Subdivision of M category for nasopharyngeal carcinoma with synchronous metastasis: time to expand the M categorization system

Table 3 Overall survival (OS) according to the locations, number of locations, and number of lesions in each location

Category and variable	Number of patients^a	Median OS (months)	3-year OS rate (%)	P value
Isolated metastasis versus multiple metastases
Number of metastatic locations				0.001
Multiple locations	199	22.4	24.0
Isolated location	306	27.4	41.6
Number of metastatic lesions in each location				<0.001
Multiple lesions	410	22.8	29.5
Isolated lesion	95	41.0	57.6
Involved locations
Bone involvement				0.404
Yes	333	26.2	35.8
No	172	23.9	33.5
Lung involvement				0.559
Yes	136	25.1	30.3
No	369	24.6	36.6
Liver involvement				<0.001
Yes	155	19.7	21.7
No	350	28.4	41.1
Distant LN involvement				0.104
Yes	144	23.2	27.6
No	361	26.7	37.6
Number of lesions and locations
Isolated bone metastasis				0.065
Single lesion	50	44.2	60.7
Multiple lesions	133	25.0	38.6
Isolated lung metastasis				0.115
Single lesion	20	57.0	62.1
Multiple lesions	36	27.2	30.9
Isolated liver metastasis				0.473
Single lesion	21	25.6	43.6
Multiple lesions	35	17.8	22.4
Isolated distant LN metastasis				–
Single lesion	4	63.7	75.0
Multiple lesions	6	21.0	54.5
Total isolated metastasis^b				0.002
Single lesion	95	41.0	57.6
Multiple lesions	210	23.3	34.6

LN lymph node.
^aThe total number of patients does not coincide exactly with the corresponding number in Table 2 because the number of lesions for some patients is not specified.
^bThese include isolated metastasis in the bones, the lungs, the liver, and distant lymph node.