PIK3CA and cervical cancer: For example, a study using ddPCR to detect ctDNA in serum found that the HPV E7 gene was the most sensitive test as it was 70% positive for cervical cancer lesions, which was significantly better than HPV integration sites and PIK3CA mutations (39%, 30%); negative HPV E7 ctDNA in serum after treatment for cervical cancer predicted better PFS for patients; E7 ctDNA could be detected about 10 months before the clinical diagnosis of recurrence [39].