain tumors both HT and RA-NCPA offered high quality of PTV coverage and dose homogeneity.

Purpose: We evaluate RapidArc volumetric modulated arc radiotherapy (VMAT) using coplanar and non-coplanar arcs for the treatment of brain tumors to achieve conformai dose distribution, homogeneous coverage of the planned target volume (PTV), improved sparing of organs at risk (OAR), and reduced treatment time as compared with conventional intensity-modulated radiation therapy (IMRT). Method and Materials: Three brain tumor patients with PTVs of 26.7, 193.4, and 425.2 cc who had completed IMRT were replanned with Varian RapidArc using single 360° arc (RASA), double 720° arc (RA-DA), and a combination of a single 360° arc and a non-coplanar partial arc with a 90° couch rotation (RA-NC). Non-coplanar partial arcs ranged from 0°–25° to 179.9°. At least 95% of the PTV was required to receive the prescribed dose. RA plans were compared with IMRT plans, and differences in dose distribution, PTV coverage, and OAR sparing were analyzed. IMRT plans used 6–8 non-coplanar beams. Results: RA-DA and RA-NC plans improved PTV coverage (D99%) from an average of 94.6% of prescription dose for IMRT plans to an average of 97.7%. Homogeneity of dose distribution in the target volume was improved from an average of 5.3% for IMRT to an average of 3.7% for RA-NC plans. Single-arc plans were slightly inferior to multiple-arc plans, but were still comparable to IMRT. Average dose to most OAR like brainstem, optic chiasm, pituitary, and optic nerves were reduced with RA. Dose to other optical structures like lenses increased compared with IMRT but remained well within the allowed limits. Conclusion: RapidArc VMAT using multiple arcs for the treatment of brain tumors may provide improved target volume coverage, highly conformai and more homogeneous dose distribution in the PTV, as compared to conventional IMRT. Organs at risk may also be spared more efficiently with VMAT.