Abstract PD04-07: The Ki-67 labeling index predicts the risk of recurrence of DIN patients treated with radiotherapy following breast conserving surgery

• Published in: Cancer research (Chicago, Ill.) Ill.), 2012-12, Vol.72 (24_Supplement), p.PD04-07-PD04-07
• Main Authors: Pruneri, G, Lazzeroni, M, Guerrieri-Gonzaga, A, Botteri, E, Leonardi, MC, Rotmensz, N, Serrano, D, Varricchio, C, Disalvatore, L, Del Castillo, A, Viale, G, Bonanni, B
• Format: Article
• Language: English
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.SABCS12-PD04-07

Purpose: To investigate the prognostic relevance of Ki-67 labeling index (LI) in patients with Ductal Intraepithelial Neoplasia (DIN) of the breast. Patients and Methods: From January 1997 to December 2007, histological samples and clinical data of 1,171 consecutive patients operated for DIN in a single institution were collected. The study was performed in accordance with the REMARK criteria. The independent prognostic role of Ki-67 LI was evaluated with a multivariable Cox regression model. A restricted cubic splines model was used to evaluate the prognostic role of Ki-67 LI as a continuous variable. Results: Overall, median age was 52 years (range 23–88), median Ki-67 LI 15% (range 1–80) and median follow-up 86 months (range 1–192). Overall, 549 (46.9%) women were premenopausal at the time of diagnosis. A total of 872 (74.5%) patients underwent breast conservative surgery (BCS). Whole breast radiotherapy (RT) was administered to 356 patients, and 506 patients received low dose tamoxifen (HT) (20mg/week or 5 mg/day). Histologically, most of the cases had a prevalent solid or cribriform pattern (75%), were DIN1c and DIN2 (80%), ER+ (80%), and showed a high (≥14%) Ki-67 LI (54%). The prevalence of the immunohistochemically defined subtypes was 39.5% for Luminal (Lum) A, 22.8% for LumB/Her-2−, 18.2% for LumB/Her2+, 15.8% for Her-2+, and 3.7% for Triple Negative. Overall, the rate of invasive and in situ recurrences (5-year cumulative incidence) was 10.7%. Firstly, we analyzed the role of RT according to Ki-67 LI as a continuous variable in DIN2/DIN3 patients after BCS. The curve and interaction model was adjusted for menopause, BMI, Her-2 and ER status, histological grade, presence of necrosis and microcalcifications, and HT. RT was protective in subjects with DIN with Ki-67 LI ≥14%, while no evidence of effect was seen for Ki-67 LI