Vol 27, No 1 (2022)
Research paper
Published online: 2022-01-24

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Dose to contralateral breast from whole breast irradiation by automated tangential IMRT planning: comparison of flattening-filter and flattening-filter-free modes

Ichiro Ogino1, Hidetaka Seto12, Daisuke Shigenaga1, Masaharu Hata3
Rep Pract Oncol Radiother 2022;27(1):113-120.


Background: The most common secondary cancer is contralateral breast (CLB) cancer after whole breast irradiation (WBI). The aim of this study was to quantify the reduction of CLB dose in tangential intensity modulated radiotherapy (t-IMRT) for WBI using flattening-filter-free (FFF) beams.

Materials and methods: We generated automated planning of 20 young breast cancer patients with limited user interaction. Dose-volume histograms of the planning target volume (PTV), ipsilateral lung, heart, and CLB were calculated. The dose of PTV, the most medial CLB point, and the CLB point below the nipple was measured using an ionization chamber inserted in a slab phantom. We compared the two t-IMRT plans generated by FFF beams and flattening-filter (FF) beams.

Results: All plans were clinically acceptable. There was no difference in the conformal index, the homogeneity for FFF was significantly worse. For the ipsilateral lung, the maximum dose (Dmax) was significantly higher; however, V20 showed a tendency to be lower in the FFF plan. No differences were found in the Dmax and V30 to the heart of the left breast cancer. FF planning showed significantly lower Dmax and mean dose to the CLB. In contrast to the calculation results, the measured dose of the most medial CLB point and the CLB point below the nipple were significantly lower in FFF mode than in FF mode, with mean reductions of 21.1% and 20%, respectively.

Conclusions: T-IMRT planning using FFF reduced the measured out-of-field dose of the most medial CLB point and the CLB point below the nipple.

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  1. Boice JD, Harvey EB, Blettner M, et al. Cancer in the contralateral breast after radiotherapy for breast cancer. N Engl J Med. 1992; 326(12): 781–785.
  2. Gao X, Fisher SG, Emami B. Risk of second primary cancer in the contralateral breast in women treated for early-stage breast cancer: a population-based study. Int J Radiat Oncol Biol Phys. 2003; 56(4): 1038–1045.
  3. Stovall M, Smith SA, Langholz BM, et al. Women's Environmental, Cancer, and Radiation Epidemiology Study Collaborative Group. Dose to the contralateral breast from radiotherapy and risk of second primary breast cancer in the WECARE study. Int J Radiat Oncol Biol Phys. 2008; 72(4): 1021–1030.
  4. Wijesooriya K. Part I: Out-of-field dose mapping for 6X and 6X-flattening-filter-free beams on the TrueBeam for extended distances. Med Phys. 2019; 46(2): 868–876.
  5. Kragl G, Baier F, Lutz S, et al. Flattening filter free beams in SBRT and IMRT: dosimetric assessment of peripheral doses. Z Med Phys. 2011; 21(2): 91–101.
  6. Dobler B, Maier J, Knott B, et al. Second Cancer Risk after simultaneous integrated boost radiation therapy of right sided breast cancer with and without flattening filter. Strahlenther Onkol. 2016; 192(10): 687–695.
  7. Karpf D, Sakka M, Metzger M, et al. Left breast irradiation with tangential intensity modulated radiotherapy (t-IMRT) versus tangential volumetric modulated arc therapy (t-VMAT): trade-offs between secondary cancer induction risk and optimal target coverage. Radiat Oncol. 2019; 14(1): 156.
  8. Zhang HW, Hu Bo, Xie C, et al. Dosimetric comparison of three intensity-modulated radiation therapies for left breast cancer after breast-conserving surgery. J Appl Clin Med Phys. 2018; 19(3): 79–86.
  9. Joosten A, Matzinger O, Jeanneret-Sozzi W, et al. Evaluation of organ-specific peripheral doses after 2-dimensional, 3-dimensional and hybrid intensity modulated radiation therapy for breast cancer based on Monte Carlo and convolution/superposition algorithms: implications for secondary cancer risk assessment. Radiother Oncol. 2013; 106(1): 33–41.
  10. Aziz MH, Schneider F, Clausen S, et al. Can the risk of secondary cancer induction after breast conserving therapy be reduced using intraoperative radiotherapy (IORT) with low-energy x-rays? Radiat Oncol. 2011; 6: 174.
  11. Donovan EM, James H, Bonora M, et al. Second cancer incidence risk estimates using BEIR VII models for standard and complex external beam radiotherapy for early breast cancer. Med Phys. 2012; 39(10): 5814–5824.
  12. Pignol JP, Keller BM, Ravi A. Doses to internal organs for various breast radiation techniques--implications on the risk of secondary cancers and cardiomyopathy. Radiat Oncol. 2011; 6: 5.
  13. Purdie TG, Dinniwell RE, Letourneau D, et al. Automated planning of tangential breast intensity-modulated radiotherapy using heuristic optimization. Int J Radiat Oncol Biol Phys. 2011; 81(2): 575–583.
  14. Radiation Therapy Oncology Group: Breast cancer atlas for radiation therapy planning: Consensus definitions. https://www.nrgoncology.org/ciro-breast (July 18 2021).
  15. Kusters JM, Bzdusek K, Kumar P, et al. Automated IMRT planning in Pinnacle : A study in head-and-neck cancer. Strahlenther Onkol. 2017; 193(12): 1031–1038.
  16. Taylor C, Correa C, Duane FK, et al. Early Breast Cancer Trialists’ Collaborative Group. Estimating the Risks of Breast Cancer Radiotherapy: Evidence From Modern Radiation Doses to the Lungs and Heart and From Previous Randomized Trials. J Clin Oncol. 2017; 35(15): 1641–1649.
  17. Fogliata A, De Rose F, Franceschini D, et al. Critical Appraisal of the Risk of Secondary Cancer Induction From Breast Radiation Therapy With Volumetric Modulated Arc Therapy Relative to 3D Conformal Therapy. Int J Radiat Oncol Biol Phys. 2018; 100(3): 785–793.
  18. Haciislamoglu E, Cinar Y, Gurcan F, et al. Secondary cancer risk after whole-breast radiation therapy: field-in-field versus intensity modulated radiation therapy versus volumetric modulated arc therapy. Br J Radiol. 2019; 92(1102): 20190317.
  19. Schneider U, Sumila M, Robotka J, et al. Dose-response relationship for breast cancer induction at radiotherapy dose. Radiat Oncol. 2011; 6: 67.
  20. Abo-Madyan Y, Aziz MH, Aly MM, et al. Second cancer risk after 3D-CRT, IMRT and VMAT for breast cancer. Radiother Oncol. 2014; 110(3): 471–476.
  21. Guo B, Shah C, Xia P. Automated planning of whole breast irradiation using hybrid IMRT improves efficiency and quality. J Appl Clin Med Phys. 2019; 20(12): 87–96.
  22. Torres MA, Gogineni K, Howard DH. Intensity-Modulated Radiation Therapy in Breast Cancer Patients Following the Release of a Choosing Wisely Recommendation. J Natl Cancer Inst. 2020; 112(3): 314–317.