Incidence Differences Between First Primary Cancers and Second Primary Cancers Following Skin Squamous Cell Carcinoma as Etiological Clues

Figures & data

Table 1 Incidence of Common Cancers as First Primary Cancer and Second Primary Cancer, and Respective Relative Risk (RR) in Men

First Primary Cancer				Second Primary Cancer After Invasive SCC
Cancer	Number of Cases	Standardized Rate 1/100,000	Rank1	Number of Cases	Standardized Rate 2/100,000	Rank2	RR	95% CI
Prostate	185,081	95.2	1	1483	110.4	1	1.16	1.10	1.22
Colorectum	60,037	32.2	2	545	42.5	3	1.32	1.21	1.44
Lung	41,165	23.5	3	372	40.9	4	1.74	1.57	1.93
Bladder	35,818	18.9	4	374	26.5	7	1.40	1.27	1.55
Melanoma	22,812	14.7	5	355	47.5	2	3.23	2.91	3.60
Leukemia	17,318	11.3	6	180	21.7	8	1.92	1.66	2.23
NHL	18,414	11.3	7	237	26.8	6	2.37	2.08	2.70
Nervous system	14,199	11.1	8	45	15.0	9	1.35	1.01	1.81
Kidney	13,922	8.7	9	98	13.3	10	1.53	1.26	1.87
Stomach	13,800	7.3	10	152	12.4	11	1.70	1.44	1.99
UAT	11,371	7.2	11	195	27.3	5	3.79	3.29	4.38
Liver	10,990	6.3	12	82	8.8	12	1.39	1.12	1.72
Myeloma	7202	4.0	13	52	4.6	14	1.15	0.88	1.51
Endocrine	5558	3.9	14	16	3.9	15	0.99	0.60	1.62
Connective tissue	3564	2.4	15	46	6.3	13	2.64	1.97	3.54
Hodgkin lymphoma	2399	2.0	16	8	3.8	16	1.91	0.95	3.85
Thyroid	2213	1.6	17	10	2.3	18	1.45	0.78	2.71
Small intestine	2423	1.5	18	21	2.5	17	1.65	1.07	2.54
Male genital	1835	1.1	19	22	2.1	19	1.94	1.27	2.96
Breast	803	0.5	20	14	1.3	20	2.62	1.54	4.47
All*	515,982	256.0	–	4662	376.3	–	1.47	1.43	1.51

Notes: *Skin cancer is removed from all cancers; some rare cancers, not listed in Table 1 are included. Bolding shows RRs>2.00.

Abbreviations: SCC, squamous cell carcinoma; NHL, non-Hodgkin lymphoma; UAT, upper aerodigestive tract.

Table 2 Incidence of Common Cancers as First Primary Cancer and Second Primary Cancer, and Respective Relative Risk (RR) in Women

First Primary Cancer				Second Primary Cancer After Invasive SCC
Cancer	Number of Cases	Standardized Rate 1/100,000	Rank1	Number of Cases	Standardized Rate 2/100,000	Rank2	RR	95% CI
Breast	143,819	83.6	1	529	103.7	1	1.24	1.14	1.35
Colorectum	56,198	24	2	354	30.0	3	1.25	1.13	1.39
Lung	31,306	16.4	3	136	22.1	4	1.35	1.14	1.60
Melanoma	23,800	15.2	4	181	39.7	2	2.61	2.25	3.02
Endometrium	28,548	14.7	5	134	19.0	5	1.29	1.09	1.53
Nervous system	16,042	11.5	6	19	7.5	10	0.65	0.41	1.02
Ovary	18,523	11	7	68	15.4	7	1.40	1.10	1.77
Leukemia	13,833	7.9	8	95	13.4	9	1.69	1.38	2.07
Cervix	11,053	7.7	9	19	7.4	11	0.96	0.61	1.51
NHL	15,152	7.6	10	132	15.9	6	2.09	1.76	2.48
Endocrine	11,393	7.2	11	20	5.5	14	0.77	0.49	1.19
Bladder	12,134	5.2	12	83	6.9	12	1.33	1.07	1.65
Kidney	9520	5	13	32	5.0	15	0.99	0.70	1.40
Liver	10,939	4.8	14	52	5.7	13	1.18	0.90	1.55
Thyroid	5758	4.1	15	9	3.3	19	0.81	0.42	1.57
Stomach	8889	3.7	16	50	4.5	16	1.22	0.92	1.61
UAT	6932	3.7	17	105	13.6	8	3.68	3.03	4.47
Myeloma	5898	2.6	18	27	2.6	21	1.00	0.69	1.47
Female genital	4450	1.9	19	44	3.5	18	1.86	1.38	2.51
Connective tissue	2903	1.8	20	17	3.2	20	1.76	1.09	2.84
Hodgkin lymphoma	1934	1.7	21	6	3.7	17	2.20	0.98	4.93
Small intestine	2112	1	22	7	0.8	22	0.83	0.39	1.74
All*	481,702	237.7	–	2371	325.6	–	1.37	1.32	1.43

Notes: *Skin cancer is removed from all cancers; some rare cancers, not listed in Table 2 are included. Bolding shows RRs>2.00.

Abbreviations: SCC, squamous cell carcinoma; NHL, non-Hodgkin lymphoma; UAT, upper aerodigestive tract.

Table 3 Spearman Rank Correlation Between Incidences of the First Primary Cancer and Second Primary Cancer After Invasive and in situ SCC

Gender	SCC	Spearman Rank Correlation Coefficient (r)	P
Invasive	Men	0.95	5.95×10^−6
	Women	0.90	3.45×10^−6
In situ	Men	0.96	6.41×10^−6
	Women	0.94	4.03×10^−6

Abbreviation: SCC, squamous cell carcinoma.

Figure 1 Relative risks (RRs) for second primary cancer in men after invasive and in situ SCC of the skin. The error bars show 95% confidence intervals.

Figure 2 Relative risks (RRs) for second primary cancer in women after invasive and in situ SCC of the skin. The error bars show 95% confidence intervals.