By applying the inclusion/exclusion criteria, the minimum number of three eligible articles required for quantitative synthesis of data was not reached for the TP53, BRAF, PIK3CA, and SMAD4 genes for both response (i.e., pCR and tumor downstaging) and prognosis (i.e., DFS/RFS, OS) endpoints. The gene discussed is PIK3CA; the disease is neoplasm.