Our findings are conceptually supported by studies of bacterial resistance, describing that genetic reversion is nearly always the main form of phenotypic reversion when mutation supply is high (as in cancer).24 Numerous studies have identified that a high tumor fraction in cfDNA is overall associated with poor prognosis, but our data here suggest that among responding patients, this effect is minimal when evaluated during treatment, with the detection of BRCA2/PALB2 reversions offering a greater insight into which patients are rapidly progressing on PARPi therapy. The gene discussed is PALB2; the disease is cancer.