E155: Ten-year real-world data on the utility of the 70-gene signature for post-surgical oncologic Breast Cancer care in the Philippines: New clinical insights for the Low-Middle income Southeast Asian population

An initial report with limited data was done in 2021 on the use of the 70-gene signature (Mammaprint) for breast cancer in the Philippines providing the first and only local documentation on possible disparities and relevant perspective on this subject. With the publication of the most recent ASCO guidelines on biomarkers for adjuvant therapy and of the updated 9-year follow up data of the Microarray In Node-negative and 1-3 nodes positive Disease may Avoid ChemoTherapy (MINDACT) study with exploratory analysis by age, yet despite continuing considerable logistical challenges in our resource-limited environment, we reappraise our now ten-year experience aiming to accrue new clinical insights on our population.

Methods:

This is a retrospective cohort analyses of available and accessible Mammaprint records done among post-surgical Southeast Asian breast cancer patients from December 2013 to September 2023. Data on age, molecular subtype, and clinical risk assessment in the MINDACT study determination to clinical low (c-low) or high (c-high) were collected and analyzed.

Results: Fifty-one females aged 36-75 years with invasive breast carcinoma who underwent surgical staging had the following overall molecular profile: Low Risk Luminal A (LLA, 25, 49%), High Risk Luminal B (HLB, 15, 29.4%), High Risk Her-2 (HHr, 3, 5.9%), High Risk Basal (HBa, 8, 15.7%). Stratification of all patients yielded an Low Risk Luminal A (LLA) genomic profile on 15 of 38 (42.9%) c-high patients and 20 of 36 (55.6%) patients aged >50 years.  All genomic low-risk patients underwent adjuvant endocrine therapy alone, foregoing otherwise recommended chemotherapy.

Conclusions:

Even with the recent MINDACT exploratory analysis finding of significant chemotherapy benefit on patients < 50 years of age with LLA profile and updated ASCO recommendation on exclusion of genomic profiling on c-low patients regardless of age and on patients < 50 years of age with high clinical risk, the 70-gene signature continues to achieve a 42.9 - 55.6% LLA profile on our population, thus avoiding overtreatment and financial toxicity with chemotherapy on them.  Strategies to improve accessibility, availability, adaptability, and affordability in this setting is still therefore of vital importance and relevance.