Table 4. Forest plot of subgroup effects for PFS in all LSCC patients.

Characteristic	Subgroup of the Characteristic	Subgroup of the model	Hazard Ratio	95%CI
				Low	High	P
Age	< 60	Middle vs Low	2.960	1.506	5.817	0.002
		High vs Low	7.542	3.699	15.379	< 0.001
	≥ 60	Middle vs Low	2.862	1.609	5.091	< 0.001
		High vs Low	10.945	6.028	19.872	< 0.001
Smoking status	Absent	Middle vs Low	1.616	0.567	4.609	0.369
		High vs Low	9.341	3.203	27.241	< 0.001
	Present	Middle vs Low	3.042	1.878	4.927	< 0.001
		High vs Low	8.637	5.214	14.308	< 0.001
Drinking status	Absent	Middle vs Low	3.024	1.789	5.113	< 0.001
		High vs Low	9.266	5.303	16.190	< 0.001
	Present	Middle vs Low	2.463	1.145	5.299	0.021
		High vs Low	7.599	3.479	16.600	< 0.001
Site	Glottic	Middle vs Low	3.191	1.458	6.984	0.004
		High vs Low	7.321	3.353	15.985	< 0.001
	Non-glottic	Middle vs Low	2.501	1.475	4.242	0.001
		High vs Low	12.002	6.605	21.812	< 0.001
T stage	I + II	Middle vs Low	2.771	1.558	4.928	0.001
		High vs Low	9.215	3.687	23.0333	< 0.001
	III + IV	Middle vs Low	2.509	1.217	5.173	0.013
		High vs Low	7.609	3.718	15.573	< 0.001
N stage	Negetive	Middle vs Low	2.974	1.915	4.619	< 0.001
		High vs Low	5.623	2.546	12.417	< 0.001
	Positive	Middle vs Low	3.149	1.739	5.705	< 0.001
		High vs Low	57.471	6.727	491.003	< 0.001
Clinical stage	I + II	Middle vs Low	2.205	1.106	4.396	0.025
		High vs Low	6.980	3.536	13.779	< 0.001
	III + IV	Middle vs Low	2.727	1.770	4.200	< 0.001
		High vs Low	8.349	5.318	13.105	< 0.001

Abbreviations: LSCC, laryngeal Squamous cell carcinoma (LSCC); PFS, Progression-free survival; Non-Glottic, Supraglottic and Subglottic; CISD2, CDGSH iron sulfur domain2; C-N model, CISD2 plus N stage model.

Subgroups are defined by factors showing significant associations between the C-N model and PFS.