Table 1.

Distribution of selected characteristics of the patient cohort (n =1,286)

Variable	Total		SPM-Free		SPM		P-valuesc
	No.	%	No.	%	No.	%
Total patients	1,286	100	1,166	90.7	120	9.3
Age
≤ median (57 years)	665	51.7	626	53.7	39	32.5	<.0001
> median (57 years)	621	48.3	540	46.3	81	67.5
Sex
Male	977	76.0	883	75.7	94	78.3	0.525
Female	309	24.0	283	24.3	26	21.7
Ethnicity
Non-Hispanic White	1,087	84.5	993	85.2	94	78.3	0.050
Other	199	15.5	173	14.8	26	21.7
Smoking
Never	343	26.7	318	27.3	25	20.8	0.129
Ever	943	73.3	848	72.7	95	79.2
Alcohol
Never	335	26.1	308	26.4	27	22.5	0.352
Ever	951	73.9	858	73.6	93	77.5
Index Cancer Site
Oral cavity	417	32.4	379	32.5	38	31.7	0.322
Oropharynx	573	44.6	525	45.0	48	40.0
Larynx/Hypopharynx	296	23.0	262	22.5	34	28.3
Index Cancer Stage
I or II	323	25.1	291	25.0	32	26.7	0.681
III or IV	963	74.9	875	75.0	88	73.3
Treatment
Surgery only	229	17.8	208	17.8	21	17.5	0.889
Surgery + Adjuvant Txa	320	24.9	287	24.6	33	27.5
XRTb	329	25.6	301	25.8	28	23.3
XRT + Chemotherapy	408	31.7	370	31.7	38	31.7

^aAdjuvant Treatment: adjuvant radiotherapy and/or chemotherapy

^bXRT: radiotherapy

^cP values were calculated from chi-square test