PIK3CB and Familial prostate cancer: In prostate cancer, Class IB PI3K genetic aberrations are less common, and include PIK3CG mutation and amplification (1.4–1.8% and 0.6–3.6% incidence respectively) as well as PIK3R5 and PIK3R6 deep deletions (0–3.3% incidence) that are indicative of a homozygous deletion (Tables S1–S3).