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abnormal US will likely undergo CT scan to confirm because
US alone has a predictive value of only 2% for equivocal
findings and 50% for positive findings. This approach adds
cost, but certainly the very high specificity significantly
limits those numbers. Concerns regarding US screening for
renal tumors are that small tumors can be missed and that
US is operator dependent.
3. How to deal with overdiagnosis
One of the main concerns with screening is the risk of
overdiagnosis. This is a prevalent concern for prostate
cancer. Identification of low-risk low-grade disease is one of
the main reasons why prostate-specific antigen screening is
criticized. However, this may not be an issue in bladder
cancer. It is rarely discovered at autopsy, suggesting that
most patients become symptomatic during their lifetime. In
a large bladder cancer screening trial, Messing et al found
that 50% of cancers identified were high grade, and yet only
5% of cancers were muscle invasive . Screening did not
diagnose more low-grade cancers than one would expect; it
just found the high-grade cancers earlier at a more curable
stage. All these data would thus support the benefit of
screening in this setting.
Kidney cancer screening is a different matter because
small renal masses are frequently benign, and many can
remain indolent for years . Although clinically insignifi-
cant prostate cancers were treated for years, active
surveillance is a reasonable and established approach for
small renal masses. Even in the case of diagnosis, one can
limit the cost and morbidity of incidental small renal
masses by surveillance while still treating those that are
more aggressive and potentially lethal.
4. Can we justify costs?
The cost of screening is always cited as the reason why it
should not be done. As stated earlier, we can identify
populations at increased risk, have tests that can identify
cancers noninvasively, and improve stage at detection with
likely survival benefits. A Markov model created to estimate
cumulative cancer-related costs and the efficacy of screen-
ing (vs no screening) of a high-risk population for bladder
cancer using a urine-based tumor marker over a 5-yr period
found that in a population with >1.6% cancer incidence,
screening with the NMP22 Bladderchek urine-based tumor
marker (Alere, Waltham, MA, USA) would result in both
improved overall survival and cost savings Patients
diagnosed with muscle-invasive bladder cancer require
very expensive treatments including cystectomy and
chemotherapy, and many still succumb to their disease.
Although there are no similar studies in kidney cancer, it is
possible that renal US testing may be reasonable in some
populations.
What is the alternative? Cost is rarely discussed as a
reason to avoid treating patients with metastatic disease
even when the treatment is not curative.
In conclusion, until we can find a cure for metastatic
disease, screening high-risk populations is a better invest-
ment than spending money on end-of-life care with
noncurative treatments.
Conflicts of interest: The author has nothing to disclose.
References
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[3] Krabbe LM, Svatek RS, Shariat SF, Messing E, Lotan Y. Bladder cancer
risk: use of the PLCO and NLST to identify a suitable screening cohort.
Urol Oncol. In press.
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