So the clinical challenges in finding the proper patient for extended endocrine therapy is that overall the benefit from extended endocrine therapy is relatively modest. We’ve seen it in several trials but it’s not a huge benefit. It’s in the range of about 20% relative reduction with absolute benefits in the range of 2 to 3 to 4%. So what we have tried to do is to first identify patients at high risk of recurrence, where the absolute benefit will be higher even with a lower relative reduction...
So the clinical challenges in finding the proper patient for extended endocrine therapy is that overall the benefit from extended endocrine therapy is relatively modest. We’ve seen it in several trials but it’s not a huge benefit. It’s in the range of about 20% relative reduction with absolute benefits in the range of 2 to 3 to 4%. So what we have tried to do is to first identify patients at high risk of recurrence, where the absolute benefit will be higher even with a lower relative reduction. And we do that with clinical pathologic factors. The more important ones, tumor size, grade, nodal status is actually a very important one, meaning that if the patients have high risk because of these factors, then the absolute benefit will be higher. And typically, we give the extended endocrine therapy to those patients more often because they tend to benefit more. But we also have tried to identify predictors of benefit from extended endocrine therapy, meaning that the relative reduction is different depending on the factor. And in that venue, we have evaluated several biomarkers in the B-42 study, the NSABP B-42 study, and other studies. And the one that has the most data with is BCI, Breast Cancer Index, and also the HOXB13 to IL17BR ratio, as we call it, to Breast Cancer Index, which has shown a significant interaction in three studies of extended endocrine therapy, meaning that if you have HOXB13 to IL17BR high, you get more relative benefits from extended endocrine therapy versus if you are low. With similar findings we found in the B-42 trial with BCI, it was statistically significant for interaction, but still the benefit was in the right direction. Ultimately, there are other factors that we potentially can use in the future. We’re looking into circulating tumor cells, circulating DNA as a factor, again, to identify high-risk patients that potentially could benefit. And, of course, even AI models have been used to develop now prognostic information, but yet the AI models so far have not shown predictive information relative to differential benefit from extended endocrine therapy. So we tend to put all this together and ultimately make a decision on who is the patient that will benefit, and of course we take into account the tolerability of the extended endocrine therapy to the patient. If the patient is miserable by taking more treatment, he’s more likely not to want to take it. But if the patient does well, we’re more likely to say okay, why don’t you continue, and we typically aim for about 10 years total, but even if you get to seven to eight years, it appears to be enough in most cases to get more benefit and not have to complete the whole 10 years.
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