SS 21 - Breast 2 - Biology and SBRT
135 - Minimal Increases in Tumor Infiltrating Lymphocytes Despite Excellent Tumor Responses After Pre-Operative Accelerated Partial Breast Irradiation in Early Stage ER+ Breast Cancer Patients
Tuesday, October 23
8:15 AM - 8:25 AM
Location: Room 214 A/B
Carmen Bergom, MD, PhD
Medical College of Wisconsin
Medical College of Wisconsin: Assistant Professor: Employee, Resident Physician: Employee
Minimal Increases in Tumor Infiltrating Lymphocytes Despite Excellent Tumor Responses After Pre-Operative Accelerated Partial Breast Irradiation in Early Stage ER+ Breast Cancer Patients
C. Bergom, J. Jorns, T. R. Kelly, J. A. Bovi, A. Kong, W. C. Chen, E. S. Paulson, and A. D. Currey; Medical College of Wisconsin, Milwaukee, WI
Purpose/Objective(s): Pre-treatment local immune activity in breast cancers, as measured by tumor infiltrating lymphocytes (TILs), has been shown to correlate with improved outcomes in both HER2+ and triple negative breast cancer (TNBC). In addition, treatments that stimulate increased %TILs in TNBC have a positive impact on patient outcomes. However, the role of TILs in predicting outcomes in ER/PR+ breast cancer is less well-established. Radiation therapy (RT) has been reported to enhance immune cell infiltration of tumors. However, breast cancer RT is typically given post-operatively, limiting the ability to determine whether RT enhances the %TILs in breast tumors. Here we examine %TILs and tumor responses after pre-operative accelerated partial breast irradiation (APBI) as part of a clinical trial to determine whether RT enhances %TILs and whether this correlates with RT response.
Materials/Methods: The % stromal TILs and % tumor cellularity were assessed blindly by a breast pathologist in biopsy and post-RT surgical specimens from an in-house pre-operative APBI trial in patients with ER/PR+ breast cancer (NCT02728076). Patients received APBI to 30 Gy in 5 fractions on non-consecutive days, followed by surgery after ≥5 weeks. Correlation between %TILs and pathologic response was assessed.
Results: Sixteen patients were available for analysis. Median age was 69 (53-80). All patients were clinically node-negative and ER/PR+; one was HER2+. Median MRI tumor size was 9 mm (6-14 mm); 63% were grade 2 and 37% grade 1. 10/16 patients had 21-gene recurrence scores (RS), with 1 intermediate and 1 high RS; 3 patients received adjuvant chemotherapy and all received endocrine therapy. Most patients demonstrated robust tumor responses to RT, with 7/16 (44%) having ≤5% cellularity after RT. With a median cellularity at diagnosis of 45%, 14/16 (88%) had a >20% decrease in cellularity, with only 1 patient having no decrease. All tumors had low levels of TILs (median 5%, range 1-10%). There was minimal change in %TILs from biopsy to surgery, with 5/16 (31%) patients having increase of TILs ≥4%, and the remainder with no %TIL increase. There was no correlation between %TILs (at diagnosis or post-RT) and tumor response to RT or 21-gene RS.
Conclusion: Pre-operative APBI in ER/PR+ breast cancers did not significantly increase the %TILs after 5 weeks, despite leading to significant tumor responses as measured by % cellularity. Low %TILs were seen, with no more than a 10% TIL increase after RT. These findings suggest only mild immune changes, as measured by TILs, occur from RT in this mostly favorable cohort of ER/PR+ cancers, or that the time point for surgery may have missed maximum TIL levels. More studies in similar cohorts and in other breast cancer subtypes are warranted to examine the role of pre-operative RT on breast cancer immune responses.
Author Disclosure: C. Bergom: None. J. Jorns: None. T.R. Kelly: None. A. Kong: None. E.S. Paulson: None. A.D. Currey: Honoraria; Wisconsin Oncology Network.