Proportion and Incidence of Prostate Cancer May Increase with Age

Both the proportions and absolute incidence rates of clinically significant prostate cancer (PCa) increase with age, according to a study published in Cancer. 

Given these data, efforts to optimize screening of this cancer type for the efficient detection of potentially lethal localized prostate cancer should account for this strong age dependence, according to the researchers.

“Detecting these cancers at an earlier stage may have permitted curative therapy and the avoidance of metastatic spread,” the authors wrote.

In this study, 20,356 men who had been diagnosed with PCa in Norway from 2014 to 2017 were identified. Researchers extracted age at diagnosis, Gleason score (including primary and secondary), and clinical stage from the participants, then assigned them each to clinical risk groups for statistical analysis including low, favorable intermediate, unfavorable intermediate, high, regional, and metastatic. 

Older age was found to be significantly associated with a higher Gleason score and more advanced disease. The percentages of men with Gleason 8 to 10 disease among men aged 55 to 59, 65 to 69, 75 to 79, and 85 to 89 years were 16.5%, 23.4%, 37.2%, and 59.9%, respectively (P < 0.001). Comparatively, the percentages of men in the same age groups with at least high-risk disease were 29.3%, 39.1%, 60.4%, and 90.6%, respectively (P < 0.001). 

The maximum age-specific incidence rates (ASIRs; per 100,000 men) for low-risk, favorable intermediate-risk, and unfavorable intermediate-risk PCa were 15.7 for those aged 65 to 69 years, 183.8 for those aged 65 to 69 years, and 194.8 for the ages of 70 to 74 years, respectively. At the same time, incidence rates of high-risk disease in men older than 65 to 69 years continued to increase sharply, with the ASIRs of high-risk disease surpassing those of the low- and intermediate-risk categories until the ages of 75 to 79 years (when the ASIR was 408.3), wherein they began to decrease.

Furthermore, at the ages of 75 to 79 years, the ASIR of high-risk disease was about 6 times greater than the ASIR at 55 to 59 years. The incidence of regional and metastatic disease always increased with age. 

“PCa screening trials may have underestimated the potential mortality benefit of screening by including many men younger than 60 years, who have long life expectancies but a relatively low incidence of unfavorable intermediate-risk disease or high-risk disease,” the authors wrote. “Screening mostly younger men (barring other risk factors) will yield higher relative rates of false-positives and low-risk cancer overdiagnosis. Meanwhile, early treatment of intermediate-or high-risk disease reduces PCa morbidity and mortality.”

The researchers suggested that age could be combined with other risk factors in order to facilitate enhanced screening strategies. However, the selection of patients for PCa screening remains an individualized one, and the average life expectancy must be weighed against each individual patient’s other comorbidities. Additionally, the diagnosis of localized PCa is generally made by biopsy, and the various decisions, made by both clinician and patient, that may lead to a biopsy also grant the potential for bias in who is diagnosed. Ultimately, the decision for screening must be based on the net benefit. 

According to the American Cancer Society, about 191,930 new cases of prostate cancer will be diagnosed in the US in 2020. Moreover, 1 in every 9 men will be diagnosed with prostate cancer during his lifetime. 

References:

1. Huynh-Le M, Myklebust TA, Feng CH, et al. Age Dependence of Modern Clinical Risk Groups for Localized Prostate Cancer – A Population-Based Study. Cancer. doi:10.1002/cncr.32702. 

2. American Cancer Society. Key Statistics for Prostate Cancer. American Cancer Society website. Published January 8, 2020. cancer.org/cancer/prostate-cancer/about/key-statistics.html. Accessed January 30, 2020.