(P026) Is Cause-Specific Survival Similar for Estrogen Receptor- and Progesterone Receptor-Negative Early-Stage Invasive Lobular and Invasive Ductal Cancers? A National Registry SEER Database Study

April 30, 2015

For early-stage breast cancer cases with ER+ and PR+ status, histology was not associated with a difference in BCSS. Alternatively, ILC cases that were ER− or PR− had an increased BCSS compared with receptor-matched IDC cases. These findings add to the growing evidence supporting ILC as a more favorable histology, which is important for guiding treatment and prognostication.

Justin M. Mann, Weisi Yan, Guojiao Wu, Dattatreyudu Nori, Akkamma Ravi; New York Presbyterian-Weill Cornell Medical Center

BACKGROUND: Invasive ductal carcinoma (IDC) and invasive lobular carcinoma (ILC) are the two most common breast cancer histologies. IDC is more common and confers a worse prognosis than ILC. Biomarkers, including estrogen receptor (ER) and progesterone receptor (PR) status, improve prognostic accuracy and will likely be added to a future edition of the American Joint Committee on Cancer (AJCC) TNM classification. As a whole, patients with an ER- and PR-negative phenotype have a worse prognosis when compared with receptor-positive phenotypes. Using Surveillance, Epidemiology, and End Results (SEER) data, we performed statistical analysis to determine if receptor-matched statuses in IDC compared with ILC differ in overall outcome.

METHODS: A total of 50,658 cases of early-stage (I–IIB) breast cancer (groups = IDC and ILC) diagnosed from 1998–2002 who underwent breast conservation surgery were queried from the SEER 18 database. Patients without known ER or PR receptor status were excluded. Kaplan-Meier survival analysis and log-rank test were used to compare breast cancer cause-specific survival (BCSS).

RESULTS: There were 2,852 (5.63%) cases of ILC and 47,806 (94.37%) cases of IDC in this analysis. A total of 40,099 (79.2%) cases were ER+, and 34,901 (68.9%) cases were PR+. For ER+ cases, 60-month BCSS was 98% for ILC and 97.7% for IDC (P = .79). For ER− cases, 60-month BCSS was 95.5% for ILC and 89.7% for IDC (hazard ratio [HR] = 0.45; P = .02). For PR+ cases, 60-month BCSS was 98.3% for ILC and 97.8% for IDC (P = .35). For PR− cases, 60-month BCSS was 96.1% for ILC and 92.0% for IDC (HR = 0.77; P = .03).

CONCLUSION: For early-stage breast cancer cases with ER+ and PR+ status, histology was not associated with a difference in BCSS. Alternatively, ILC cases that were ER− or PR− had an increased BCSS compared with receptor-matched IDC cases. These findings add to the growing evidence supporting ILC as a more favorable histology, which is important for guiding treatment and prognostication.

Proceedings of the 97th Annual Meeting of the American Radium Society - americanradiumsociety.org