PIK3CA and cancer: We analyzed plasma-derived ctDNA for the five different cancer-associated genes (BRAF, EGFR, KRAS, NRAS, PIK3CA) from 241 timepoints of 39 melanoma patients, of which 89.7% were in metastatic American Joint Committee on Cancer (AJCC) stage IV and 10.3% in unresectable AJCC stage III; 66.7% of these patients were male and 33.3% were female.