External-beam accelerated partial breast irradiation using multiple proton beam configurations.
OBJECTIVE
To explore multiple proton beam configurations for optimizing dosimetry and minimizing uncertainties for accelerated partial breast irradiation (APBI) and to compare the dosimetry of proton with that of photon radiotherapy for treatment of the same clinical volumes.


METHODS
Proton treatment plans were created for 11 sequential patients treated with three-dimensional radiotherapy (3DCRT) photon APBI using passive scattering proton beams (PSPB) and were compared with clinically treated 3DCRT photon plans. Monte Carlo calculations were used to verify the accuracy of the proton dose calculation from the treatment planning system. The impact of range, motion, and setup uncertainty was evaluated with tangential vs. en face beams.


RESULTS
Compared with 3DCRT photons, the absolute reduction of the mean of V100 (the volume receiving 100% of prescription dose), V90, V75, V50, and V20 for normal breast using protons are 3.4%, 8.6%, 11.8%, 17.9%, and 23.6%, respectively. For breast skin, with the similar V90 as 3DCRT photons, the proton plan significantly reduced V75, V50, V30, and V10. The proton plan also significantly reduced the dose to the lung and heart. Dose distributions from Monte Carlo simulations demonstrated minimal deviation from the treatment planning system. The tangential beam configuration showed significantly less dose fluctuation in the chest wall region but was more vulnerable to respiratory motion than that for the en face beams. Worst-case analysis demonstrated the robustness of designed proton beams with range and patient setup uncertainties.


CONCLUSIONS
APBI using multiple proton beams spares significantly more normal tissue, including nontarget breast and breast skin, than 3DCRT using photons. It is robust, considering the range and patient setup uncertainties.
Wang
Xiaochun
X
Department of Radiation Physics, The University of Texas, M D Anderson Cancer Center, Houston, TX 77030, USA.
Amos
Richard A
RA
Zhang
Xiaodong
X
Taddei
Phillip J
PJ
Woodward
Wendy A
WA
Hoffman
Karen E
KE
Yu
Tse Kuan
TK
Tereffe
Welela
W
Oh
Julia
J
Perkins
George H
GH
Salehpour
Mohammad
M
Zhang
Sean X
SX
Sun
Tzou Liang
TL
Gillin
Michael
M
Buchholz
Thomas A
TA
Strom
Eric A
EA
D001940:Breast / Q000473:pathology / Q000528:radiation effects*; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D009010:Monte Carlo Method; D009068:Movement; D017785:Photons / Q000627:therapeutic use; D061766:Proton Therapy; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D012119:Respiration; D012542:Scattering, Radiation; D012867:Skin / Q000528:radiation effects; D047368:Tumor Burden; D011522:Protons
D011522:Protons