Variation in post-surgical lumpectomy cavity volume with delay in initiation of breast irradiation because of chemotherapy.
OBJECTIVE
The addition of a radiotherapy boost has been shown to improve local control in breast conservation therapy. Three dimensional planning provides more accurate targeting of the operative bed than clinical setup using the lumpectomy scar. However, contraction of the lumpectomy cavity over time may have implications for the volume of tissue included in the boost field.


METHODS
The clinical variables and treatment planning volumes for patients receiving whole-breast radiotherapy at a single institution between July 1, 2006, and December 31, 2007 were analyzed retrospectively.


RESULTS
Of the 93 patients identified, 29 received chemotherapy (CTX) and 64 did not; CTX was sequenced before radiotherapy in all patients. Patients receiving CTX were more likely to have higher T and N stage and a longer interval between definitive breast surgery and radiation. The lumpectomy specimens of women receiving CTX trended toward being larger than those of women not receiving CTX (113.4 cm(3) vs. 74.6 cm(3), p = 0.08). Despite this, the volume of the lumpectomy cavity measured on computed tomography was smaller in patients receiving CTX (9.1cm(3) vs. 16.8 cm(3), p = 0.02), as was the volume of the planning target volume (56.6 cm(3) vs. 79.9 cm(3), p = 0.02).


CONCLUSIONS
Patients receiving CTX were at higher risk for local recurrence. However, as a result of lumpectomy bed contraction, these patients received a boost to a smaller volume than patients not receiving CTX. This finding is counterintuitive and supports re-evaluation of the optimal size of the boost field. In addition, these results may have implications for patients treated with partial breast irradiation.
Rush University Medical Center, Department of Radiation Oncology, Chicago, IL, USA. Jonathan1804@gmail.com
Jonathan B
JB
Strauss
Benjamin T
BT
Gielda
Sea S
SS
Chen
Anand P
AP
Shah
Ross A
RA
Abrams
Katherine L
KL
Griem
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001940:Breast / Q000187:drug effects / Q000473:pathology / Q000528:radiation effects / Q000601:surgery; D001943:Breast Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy / Q000601:surgery; D003131:Combined Modality Therapy / Q000379:methods; D003286:Contracture; D005260:Female; D006801:Humans; D015412:Mastectomy, Segmental; D008875:Middle Aged; D009367:Neoplasm Staging; D009929:Organ Size / Q000187:drug effects / Q000528:radiation effects; D012189:Retrospective Studies