Evaluation of volumetric modulated arc therapy for postmastectomy treatment

Abstract

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.

Evaluation of a mixed beam therapy for postmastectomy breast cancer patients: Bolus electron conformal therapy combined with intensity modulated photon radiotherapy and volumetric modulated photon arc therapy

“…The IMC area included the internal mammary vessels in the first three intercostal spaces. The patients had a 1‐cm thick Superflab bolus (Superflab Bolus, Radiation Products Design, Inc., Albertville, MN, USA) placed on the surface of their ipsilateral chest wall for the purpose of dose buildup …”

“…Due to prevalence of microscopic disease after mastectomy, postmastectomy radiotherapy (PMRT) is commonly performed to sterilize residual tumor cells; it has been shown to improve the overall survival for invasive breast cancer patients by reducing the risk of tumor recurrence and cancer mortality . At our institution, the standard of care for PMRT has been Helical Tomotherapy or Volumetric Modulated photon Arc Therapy (VMAT) . Both modalities provide good target coverage and dose homogeneity, but the large volume of stray radiation dose to normal tissues like lung, heart, and contralateral breast is a concern because that can potentially cause radiogenic side effects like radiation pneumonitis, cardiac toxicity, and secondary cancers …”

“…1 At our institution, the standard of care for PMRT has been Helical Tomotherapy 2,3 or Volumetric Modulated photon Arc Therapy (VMAT). 4 Both modalities provide good target coverage and dose homogeneity, but the large volume of stray radiation dose to normal tissues like lung, heart, and contralateral breast is a concern because that can potentially cause radiogenic side effects like radiation pneumonitis, cardiac toxicity, and secondary cancers. [5][6][7][8] The inherent rapid distal dose fall-off of therapeutic electron beams makes them suitable for treatment of the chest wall where the target volume is superficial and organs at risk (OARs) like the lungs and heart underlie the target.…”

A treatment planning comparison of volumetric modulated arc therapy and proton therapy for a sample of breast cancer patients treated with post-mastectomy radiotherapy

“…These values fall within previously reported clinical incidence rates of 1 to 5% following breast cancer radiotherapy. 30 Average SCCP values for the lungs using the linear-exponential model in a PMRT study by Nichols et al 6 predicted a value of 5.3%±0.1% for VMAT. We had a similar result at 4.1%±0.6% for VMAT using the linear-exponential model as well.…”

“…2–5 While modern PMRT techniques such as volumetric modulated arc therapy (VMAT) minimize high dose radiation to surrounding normal tissues, there is an increase in low dose to normal tissues due to the complex geometry of the treatment field, which can lead to radiation induced complications in organs such as the heart and lungs. 6 Comparative treatment planning studies have consistently predicted proton beam therapy can substantially decrease dose to OARs for the treatment of early or locally-advanced breast cancers compared to conventional and IMRT photon techniques. 7–11 However, none of these studies considered uncertainties associated with radiation therapies, even though advanced technology like proton therapy is known to contain considerable range and other uncertainties.…”