Table I.

Distribution of Selected Characteristics of the Patient Cohort (n = 1384)

Variable	Total		SPM-Free		SPM		P-values*
	No.	%	No.	%	No.	%
Total patients	1384	100	1274	92.1	110	7.9
Age
≤ median (57 years)	726	52.5	690	54.2	36	32.7	< 0.001
> median (57 years)	658	47.5	584	45.8	74	67.3
Sex							0.761
Male	1053	76.1	968	76.0	85	77.3
Female	331	23.9	306	24.0	25	22.7
Ethnicity							0.100
Non-Hispanic White	1160	83.8	1074	84.3	86	78.2
Other	224	16.2	200	15.7	24	21.8
Smoking							0.021
Never	382	27.6	362	28.4	20	18.2
Ever	1002	72.4	912	71.6	90	81.8
Alcohol							0.052
Never	373	26.9	352	27.6	21	19.1
Ever	1011	73.1	922	72.4	89	80.9
Index Cancer Site							0.114
Oral cavity	453	32.7	419	33.0	34	30.9
Oropharynx	623	45.1	580	45.5	43	39.1
Larynx/Hypopharynx	307	22.2	274	21.5	33	30.0
Index Cancer Stage							0.819
1 or 2	352	25.4	323	25.4	29	26.4
3 or 4	1031	74.6	950	74.6	81	73.6
Treatment							0.983
Surgery only	247	17.9	228	17.9	19	17.3
Surgery + Adjuvant Tx1	343	24.8	314	24.6	29	26.4
XRT2	348	25.1	321	25.2	27	24.5
XRT + Chemotherapy	446	32.2	411	32.3	35	31.8

^*P values were calculated from chi-square test

¹Adjuvant Tx: adjuvant radiotherapy and/or chemotherapy

²XRT: radiotherapy