MRI predicts prostate cancer prognosis

Researchers in San Francisco have found that MR imaging can accurately predict recurrence and development of metastatic disease in patients who are about to undergo radiation therapy for prostate cancer. Study findings suggest a stronger role for MRI in the management of the condition.

Nearly 200,000 new cases of prostate cancer will be diagnosed in the U.S. during 2008, according to the National Cancer Institute. Scientific evidence shows that early diagnosis and treatment may assure a five-year survival rate of almost 100%. Biopsy remains the standard of care for diagnosis and staging, but it can miss disease features that are critical for tailoring treatments that could improve the clinical outcomes of patients at higher risk of recurrence.

MRI could do a much better job in this setting, according to coauthor Dr. Fergus V. Coakley, a professor of radiology and urology at the University of California, San Francisco.

"This is the first study to show that MRI detection and measurement of the spread of prostate cancer outside the capsule of the prostate is an important factor in determining outcome for men scheduled to undergo radiation therapy," Coakley said.

Coakley and colleagues retrospectively analyzed images from 80 men with prostate cancer who had an MR scan before undergoing external-beam radiation therapy. The investigators recorded tumor findings, treatment, and outcomes and used a regression analysis technique to correlate survival with specific characteristics of prostate disease. They found that MRI could accurately predict post-treatment recurrence and disease spread. They published their findings in the April issue of Radiology.

Three of five patients with extracapsular extension larger than 5 mm on MRI developed metastases at 24, 43, and 63 months after therapy. Univariate Cox analysis showed that correlations between baseline serum prostate-specific antigen level, presence of extracapsular extension at MR imaging, and degree of extracapsular extension in relation to the development of metastases were all statistically significant (p<0.05). Multivariate Cox analysis also showed that the mean diameter of extracapsular extension could be an independent prediction variable (p = 0.007).

According to Coakley, an important question raised by the study is whether every patient planning to undergo external-beam radiation therapy for prostate cancer should have endorectal MRI. There is a good argument that the information provided by MRI is prognostically useful and may influence therapy.

The reality, however, is that the technology and interpretive expertise required are still not widely available and that reimbursement policies by third-party payers vary. Larger and more systematic prospective multicenter trials may help elucidate the true role and utility of endorectal MRI in this setting, he said.

"The decision to use such advanced imaging should be discussed with the patient by his treating physicians, with acknowledgment of local practice and insurance coverage issues," Coakley said.

For more information from the Diagnostic Imaging archives:

High-field MR begins to define parameters of prostate cancer

Young Investigator Awards add luster to MRI's scientific stars

Three-D adds accuracy to prostate evaluation

Lack of national diagnosis, care plan spurs call for action