That's not what hearsay is, hearsay is essentially an out of court statement used to prove the truth of the matter asserted. (It would be hearsay if someone other than the doctor where testifying as to what the doctor said).
This might, subject to other objections, be admissible as circumstantial evidence. Circumstantial evidence is valid evidence in court. However, it might be improper expert opinion, but I am not going to go through the analysis here either way, because:
In any event, we are not in a court of law, we are before the FDA, who has their own rules requiring double blinded studies and p-values.
...that's the reason for Brazil.