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Hi everyone,
I think that you're getting confused by the statistical terms. I have looked at the HERA study closely and for all categories from no node to 4+ nodes, the reduction in risk was around 46%, but this translates into difference percentage POINT gains for different groups, since they start with different chances of recurrence.
I'll try to keep this simple, since I know that stats are confusing (I was one the teaching assistant for a new stats teacher who couldn't teach. Boy did he confuse them).
First you take the chance of recurrence and multiply it by 46% (.46) to get the estimated benefit of one year of herceptin by itself. Then add that number to the existing chance of disease free survival to get the new odds.
So, if there is a person with a 20% chance of recurrence, the gain is 9.2 percentage points (20 * .46). The new chance of disease free survival would be 80% plus 9.2% which is 89.2%.
If someone has a 60% chance of recurrence, the gain is (60*.46) = 27.6 percentage points. The new chance of a disease free survival is 40% + 27.6% which is 67.6%.
Likewise, in the herceptin studies, herceptin reduced the risk of recurrence from somewhere around 30% to 15% or 15 percentage points, but this meant that it reduced the risk of recurrence by 52% (30 * .52). (HERA and the herceptin-based chemo results are not directly comparable, since there was no one standard type of chemo used in HERA).
While I know that the chemo-based herceptin option has had a longer followup time, I am just worried that this misunderstanding may cause people to press for an option that may not benefit them as much as they expect and that has risks.
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