Tumor-Stroma Ratio in ER+/HER2- Breast Cancer: Is it a Tool for Treatment Decision?

Purpose: The primary aim of this study is to determine the relationship between tumor-stroma ratio (TSR) and traditional prognostic factors in luminal early breast cancer in women treated at the medical oncology department of the military hospital of Rabat in Morocco.

Methods: A retrospective study was performed on primary invasive ER+/HER2- breast cancer in the period from January 1st, 2019 to December 31st, 2019. Prognostic factors included age, tumour size, lymph nodes status, Scarff-Bloom-Richardson grading, lymphovascular invasion (LVI), Ki67 and the stage of the disease. The type of Adjuvant systemic therapy was also reported .Two independent pathologists have assessed TSR by microscopic evaluation of haematoxylin and eosin tumor slides .Patients with less than 50% stroma were classified as low-stroma, the others are classified as high-stroma.

Results: Of 53 ER+/HER2- operable breast cancer, 41.5% patients had low-stroma and 58.5% patients had high stroma-tumour. High stroma was significantly associated with more stage III (p=0.041), more LVI (0.034), high Ki-67 (p=0.002) and more luminal B disease (p=0.001). Also, high stroma received more adjuvant chemotherapy (p=0.005). The results are maintained in univariate analysis.

Conclusions: Data suggest that TSR can be used to guide decisions on adjuvant systemic therapy for ER+/HER2- breast cancer. The integration in routine of this simple and reproducible parameter requires a homogenization of the techniques as well as a prospective validation.