Because they haven't been directly compared to one another? The BED of 2.66 x 16 is closer to 50/2 than 2.67 x 15.
I like Canadians more than I like the British. Canadians have given us Palma and the Toronto Raptors. UK has given us Jayant Vaidya and Brexit.
I find myself thinking that folks in the UK are driven by a perverse interest to minimize number of fractions at all costs, so as to the cut the costs to their failing NHS system, and they want us all to be on their level of dissatisfaction of lives as doctors. Beyond START, there's FAST and now FAST FORWARD.
Canadians seem to be less so in that vein, and more interested in expanding indications for radiation or more technical forms of RT (see Palma, Arjun Sahgal, etc), while the Brits just seem to be less, and less, and less. To the point where they seem less interested in the science and more towards pushing the agenda to fewest treatments possible (see the cosmesis data from FAST-FORWARD 5-year data)
The first big (and clear i.e. no A/B 4 arms behemoth) randomized trial reported was the Whelan trial and he came to America and pimped it to anyone who'd listen. We started doing it. It worked. Patients did well. There was no reason to change.
The (much) better question is, "why would anyone care if their colleague is doing 15 or 16 fractions?"
Whelan did it first, so that is best. The British scientists are bad people who hate radiation. Ok, got it. Convinced me.
Both are standards of care, I have plenty of colleagues that use 16 and I believe them to take perfectly good care of their patients. Not sure why people are so offended about such a simple question.
evilbooyaa: In regards to BED, I disagree that 4256/16 is necessarily closer to 50/2, depends what a/b you use. Local control did not suffer in START and actually favored hypofx crudely.
I would never advocate for a completely asinine trial such as 15 vs 16, but still am left to decipher them to the best of my ability. I guess caring about such small details is below you?
There is a such thing as normal tissue complication probability curves. FAST FORWARD proved that a very small difference in dose in whole breast can greatly impact cosmesis. Given START was only one that showed significantly improved cosmesis, I posit that we are seeing a similar phenomenon between it and Whelan, but cannot prove that without a trial.
I know, I know, all makes too much sense but does not fit with what you do and might lose you a fraction, just go back to the drive bys and snide remarks and ignore the rest.