Treatments? Cancer patients can have low platelets for a few reasons (i think this is what you're asking). 1-chemo treatments can reduce platelet counts by a direct toxic effect. Usually this recovers prior to the next treatment. 2-liver disease from metastases can lead to low platelets. 3-i suppose malnutrition itself could cause low platelets.
Complicated. Platelets are an a 'acute phase reactant' that change with infection, inflammation, tumors, and various chemptherapies among other things. Platelets are involved in blood clotting.