Below is a comment I received from an active cancer researcher, who runs an interesting blog called biopolyverse.
As for the bicarb thing, there is a lot of current interest in the microenvironment of solid tumors and its effect on tumor cell growth, survival, and metastasis – and low pH may indeed help them along. Hence a possible role for bicarb or something similar, if they can indeed raise local pH – although as you noted, for bicarb at least other mechanisms might be operative.
I think it unlikely that bicarb alone would offer much of a solution, but it would be interesting to see what its effects might be in combination with other agents. ‘Combo’ treatments are seen as the way to go in oncology trials these days. I had a look at the NIH clinicaltrials.gov site for bicarb-related trials, and a combo of bicarb and gemcitabine (a deoxycytidine analog) in pancreatic cancer is currently underway.
(This was just a quick search – may be other relevant things out there).
The thing is, obviously bicarb is of no use as a patentable, profit-making drug – but you can potentially patent a bicarb-drug combo package as a therapeutic entity, if it proved to be valuable. So it would be too early to write off big pharma interest in this area, especially if current trials give interesting results.