Impact assessment of implementing evidence-based de-escalation strategies in early breast cancer management in South Africa.

e12744 Background: In South Africa, where oncology resources are limited, adopting evidence-based radiation and chemotherapy de-escalation strategies may reduce patient toxicity and enhance resource efficiency. The applicability and impact of these strategies, validated in high-income countries as non-inferior in low-risk breast cancer patients, remain unknown in South Africa. Methods: We conducted a retrospective analysis of the South Africa Breast Cancer & HIV Outcomes (SABCHO) cohort drawn from five public hospitals in Gauteng and KwaZulu-Natal provinces. Patients were aged ≥18 years with stage I–III breast cancer diagnosed and treated between 2015 and 2019. Radiation de-escalation eligibility was based on CALGB 9343 and PRIME II trials, adjusted for the life expectancy in South Africa. Chemotherapy de-escalation eligibility was based on TAILORx and RXPONDER trials utilizing calculated Magee recurrence scores (MRS) in lieu of Oncotype (eligible if MRS < 18 or < 25 with mitosis score = 1). We assessed the prevalence of de-escalation eligibility, treatment receipt patterns, and compared overall survival (OS) by treatment receipt using Cox proportional hazard models and Kaplan-Meier curves. Results: Among 2,369 patients, 210 (8.6%) were eligible for radiation de-escalation and 440 (18.6%) for chemotherapy de-escalation. Of these, 26.3% received adjuvant radiation and 45.2% received chemotherapy. OS stratified by receipt of treatment did not differ significantly in either group. 5-year median OS was 94.5 months and 93.3 months in patients who received radiation and those who did not, respectively (HR 1.42, 95% CI 0.82-2.43). Median OS was 96.8 months and 98.4 months in patients who received and did not receive chemotherapy, respectively (HR 0.93, 95% CI 0.60-1.42). Conclusions: Many patients receiving adjuvant radiation and chemotherapy in this South African cohort may have been appropriate for treatment de-escalation, highlighting an opportunity to mitigate toxicity and reallocate scarce resources without reducing survival. Prospective research into the clinical impact of de-escalation strategies in South Africa is warranted. Sociodemographic and clinical characteristics of early breast cancer patients in SABCHO cohort. Characteristic Overall (N = 2369) Age, years (median [IQR]) 54.0 [44.0 – 65.0] Race Asian/Indian 190 (8.0%) Black 1915 (80.8%) Mixed 107 (4.5%) White 159 (6.7%) HIV status Positive 470 (19.8%) Overall Stage Stage I 445 (18.8%) Stage II 1225 (51.7%) Stage III 699 (29.5%) Tumor stage T0 170 (7.2%) T1 502 (21.2%) T2 933 (39.4%) T3 312 (13.2%) T4 91 (3.8%) Other/Unknown 361 (15.2%) Nodal stage N0 914 (38.6%) N1 808 (34.1%) N2 212 (8.9%) Tumor size, mm 30.0 [21.7 – 45.0] Hormone receptor (HR) Positive