Does a three-field electron/minitangent photon technique offer dosimetric advantages to a multifield, photon-only technique for accelerated partial breast irradiation?
OBJECTIVE
To determine whether 3-field electron/minitangent photons (mixed-modality) technique improved dosimetry compared with a multifield, photon-only technique for accelerated partial breast irradiation (APBI).


METHODS
Subjects were 20 breast cancer patients previously treated with photon-only APBI as part of a clinical trial to a dose of 38.5Gy/10 fractions in 5 days. Mixed-modality replans were compared with the photon-only plans with regards to planning target volume (PTV) coverage, conformity, homogeneity, and doses to normal tissues.


RESULTS
The mixed-modality plans had similar PTV coverage, with more conformality, and reduced the volume of the ipsilateral breast receiving > or =95% and > or =50% doses, but had the pitfalls of less homogeneity and increased exposure of the ipsilateral lung and heart receiving low-dose radiation because of the exit dose of the electron beam. Factors associated with this increase were medial/deep-seated tumor beds, large tumor beds with PTV/Ipsilateral Breast ratio >20%, and use of high energy electrons.


CONCLUSIONS
The three-field electron/minitangent photon APBI technique was more conformal and reduced the dose to the ipsilateral breast but had the disadvantage of exposing increased volumes of heart and ipsilateral lung to low-dose radiation compared with the photon-only technique.
Mydin
Aminudin R
AR
Vancouver Island Centre, Victoria, British Columbia, Canada.
Gaffney
Helene
H
Bergman
Alanah
A
McDonald
Rachel
R
Beckham
Wayne A
WA
Truong
Pauline T
PT
Olivotto
Ivo A
IA
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy* / Q000601:surgery; D003131:Combined Modality Therapy; D005260:Female; D006801:Humans; D008875:Middle Aged; D009367:Neoplasm Staging; D017785:Photons / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods; D014057:Tomography, X-Ray Computed