I'm not the right kind of Dr. to know the answer to that question PlanTrader. PhD not MD - genetics and molecular biology.
My guess - chemo is used on more advanced cases. But it could just be whatever a particular hospital or set of doctors think is best on a case by case basis.
I wonder too what the success rate is if MK is applied for a longer period of time with no chemo follow up? That could really change the SOC and reset the course of chemo therapy. Of course that would be yet another 10 year study, just how long will it take to see success on this ticker?