The spacing distribution for TP53 doublets in lung cancer occurring in the same exon (43%, 23/54) also shows proximal spacing (<86 bp, average 20.2±20.9 bp) and fits to an exponential distribution (R2 = 0.979) (Table S2, Figure S1) with a half-life of mutation spacing of 15 bp. The gene discussed is TP53; the disease is lung cancer.