In the USA:
if riskFromTreatment <= riskFromNoTreatment: doTreatment
In most public systems:
if (treatmentCost <= someThresholdPerBenefit) && (riskFromTreatment <= riskFromNoTreatment): doTreatment
In practice, treatment outcomes are pretty similar, but more treatments are preformed in the USA system. Being a for-profit system is one cause, but so is the litigation culture. Not doing every possible treatment and test can lead to the physician being accused of being negligent.