Regional- and Distant-Stage Prostate Cancer Incidence Continues to Increase

A study published in the Journal of National Cancer Institute (JNCI) found that regional- and distant-stage prostate cancer incidence continues to increase in US men aged ≥50 years. 

Additionally, the study identified a substantial decline in racial disparity in the incidence of distant-stage disease, largely confined to men aged 50 to 74 years, which coincided with the steeper increase in distant-stage incident in non-Hispanic white men. Nevertheless though, incidence rates in non-Hispanic black men still remain 2 to 3 times as high as in non-Hispanic white men.

“The persistently increasing regional- and distant-stage prostate cancer incidence during the past 5 years has public health implications given the substantial morbidity and premature mortality associated with it and the recent stabilization of prostate cancer death rates after a steady decline since the early 1990s,” the authors wrote. 

Using the US Cancer Statistics Public Use Research Database, researchers examined temporal trends in invasive prostate cancer incidence from 2005 to 2016 in men aged ≥50 years stratified by stage (local, regional, and distant), age group (50 to 74 and ≥75), and race/ethnicity (all races and ethnicities, non-Hispanic whites, and non-Hispanic blacks) with join-point regression models to estimate annual percentage changes. 

For all races and ethnicities combined, the incidence of local-stage disease declined beginning in 2007 in men aged 50 to 74 and ≥75 years, though the decline stabilized from 2013 to 2016 in men aged ≥75 years. Moreover, incidence decreased by 6.4% (95% CI, 4.9%-7.9%) per year from 2007 to 2016 in men aged 50 to 74 years and by 10.7% (95% CI, 6.2%-15.0%) per year from 2007 to 2013 in men aged ≥75 years. 

Contrastingly, incidence for regional- and distant-stage disease increased in both age groups throughout the study. For instance, distant-stage incidence in men aged ≥75 years increased by 5.2% (95% CI, 4.2%-6.1%) per year from 2010 to 2016. 

“Reasons for the continued increase in regional- and distant-stage incidence rates are unknown,” the authors wrote. “Family history, an established risk factor for prostate cancer, is unlikely to change during the study period. Cigarette smoking, which increases the risk of fatal prostate cancer, is also unlikely to account for observed trends because of the long-term declines in smoking and in tobacco-related cancers.” 

Additionally, researchers indicated that excess body weight, another risk factor generally associated with fatal prostate cancer, has increased among men since the 1970s, though the extent of its contribution has yet to be determined. 

“These data illustrate the trade-off between higher screening rates and more early-stage disease diagnoses (possibly over diagnosis and over treatment) and lower screening rates and more late-stage (possibly fatal) disease,” the authors wrote.

Of men aged 20 to 49 years, the black-to-white incidence rate ratios (IRRs) declined from 3.55 (95% CI, 2.85-4.40) during 2005 to 2006 to 2.22 (95% CI, 1.75-2.81) during 2011 and 2012, and then non-statistically significantly increased to 3.11 (95% CI, 2.48 to 3.88). In contrast, for men aged 50 to 74 years and ≥75 years, the black-white IRRs for distant-stage disease continued to decrease from 2005 to 2006 through 2015 to 2016, from 3.11 (95% CI, 2.95-3.27) to 2.58 (95% CI, 2.48-2.68) in men aged 50 to 74 years and from 2.29 (95% CI, 2.14-2.45) to 1.65 (95% CI, 1.55-1.75) in men aged ≥75 years. 

“Reasons for this disparity are not fully understood, but in part thought to reflect differences in life-style factors, biological susceptibility, and access to care. Obesity and cigarette smoking are more prevalent in (non-Hispanic black) than (non-Hispanic white) men,” the authors wrote. “Furthermore, the association of obesity with prostate cancer risk is stronger in (non-Hispanic black) men.”

Notably, the study data were not adjusted to account for a delay in reporting of cases, and may have therefore underestimated the increasing trends for distant-stage disease but overestimated the declining trends for early-stage disease. In addition, the researchers could not make causal inferences given the nature of the study. 

“Future studies are needed to elucidate reasons for the rising incidence trends for regional- and distant-stage diseases and for the disproportionately high burden of the disease in black men,” the authors wrote.

Reference:

Jemal A, Culp MB, Ma J, Islami F, Fedewa SA. Prostate Cancer Incidence 5 Years After US Preventive Services Task Force Recommendations Against Screening. JNCI. doi:10.1093/jnci/djaa068.