I would say no, Igor. Alpha/beta ratio is a characteristic of the cellular radiosensitivity and is defined for each tumour type. The question is perhaps the other way round: does the alpha/beta ratio dictate the treatment choice? And the answer would be - yes.

Thanks, Loredana! The conventional wisdom is as you say, of course. But I am starting to wonder whether this is always applicable after looking at data like the ones in the attached papers. Basically, the findings there are that it is difficult to describe survival curves for the same cell type, but with different doses per fraction, by the same alpha/beta ratio. But perhaps they can be explained by an alpha/beta ratio which depends on dose per fraction - e.g. because of dose-dependent effects on cell cycle distribution and DSB repair pathway choice.

This is the second paper I mentioned.

I get your point, Igor. And the two papers clearly demonstrate it!

The discrepancy between the alpha/beta ratio in the two RT protocols (conventional vs stereotactic RT) is just too big to be ignored. So if the alpha/beta ratio is not constant (i.e. varies as a function of fractionation schedule) for a given cell line, this is perhaps due to variations in cellular redistribution and repair (getting back to your former question :-))

The same research group as the one you recommended, published a recent paper where they looked into extended LQ models in order to facilitate dose conversion from hypofractionation to single-dose treatment.

Thanks for the paper, Loredana! There are indeed multiple models which can fit mammalian cell survival curves better than the LQ model (e.g. see http://www.ncbi.nlm.nih.gov/pubmed/23098282). However, in my opinion, there are 2 negative sides to many of them: (1) the number of model parameters is much more than 2, which makes the models much less convenient to use, (2) the mechanistic (biologically-based) justification for many of these models is not as strong as for the LQ model.