In medicine, in general, and cancer management, in particular, the term standard of care is often poorly defined. From use of this expression in the setting of a malpractice case to a pronouncement that justifies denial of health benefits by a third-party insurer, this three-word statement can have vastly different, often profound, and sometimes problematic as well as controversial meanings. Consider, for example, the common situation of the recently reported statistically significant results of a phase III trial in a particular setting that reveals a two-drug combination containing commercially available antineoplastic agents improves progression-free survival and overall survival, compared with single-agent therapy.

Or, perhaps, we should recognize that attempting to define the standard of care in oncology is often a profoundly futile endeavor, due to the remarkable complexity of the disease processes (eg, stage, grade), individual patient (eg, preexisting comorbidity, prior therapy), and provider (eg, availability of technology in specific geographical settings) differences, and the rapidly changing science of cancer care

Finally, in the opinion of this commentator, while the fundamental question remains unanswered as to who should decide what falls within the category of standards of care, and whether it is the physician, patient, or third-party payer who will have the ultimate say as to the specific choice of disease management, recognition that this discussion rationally should focus on multiple reasonable options, rather than a single rarely changing standard, will begin to move this important, complex, and often highly contentious debate, in the right direction.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2793775/