Toxicity of three-dimensional conformal radiotherapy for accelerated partial breast irradiation.
OBJECTIVE
To assess the incidence and severity of late normal tissue toxicity using three-dimensional conformal radiotherapy to deliver accelerated partial breast irradiation.


METHODS
A total of 60 patients were treated with three-dimensional conformal radiotherapy for accelerated partial breast irradiation. Treatment planning and delivery were in strict accordance with the technique and specified dose-volume constraints of the National Surgical Adjuvant Breast and Bowel Project B-39/Radiation Therapy Oncology Group 0413 protocol. Late toxicity was evaluated according to the Radiation Therapy Oncology Group grading schema. The cosmetic outcome was scored using the Harvard criteria. Univariate logistic regression analysis was performed to evaluate the correlation of dosimetric variables with outcome.


RESULTS
At a median follow-up of 15 months, moderate-to-severe late toxicity developed in 10% of patients. The most pronounced late toxicity was subcutaneous fibrosis: 25% Grade 2-4 and 8.3% Grade 3-4. The modified planning tumor volume/whole breast volume ratio, ratio of the volume of breast tissue receiving 5%, 20%, 50%, and 80% of the prescription dose to the whole breast volume, and maximal dose within the breast correlated with the development of fibrosis (p = .10, p = .03, p = .04, p = .06, p = .09, and p = .046, respectively). The overall cosmetic outcome was good to excellent in 81.7%, fair in 11.7%, and poor in 6.7%. The presence of subcutaneous fibrosis, modified planning tumor volume/whole breast volume ratio, ratio of the volume of breast tissue receiving 5% and 20% of the prescription dose to the whole breast volume, and pathologic specimen volume correlated with the risk of a fair/poor cosmetic outcome (p < .001, p = .02, p = .05, p = .04, p = .01, respectively).


CONCLUSIONS
The three-dimensional conformal radiotherapy technique for accelerated partial breast irradiation as specified in the National Surgical Adjuvant Breast and Bowel Project B-39/Radiation Therapy Oncology Group 0413 protocol resulted in a remarkably high rate of moderate-to-severe late normal tissue effects, despite the relatively brief follow-up period. The toxic events correlated clearly with several dose-volume parameters.
Hepel
Jaroslaw T
JT
Department of Radiation Oncology, Tufts University, Tufts Medical Center, Boston, MA, USA. jhepel@tuftsmedicalcenter.org
Tokita
Mari
M
MacAusland
Stephanie G
SG
Evans
Suzanne B
SB
Hiatt
Jessica R
JR
Price
Lori Lyn
LL
DiPetrillo
Thomas
T
Wazer
David E
DE
D000368:Aged; D000369:Aged, 80 and over; D001940:Breast / Q000473:pathology / Q000528:radiation effects*; D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D005355:Fibrosis / Q000473:pathology; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D011832:Radiation Injuries / Q000473:pathology*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000009:adverse effects* / Q000379:methods; D012044:Regression Analysis; D040521:Subcutaneous Tissue / Q000473:pathology / Q000528:radiation effects*