Abstract P4-12-09: Improvement of survival with radiation therapy in early stage triple negative breast cancer patients with high level of tumor infiltrating lymphocytes
Authors: Mouabbi Jason Aboudi , Chand Momal , Sakhi Ramen , Ockner Daniel , Szpunar Susan , Dul Carrie L , Hadid Tarik , Kafri Zyad , Aref Amr 
Published: March 2020

Background: There is a strong evidence indicating that locoregional control of early-stage breast cancer either by lumpectomy with radiation therapy or by mastectomy yields similar rates of disease-free survival (DFS) and overall survival (OS). Recent retrospective review of a Danish prospective database demonstrated a strong favorable interaction between radiotherapy (RT) and all breast cancer subtypes that contain high amount of tumor infiltrating lymphocytes (TILs).

Objective: We aim to compare the DFS and OS rates in patients with early-stage triple negative breast cancer (TNBC), whose tumors demonstrate high involvement by TILs after locoregional management by either mastectomy or lumpectomy and whole breast radiotherapy.

Methods: We retrospectively reviewed the charts and histopathology slides of patients with TNBC with the clinical stage of T1-T2 N0 who were treated in our center between January 2009 and December 2018. Locoregional management included either mastectomy (no radiation group) or lumpectomy with whole breast irradiation (radiation group). Stromal TILs were estimated by 3 pathologists independently using hematoxylin-eosin staining, following the recommendations of the TILs working group 2014. A competing risk model, Kaplan-Meier analysis and multivariate Cox regression analysis were used to analyze correlations between TILs and clinical outcome.

Results: A total of 101 charts were reviewed and 91 were included in the final analysis. Patients were dichotomized into groups of “low TILs” and “high TILs” using a 40% cut off. Approximately 26% of patients (24/91) were “high TILs”. About 46% of the “high TILs” group and 52% of “low TILs” group received RT. In patients with high TILs, 82% received chemotherapy in the "radiation group" and 100% in "no radiation group". In the patients with low TILs, 77% received chemotherapy in the "RT group" and 75% in "no RT group”. Table 1 and 2 depict the 5-year DFS and 5-year OS in "high TILs" and "low TILs" groups in relation to RT, respectively.

Conclusion: Our data indicate that in a selected group of high TILs TNBC, RT is associated with significant improvement of 5-year DFS and OS. This improvement is unlikely to be due to improved locoregional control as local failure was rare in all patient groups. This study is limited by its retrospective nature and the low number of subjects. Despite that, our results are important and deserve further confirmation using larger prospective clinical trials.

Table 1. 5-year DFS5-year DFSHigh TILsLow TILsRT group100%83.9%No RT group47.1%79.3%p-value0.010.96

Table 2. 5-year OS5-year OSHigh TILsLow TILsRT group100%83.7%No RT group65.6%76.7%p-value0.050.98

Citation Format: Jason Aboudi Mouabbi, Momal Chand, Ramen Sakhi, Daniel Ockner, Susan Szpunar, Carrie L Dul, Tarik Hadid, Zyad Kafri, Amr Aref. Improvement of survival with radiation therapy in early stage triple negative breast cancer patients with high level of tumor infiltrating lymphocytes [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 P4-12-09.