Abstract P4-13-01: Trends in primary management of invasive lobular carcinoma: An analysis of the National Cancer Database (NCDB)
Authors: Mukhtar Rita A , Hoskin Tanya L. , Habermann Elizabeth B. , Boughey Judy C. 
Published: March 2020

Abstract
Background: Invasive lobular carcinoma (ILC) is typically strongly hormone receptor (HR) positive, with unique characteristics. It has been shown to have poor response to neoadjuvant chemotherapy (NAC) and recent studies describe the benefits of neoadjuvant endocrine therapy (NET).
We sought to determine how the primary management strategy in ILC has changed over time, and the impact of ILC tumor biology on its management. Specifically, we hypothesized that use of NAC has decreased, while NET use increased. Additionally, we investigated whether NET is associated with higher rates of breast conservation surgery (BCS) than other primary management strategies.
Methods: We queried the NCDB from 2010-2016 and identified all women with ILC who underwent surgical therapy. Patients with stage IV disease were excluded. First course of treatment was classified as: NAC (chemotherapy starting 31-365 days before surgery), NET (short course defined as 7-30 days before surgery; long course defined as 31-365 days before surgery), and primary surgery. Tumors were considered HR+ if they were estrogen receptor and/or progesterone receptor positive. Trends over time in first treatment strategy were compared using Cochrane-Armitage tests. The association between first treatment strategy and use of BCS was assessed using multivariable logistic regression.
Results: Among 79,709 women with ILC, 94.0% were HR+/HER2-, 4.7% were HER2+, and 1.3% were triple negative. The most common primary treatment strategy was surgery (92.3%), but the percent undergoing systemic treatment before surgery increased from 7.1% in 2010 to 8.8% in 2016 (p&lt;0.001). The use of NAC increased significantly over the study period in patients with triple negative (12.1% in 2010 to 23.7% in 2016, p=0.007) and HER2+ (12.2% in 2010 to 29.1% in 2016, p&lt;0.001) ILC tumors. Among patients with HR+/HER2- tumors, however, the use of NAC decreased from 4.7% in 2010 to 4.2% in 2016, p=0.007, and the use of long course NET increased significantly, from 1.6% in 2010 to 2.7% in 2016, p&lt;0.001. The use of short course NET in HR+/HER2- patients remained very low over the study period (0.4% in 2010 to 0.5% in 2016, p=0.14).
Analyzing the HR+/HER2- subset, 48.4% (295/609) of patients undergoing long course NET with a cT2 tumor underwent BCS compared to 35.3% for primary surgery, 27.3% for NAC, and 24.8% for short course NET (p&lt;0.001). Long course NET was also associated with a higher BCS rate in cT3/cT4 tumors: 22.6% BCS for long course NET, 8.3% BCS for primary surgery, 9.6% BCS for NAC, 7.8% BCS for short course NET (p&lt;0.001). In multivariable analysis including a clinical T category by treatment interaction, long course NET was the only treatment that was associated with higher rates of BCS compared to primary surgery in cT2 (OR 1.51, 95% CI: 1.27-1.79) tumors, while both long course NET (OR 2.52, 95% CI: 1.97-3.22) and NAC (OR 1.54, 95% CI: 1.27-1.88) were associated with increased use of BCS in cT3/cT4 tumors, see Table.
Conclusions: The primary management of ILC is slowly evolving over time with a decrease in primary surgery. NAC use has increased appropriately in tumor subtypes with greatest potential benefit (i.e., triple negative or HER2 positive). In HR+/HER2- disease, NAC use has decreased, however NET use has increased and in cT2+ tumors NET was associated with higher rates of BCS.
Variable1Odds ratio for BCS (95% CI)p-valueAge, per 1 year increase1.04 (1.03-1.04)&lt;0.001Charlson-Deyo comorbidity score&lt;0.0011 vs 00.86 (0.82-0.90)2+ vs 00.72 (0.66-0.79)Grade2&lt;0.001Moderately/Poorly vsWell Differentiated0.91 (0.88-0.95)Clinical N category2&lt;0.001cN1 vs cN00.49 (0.46-0.52)cN2/cN3 vs cN00.41 (0.35-0.47)Multicentric&lt;0.001Yes vs No0.36 (0.34-0.38)Primary treatment by clinical T category2&lt;0.001For cT1 tumorsLong course NET vs primary surgery0.65 (0.51-0.83)NAC vs Primary surgery0.31 (0.24-0.41)Short course NET vs primary surgery0.85 (0.58-1.24)For cT2 tumorsLong course NET vs primary surgery1.51 (1.27-1.79)NAC vs primary surgery1.04 (0.90-1.20)Short course NET vs primary surgery0.53 (0.33-0.85)For cT3/cT4 tumorsLong course NET vs primary surgery2.52 (1.97-3.22)NAC vs primary surgery1.54 (1.27-1.88)Short course NET vs primary surgery0.79 (0.31-2.02)1Model additionally adjusted for year of diagnosis, race, ethnicity, and insurance status.2Unknown level included in the model but not reported
Citation Format: Rita A Mukhtar, Tanya L. Hoskin, Elizabeth B. Habermann, Judy C. Boughey. Trends in primary management of invasive lobular carcinoma: An analysis of the National Cancer Database (NCDB) [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-13-01.