Preliminary results from 4,635 patients, based on local testing of HR status, showed that the reduction in risk of recurrence with letrozole compared with placebo was greatest in women with the most hormone-dependent tumors.
A total of 158 samples from the phase III trial (24 HER2+, 43 ER−/PR−/HER2−, and 91 ER and/or PR+/HER2− based on local testing) were chosen at random and centrally confirmed for ER, PR, and HER2.
In other words, we can introduce them into new therapeutic regimens based on local susceptibility tests.
Eligibility for this trial was based on local HER2 test results, but it was estimated that 18% of tumors were tested as false positive due to inaccurate test and/or interpretation methods.
Vaz-Luis and colleagues are to be congratulated for gathering outcome data from 3,394 patients, diagnosed with HER2-positive breast cancer based on local laboratory testing between 2000 and 2007, and grouping them based on hormone receptor status.
The study was designed to enroll approximately 50% cases with positive HER2 status and 50% with negative HER2 status as determined by study sites based on local HER2 testing.
Logistic regression models were constituted using backward selection based on local Likelihood Ratio tests at the nominal 1% level; the overall goodness of fit of a model was then estimated by means of Nagelkerke's R[ 2] coefficient.
Eligibility criteria for N9831 trial enrollment were initially based on local laboratory HER2 test results (IHC score of 3+ or HER2/control probe ratio ≥2.0 or five or more gene copies of HER2) [ 12, 32].
Hormone receptor status was defined as ER and/or progesterone receptor (PR) testing based on local analysis as described in their database; details of the type of testing or definition of positivity are not described.
Our group's published data derived from prospectively conducted phase III trials in which central HER2 testing was performed along with hormone receptor status based on local laboratories (central hormone receptor testing is ongoing) are especially relevant [ 6, 7, 10].
