Victor Gonzalez MD, Presenter: Nothing to Disclose

Daniel J. Buchholz MD, Abstract Co-Author: Nothing to Disclose

Katja Langen PhD, Abstract Co-Author: Nothing to Disclose

Gustavo Olivera, Abstract Co-Author: Nothing to Disclose

Ken Ruchala PhD, Abstract Co-Author: Nothing to Disclose

Jason Haimerl PhD, Abstract Co-Author: Nothing to Disclose

Bobby Chauhan, Abstract Co-Author: Nothing to Disclose

Sanford Meeks PHD, Abstract Co-Author: Nothing to Disclose

Patrick Kupelian MD, JD, Abstract Co-Author: Nothing to Disclose

et al, Abstract Co-Author: Nothing to Disclose

G.O.,K.R.,J.H.: Tomotherapy Inc. employee

Purpose/Objective: To compare two different helical tomotherapy techniques for whole breast irradiation. Materials/Methods: CT scans from five breast cancer patients (4 left and 1 right sided) were utilized for the study. Treatment plans were generated using two separate techniques. The first technique uses the standard helical tomotherapy delivery (Tomo). The second technique, called Topotherapy (Topo), is a novel method which utilizes the tomotherapy unit in fixed gantry positions. In Topotherapy, beam intensity is modulated via the binary collimators in the fan beam path while the patient is advanced through the stationary gantry. This technique is under investigation and not yet available clinically. Topo plans were generated using prototype software from TomoTherapy Inc. All contours were drawn by a physician (DB). The clinical target volume encompassed all radiographically visible breast tissue with a 1.0 cm expansion used to generate the planning target volume (PTV). The prescription dose was 50.4 Gy. Left ventricle, lungs, and contralateral breast were treated as avoidance structures, with no beams passing through the contralateral lung or breast. Comparison endpoints included the following: PTV coverage defined as the relative volume of the PTV receiving 95% of the prescribed dose (Target V95), relative volume of ipsilateral lung receiving ≥20 Gy (V20), relative volume of left ventricle receiving ≥30 Gy (V30), contralateral breast and lung doses, and soft tissue volumes receiving ≥50.4 Gy (soft tissues defined as tissues within the irradiated volume minus PTV and critical structures). Results: Results are summarized in Table 1. Both plans achieved excellent coverage. Tomo plans were slightly more homogeneous: the average percentage of the target volume receiving more than 110% of the prescribed dose was <1% for all Tomo plans, versus 8% for Topo plans. The ipsilateral lung V20 values were higher with Tomo plans (Table 1). The percentage (±S.D.)of the ipsilateral lung volume receiving ≥50.4 Gy was 0.3%±0.7 for Tomo plans and 2.5%±2.7 for Topo plans. The left ventricle doses were lower with the Topo plans (Table 1). However, with both techniques the contralateral lung and breast doses were very low: the mean cumulative dose to contralateral breast and lung on all plans was less than 1.5 Gy. Conclusions: Helical tomotherapy provides improved target dose homogeneity and conformality over the tangential beam arrangement of topotherapy. These gains are associated with increased volumes of heart and ipsilateral lung receiving low dose radiation. By emulating the beam arrangement used in conventional whole breast RT, Topotherapy yields normal-tissue dose distributions comparable to conventional opposed-tangent radiation. However, unlike conventional tangents, both Tomotherapy and Topotherapy techniques offers the advantages of daily target localization and treatment verification. Both techniques are also associated with extremely low contralateral breast and lung doses. Both techniques are viable options for whole breast irradiation.

Gonzalez, V, Buchholz, D, Langen, K, Olivera, G, Ruchala, K, Haimerl, J, Chauhan, B, Meeks, S, Kupelian, P, et al, , Whole Breast Tomotherapy: A Comparison of Two Techniques.  Radiological Society of North America 2005 Scientific Assembly and Annual Meeting, November 27 - December 2, 2005 ,Chicago IL. http://archive.rsna.org/2005/4420639.html