How many samples are needed to infer truly clonal mutations from heterogenous tumours?

• Published in: BMC cancer Vol. 19; no. 1; p. 403
• Main Authors: Opasic, Luka, Zhou, Da, Werner, Benjamin, Dingli, David, Traulsen, Arne
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 29.04.2019; BioMed Central; BMC
• Subjects: Biopsy; Cancer; Cancer cells; Cancer treatment; Care and treatment; Cell division; Clonal mutations; Epigenetic inheritance; Genetic aspects; Genomes; Intratumour heterogeneity; Kinase inhibitors; Kinases; Mutation; Phylogenetics; Population; Probability; Sampling; Somatic evolution; Spatial model; Targeted therapy; Truncal mutations; Tumors; Intratumour heterogeneity; Somatic evolution; Spatial model; Clonal mutations; Targeted therapy; Truncal mutations
• ISSN: 1471-2407; 1471-2407
• DOI: 10.1186/s12885-019-5597-1

Modern cancer treatment strategies aim to target tumour specific genetic (or epigenetic) alterations. Treatment response improves if these alterations are clonal, i.e. present in all cancer cells within tumours. However, the identification of truly clonal alterations is impaired by the tremendous intra-tumour genetic heterogeneity and unavoidable sampling biases. Here, we investigate the underlying causes of these spatial sampling biases and how the distribution and sizes of biopsies in sampling protocols can be optimised to minimize such biases. We find that in the ideal case, less than a handful of samples can be enough to infer truly clonal mutations. The frequency of the largest sub-clone at diagnosis is the main factor determining the accuracy of truncal mutation estimation in structured tumours. If the first sub-clone is dominating the tumour, higher spatial dispersion of samples and larger sample size can increase the accuracy of the estimation. In such an improved sampling scheme, fewer samples will enable the detection of truly clonal alterations with the same probability. Taking spatial tumour structure into account will decrease the probability to misclassify a sub-clonal mutation as clonal and promises better informed treatment decisions.