Abstract P1-22-07: Surgical outcomes of lobular carcinoma in situ diagnosed on core biopsy in Dutch women between 2011 and 2020

Abstract

Abstract Background Lobular carcinoma in situ (LCIS) can be divided into classic LCIS and pleomorphic LCIS. Current treatment guidelines recommend that pleomorphic LCIS should be treated as a ductal carcinoma in situ (DCIS). This is because of the high upgrade rate to DCIS or invasive carcinoma. Classic LCIS, on the contrary, has a low upgrade rate. Active surveillance, such as an annual mammogram, is sufficient. Widely divergent upgrade rates have been published for both classic and pleomorphic LCIS, probably due to selection bias and the limited number of patients included in each study. We report a population based study in patients with a biopsy-based diagnosis of LCIS. Methods In this retrospective nationwide cohort study, patients with a primary diagnosis of LCIS in the period from 2011 to 2020 were identified. Patients with a concurrent high-risk lesion or with a history of a high-risk lesion in the same breast were excluded. Data were received from the Dutch Pathology Registry. In addition to classic LCIS and pleomorphic LCIS, there was a residual group of non-classical LCIS. Results 1185 biopsies from 1183 patients were included in the study. All patients were female. In two patients, the LCIS was bilateral. 1024 biopsies contained classic LCIS, 130 pleomorphic LCIS, and 31 non-classic LCIS. The mean age was 54.7 years for classic LCIS, 60.8 for pleomorphic LCIS, and 60.6 for non-classic LCIS. Of the classic LCIS patients 18.4% underwent surgery. This was 83.1% for pleomorphic LCIS and 83,9% for non-classic LCIS. Of the classic LCIS , 34.0 % had an upgrade to invasive carcinoma or DCIS. This was 31.5 % for pleomorphic LCIS and 30.8 % for non-classic LCIS. A high incidence of invasive lobular cancer (ILC) was found with the invasive cancers being predominantly ER positive and HER2 negative (table). Conclusions Between 2011 and 2020, the incidence of biopsies with LCIS was 119 per year (For comparison, the annual incidence of DCIS biopsies is approximately 2500 per year). Of all biopsies, approximately 11 % were pleomorphic LCIS. Approximately 2.5 % of all biopsies were non-classic LCIS. The upgrade rate for classic LCIS, pleomorphic LCIS, and non-classic LCIS was comparable, however the operation rates were not comparable. In contrast to pleomorphic and non-classic LCIS, only selected cases of classic LCIS were followed up with surgical operation. Surgical outcomeClassic LCISPleomorphic LCISNon-classic LCISTotalP-valueN=188N=108N=26N=322Mean Age (SD)54.4 (9.3)60.6 (8.6)60.4 (6.8)57.0 (9.3)Type surgery N (%)0.269Lumpectomy158 (84.0)83 (76.9)23 (88.5)264 (82.0)Ablation30 (16.0)25 (23.1)3 (11.5)58 (18.0)Upgraded N (%)0.915Yes64 (34.0)34 (31.5)8 (30.8)106 (32.9)No124 (66.0)74 (68.5)18 (69.2)216 (67.1)Type upgrade N0.815DCIS187126classic ILC3623564Pleomorphic ILC0101Invasive carcinoma NST82212Tubular carcinoma1101Papillary carcinoma1001 Citation Format: Pieter J Westenend, Crystal Kerkhoven, Claudia JC Meurs, Sabine Siesling. Surgical outcomes of lobular carcinoma in situ diagnosed on core biopsy in Dutch women between 2011 and 2020 [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-22-07.