Abstract PO4-26-02: Evaluation of Tumor Infiltrating Lymphocytes as a predictive biomarker of recurrence in patients with Ductal Carcinoma In Situ of the breast

Abstract Introduction: Ductal carcinoma in situ (DCIS) represents around 20% of early breast cancer diagnoses globally. Some studies evaluated risk factors associated with DCIS recurrence. Among these, age, surgical margins, comedonecrosis (CN), high nuclear grade, negative hormone receptors and HER2 expression stand out. Recent approaches have been evaluating the role of the immune microenvironment and its association with recurrence and progression of DCIS. Objective: To evaluate the association between Tumor Infiltrating Lymphocytes (TILs) in DCIS samples and disease recurrence. To characterize the immunological microenvironment of DCIS, analyzing the presence of TILs, “touching TILs” and desmoplastic reaction and their association with recurrence. Epidemiological, clinical, histological and immunohistochemical (IHC) characteristics were also evaluated. Methods: This is a retrospective cohort study with patients diagnosed with DCIS and treated at Sao Paulo State Cancer Institute and Hospital das Clinicas of University of Sao Paulo. We included women over 18 years old with a diagnosis of DCIS who underwent treatment from Jan/2007 to Dec/2020. Male patients, patients with a diagnosis of invasive or microinvasive disease in the anatomopathological examination of the surgical specimen or patients with history of any neoplasm were excluded. The main outcome was survival analysis according to the quantification of TILs, adjusted for potential confounders. For that, we collected data on age, presence of palpable mass, imaging findings, histological and IHC characteristics, such as expression of estrogen receptor (ER), progesterone receptor (PR) and hyperexpression of HER2, type of surgical approach, type of radiation therapy, use of endocrine therapy, length of follow-up, recurrence, and its type. Two pathologists evaluated TILS in the sample with the highest tumor representation and numerically quantified it as percentage. They also evaluated the presence of “touching tils” (lymphocytes in contact with the basement membrane) and desmoplastic reaction in the tumor stroma. Kaplan-Meier curves, log-rank tests and Cox regression models were used to evaluate survival. Chi-square tests were used to evaluate the association between categorical variables. Results: 283 patients met the eligibility criteria. Mean age of patients was 55 years. 15% had a palpable nodule at physical examination. Clustered amorphous microcalcifications were the most prevalent mammographic presentation, found in 41% of the patients. The most frequent histological and IHC features were cribriform presentation (73%) and ER positivity (86%), respectively. Desmoplastic reaction was absent in 10.5%, discreet in 51.9%, moderate in 24% and intense in 13.6% of the patients. Breast conserving surgery was performed in 189 patients, and 100 of them received adjuvant radiation therapy. Mean follow-up was 77.2 months, with a recurrence rate of 9.2%. We observed that tumors with focal necrosis (HR 6.4 1.39-34.71 p 0.018) or CN (HR 4.53 1.34 – 15.28 p 0.015) had higher risks of recurrence. Patients with a percentage value of TILs greater than or equal to 17% also had a higher risks of recurrence (HR 2.97 (1.17-7.51) p 0.02). These patients were mostly under 65 years of age (OR 0.45 0.21 - 0.97 p 0.049). In a multivariate model, CN and TILs17% remained significantly associated with recurrence (p=0.034 and p=0.035 respectively). There was a trend for invasive recurrence in 76.9% of the patients that relapsed when TILS were greater than or equal to 17% (p 0.062). “Touching TILs” were present in 12.9% of the patients but were not associated with recurrence (p=0.575). Conclusion: In our cohort, high value of TILs (= 17%) and presence of CN were independently associated with DCIS recurrence. Our findings suggest that TILS are a prognostic immunological biomarker in DCIS and warrant further investigation in prospective trials to determine the most adequate cut-point. Citation Format: Camila Pasetto, Fernando Aguiar, Marcella Peixoto, Maira Doria, Bruna Mota, Jonathan Maesaka, Jose Roberto Filassi, Edmund Baracat, Rodrigo Gonçalves. Evaluation of Tumor Infiltrating Lymphocytes as a predictive biomarker of recurrence in patients with Ductal Carcinoma In Situ of the breast abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-26-02.