Table 1.

Baseline characteristics of patients.

Variables	Primary bone- metastatic cohort, No (%) (n = 142)	Secondary bone- metastatic cohort, No (%) (n = 158)	P
Follow-up, median (range)	25.2 (3.9–106.7)	22.3 (4.2–134.3)
Gender			0.30
Male	117 (82.3)	137 (86.7)
Female	25 (17.6)	21 (13.3)
Age (years)			0.86
≤45	68 (47.9)	74 (46.8)
>45	74 (52.1)	84 (53.2)
Number of BM lesions			0.38
≤3	95 (66.9)	98 (62.0)
>3	47 (33.1)	60 (38.0)
Imaging feature of BM destruction			0.99
Osteogenic	79 (55.6)	88 (55.7)
Osteolytic	63 (44.4)	70 (44.3)
Concomitant metastasis in other organs			0.49
Yes	41 (28.9)	40 (25.3)
No	101 (71.1)	118 (74.7)
Pre-RT ALP level (U/L)			0.97
≤110	121 (87.1)	126 (86.9)
>110	18 (12.9)	19 (13.1)
Pre-RT LDH level (U/L)			0.23
≤250	112 (80.0)	123 (85.4)
>250	28 (20.0)	21 (14.6)
Pre-RT EBV DNA level (copies/ml)			0.08
≤4,000	43 (33.6)	51 (44.7)
>4,000	85 (66.4)	63 (55.3)
Dose prescription of RT			< 0.001
60–75 Gy/30–35f	61 (43.0)	34 (21.5)
36–54 Gy/12–27f	39 (27.5)	50 (31.6)
12–30 Gy/3–10f	39 (27.5)	65 (41.1)
Others	3 (2.1)	9 (5.7)
Chemotherapy regimen			< 0.001
TP	41 (28.9)	37 (23.4)
PF	32 (22.5)	43 (27.2)
GP	11 (7.7)	33 (20.9)
TPF	51 (35.9)	17 (10.8)
Others	7 (4.9)	28 (17.7)
Other systemic therapies*			0.99
None	101 (71.1)	111 (70.3)
EGFR targeted therapy	28 (19.7)	31 (19.6)
VEGF targeted therapy	2 (1.4)	3 (1.9)
Immunotherapy	11 (7.7)	13 (8.2)
Administration of ZA			0.26
Yes	96 (67.6)	97 (61.4)
No	46 (32.4)	61 (38.6)

BM, bone metastasis; RT, radiotherapy; ALP, alkaline phosphatase; LDH, lactic dehydrogenase; EBV, Epstein-barr virus; TP, paclitaxel plus cisplatin; PF, cisplatin plus 5-fluorouracil; GP, gemcitabine plus cisplatin; TPF, paclitaxel plus cisplatin and 5-fluorouracil; EGFR, epidermal growth factor receptor; VEGF, vascular endothelial growth factor; ZA, zoledronic acid.

All statistical tests were two-sided.

^*P-value was calculated with the Fisher's exact test.