You can hear it claimed-- or in any case read it on the interwebs -- sometimes by religious people, sometimes by young men who think selfishness is cool, that if you take a scientific worldview, there is no reason not to place your personal pleasure above that of everyone else.
I do not think that claim holds water. It is true that science itself cannot give you a reason for why you should value pleasure, or oppose to suffering. Pleasant and unpleasant are subjective, not directly measurable concepts. We can measure things that associate with suffering -- we can measure blood pressure or stress hormones, we can observe nutritional state and death, we can ask people to rate their pain on a scale of 1 to 10 -- but the fact that we designate pain and suffering as unpleasant is, well, consensus based on personal observation.
At the heart of science is a set of core assumptions of how knowledge can be acquired. One of these is that personal observation is not enough to draw conclusions about external realities, but that to be considered true, the result of an experiment must be replicable -- that is, others must be able to say "yes, I did the same experiment, and I saw the same thing". Another is the so called "Occam's razor" principle, which states (among other things) that if an explanation is sufficient to fully explain a phenomenon, there is no need to, and indeed you should not, add to that explanation something that there are no consistent observations of.
If we accept the personal observation that pain and suffering are unpleasant and something we would like to avoid, I do not think there is any scientific way to claim that you should consider your pain and suffering any more (or any less) important than that of someone else. Science, first of all, assumes at its core that other humans exist; the whole idea of trying to contruct experiments that function the same regardless of who performs them has built-in the idea. Second, even if it did not, I think Occam would force us to conclude that the likeliest explanation for our perception that others like us exist is that they indeed do so.
In any case, given that other people do exist, it does seem to me that there is no scientific evidence whatsoever that would suggest that our own pain and suffering are somehow more important than those of others. We can of course construct possibilities where it might be so -- maybe all the world is illusion except our own consciousness, say -- but by the Occam's razor principle these must then be discarded.
Science does not give you any reason why you should value the avoidance of pain, or the gain of pleasure. But given that you do value them in your own case, I think science does not give you any excuse to not value them in everyone else's case too.