Medical Dosimetry
Volume 31, Issue 4 , Pages 283-291, Winter 2006

Inverse-planned, dynamic, multi-beam, intensity-modulated radiation therapy (IMRT): A promising technique when target volume is the left breast and internal mammary lymph nodes

  • Carmen C. Popescu, M.S.

      Affiliations

    • Radiation Therapy Program, British Columbia Cancer Agency–Vancouver Island Centre, Victoria, British Columbia, Canada
    • Corresponding Author InformationReprint requests to: Carmen Popescu, Radiation Therapy Program, British Columbia Cancer Agency–Vancouver Island Centre, 2410 Lee Avenue, Victoria, BC, Canada, V8R 6V5
    • ,
  • Ivo Olivotto, M.D.

      Affiliations

    • Radiation Therapy Program, British Columbia Cancer Agency–Vancouver Island Centre, Victoria, British Columbia, Canada
    • Division of Radiation Oncology and Developmental Radiotherapeutics, University of British Columbia, Vancouver, British Columbia, Canada
    • ,
  • Veronica Patenaude, B.Sc.

      Affiliations

    • Radiation Therapy Program, British Columbia Cancer Agency–Vancouver Island Centre, Victoria, British Columbia, Canada
    • ,
  • Elaine Wai, M.D.

      Affiliations

    • Radiation Therapy Program, British Columbia Cancer Agency–Vancouver Island Centre, Victoria, British Columbia, Canada
    • Division of Radiation Oncology and Developmental Radiotherapeutics, University of British Columbia, Vancouver, British Columbia, Canada
    • ,
  • Wayne A. Beckham, Ph.D.

      Affiliations

    • Radiation Therapy Program, British Columbia Cancer Agency–Vancouver Island Centre, Victoria, British Columbia, Canada
    • Physics & Astronomy Department, University of Victoria, Victoria, British Columbia, Canada

Received 1 September 2005; accepted 1 May 2006.

Abstract 

The purpose of this study was to determine the optimum beam number and orientation for inverse-planned, dynamic intensity-modulated radiation therapy (IMRT) for treatment of left-sided breast cancer and internal mammary nodes (IMNs) to improve target coverage while reducing cardiac and ipsilateral lung irradiation. Computed tomography (CT) data was used from 5 patients with left-sided breast cancer in whom the heart was close to the chest wall. The planning target volume (PTV) was the full breast plus ipsilateral IMNs. Two geometric beam arrangements were investigated, 240° and 190° sector angles, and the number of beams was increased from 7 to 9 to 11. Dose comparison metrics included: PTV homogeneity and conformity indices (HI, CI), heart V30, left lung V20, and mean doses to surrounding structures. To assess clinical application, the IMRT plans with 11 beams equally spaced in a 190° sector angle were compared to conventional plans. Treatment times were modeled. The 190° IMRT plans improved PTV HI and CI and reduced mean dose to the heart, lungs, contralateral breast, and total healthy tissue (all p < 0.05) compared to a 240° sector angle. The 11-beam plan significantly improved PTV HI and CI, heart V30, left lung V20, and healthy tissue V5 compared to a 7-beam plan (all p < 0.05). The 11-beam plan reduced heart V30 and left lung V20 (p < 0.05) without compromising PTV coverage, compared to a 9-beam plan. Compared to a conventional plan, the IMRT class solution significantly improved PTV HI and CI (both p < 0.01), heart V30 (p = 0.01), and marginally reduced left lung V20 (p = 0.07) but increased contralateral breast and lung mean dose (p < 0.001) and healthy tissue V5 (p < 0.001). An 11-beam 190° sector angle IMRT technique as a class solution is clinically feasible.

Key Words: IMRT, Inverse planning, Left breast, Internal mammary nodes

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 Supported in part by a grant from the Canadian Breast Cancer Foundation, British Columbia/Yukon Chapter.Presented in part at the Canadian Association of Radiation Oncologists Annual Meeting, September 9–12, 2004, Halifax, Canada.

PII: S0958-3947(06)00127-0

doi:10.1016/j.meddos.2006.05.003

Medical Dosimetry
Volume 31, Issue 4 , Pages 283-291, Winter 2006

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