Table 1.

Patient, tumor, and treatment characteristics

		N (%) or Median [IQR]
Age		51.0 [45.0–57.0]
Subtype of breast tumor	HR positive/HER2 negative	48 (36.1)
	HR positive/HER2 positive	19 (14.3)
	HR negative/HER2 positive	19 (14.3)
	TN	47 (35.3)
Disease extent at initial breast cancer diagnosis
	Lymph node	49 (36.8)
	Liver	23 (17.3)
	Lung	52 (39.1)
	Bone	65 (48.9)
	Brain	1 (0.8)
Treatment era	2010–2015	52 (39.1)
	2016–2021	81 (60.9)
Numbers of previous systemic treatments (lines)		2 [1–4]
Systemic treatment-free interval (months)		0.8 [0.0–1.2]
Number of metastatic lesions	Oligometastasis (≤ 5 lesions)	13 (9.8)
	Polymetastasis (> 5 lesions)	120 (90.2)
Number of organ systems metastases	1	65 (48.8)
	2	38 (28.6)
	3–4	30 (22.6)
Disease extent at breast palliative RT	Lymph node	61 (45.9)
	Liver	26 (19.5)
	Lung	59 (44.4)
	Bone	72 (54.1)
	Brain	5 (3.8)
Status	De novo stage IV	30 (22.6)
	Progressive stage IV	76 (57.1)
	Recurrent stage IV	27 (20.3)
Disease burden outside the breast	Stable disease	104 (78.2)
	Progressive disease	17 (12.8)
	Mixed response	12 (9.0)

HR Hormone receptor, HER2 Human epidermal growth factor receptor 2, TN Triple negative, RT Radiation therapy