Abstract P3-05-03: Long-term survival and intra-tumor heterogeneity of progesterone receptor expression in estrogen receptor-positive/progesterone receptor-positive premenopausal women with breast cancer
Authors: Danielsson Oscar , Dar Huma , Perez-Tenorio Gizeh , Nordenskjöld Anna , Yau Christina , Benz Christopher C. , Esserman Laura J. , Nordenskjöld Bo , Stål Olle , Fornander Tommy , Johansson Annelie , Lindström Linda S. 
Published: March 2023

Background: Women with estrogen receptor (ER)-positive disease have a long-term risk of distant recurrence. The poor survival of premenopausal women diagnosed with breast cancer combined with the otherwise long life expectancy makes it especially important to identify tumor characteristics associated with long-term survival. Intra-tumor heterogeneity, having cancer cells of varying characteristics across the tumor, may promote therapeutic resistance and metastatic capacity. We have previously shown that high intra-tumor heterogeneity of ER increases the risk of fatal breast cancer. To our knowledge, the relation between intra-tumor heterogeneity of progesterone receptor (PR) expression and long-term survival is not known. We aimed to study the association between intra-tumor heterogeneity of PR and long-term survival of premenopausal women in the Stockholm tamoxifen trial (STO-5), with 20-years complete follow-up.

Methods: This study was a secondary analysis of 504 ER-positive/PR-positive premenopausal women from the STO-5 trial (1990-1997). 451 women had human epidermal growth factor receptor 2 (HER2)-negative tumors. Patients were randomized to receive either 2 years of endocrine treatment (tamoxifen and/or goserelin) or no endocrine treatment. Lymph node-positive patients (n=251) also received standard chemotherapy (CMF). Immunohistochemical analysis, including estimating the proportion of tumor cells for each PR intensity level (0, 1+, 2+, or 3+), was completed in 2020. Intra-tumor heterogeneity of PR was calculated using Rao’s quadratic entropy and then categorized into low and high intra-tumor heterogeneity groups, using a predefined cutoff at the second tertile. Complete long-term (20 year) follow-up was obtained from high-quality Swedish registries. Long-term distant recurrence-free interval (DRFI) was assessed using univariate Kaplan-Meier analysis and multivariable Cox proportional hazard modeling, adjusting for patient and tumor characteristics.

Results: A statistically significant difference in 20-year DRFI was seen between patients with high and low intra-tumor heterogeneity of PR in the univariate Kaplan-Meier analysis (log-rank P&lt; 0.01). Survival proportions for DRFI at 20 years were 60.2% (95% CI, 53.2%-68.1%) and 73.3% (95% CI, 68.6%-78.3%) for patients with high and low PR intra-tumor heterogeneity, respectively. Analysis in patients with HER2-negative tumors yielded similar results. In the multivariable analysis, women with high intra-tumor heterogeneity of PR had a significantly increased long-term risk of distant recurrence, compared to women with low intra-tumor heterogeneity, hazard ratio (HR)=1.49 (95% CI, 1.08-2.06). The same pattern was seen in HER2-negative women, HR=1.50 (95% CI, 1.06-2.12), see Table.

Conclusions: This study suggests an increased long-term risk of distant recurrences in ER-positive/PR-positive premenopausal women with high intra-tumor heterogeneity of PR as compared to women with low intra-tumor heterogeneity of PR, independent of HER2 status. Ongoing analyses include using deep learning for image analysis of breast cancer tumors to examine intra-tumor heterogeneity at higher resolution and for various tumor characteristics. Better understanding of tumor characteristics associated with long-term risk in premenopausal women is needed, given the poor prognosis and early onset of the disease.

Long-term risk of distant recurrence by PR intra-tumor heterogeneity and HER2 status Multivariable Cox proportional hazard regression modeling of 20-year distant recurrence-free interval (DRFI) by high and low PR intra-tumor heterogeneity. ER-positive/PR-positive and ER-positive/PR-positive/HER2-negative premenopausal women were analyzed separately. The crude model was adjusted for age, randomization year, lymph node status, and endocrine treatment. The full model was adjusted for age, randomization year, lymph node status, endocrine treatment, tumor size, Ki-67 status, and HER2 status.

Citation Format: Oscar Danielsson, Huma Dar, Gizeh Perez-Tenorio, Anna Nordenskjöld, Christina Yau, Christopher C. Benz, Laura J. Esserman, Bo Nordenskjöld, Olle Stål, Tommy Fornander, Annelie Johansson, Linda S. Lindström. Long-term survival and intra-tumor heterogeneity of progesterone receptor expression in estrogen receptor-positive/progesterone receptor-positive premenopausal women with breast cancer [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P3-05-03.