Impact of the number of cautionary and/or unsuitable risk factors on outcomes after accelerated partial breast irradiation.
OBJECTIVE
To examine clinical outcomes of accelerated partial-breast irradiation (APBI) stratified by the number of American Society for Radiation Oncology consensus statement cautionary/unsuitable risk factors (RFs) present.


METHODS
A total of 692 patients were treated with APBI at a single institution between April 1993 and January 2012 using interstitial (n=195), balloon (n=292), and 3-dimensional conformal radiation therapy (n=205) techniques. Clinical outcomes were evaluated by risk group and number of RFs.


RESULTS
Median follow-up was 5.2 years (range, 0-18.3 years). Most patients were classified as suitable (n=240, 34%) or cautionary (n=343, 50%) risk, whereas 16% (n=109) were unsuitable. In patients with increasing total RFs (1 RF, 2 RF, 3+ RF), higher rates of grade 3 histology (10% vs 18% vs 32%, P<.001), estrogen receptor negativity (0 vs 12% vs 29%, P<.001), close/positive margins (0 vs 6% vs 17%, P<.001), and use of adjuvant chemotherapy (3% vs 12% vs 33%, P<.001) were noted. When pooling cautionary and unsuitable patients, increased ipsilateral breast tumor recurrence/regional recurrence was most notable for patients with 3 or more combined RFs versus 2 or fewer combined RFs (P<.001).


CONCLUSIONS
Patients with 3 or more cautionary or unsuitable RFs may be at risk for higher local, regional, and distant recurrence after breast-conserving therapy using APBI. Patients with 2 or fewer total RFs have 98% locoregional control at 5 years. Inclusion of total number of RFs in future risk stratification schemes for APBI may be warranted.
Department of Radiation Oncology, Beaumont Cancer Institute, Oakland University William Beaumont School of Medicine, Royal Oak, Michigan, USA.
Jessica
J
Wobb
J Ben
JB
Wilkinson
Chirag
C
Shah
Christina
C
Mitchell
Michelle
M
Wallace
Hong
H
Ye
Jannifer
J
Stromberg
Inga
I
Grills
Peter Y
PY
Chen
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000379:methods; D001943:Breast Neoplasms / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000188:drug therapy / Q000473:pathology / Q000532:radiotherapy*; D032921:Consensus; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D016609:Neoplasms, Second Primary; D018579:Patient Selection; D017410:Practice Guidelines as Topic; D018787:Radiation Oncology; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000379:methods; D012307:Risk Factors; D047368:Tumor Burden