PurposeTo examine the feasibility of volumetric modulated arc therapy (VMAT) for post mastectomy radiotherapy (PMRT).Methods and materialsFifteen PMRT patients previously treated at our clinic with helical tomotherapy (HT) were identified for the study. Planning target volumes (PTV) included the chest wall and regional lymph nodes. A systematic approach to constructing VMAT that met the clinical goals was devised. VMAT plans were then constructed for each patient and compared with HT plans with which they had been treated. The resulting plans were compared on the basis of PTV coverage; dose homogeneity index (DHI) and conformity index (CI); dose to organs at risk (OAR); tumor control probability (TCP), normal tissue complication probability (NTCP) and secondary cancer complication probability (SCCP); and treatment delivery time. Differences were tested for significance using the paired Student’s t-test.ResultsBoth modalities produced clinically acceptable PMRT plans. VMAT plans showed better CI (p < 0.01) and better OAR sparing at low doses than HT plans, particularly at doses less than 5 Gy. On the other hand, HT plans showed better DHI (p < 0.01) and showed better OAR sparing at higher doses. Both modalities achieved nearly 100% tumor control probability and approximately 1% NTCP in the lungs and heart. VMAT showed lower SCCP than HT (p < 0.01), though both plans showed higher SCCP values than conventional mixed beam (electron-photon) plans reported by our group previously. VMAT plans required 66.2% less time to deliver than HT.ConclusionsBoth VMAT and HT provide acceptable treatment plans for PMRT. Both techniques are currently utilized at our institution.

Purpose: To investigate the feasibility of volumetric modulated arc therapy (VMAT) for post‐mastectomy radiotherapy (PMRT) and to compare dual‐ arc VMAT treatment plans to helical tomotherapy (HT) plans on the basis of dosimetric quality, radiobiological calculations and delivery efficiency. Methods: Dual‐arc VMAT and HT treatment plans were created for fifteen patients previously treated at our clinic. Planning target volumes (PTV) included the chest wall (CW) and regional lymph nodes. The following metrics were used to compare treatment plans for each patient: dose homogeneity index (DHI) and conformity index (CI); coverage of the PTV; dose to organs at risk (OAR); tumor control probability (TCP), normal tissue complication probability (NTCP) and secondary cancer complication probability (SCCP); and treatment delivery time. Differences between treatment plans were tested for significance using the paired Student's t‐test. Results: Both modalities produced clinically acceptable PMRT plans. VMAT plans showed better CI (p < 0.01), and better OAR sparing at low doses than HT plans. For example, VMAT plans showed a 26% (p < 0.01) and 9% (p < 0.01) decrease in V5Gy in the lungs and heart respectively. On the other hand, HT plans showed better DHI (p < 0.01) and PTV coverage (p < 0.01). HT plans also showed slightly better OAR sparing at higher doses, including 8% (p < 0.01) and 9% (p < 0.01) lower maximum doses to the lungs and heart, respectively. Both modalities achieved nearly 100% tumor control and approximately 1% NTCP in the lungs and heart, with VMAT showing lower SCCP (p < 0.01). VMAT plans also required 66.2% less time to deliver. Conclusions: Both VMAT and HT are suitable treatment options for PMRT. Our study showed that VMAT“‘in addition to being significantly faster’”achieved better CI and low dose OAR sparing while HT achieved better DHI. This work was supported in part by a research support from Elekta, Ltd. However, Elekta, Ltd., did not participate in the study design; in the collection, analysis, and interpretation of data; in the writing of the manuscript; or in the decision to submit

Purpose: To compare plan quality for a comprehensive set of OAR & PTV geometries considering relative risk estimates for the induction of secondary bladder and rectal cancers due to prostate radiotherapy using several modern delivery techniques. Methods: IMRT / 3D‐conformal, volumetric‐arc (VMAT), and Tomotherapy (TT) plans were generated using PlanUNC, Pinnacle3 ver. 9.2, and TomoTherapy treatment planning systems, respectively, for 12 prostate cases using, RTOG 0815‐derived planning goals. Selected cases were representative of relative (i.e. small (Svol), medium (Mvol), large (Lvol)) PTV, rectal & bladder structure volumes encountered clinically. PlanUNC was used to calculate the elevated relative‐risk (ERR) of secondary cancer induction in normal tissues, the bladder and rectal ERR, PTV conformity index (CI), dose heterogeneity index (DHI), and bladder and rectal V5, V15, V35, V50 (Bvx / Rvx) for all cases. All metrics were averaged for each relative tissue / target volume, and normalized to corresponding 3D‐conformal cases for comparison. Results: Considering relative rectal volumes, all metrics fell within the standard error for each modality excluding bladder ERR (TT 13%ave, IMRT −9% ave & VMAT −18% ave) and BV15 (VMAT −24% ave) for Lvol rectum cases. Considering relative bladder volumes, bladder ERR (TT 4%, IMRT −10%, VMAT −18%) for Lvol and (VMAT −20%) for Mvol; rectal ERR (TT −40%) for Mvol were observed to be significant in addition to bladder ERR (TT 13%) for Svol PTV cases. Generally, all modalities performed better when compared to 3D conformal delivery excluding nominal (<5%) increases in normal tissue dose and increased bladder ERR for several TT cases. Conclusion: We compared three prostate EBRT modalities considering OAR ERR as well as traditional plan quality metrics for a class of cases defined by relative structure size. Preliminary results indicate comparable improvements in PTV conformity & OAR dosing for each modality but differences in OAR ERR.

Purpose: To develop a set of procedures that utilize radiochromic film, a conventional kV simulator, and commonly‐available, vendor‐supplied QA devices to commission an HDR brachytherapy multi‐channel vaginal cylinder (MCVC) for clinical use. Methods: A series of images were acquired utilizing a combination of radiochromic film, planar kV imaging, and device immobilization. Using this information, relative coordinates used for source localization were registered absolutely with respect to MCVC and afterloader coordinate systems. With this knowledge, a method for MCVC channel identification and treatment planning was developed. Absolute dosimetry of resulting plans was verified utilizing radiochromic film measurements in water. Results: Vendor‐supplied index lengths of 1293 and 1500 mm were confirmed for the peripheral and central MCVC channels, respectively. For treatment planning purposes, the distance from the distal tip of each peripheral MCVC channel was verified to be consistent for each supplied cylinder diameter: 25, 30, and 35 mm. Additionally, a method that exploits physical characteristics of the applicator has been developed to facilitate precise and reproducible dwell position localization and catheter identification. Preliminary analysis of measured and planned dose delivered to planes parallel to the long‐axis of the cylinder show agreement within 7% in water for a variety of cylinder diameters and loadings. Conclusion: A method has been developed to commission a commonly available MCVC for clinical use without the use of radiographic film.