Mapping papillary thyroid cancer evolution for improved prognosis

Khawla Al-Kuraya at King Faisal Specialist Hospital and Research Center in Saudi Arabia and co-workers used genetic sequencing to explore the path of tumour evolution and mutations in tissue samples taken from 79 PTC patients at their hospital. Six patients were sampled twice: once for the primary tumour and again, following relapse, after surgery to remove the thyroid.  

Tumours are naturally genetically diverse, and therefore evolve in different ways. This is the case not just between individuals with the same cancer, but also within tumour tissues in a single patient. Tumour cell evolution can be linear, with the successive growth of dominant clones, or branching, with clone subpopulations (or subclones) diverging from a single ancestor. The fittest, often treatment-resistant subclones are thought to assist relapse. 

The researchers found that PTC evolution followed both linear and branching paths across the cohort, and that patients with high levels of subclonal mutations had a significant chance of relapsing.   

The researchers say their findings have potential implications for individualising prognosis and highlight the importance of evolutionary development as the engine that drives cancer relapse.

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