The following is an excerpt from Taking Charge of Cancer: Chapter 6 - Is Your Doctor’s Recommendation Best for You?
For many types of cancer, the best treatment approach is well-established. Sometimes surgery is the #1 choice. This is true for early-stage breast and colon cancers. Other times, it's radiation as the top choice. This is the case for some head and neck cancers. When the best approach is clear, there is very little debate.
But in some scenarios, the debate is intense. Let’s consider a patient with stage I lung cancer. Stage I means that the lung cancer is small - 5 cm (2 inches) or less - and hasn’t spread to any other parts of the body. These cancers are highly curable. The disagreement over how this patient should be treated illustrates some of the biases inherent to medicine.
For more than 50 years, the standard treatment in this situation has been surgery, giving the best chance of cure. Radiation has been the second-choice treatment option, used mostly for patients who were too unwell to undergo surgery.
But the tides are shifting. A new type of precise radiation treatment has been developed, stereotactic radiation. The results have been very good, generally with few side effects. Some doctors are now calling for stereotactic radiation to replace surgery as the treatment of choice. Ideally, we would now have randomized trials to compare these two options, but we don’t. A few were tried, but not enough patients joined to allow for any strong conclusions. [You can read the report from two of the trials here].
Since we don’t have randomized data, the truth is that we don’t know for sure which of the two treatment options is better, because we have incomplete evidence. If you took a poll of doctors, some might favor surgery, some might favor stereotactic radiation, and some might be undecided.
The problem is that doctors’ beliefs are heavily dependent on what they do for a living. If you ask radiation doctors, 80 percent believe that surgery and radiation are equally effective in this situation. If you ask surgeons, the number is only 20 percent. And if you ask a neutral party (in this case, lung specialists who don’t do surgery or radiation), the number is almost exactly in the middle: 49 percent. 
Clearly, doctors are being swayed more by their profession than by the scientific evidence. We see the same pattern in the treatment of men with early prostate cancer: the large majority of surgeons believe that surgery is better, but the large majority of radiation oncologists think that radiation and surgery are equally effective. 
The same biases also arise when you ask doctors about side effects of treatment. Radiation oncologists predict worse quality of life after surgery than surgeons do, and surgeons predict worse quality of life after radiation than radiation oncologists do. 
It appears that doctors have a rosy view of the treatments that they provide themselves and a less rosy view of treatments provided by other specialties.
The Impact of Biases
Because of these biases, the type of doctor that a patient meets can have a big impact on the type of treatment that he or she gets. For men with early prostate cancer, a big determinant of treatment choice is the type of doctor the patient is seeing, whether it’s a radiation doctor or a surgeon.  If you see a surgeon, you are more likely to have surgery, and if you see a radiation doctor, you are more likely to have radiation. The type of physician seen is even more strongly associated with the ultimate treatment choice than the patient’s own preferences about side effects! This suggests that physician bias is spilling over into treatment decisions. We should be providing patient-centered care, where treatment is based on the beliefs and preferences of individual patients, but this data suggests that we are not. 
The bottom line is that specialists tend to favor whichever treatment they themselves provide. This bias, specialty bias, can be a major problem for patients. Patients rely on doctors to provide balanced information so that they can make an informed decision. If our opinion is skewed in favor of our own treatment—favoring our own specialty—can we really provide balanced information? Compounding the issue is that once the bias sets in, doctors may be less willing to do studies to test their own treatments, for fear that they may lose out.
Tom Treasure, MD is a British thoracic surgeon who has dedicated much of his career to undertaking rigorous assessments of surgery, including randomized trials, and challenging conventional beliefs. In discussing the debate about the optimal treatment of early lung cancer (the comparison of surgery and stereotactic radiation we discussed above), he states that “in an era when evidence is expected for treatments, the fact that these interventions have still not been properly assessed is shameful.” 
A big problem with these turf wars is that patients are caught in the middle, with no easy way to determine the best approach. “Trust me, I’m your doctor does not have the ring of truth,” continues Dr. Treasure, “when different doctors claim to know what is best while consistently failing to encourage trials to put their beliefs to the test.”
Questions to Ask Your Team
For a patient diagnosed with cancer today, there’s not time to wait for future trials to be completed. Here are some questions you can ask of your treatment team:
 Hopmans, W., et al. 2015. "Differences Between Pulmonologists, Thoracic Surgeons and Radiation Oncologists in Deciding on the Treatment of Stage I Non-Small Cell Lung Cancer: A Binary Choice Experiment.” Radiotherapy and Oncology 115(3): 361–66.
 Fowler, F. J., Jr., et al. 2000. "Comparison of Recommendations by Urologists and Radiation Oncologists for Treatment of Clinically Localized Prostate Cancer.” Journal of the American Medical Association 283(24): 3217–22.
 For data showing how doctors tend to overestimate side effects from other specialties’ treatments and underestimate side effects overall, see Kim, S. P., et al. 2014. "Specialty Bias in Treatment Recommendations and Quality of Life Among Radiation Oncologists and Urologists for Localized Prostate Cancer.” Prostate Cancer and Prostatic Diseases 17(2): 163–69.
 See Sommers, B. D., et al. 2008. "Predictors of Patient Preferences and Treatment Choices for Localized Prostate Cancer.” Cancer 113(8): 2058–67; and Jang, T. L., et al. 2010. "Physician Visits Prior to Treatment for Clinically Localized Prostate Cancer.” Archives of Internal Medicine 170(5): 440-50.
 For a commentary on this topic of physician-driven treatment choice, see Barry, M. J. 2010. "The Prostate Cancer Treatment Bazaar: Comment on ‘Physician Visits Prior to Treatment for Clinically Localized Prostate Cancer.’” Archives of Internal Medicine 170(5): 450–52.
 In Treasure, T., R. C. Rintoul, and F. Macbeth. 2015. "SABR in Early Operable Lung Cancer: Time for Evidence.” Lancet Oncology 16(6): 597–98.