Abstract P3-03-34: Sentinel lymph node biopsy is unnecessary in ductal carcinoma in situ patients diagnosed by biopsy

Abstract

Abstract Background: Japanese Breast Cancer Society Clinical Practice Guidelines for Breast Cancer 2018 state that sentinel lymph node (SN) biopsy is unnecessary for patients treated with breast-conserving therapy (BCT) and with an expected final pathological diagnosis of ductal carcinoma in situ (DCIS). Regardless of whether they were diagnosed with DCIS by biopsy before surgery, 78% of patients currently undergo axial procedures in Japan because invasive lesions may be detected in surgical specimens. This study examined whether SN biopsy can be omitted in DCIS patients diagnosed by biopsy and which factors are associated with invasion. Methods: Patients who underwent definitive surgery for DCIS diagnosed by preoperative biopsy at our institution from May 2004 to January 2018 were investigated retrospectively. The factors associated with upstaging to invasive cancer from DCIS were examined with Fisher's exact test and the t-test. (Age, Tumor size, Operation (Mastectomy or BCT), Biopsy method (Core Needle Biopsy or Vaccume-Assisted Biopsy), Mammography (ditected or not-detected), Ultrasound (ditected or not-detected, mass or non-mass), Comedo, ER, PgR, HER2) Results: A total of 311 patients were enrolled in this study, of whom 277 (89.1%) underwent SN; six of these (2.2%) had SN metastasis. All six cases were upstaging to invasive cancer: five (1.8%) had micrometastasis and one had macrometastasis (0.4%). From a surgical viewpoint, SN metastasis were detected in 3/161 (1.9%) cases treated with mastectomy and 3/150 (2.4%) cases treated with BCT. Although all three cases treated with BCT had micrometastasis, one case treated with mastectomy had macrometastasis (the other two cases had micrometatastasis). A total of 80/311 cases (25.7%) upstaged to invasive cancer and the only predictor of invasion was tumor size on images (p=0.0002). We could not determine the effective cut-off for tumor size because the area under the receiver operating characteristic curve was 0.63<0.70. Tabule 1.Tumor size on images was the only predictor of invasion. Upstaging (N=80)DCIS (N=231)P valueTumor size: mm (95% Confidence Interval)47.5 (41.9-53.2)33.9 (30.5-37.3)0.0002 Conclusion: Tumor size was found to be the only predictor of invasion. Only 2.2% of DCIS patients had SN metastasis despite the fact that 25.7% patients were upstaged to invasive cancer. We conclude that SN biopsy is not necessary for DCIS patients diagnosed by biopsy. Citation Format: Uemoto Y, Kondo N, Wanifuchi-Endo Y, Hisada T, Nishikawa S, Katagiri Y, Kato H, Takahashi S, Toyama T. Sentinel lymph node biopsy is unnecessary in ductal carcinoma in situ patients diagnosed by biopsy [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-03-34.