Best practice is typically based on clinical research:

	From evidence from controlled clinical trials assessed independently (not provided exclusively by the drug company).
	From the outcomes of trials that have been reproduced by independent groups.

The high ethical standards and training within the medical profession

The peer review system

The use of scientific methods and standards, such as prospective study design and randomized controls
to minimize the impact of reporting bias and patient selection bias.

A prospective design predefines the number of patients that will take part in the study.

Randomized selection of participants to the compared therapies ensures that the participants in the two study arms have similar risk factors.

The key standard for medical evidence is reproducibility - that other independent scientists achieve similar results when the therapy is tested in a similar population.

Institutional Review Board (IRB) oversight of clinical trials

FDA oversight of clinical trial design and the rigorous review of data for drugs that are submitted by the sponsor for marketing approval.
 

Do not do that trial (if the consulted provider is not the investigator of the trial)

Do the trial
(if the consulted provider is the investigator or owner of the idea)

Do the test
(if the provider owns an interest in the imaging company, or the provider doesn't want to be found negligent - even if the test is unlikely to be informative)

Do maintenance therapy
(if the consulted provider administers it)

Does not discuss Radioimmunotherapy
(if the consulted provider does not administer it)

Again, NONE of the above examples are unethical when there is no standard of care,
but the opinions we receive can be unconsciously influenced by financial interest.

Seek multiple opinions and ask also for rationales and supporting evidence
(do all your providers agree and why not?)

Seek opinions from non-treating, independent experts
(who will not be involved in administration of therapy)

Do our homework in order to ask informed questions.
 

Conflict of Interest in Medical Research, Education, and Practice - NCBI Bookshelf http://bit.ly/2pYGhlV

2016 - recommended reading
Conflict of Interest: Time for Reevaluation - Clinical Oncology News http://bit.ly/2b9bhx9

I believe that the term “conflict of interest” itself should be reconsidered. New language, such as a statement of transparency, can readily replace it. A voluntary statement of transparency would cite all influencing circumstances and provide a complete description of existing relationships. For example, on a research paper the listing of sources of grant support should present government funding (e.g., NIH) along with citations of an industry grant or consultantship. Such an encompassing statement would present all of the facts in an open declaration to the reader.

Where, then, should there be control that deters financial or other malfeasance? I suggest it should be where it has always been: in the scientific method. The essence of science, and the proof of the issue, is in its reproducibility. Henry Buchwald, MD, PhD

Conflict of Interest commentary - hmohardball.com 

The Dirt on Coming Clean: The Perverse Effects of Disclosing Conflict of Interest cbdr.cmu.edu/  

Evaluating Medical Claims and Data - PAL

Doc financial disclosure information by state  http://projects.propublica.org/docdollars/states/1