Discerning the survival advantage among patients with prostate cancer who undergo radical prostatectomy or radiotherapy: The limitations of cancer registry data

Abstract

Objective To compare overall survival of patients who underwent radical prostatectomy or radiotherapy versus non-cancer controls in order to discern if there is a survival advantage according to prostate cancer treatment and the impact of selection bias on these results. Patients and Methods A matched cohort study was performed using the Surveillance, Epidemiology, and End Results (SEER)-Medicare linked database. We identified 34,473 patients age 66 to 75 years without significant comorbidity from who were diagnosed with localized prostate cancer treated with surgery or radiotherapy between 2004 and 2011. These patients were matched to a non-cancer control cohort. We compared the rates of all-cause mortality that occurred within the study period. We used Cox Proportional Hazards Regression analysis to identify determinants associated with overall survival. Results Of the total 34,473 patients who were included in the analysis, 21,740 (63%) received radiation therapy and 12,733 (37%) received surgery. There was improved survival in patients treated with surgery (hazard ratio [HR], 0.35; 95% CI, 0.32-0.38) as well as with radiotherapy (HR, 0.72; 95% CI, 0.68-0.75) when compared to non-cancer controls. There was significantly improved overall survival among both treatment groups with most benefit observed among patients who underwent surgery (log rank p<0.001). Conclusions Using population based data, treatment with either surgery or radiotherapy demonstrated improved overall survival when compared to a cohort of matched non-cancer controls. Treatment with surgery resulted in longer survival compared to those receiving radiation therapy. These results suggest inherent selection-bias due to unmeasured confounding variables.

Association between type 2 diabetes, curative treatment and survival in men with intermediate‐ and high‐risk localized prostate cancer

“…The selection of healthy men for curative treatment is also highlighted by the lower 90‐day mortality after RP compared with the background population in a previous Swedish study . Williams and Huo have also demonstrated this selection bias, showing a survival advantage in men receiving both RP and RT vs a PCa‐free comparison cohort. This selection was also reflected in the present study in PCa‐specific mortality (Fig.…”

Comparative effectiveness of radical prostatectomy with adjuvant radiotherapy versus radiotherapy plus androgen deprivation therapy for men with advanced prostate cancer

“…Though propensity score analysis can also reduce the bias associated with unobserved factors, so long as relationships between unobservable and measured factors exist, there is likely to be unmeasured confounding and selection biases that we are not able to control for that may have accounted for a portion of the survival differences observed in our study, as has been reported in other studies using cancer registry data. 38, 39 To further reduce residual confounding by controlling for proxies of unmeasured confounders, high-dimensional propensity score adjustment was also applied. 13 In an attempt to further balance observed and unobserved characteristics between treatment groups over what is possible with propensity score adjustments, we explored the possibility of utilizing instrumental variable analysis.…”

Impact of prior local therapy on overall survival in men with metastatic castration‐resistant prostate cancer: Results from Shared Equal Access Regional Cancer Hospital

“…(17, 18) Although these studies have provided a rationale for further studying the impact of local therapy in advanced prostate cancer, the inherent patient and tumor selection bias associated with survivorship outcomes in observational studies limits the ability to make meaningful recommendations based on them. (19, 20) Recent studies have examined the feasibility of RP in men with metastatic hormone sensitive prostate cancer with all showing complication rates comparable to those reported in a series of RP in high-risk localized disease. (21 – 24) Similar results have also been shown in those with castration resistant metastatic disease.…”