Table 2.

Incidence Proportion of Brain Metastases in the United States at Diagnosis of Malignancy by Primary Site

Primary Site	Sub-Site	Incidence Proportion Among Entire Cohorta	Incidence Proportion Among Subset With Metastatic Diseaseb
Breast
	HR+/HER2−	0.22	5.46
	HR+/HER2+	0.61	7.98
	HR−/HER2+	1.09	11.45
	Triple-negative	0.68	11.37
Head and Neck	All	0.20	5.06
Gastrointestinal
	Esophagus	1.66	5.31
	Gastric	0.64	1.96
	Hepatobiliary	0.36	1.77
	Pancreatic	0.41	0.82
	Colorectal	0.27	1.36
	Anal	0.11	1.58
	Other gastrointestinal	0.68	2.08
Genitourinary
	Renal	1.48	10.84
	Bladder	0.25	3.45
	Prostate	0.07	1.47
	Testicular	0.88	7.61
	Other genitourinary	0.23	2.88
Gynecologic
	Ovarian	0.24	0.94
	Endometrial	0.22	3.40
	Cervical	0.38	2.94
	Other gynecologic	0.21	2.19
Lung
	Small cell	15.83	23.46
	Squamous cell	5.29	15.86
	Adenocarcinoma	14.44	26.82
	Bronchioloalveolar	2.31	15.47
	Non-small cell not otherwise specified	12.81	25.56
Melanoma	Any	0.65	28.16
Sarcoma	Any	0.74	4.44
Thyroid	Thyroid	0.12	5.86
All others	All others	1.73	9.94

Abbreviations: HER2, human epidermal growth factor receptor 2; HR, hormone receptor.

^aIncidence proportion was defined as the number of patients diagnosed with brain metastases and a specific primary cancer divided by the total number of individuals diagnosed with that primary cancer.

^bIncidence proportion was defined as the number of patients diagnosed with brain metastases and a specific primary cancer divided by patients with de novo metastatic disease to any distant site.