While no significant association between PIK3CA mutations and recurrence-free interval was observed overall, a strong trend for impaired recurrence-free interval was noted in hormone receptor-positive breast cancers with PIK3CA mutations (adjusted HR 1.64), and a significantly detrimental prognostic impact was observed in hormone receptor-positive, HER2-negative patients treated with aromatase inhibitors alone (adjusted HR 4.44) but not in tamoxifen-treated patients, suggesting that estrogen deprivation may be ineffective in the presence of PIK3CA mutations [ 57 ].
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