could you find some relation between your research and cancer or other disease? Say, the research of cell function can improve the technology to cure cancer. But you do need to find some articles/papers to partially prove it (it do not need to be strict proof, the INS officer don't understand and don't care too much either.)
The INS officers are not research expert, so it is easy to "convince" them.
The INS officers are not research expert, so it is easy to "convince" them.