Bladder cancer misdiagnosed as IC in 1% of patients

San Francisco-Just because it looks like interstitial cystitis doesn't mean it is interstitial cystitis. Some irritative voiding symptoms that look like IC may be symptoms of bladder cancer, even in patients who do not have the usual bladder cancer risk factors.

A team of urologists at the William Beaumont Hospital, Royal Oak, MI, found bladder cancer in 1% of 600 patients initially referred to them with "interstitial cystitis" between 1998 and 2002. Of concern is that a growing number of patients are diagnosed with IC based on the minimally invasive potassium sensitivity test and the pelvic pain urgency/frequency questionnaire, which have been promoted heavily to primary care physicians and gynecologists.

According to urology resident William Tissot, MD, this could mean more transitional cell carcinomas could be missed.

Bladder cancer, bacterial cystitis, and other inflammatory diseases also produce positive results on the potassium sensitivity test, said lead author Kenneth Peters, MD, director of clinical research.

"The problem is that this test has never been validated against what we normally consider for IC, so it's not really specific for the disease," Dr. Peters said.

"You've got to rule out infection and bladder cancer as a cause of irritative symptoms," Dr. Tissot added. "That's why IC remains a diagnosis of exclusion."

According to the researchers, patients with irritative voiding symptoms need to undergo a very thorough history and physical examination. Cystoscopy with hydrodistension under anesthesia is still the gold standard, Dr. Tissot said, adding patients may need urine cytology and upper-tract imaging.

"What was really striking and worrisome [about the missed TCCs] is that many patients didn't have the usual risk factors," said Dr. Peters. "Unfortunately, in this series, hematuria and smoking were poor predictors of cancer."

The age of the patients found to have bladder cancer ranged from 39 to 78 years, and three were nonsmokers, even though smoking is bladder cancer's most common risk factor. Four of the six had no gross or microscopic hematuria, which often triggers the cancer workup in clinical practice. Three had negative results of urine cytology.

The cancers were not just superficial bladder cancers, but significant ones. Five of the six cancers were grade 3 lesions, and one patient had TCC of the distal ureter as well. The irritative symptoms resolved once the cancers were treated in all patients.

The time between the IC and the bladder cancer diagnosis ranged from 4 months to 5 years, with a mean of about 30 months. That long lag offers an important clinical message, Dr. Tissot said.

"When patients are diagnosed with IC, you cannot forget about them years down the road. When a woman diagnosed [with IC] in her 20s still has irritative symptoms when she's 30, 40, or 50, that doesn't mean she still has just IC," he said.

"We have to be clinicians and continue to look at the patient as a whole and make appropriate diagnostic decisions," Dr. Peters added.