A comparison of Monte Carlo and Fermi-Eyges-Hogstrom estimates of heart and lung dose from breast electron boost treatment.
OBJECTIVE
Electrons are commonly used in the treatment of breast cancer primarily to deliver a tumor bed boost. We compared the use of the Monte Carlo (MC) method and the Fermi-Eyges-Hogstrom (FEH) algorithm to calculate the dose distribution of electron treatment to normal tissues.


METHODS
Ten patients with left-sided breast cancer treated with breast-conservation therapy at the University of California, San Francisco, were included in this study. Each patient received an electron boost to the surgical bed to a dose of 1,600 cGy in 200 cGy fractions prescribed to 80% of the maximum. Doses to the left ventricle (LV) and the ipsilateral lung (IL) were calculated using the EGS4 MC system and the FEH algorithm implemented on the commercially available Pinnacle treatment planning system. An anthromorphic phantom was irradiated with radiochromic film in place to verify the accuracy of the MC system.


RESULTS
Dose distributions calculated with the MC algorithm agreed with the film measurements within 3% or 3 mm. For all patients in the study, the dose to the LV and IL was relatively low as calculated by MC. That is, the maximum dose received by up to 98% of the LV volume was < 100 cGy/day. Less than half of the IL received a dose in excess of 30 cGy/day. When compared with MC, FEH tended to show reduced penetration of the electron beam in lung, and FEH tended to overestimate the bremsstrahlung dose in regions well beyond the electron practical range. These differences were clinically likely to be of little significance, comprising differences of less than one-tenth of the LV and IL volume at doses > 30 cGy and differences in maximum dose of < 35 cGy/day to the LV and 80 cGy/day to the IL.


CONCLUSIONS
From our series, using clinical judgment to prescribe the boost to the surgical bed after breast-conserving treatment results in low doses to the underlying LV and IL. When calculated dose distributions are desired, MC is the most accurate, but FEH can still be used.
Coleman
Joy
J
Department of Radiation Oncology, University of California, San Francisco, CA 94115, USA.
Park
Catherine
C
Villarreal-Barajas
J Eduardo
JE
Petti
Paula
P
Faddegon
Bruce
B
D000465:Algorithms; D001943:Breast Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D004583:Electrons / Q000627:therapeutic use*; D005260:Female; D006321:Heart; D006352:Heart Ventricles; D006801:Humans; D008168:Lung; D015412:Mastectomy, Segmental; D009010:Monte Carlo Method; D011829:Radiation Dosage; D011879:Radiotherapy Dosage