That depends.
There are at least 4 kinds of myeloproliforative disorders. (MPDs)
If you are talking about polycythemia vera, (most common), conventional treatment is available.
There are meds that inhibit platelet production.

It is important to note that this is not leukemia.
There is evidence that supports cannabis for treating leukemia.
(I am unfamiliar with any MPD/cannabis trials.)

You may be able to supply evidence that it is effective for the treatment of polycythemia vera.

What I'm suggesting, is getting the first few blood tests to determine severity, and to track the rate of overproduction.
Then begin a trial with Simpson oil and note the numbers in the next blood test.
Document it here, and we will all know if it is effective, yah?

Disclaimer:
I am not a doctor, and would not suggest self medication with anything that might do more harm than good.

That said, I have no reservations suggesting a cannabis trial.
It may be the most harmless medication that you will ever find.

So, if you are willing to try it, and document the trial, you could do a great service to us all, with minimum personal risk.
(Other than legal issues, that is.)

What say you?

Aloha,
Weezard