2803 - Prognostic Determinants of Survival in Oligometastatic Breast Cancer (OMBC): The Role of Timing and Metastatic Burden

Purpose/Objective(s):

To evaluate incidence, survival outcomes and prognostic factors in patients with oligometastatic breast cancer (OMBC) treated in a real-world setting.

Materials/Methods:

Patients with OMBC (=5 metastases, =5 cm, =3 organs) treated at a tertiary care centre between 2014 and 2024 were identified via text mining of medical files. Demographic, clinical, and treatment variables were abstracted from case records. OMBC was subclassified as synchronous (within 6 months of diagnosis) or metachronous. Crude percentages were calculated, the Kaplan-Meier method was used to estimate overall survival (OS), and the Cox proportional hazards regression was used to assess prognostic factors.

Results:

Among 2,567 breast cancer patients screened, 116 (4.5%) were diagnosed with OMBC; 65% were synchronous and 35% metachronous. PET-CT was used for staging in 36% of patients. Solitary metastasis was present in 50 patients (43%), and 94 (81%) had disease confined to a single organ. The most common metastatic site was bone (44%), followed by brain (22.4%), liver (19%), lung (19%), and lymph nodes (10%). Median age at presentation was 48 years (IQR: 41–56). ER/PR positivity was observed in 35%, HER2 positivity in 47%, and triple-negative disease in 34%. The median time to diagnosis of metachronous OMBC was 27 months (IQR: 18–49).

Table1: Univariable and Multivariable Cox Regression analysis of prognostic factors

At a median follow-up of 63 months, median OS was 28 months for the overall cohort and 33 versus19 months for synchronous versus metachronous OMBC and 5-year OS of 37% vs 24% (p = 0.018). Univariable and multivariable analysis is depicted in Table 1. On multivariable analysis, brain metastasis was independently associated with inferior OS (HR 2.72; 95% CI: 1.43–5.16; p = 0.002). Synchronous presentation (HR 0.55; 95% CI: 0.29–1.04; p = 0.07) and locoregional radiotherapy (HR 0.53; 95% CI: 0.25–1.09; p = 0.08) demonstrated a trend toward improved OS.

Conclusion: OMBC represented a distinct subset with heterogeneous outcomes in this real-world cohort. Synchronous presentation was associated with improved survival, whereas brain metastasis independently predicted poorer outcomes.

Variable	Univariable Analysis		Multivariable Analysis
	HR (95% CI)	p value	HR (95% CI)	p value
Age	0.83 (0.51-1.35)	0.45
PET-CT for diagnosis	0.66 (0.39-1.1)	0.11
HR +ve	0.49 (0.29-0.82)	0.007
HER2neu+ve	0.66 (0.41-1.06)	0.08
Surgery (Yes)	0.48 (0.29-0.78)	0.003	0.71 (0.29-1.74)	0.46
No. of metastasis (1vs >1)	0.83 (0.51-1.34)	0.44
No. of organs (1vs>1)	0.71 (0.40-1.27)	0.25
Bone metastasis (Yes)	0.58 (0.33-1.02)	0.056	0.64 (0.35-1.16)	0.14
Brain metastasis (Yes)	2.6 (1.42-4.74)	0.002	2.72 (1.43-5.16)	0.002
Synchronous (Yes)	0.56 (0.35-0.91)	0.02	0.55 (0.29-1.04)	0.07
Locoregional RT(Yes)	0.40 (0.25-0.64)	0.000	0.53 (0.25-1.09)	0.08
RT to metastatic site (Yes)	0.86 (0.52-1.42)	0.55
Chemotherapy (Yes)	0.40 (0.20-0.79)	0.008	0.91 (0.41-2.0)	0.80
Hormonal therapy(Yes)	0.53 (0.30-0.94)	0.03	0.87 (0.38-2.0)	0.74