BACKGROUND: Approximately 70% of all suicides in patients aged >60 years are attributed to physical illness, with higher rates noted in patients with cancer. The purpose of the current study was to characterize suicide rates among patients with genitourinary cancers and identify factors associated with suicide in this specific cohort. METHODS: Patients with prostate, bladder, kidney, testis, and penile cancer were identified in the Surveillance, Epidemiology, and End Results database . Standardized mortality ratios (SMRs) and 95% confidence intervals (95% CIs) were calculated for each anatomic site. Multivariable logistic regression models generated odds ratios (ORs) for the identification of factors associated with suicide for each malignancy. RESULTS: There were 2268 suicides identified among 1,239,522 individuals with genitourinary malignancies observed for 7,307,377 person-years. The SMRs for patients with cancer were 1.37 for prostate cancer (95% CI, 0.99-1.86), 2.71 for bladder cancer (95% CI, 2.02-3.62), 1.86 for kidney cancer (95% CI, 1.32-2.62), 1.23 for testis cancer (95% CI, 0.88-1.73), and 0.95 for penile cancer (95% CI, 0.65-1.35). On multivariable analysis, male sex was found to be associated with odds of suicide among patients with bladder cancer (OR, 6.63) and kidney cancer (OR, 4.98). Increasing age was associated with suicide for patients with prostate, bladder, and testis cancer (OR range, 1.03-1.06). Distant disease was associated with suicide in patients with prostate, bladder, and kidney cancer (OR range,). Among patients with prostate, bladder, and kidney cancer, African American patients were less likely to commit suicide compared with white individuals (OR range, 0.26-0.46). CONCLUSIONS: Suicide in patients with genitourinary malignancies poses a public health dilemma, especially among men, the elderly, and those with aggressive disease. Clinicians should be aware of risk factors for suicide in these patients.
Signal regulatory proteins (SIRP-α, -β, and -γ) are important regulators of several innate immune functions that include leukocyte migration. Membrane distal (D1) domains of SIRPα and SIRPγ, but not SIRPβ, mediate binding to a cellular ligand termed CD47. Because the extracellular domains of all SIRPs are highly homologous, we hypothesized that some of the 16 residues unique to SIRPα.D1 mediate binding to CD47. By site-directed mutagenesis, we determined that SIRPα binding to CD47 is independent of N-glycosylation. We also identified three residues critical for CD47 binding by exchanging residues on SIRPα with corresponding residues from SIRPβ. Cumulative substitutions of the critical residues into SIRPβ resulted in de novo binding of the mutant protein to CD47. Homology modeling of SIRPα.D1 revealed topological relationships among critical residues and allowed the identification of critical residues common to SIRPα and SIRPβ. Mapping these critical residues onto the recently reported crystal structure of SIRPα.D1 revealed a novel region that is required for CD47 binding and is distinct and lateral to another putative CD47 binding site described on that crystal structure. The importance of this lateral region in mediating SIRPα.D1 binding to CD47 was confirmed by epitope mapping analyses of anti-SIRP Abs. These observations highlight a complex nature of the ligand binding requirements for SIRPα that appear to be dependent on two distinct but adjacent regions on the membrane distal Ig loop. A better understanding of the structural basis of SIRPα/CD47 interactions may provide insights into therapeutics targeting pathologic inflammation.
Clinicians should be aware of risk factors for suicide in patients diagnosed with bladder cancer, particularly older, white, unmarried patients with distant disease, and/or those who have undergone radical cystectomy. A multidisciplinary team-based approach, including wound ostomy care trained nursing staff and mental health care providers, may be essential to provide care required to decrease suicide rates in this at-risk population.
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