Abstract P2-01-12: Impact of the ASOCOG Z0011 trial on a multi-institutional mixed practice setting
Authors: Kachare Swapnil D , Vohra Nasreen A , Verbanac Kathyrn M , Fitzgerald Timothy L , Zervos Emmanuel E , Wong Jan H 
Published: May 2015

Background

The ASOCOG Z0011 trial is widely considered to be practice changing, but reports to date on the adoption of Z0011 are largely confined to tertiary academic institutions with breast cancer surgical specialty services. The aim of this study was to assess the impact of Z0011 on the care of breast cancer patients in a mixed academic/ non-academic practice setting.

Methods

All patients who underwent surgical treatment for breast cancer in the Vidant Healthcare System, a multi-county network, between the years January 1, 2009 and September 20, 2013 were identified. Patients with Stage IV disease and ductal carcinoma in situ were excluded.

Results

One thousand six hundred four patients met initial inclusion criteria, 661 in the pre-Z0011 period and 973 in the post-Z0011 period. The majority of patients were female (99%) and Caucasian (65%). Infiltrating ductal cancer (67%) was the most common tumor type. Tumors on average were 23mm in size with the majority being ER (74%), PR (63%) positive and Her2 (82%) negative. Most patients had node negative disease (73%). Table 1 summarizes the characteristics of the pre- and post-Z0011 study populations.

Patient and Tumor CharacteristicsVariablePre-Z0011Post-Z0011p valueFemale (%)656 (99.2)968 (99.4)0.86Race (%)  0.49White448 (67.8)642 (65.9) Black205 (31.0)314 (32.2) Mean size (mm)19.922.30.06Histology (%)  0.07Infiltrating ductal cancer434 (65.7)663 (68.1) Infiltrating lobular cancer30 (4.5)62 (6.4) ER Positive (%)484 (73.3)722 (74.2)0.92PR Positive (%)406 (61.5)622 (63.9)0.61Her2 Negative (%)304 (78.4)897 (83.5)0.01Triple Negative Subtype (%)83 (23.9)168 (18.9)0.07Node Positive Status175 (27.5)926 (26.7)0.71

A total of 142 patients met Z0011 criteria, with T1-2 disease, underwent partial mastectomy and had a positive SNB. There were a similar number of patients who met Z00111 criteria in the pre- (n=63) and post-Z0011 (n=79) periods, p&gt;0.05. In the post-Z0011 period, patients were more likely to undergo SNB alone (56 vs. 19%, p&lt;0.001). Post-Z0011 the decrease in ALND was in those who had immediate ALND (34% vs. 71%), with no substantive change in the delayed group (10.1 vs. 9.5%), p&lt;0.001. Patient who underwent SNB alone had smaller tumors (22 vs. 32mm, p&lt;0.001), but similar histologic subtypes (p=0.60) and receptor status (p≥0.15) as compared to patients who underwent SNB with ALND. Over the entire study period patients in an academic practice were less likely to undergo SNB alone (31 vs. 43%). In the post-Z0011 period, patients cared for in an academic practice had an increase in SNB alone from year 1 (2012) to year 2 (2013) (40% to 57%), while the non-academic practices had a decrease in SNB alone from year 1 to year 2, (63% to 56%).

Conclusion

In this mixed practice setting there was an overall decrease in ALND in T1/T2 patients with low metastatic axillary burden following publication of Z0011. Immediately post-Z0011 the non-academic practices more rapidly adopted SNB alone, however these differences were no longer apparent two years following Z0011. Continued longitudinal studies will further assess the variability in the incorporation of Z0011 among various surgical practices.

Citation Format: Swapnil D Kachare, Nasreen A Vohra, Kathyrn M Verbanac, Timothy L Fitzgerald, Emmanuel E Zervos, Jan H Wong. Impact of the ASOCOG Z0011 trial on a multi-institutional mixed practice setting [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P2-01-12.