Evidence of Stage Migration to Higher Risk Prostate Cancer and its Financial Implications in a Single Institution

Abstract

The association between the United States Preventive Services Task Force (USPSTF) recommendations limiting PSA screening in 2012 and the subsequent increased detection of higher risk prostate cancer has been characterized in cancer registries. We investigated whether this phenomenon of stage migration could be measured in a high volume department and examine its impact on the cost of treatment. We analyzed an IRB approved database of patients with newly diagnosed prostate cancer treated at our institution from 2006-2018. Patients were stratified according to NCCN Risk groups (Low, Intermediate, and High), as well as by the modified Zumsteg/Zelefsky classification including Favorable and Unfavorable Intermediate risk disease. The frequency of risk group change across time was investigated. Differences in proportions were tested using the Pearson chi-square test. Treatment costs of radiation and androgen deprivation therapy were also obtained at our institution for risk groups. Between 2006 and 2018, 3447 consecutive patients with clinically localized prostate cancer were treated in our practice. The overall risk distribution of treated patients was 31% Low risk, 51% Intermediate risk, and 18% High risk. Further characterization of the Intermediate grouping revealed 25% for Favorable Intermediate risk and 25% for Unfavorable Intermediate risk by Zumsteg/Zelefsky criteria. The distribution of Low risk patients decreased from 48% to 23% in years 2006-2011 compared with 2012-2018; there was a corresponding increase in the High risk cohort from 14% to 19% (p<.0001). Further stratification demonstrated a decrease in patients treated with Low or Favorable Intermediate risk disease (69% vs. 47%) in years 2006-2011 compared with 2012-2018 with a significant increase in those treated with Unfavorable Intermediate or High risk disease (31% vs. 53%, p<.0001). The added cost to our institution due to stage migration was $5,593,500 in 2017. Despite a decreasing incidence of newly diagnosed prostate cancer cases occurring nationally, we have seen an increased percentage of aggressive prostate cancer at our practice over time. Stratified before and after the 2012 release of the USPSTF recommendation to cease PSA screening, this data validates registry series showing an associated stage migration towards more aggressive variants. Over 50% of patients treated in our department now have Unfavorable Intermediate or High risk disease, with only 23% harboring Low risk prostate cancer adding significant cost to treatment. As higher risk subtypes have poorer disease free outcomes compared to lower risk disease, the long-term effects on biochemical control, metastatic-free disease states, and prostate cancer specific survival will need to be assessed over time. While a strong correlation with the 2012 USPSTF recommendation is statistically compelling, competing factors which could also explain these findings should continue to be explored.