The Harvard study also showed an increased risk of death among heart attack patients older than 75 who received clot-busting drugs.
He said investigators believe that at least 10 physicians could have received diluted drugs.
These patterns change if only a few members receive psychoactive drugs.
The child may have received drugs or treatment to relieve symptoms caused by the tumor.
Similar calculations were not reported for patients who received drugs.
Boys are much more likely than girls to receive such drugs when they visit doctors' offices and clinics.
She also declined to say if the four who died were receiving drugs through such a program.
Their diagnostic tests were done in the usual exam rooms, and they received drugs just like private patients.
The majority of these patients also had received other drugs known to affect the immune system.
While undergoing treatment, the patient received several drugs, including Lisinopril.