Factors affecting successful breast conservation for ductal carcinoma in situ.
BACKGROUND
Successful breast-conserving therapy in DCIS is restricted by high rates of residual disease resulting in the need for radiotherapy and/or re-excision. This study identifies patients with DCIS who are most at risk of compromised margins and of residual disease.


METHODS
All patients undergoing breast-conserving surgery for DCIS over a 6-year period were included. Method of diagnosis, mammographic size, pathological size, DCIS-margin distance and residual disease on re-excision were analysed.


RESULTS
One hundred and thirty-five patients underwent initial breast-conserving surgery for DCIS. The compromised margin rate was 72%, and the rate of residual disease on re-operation was 54%. On univariate analysis, underestimation of pathological size by mammography by >1 cm occurred in 40% of those with compromised margins undergoing a therapeutic operation compared to only 14% of those with clear margins (P = 0.02). However, on multivariate analysis only pathological size (P < 0.0001, OR = 1.0,95% CI 1.037-1.128) and lack of a preoperative diagnosis by core biopsy (P < 0.0001, OR = 5.3,95% CI 1.859-15.08) were predictive of compromised margins. The presence of residual disease on re-excision was associated with increasing pathological size (P < 0.0001, OR = 1.085,95% CI 1.038-1.134) and decreasing DCIS-margin distance (P = 0.03, OR = 6.694,95% CI 1.84-37.855). Twenty-nine percent (n = 13/45) of lesions < or =3 cm compared to 84% (n = 27/32) of lesions >3 cm had residual disease on re-operation (P < 0.0001). Residual disease was present in 62% (n = 34/55), 64% (n = 7/11) and 17% (n = 2/12) of patients with DCIS-margin distances < or =1, 1-2 and 2-5 mm, respectively.


CONCLUSIONS
Considerable underestimation of DCIS extent by mammography occurs in a high proportion of patients with compromised margins in breast conservation. Patients at particularly high risk of residual disease on re-excision are those with lesions >3 cm and those with DCIS-margin distances of < or = 2mm.
Dillon
Mary F
MF
Department of Surgery, St Vincent's University Hospital, Dublin, Ireland. maryfdillon@hotmail.com
Mc Dermott
Enda W
EW
O'Doherty
Ann
A
Quinn
Cecily M
CM
Hill
Arnold D
AD
O'Higgins
Niall
N
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000473:pathology* / Q000601:surgery; D018270:Carcinoma, Ductal, Breast / Q000473:pathology / Q000601:surgery; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000473:pathology* / Q000601:surgery; D005260:Female; D006801:Humans; D008327:Mammography; D008875:Middle Aged; D018365:Neoplasm, Residual / Q000175:diagnosis; D011379:Prognosis