PIK3CA and atrial fibrillation: Interestingly, in the ctDNA from the third plasma sampling (week 42, with progressive liver metastases), the PIK3CA c.1633G>A variant AF increased by nearly 32-fold (AF = 82.5%) while those KIT variants were reduced by at least 14.2-fold (exon 11 c.1673_1687del, AF = 0.15%; exon 17 c.2485G>C, AF = 0.24%).