Repeat computed tomography simulation to assess lumpectomy cavity volume during whole-breast irradiation.
OBJECTIVE
To determine whether the lumpectomy cavity (LPC) decreases in volume during whole-breast radiotherapy (RT) and what factors influence the decrease.


METHODS
Forty-three women with 44 breast lesions were prospectively enrolled. Eligible patients underwent lumpectomy followed by a CT simulation (CT1) within 60 days of surgery. Patients were treated to the entire breast to a dose of 45-50.4 Gy. After 21-23 treatments, a second planning CT simulation (CT2) was done. The LPC was contoured on CT2, and the volumes (LCV) were compared between CT1 and CT2.


RESULTS
The median LCV on CT1 and CT2 was 38.2 cm(3) and 21.7 cm(3), respectively. The median percent change and volume decrease between CT1 and CT2 was -32.0% and 11.2 cm(3), respectively (n = 44). The LCV decreased in 38 of 44 patients (86%). There was a significant correlation between initial LCV and decrease in volume (p = 0.001) and initial LCV and percent decrease in volume (p < 0.001). There was no correlation between time from surgery to CT1, to start of RT, or to CT2 and change in volume.


CONCLUSIONS
Patients who undergo lumpectomy almost always have a decrease in their LCV during whole-breast RT. There was a correlation between the initial LCV and decrease in volume on repeat CT simulation. Evaluating patients for this change can potentially lead to decreased doses of radiation to the remaining breast and other critical structures when delivering a small-field boost. Repeat CT simulation should be considered in patients with larger cavities or cavities near critical structures.
Flannery
Todd W
TW
Department of Radiation Oncology, University of Maryland School of Medicine, 22 S. Greene Street, Baltimore, MD 21201, USA.
Nichols
Elizabeth M
EM
Cheston
Sally B
SB
Marter
Kimberley J
KJ
Naqvi
Shahid A
SA
Markham
Kristen M
KM
Ali
Imran
I
Mohiuddin
Majid M
MM
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000601:surgery; D002278:Carcinoma in Situ / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000601:surgery; D018270:Carcinoma, Ductal, Breast / Q000000981:diagnostic imaging / Q000532:radiotherapy / Q000601:surgery; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D011446:Prospective Studies; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D013997:Time Factors; D014057:Tomography, X-Ray Computed / Q000379:methods