The effect of selection and referral biases for the treatment of localised prostate cancer with surgery or radiation.

Background: Consultation with radiation oncologists, in addition to urologists, is advocated for patients diagnosed with prostate cancer. Treatment patterns for patients receiving consultation from radiation oncologists in addition to urologists have not previously been described.
Methods: We conducted a matched cohort study of men with newly diagnosed non-metastatic prostate cancer in Ontario, Canada. Patients who underwent consultation with a radiation oncologist prior to treatment were matched 1:1 with patients managed by a urologist alone based on tumour and patient characteristics. We examined rates of active treatment (surgery or radiotherapy) within one year following diagnosis.
Results: Among 5708 matched pairs (11,416 patients), those who received radiation oncology consultation were more likely to undergo active treatments whether they had intermediate or high-risk disease (88.6% vs. 65.9%, p < 0.0001; adjusted odds ratio 4.0, 95% CI: 3.6-4.4) or low-risk disease (56.1% vs. 13.3%, p < 0.0001; adjusted odds ratio 8.4, 95% CI: 6.7-10.6). This effect persisted after considering age, comorbidity, tumour volume and year of diagnosis.
Conclusions: Patients newly diagnosed with prostate cancer who receive radiation oncology consultation are associated with a higher rate of active treatment, compared to patients managed by urologists only. Selection and referral biases, and unmeasured confounding such as patient preference must be considered as important factors attributing this association.