The potential relationship between PIK3CA and the response to pyrotinib treatment was firstly indicated in a metastatic setting in 2017, which reported that PIK3CA and TP53 double mutations in circulating tumour DNA (ctDNA) is a potential predictor for the insensitive treatment response of pyrotinib (P = 0.013); however, this conclusion requires further evaluation given the limited sample size (n = 18), and lack of data concerning PIK3CA mutation alone [47]. The gene discussed is PIK3CA; the disease is neoplasm.