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Background:
Screening for colorectal cancer using the faecal occult blood test (FOBt) has been shown to reduce cancer specific mortality through the detection of early stage disease. However, it is recognised that there are additional tumour factors, such as the presence of venous invasion, and host factors, including the systemic inflammatory response, that are key determinants of outcome independent of stage. To date, the prevalence of such factors has not been examined in screen-detected colorectal cancer (1).
Aim:
The aim of this study was to compare the prevalence of tumour and host determinants of outcome in patients with screen detected (SD) and non-screen detected (NSD) colorectal cancer in a contemporaneous group.
Methods:
All patients who underwent potentially curative surgery for colorectal cancer either via the national FOBt screening programme (SD) or presented symptomatically in a single institution (NSD) between May 2009 and April 2011 were identified from prospectively maintained databases.
Results:
A total of 394 (288 SD, 106 NSD) patients were identified. Compared with the NSD patients, SD patients were more likely to be younger (p<0.001) and have tumours that were colonic (p=0.001), left sided (p<0.001) and of an earlier stage (50% Dukes A vs 17% Dukes A, p<0.001). When high risk tumour features were examined, vascular invasion (p=0.023), margin involvement (p=0.009), poor differentiation (p=0.009) and tumour perforation (p=0.093) were all less likely to be present in SD tumours. The systemic inflammatory response, as measured by the Neutrophil to Lymphocyte Ratio (NLR), was elevated in significantly less SD patients than NSD patients (NLR>5 in 7% vs 24%, p<0.001). In addition, less SD patients were anaemic (22% vs 50%, p<0.001).
When node negative patients were examined independently (n=242 ;177 SD, 65 NSD), the differences in both the tumour and host determinants of outcome remained. SD patients had less evidence of vascular invasion (p=0.034), margin involvement (p=0.039) and tumour perforation (p=0.059), in addition to having a lower systemic inflammatory response (NLR>5 in 7% vs 23%, p<0.001) and less anaemia (18% vs 54%, p<0.001) than NSD patients.
Conclusions:
The results from this study suggest that, compared with NSD tumours, SD tumours, in addition to being of an earlier stage, have more favourable tumour pathological features. Furthermore, adverse host prognostic factors such as the presence of anaemia and an elevated systemic inflammatory response are also less likely to be present in patients with SD tumours.
References:
1.Mansouri D, et al. Screening for colorectal cancer: What is the impact on the determinants of outcome? Crit Rev Oncol Hematol. 2012. Epub September 2012
Comparison of tumour and host determinants of outcome in screen detected vs non-screen detected colorectal cancer

	Screen detected n(%)	Non-screen detected n(%)	p-value
	288 (100)	106 (100)
Tumour stage
A	144 (50)	17 (17)
B	67 (23)	50 (47)
C	70 (24)	31 (29)
D	7 (2)	8 (8)	<0.001
Vascular invasion (a)
Y/N	121 (42) / 160 (56)	61 (58) / 43 (41)	0.023
Peritoneal involvement
Y/N	11 (4) / 277 (96)	22 (21) / 85 (79)	<0.001
Margin involvement
Y/N	6 (2) / 282 (98)	8 (8) / 98 (92)	0.009
Tumour perforation
Y/N	2 (1) / 286 (99)	3 (3) / 103 (97)	0.093
Poorly differentiated
Y/N	6 (2) / 282 (98)	8 (8) / 98 (92)	0.009
Neutrophil:Lymphocyte Ratio (b)
>=5/<5	16 (7) / 230 (93)	25 (24) / 79 (76)	<0.001
Anaemia (b)
Y/N	53 (22) / 193 (78)	52 (50) / 52 (50)	<0.001

[a. n=385 (98%): b. n=350 (89%)]