R. A. Mukhtar1, J. M. Wong1, K. E. Fahrner-Scott1, C. Ewing1, M. D. Alvarado1, L. J. Esserman1, J. C. Boughey3, A. J. Chien4 1University Of California – San Francisco,General Surgery,San Francisco, CA, USA 3Mayo Clinic,General Surgery,Rochester, MN, USA 4University Of California – San Francisco,Hematology/Oncology,San Francisco, CA, USA
Introduction: Although neoadjuvant therapy (NAT) increases breast conserving surgery rates in women with breast cancer, its effectiveness in invasive lobular carcinoma (ILC) has been questioned. Since surgeons must identify which patients may benefit from a neoadjuvant approach, we sought to determine factors associated with NAT in women with ILC. Additionally, we explored associations with neoadjuvant chemotherapy versus neoadjuvant endocrine therapy use.
Methods: We queried a prospectively maintained surgical database and identified 679 cases of clinical stage 1-3 ILC treated at our institution from 1981-2017. We collected patient characteristics, tumor size, subtype, stage, therapy, and era of treatment. Data were analyzed in Stata 14.2 using t-tests for continuous variables, and chi-squared test for categorical variables.
Results: NAT was used in 21.8% of cases, with 12.4% receiving neoadjuvant chemotherapy and 9.4% receiving neoadjuvant endocrine therapy. Overall, women receiving NAT were significantly younger (57.3 vs 60.4 years, p = 0.0065), had larger tumors (2.9 vs 2.2 cm, p=0.0058), and had tumor subtype other than ER+ PR+ Her2- (p<0.001). NAT use significantly increased over time, initially consisting exclusively of neoadjuvant chemotherapy, but with an increasingly higher proportion of neoadjuvant endocrine therapy use in recent years (p=0.007, Figure).
We then analyzed ER+ Her2- cases (n=546, with 438 PR+ and 108 PR -), since NAT is questioned most in this group. Among these patients, NAT was significantly more common in younger women (56.8 vs 60.4 years, p=0.0033), and those with PR- disease (37.1% vs 17.8%, p<0.001). There was no difference in tumor size, treatment era, tumor grade, or histologic subtype. Lastly, within the ER+ Her2- cases who received NAT, those who received neoadjuvant chemotherapy were significantly younger (52.1 vs 61.9 years, p<0.0001), more likely to be premenopausal (45.1% vs 21.2%, p=0.01), and less likely to be diagnosed within the last 10 years (p=0.002). Among premenopausal women with ER+ Her2- ILC receiving NAT, the only factor associated with receipt of neoadjuvant endocrine therapy versus chemotherapy was era of diagnosis, with significantly less chemotherapy in the last ten years (p=0.034).
Conclusion: Although many studies question the utility of NAT in ILC, our data show a striking change in management patterns over time, with a steady increase in NAT use and a shift from neoadjuvant chemotherapy to neoadjuvant endocrine therapy, even in premenopausal women. The long term impact of this new management strategy in ILC, and the utility of the information garnered about response to therapy, warrant additional study.
