Value of circulating DNA concentration and integrity as a screening test for detection of cancer in an Egyptian cohort

Peer review under responsibility of Alexandria University Faculty of Medicine.

Available online 17 July 2012

Figures & data

Table 1 Levels of plasma DNA (ng/μl) in cancer, benign, and control groups and in cancer subgroups.

Groups	M ± SE	Range	p1	p2
Cancer group (n = 85)	765.1 ± 84.8^*,x	105–4891	0.000	0.000
			U = 54	U = 75
Breast (n = 24)	902.0 ± 226.2^*,x	105–4891	0.000	0.001
			U = 26	U = 26
Lung (n = 14)	744.3 ± 157.1^*,x	351–2000	0.003	0.014
			U = 10	U = 10
Colon (n = 14)	517.5 ± 120.6^*,x	229–1550	0.008	0.016
			U = 16	U = 16
Stomach (n = 13)	657.3 ± 83.6^*,x	232–1111	0.003	0.013
			U = 7	U = 7
HCC (n = 10)	471.3 ± 106.4^*,x	142–968
Lymphoma (n = 10)	1366.1 ± 333.4^*,x	171–2660
Benign (n = 30)	141.0 ± 40.2	38–597	0.237
		U = 80
Control (n = 30)	75.8 ± 20.8	0–300

p1 = significance when compared to control group by Mann–Whitney U test.

p2 = significance when compared to benign group by Mann–Whitney U test.

*,x The mean difference is significant at p < 0.05 when compared to the control and benign groups respectively, by Mann–Whitney U test.

Figure 1 ROC curve for discrimination between (a) cancer and control, and (b) cancer and benign groups.

Figure 2 ROC curve for discrimination between various cancer subgroups and control (solid line) and benign (dotted line) groups.

Table 2 ROC curve values for CFDNA versus control and benign groups, showing area under each curve different, significance, cutoff values of plasma dna with their sensitivity, specificity, positive predictive value, and negative predictive value.

	Cancer versus control	Cancer versus benign
Area under the curve (%)	96.2	92.7
p	0.000	0.000
Standard error	0.015	0.030
95% Confidence interval	0.932–0.992	0.867–0.987
Cutoff values	100	600
Sensitivity (%)	100	53.4
Specificity (%)	75	100
Positive predictive value %	94	100
Negative predictive value %	100	23

Figure 3 Electrophoresis for PCR products of two control subjects (lanes 1–3), two cancer patients (lanes 4 and 5) and negative control (lane 2).

Figure 4 Electrophoresis for PCR products of two cancer patients.

Figure 5 (a) Percent of cases with 100, 200, 400 and 800 bp in cancer, benign and control groups; (b) percent of cases with 800 bp in all cancer subgroups.

Table 3 M ± SE of CFDNA band intensity in AU at 100, 200 and 400 bp and CFDNA integrity index (400/100) in different subgroups of cancer, benign and control groups.

Groups	Band intensity in AU (M ± SE)					Integrity index
	100 bp		200 bp		400 bp
Cancer (n = 85)	83.0 ± 4.2^a	p1 = 0.000	80.9 ± 2.4^a	p1 = 0.000	85.2 ± 3.8	1.3 ± 0.13
		p2 = 0.000		p2 = 0.000
Breast (24)	94.4 ± 6.3^a	p1 = 0.000	72.2 ± 5.4^a	p1 = 0.000	64.7 ± 8.2	0.66 ± 0.096
		p2 = 0.000		p2 = 0.000
Lung (14)	63.4 ± 8.3^a	p1 = 0.000	77.6 ± 7.5^a	p1 = 0.000	76.4 ± 9.5	1.42 ± 0.21
		p2 = 0.001		p2 = 0.000
Colon (14)	65.2 ± 12.8^a	p1 = 0.000	92.4 ± 5.9^a	p1 = 0.000	91.3 ± 7.0	1.97 ± 0.35
		p2 = 0.002		p2 = 0.000
Stomach (13)	86.4 ± 12.6^a	p1 = 0.000	93.6 ± 2.3^a	p1 = 0.000	92.2 ± 9.2	1.44 ± 0.39
		p2 = 0.000		p2 = 0.000
HCC (10)	64.0 ± 15.1^a		77.8 ± 2.8^a		111.8 ± 3.2	2.14 ± 0.55
Lymphoma (10)	104.0 ± 3.6^a		74.2 ± 3.7^a		97.9 ± 8.2	0.93 ± 0.065
Benign (n = 30)	27.8 ± 5.9	p1 = 0.678	27.9 ± 5.9	p1 = 0.334	–	–
Control (n = 30)	24.0 ± 4.3		21.8 ± 4.8		–	–

p1 = significance when compared to control group.

p2 = significance when compared to benign group.

a The mean difference is significant at p < 0.05 when compared to the control and benign groups, respectively.

Table 4 Correlation between plasma DNA levels and clinicopathological parameters.

Parameters	Correlation with CFDNA concentration		Correlation with CFDNA integrity index		Correlation with intensity of 800 bp band
	r	p	r	p	r	p
Pathological stage	−0.157	0.216	−0.335	0.113	−0.430	0.249
Histological grade	−0.227	0.067	0.126	0.080	0.292	0.082
Tumor size	−0.192	0.229	0.276	0.314	0.157	0.163
Lymph node metastases	−0.320	0.128	−0.239	0.207	−0.316	0.167
Vascular invasion	−0.252	0.384	0.351	0.294	0.940	0.005

P is significant at <0.05.

Table 5 Conventional tumor markers routinely used in cancer diagnosis in cancer patients and control group, cutoff, sensitivity, specificity and AUC.

Tumor marker	Control		Cancer		Cutoff	Sensitivity (%)	Specificity (%)	AUC
	Mean	Range	Mean	Range
CA 15.3 (U/ml) 24 breast cancer	8.8	0–32.5	14.5	0–200	28	62.0	70.0	0.61
AFP (ng/ml) 10 HCC	7.5	1.5–113	116	3–3300	19.8	68.2	75.4	0.70
CA 19.9 (U/ml) 27 GIT cancer	8.9	1.7–44.5	19	1–540	37	67.1	74.7	0.63
Cyfra 21.1 (ng/ml) 14 lung cancer	2.3	0.5–11	15	0.6–126	4	65.4	69.7	0.71