The doses Jodi gave are what I use. I have used the formula long term with no significant adverse effects other than development of blood deficiency which can be managed with Blood tonic formulas added to the XFZYT. The length of time I use the formula depends on the setting I am using it in.
If you are treating non-resectable or gross disease, then they usually have to be on the formula very long term, maybe for life, to prevent relapse. As Jodi mentioned, maybe I am also missing an underlying imbalance. But that is how I approach things. After 6 months, if disease is controlled, I usually maintain them on XFZYT without the added E Zhu and San Leng and they seem to do well with that.
If you are treating dirty margins and trying to prevent recurrence in a grade II tumor, then I will usually treat for 6-12 months and then discontinue the formula depending on how well their tongue and pulse has responded to treatment. Some incompletely excised grade II MCTs don't recur even with no further treatment, but others are more aggressive. Proliferation panel is the only way to really try and predict which ones are more likely to behave more aggressively from a conventional standpoint....but I digress.
For grade III tumors, even if completely excised, they should probably be on treatment long term since grade III tumors are so aggressive and prognosis is generally poor.
As a side note, MCT patients should not ever be vaccinated again unless absolutely necessary. Mast cell tumor and LSA patients commonly relapse after vaccination. I recommend vaccine titers in all MCT patients and most cities and kennels will now accept titers and a letter from the DVM stating why vaccination is a risk to their health.
Probably more than you wanted to know!
Erin