People with color blindness are more likely to die after being diagnosed with bladder cancer than those with full color vision, researchers have discovered.
The investigators suggest that some patients with color vision deficiency (CVD) may not be able to spot blood in their urine, which is an early warning sign of that cancer.
The findings suggest that these patients may therefore benefit from extra screening.
“The fact that bladder cancer is more prevalent in men, who also have an increased prevalence of CVD, makes such a study potentially important,” commented Masahito Jimbo, PhD, from the University of Illinois in Chicago in a News&Views article accompanying the research article in Nature Health.
“If it is shown that screening patients with CVD for bladder cancer indeed saves lives, guidelines should be modified to tailor such screening to this select population.”
CVD is one of the most commonly inherited visual disorders, affecting one in 12 men and one in 200 women, and mostly affects the ability to see red.
This could impact on noticing blood in the urine or stools, which are signs of both bladder and colorectal cancer, and thereby potentially delay diagnosis and treatment.
To investigate further, Ehsan Rahimy, MD, from Stanford University, and co-workers studied data on the TriNetX network, which aggregates deidentified data from the electronic health records of millions of patients. Propensity score matching was used to account for age, comorbidities, and other factors.
The authors found that 135 patients with diagnostic codes for bladder cancer and CVD had a lower probability of survival as measured by a Kaplan-Meier survival analysis than 135 with bladder cancer and no CVD.
Patients with CVD also had a 52% greater chance of dying in the two decades after a bladder cancer diagnosis than those with full color vision.
However, there was no significant difference in survival from colorectal cancer between the 187 patients with CVD and 187 patients who did not have CVD.
The researchers suggest that the different symptom profile could partially account for their findings.
Bladder cancer tends to present as painless hematuria, meaning that the only sign of disease is blood in the urine. However, colorectal cancer often presents with a multitude of other symptoms that could provide warning signs, even for patients who cannot see blood in their stools.
Screening could be another factor, the team suggests. It is not currently recommended for bladder cancer, making detection dependent on patients noticing symptoms, whereas colorectal cancer screening is recommended in the U.S. from the age of 45 years, and typically involves colonoscopy or a stool-based blood test.
Rahimy and colleagues concluded: “While these hypothesis generating findings should increase clinicians’ suspicion of bladder cancer among patients with CVD and nonspecific signs of malignancy (for example, weight loss and fatigue), the results should be further validated in future work to assess whether formal changes to clinical practice would be merited, such as screening patients with CVD who are at high risk for bladder cancer.”
