The durability of previous examinations for cancer: Danish nationwide cohort study

Figures & data

Figure 1. Drawing of the study design. Dashed double arrow lines indicate periods with no investigation. Abbreviation: EOS: End of study.

Table 1. Diagnosis- and procedure codes for cancers and the related investigation.

Cancer type	ICD-10 codes	Investigation	Procedure and service codes
Lung	C33-34	CT-Thorax	UXCC00, UXCC75, or UXCC77
Upper gastrointestinal (Oesophagus or stomach)	C15-16	Gastroscopy	KUJD, KUJD02, or KUJD05 Primary care: 172303, 282303, 086409, 092302, 172307, 282307, 082302, or 082402
Colorectal	C18-C20	Colonoscopy	KUJF32, KUJF35 or KJFA15 Primary care: 082308 or 092114
Breast	C50	Clinical mammography	UXRC40 or UXRC40A
Bladder	C67	Cystoscopy	KUKA, KUKB, KUKB02, KUKB05, KUKC, KUKC02, KUKC05,Primary care: 072306, 092105, 092306, 096404, 096416, 096418, 172304, or 282304

Abbreviations: ICD-10: International classification of diseases 10th revision; primary care are the service codes used. All codes available can be found at Danish Board of Health Data: https://medinfo.dk/sks/brows.php.

Table 2. Numbers and proportions of individuals in the Danish 30–85-year-old population, 1 January 2017, who had had a cancer-related examinations during the previous 10 years and had not earlier been diagnosed with the specific type of cancer.

Total population 3,316,784*		Time interval since the last examination before January 1, 2017
Investigation	Measure	Not exam.	0–5 months	6–11 months	12–23 months	2–4 years	5–10 years
CT Thorax	Number	2,943,747	51,693	44,479	63,768	118,512	84,662
	% row	89.0	1.6	1.3	1.9	3.6	2.6
Clinical mammography	Number	1,411,840	14,883	16,798	30,945	74,578	102,798
	% row	85.5	0.9	1.0	1.9	4.5	6.2
Colonoscopy	Number	2,944,518	36,136	37,711	67,251	120,291	87,072
	% row	89.4	1.1	1.2	2.0	3.7	2.6
Gastroscopy	Number	3,049,257	22,587	21,163	36,101	86,153	99,997
	% row	92.0	0.7	0.6	1.1	2.6	3.0
Cystoscopy	Number	3,160,593	12,636	12,195	20,895	50,495	56,243
	% row	95.4	0.4	0.4	0.6	1.5	1.7

*The total population includes all 30–85 years old persons resident in Denmark on 1 January 2017, and continuously during the 10 years before. For each examination type, the table only includes those not diagnosed with the specific cancer during 10 years before 1 January 2017. For clinical mammography only the female population is included.

Table 3. Previous cancer-related examinations among patients in the Danish population who were first-time diagnosed with the cancer during year 2017 and the hazard ratios of being diagnosed with the cancer comparing to the not previously examined persons.

Population 3,316,784*		Time interval since the patient’s latest examination before 1 January 2017
Cancer/exam.	Measure	Not examined	0–5 months	6–11 months	12–23 months	2–4 years	5–10 years
Lung/CT Thorax	No (% row)	2878 (78)	199 (5.4)	87 (2.4)	107 (2.9)	254 (6.9)	171(4.6)
	HR (CI95)	1 (ref)	2.25 (1.90–2.67)	0.98 (0.74–1.28)	0.94 (0.74–1.19)	1.19 (1.01–1.40)	1.25(1.03–1.51)
Breast/Clinical mammography	No (% row)	3118 (81)	45 (1.2)	41 (1.1)	102 (2.7)	222 (5.7)	346(8.9)
	HR (CI95)	1 (ref)	1.58 (1.17–2.12)	1.26 (0.92–1.71)	1.64 (1.35–2.00)	1.36 (1.18–1.56)	1.37(1.23–1.53)
Colorectal/Colonoscopy	No (% row)	2388 (87)	91 (3.3)	34 (1.2)	54 (2.0)	115 (4.2)	76(2.8)
	HR (CI95)	1 (ref)	1.89 (1.58–2.27)	0.53 (0.38–0.74)	0.57 (0.45–0.73)	0.66 (0.55–0.78)	0.60(0.48–0.74)
Upper gastroint/Gastroscopy	No (% row)	754 (84)	46 (5.1)	32 (3.6)		29 (3.2)	39 (4.3)
	HR (CI95)	1 (ref)	4.90 (3.34–7.18)	1.51 (0.97–2.34)		1.09 (0.71–1.68)	1.21 (0.82–1.78)
Bladder/Cystoscopy	No (% row)	640 (90)	21 (3.0)	11(1.6)		20 (2.8)	16 (2.3)
	HR (CI95)	1 (ref)	2.87 (1.73–4.75)	0.70(0.36–1.36)		0.80 (0.47–1.37)	0.74 (0.43–1.26)

*The total population includes all 30–85 years old persons resident in Denmark on 1 January 2017, and continuously during the 10 years before. For clinical mammography, only the female population is included. Abbreviations: No: total number of patients diagnosed with the cancer type during 2017 among those not diagnosed with it during the previous 10 years; HR(CI95): age- and sex-adjusted one year hazard ratio of being diagnosed with the cancer with 95% confidence interval comparing to non-investigated persons. For upper gastrointestinal- and bladder cancer the 6–11- and 12–23-months groups were collapsed due to low numbers.

Figure 2. Hazard ratios for cancer after completed examination compared to not-examined persons.

Data availability statement

Data supporting the findings of this study was used under a license granted specifically for the current study and therefore is not publicly available according to the data protection regulations of Danish Data Protection Agency, Statistics Denmark and the Danish Health and Medicines Authority.