Early detection of cancer in the general population: a blinded case-control study of p53 autoantibodies in colorectal cancer

Abstract

Background: Recent reports from cancer screening trials in high-risk populations suggest that autoantibodies can be detected before clinical diagnosis. However, there is minimal data on the role of autoantibody signatures in cancer screening in the general population.

Methods: Informative p53 peptides were identified in sera from patients with colorectal cancer using an autoantibody microarray with 15-mer overlapping peptides covering the complete p53 sequence. The selected peptides were evaluated in a blinded case-control study using stored serum from the multimodal arm of the United Kingdom Collaborative Trial of Ovarian Cancer Screening where women gave annual blood samples. Cases were postmenopausal women who developed colorectal cancer following recruitment, with 2 or more serum samples preceding diagnosis. Controls were age-matched women with no history of cancer.

Results: The 50 640 women randomised to the multimodal group were followed up for a median of 6.8 (inter-quartile range 5.9-8.4) years. Colorectal cancer notification was received in 101 women with serial samples of whom 97 (297 samples) had given consent for secondary studies. They were matched 1 : 1 with 97 controls (296 serial samples). The four most informative peptides identified 25.8% of colorectal cancer patients with a specificity of 95%. The median lead time was 1.4 (range 0.12-3.8) years before clinical diagnosis.

Conclusion: Our findings suggest that in the general population, autoantibody signatures are detectable during preclinical disease and may be of value in cancer screening. In colorectal cancer screening in particular, where the current need is to improve compliance, it suggests that p53 autoantibodies may contribute towards risk stratification.

Figure 1

Autoantibodies to p53 peptide (microarray) and p53 protein (ELISA) in time of diagnosis set I, time of diagnosis set II, and the UKCTOCS set. DOTPLOT of serum IgG autoantibodies binding to 15-mer scanning p53 peptides measured by peptide-array assay and expressed as relative fluorescence units (RFU) (y-axis). (A) Serum from healthy (n=53) and colorectal cancer individuals (n=58) (time of diagnosis #1). (B) Serum from healthy (n=40) and colorectal cancer individuals (n=157) in time of diagnosis set #2 (training set). (C) Serum from last sample before diagnosis in controls (n=94) and colorectal cancer (n=97) individuals from the UKCTOCS set. Bar graphs represent the sensitivity for each p53 peptide at 95% specificity.

Figure 2

Autoantibodies in pre-diagnostic serial samples from colorectal cancer patients (n=97) to selected p53 peptides. Each graph represents the autoantibody reactivity to peptide p53-9, p53-10, p53-25, p53-78. Each symbol represents a single cancer patient. Number of years before diagnosis is indicated on the x-axis. y-axis represents relative fluorescence units (RFU).

Figure 3

Pre-diagnostic serial samples from selected colorectal cancer patients to p53 peptides. Each graph represents a single colorectal cancer patient and autoantibodies to all the 18 p53 peptides investigated in the validation set. x-axis represents number of years before diagnosis. Graphs for p53 protein ELISA are marked with red colour. Left y-axis represents relative fluorescence units (RFU). Right y-axis represents U ml⁻¹ for ELISA results.