April 21 (HealthDay News) -- Researchers were able to shrink prostate cancer cells in mice using a new drug delivery method that combines imaging with chemotherapy in a single agent.

"It's like a smart bomb, to use a military analogy," Dr. John P. Sedelaar, a postdoctoral research fellow at Johns Hopkins University, said in a news release from the American Association for Cancer Research. "By retooling chemotherapy agents, we may be able to get more accurate treatment monitoring and follow-up."

The study was to be presented at the association's 100th annual meeting, in Denver.

Sedelaar said that current clinical practice uses multimodality MRI to examine the urological system and diagnose prostate cancer. This tool, however, is mostly thought of as a prostate imaging method rather than a prostate cancer imaging method.

"An increasing number of patients have minimal prostate cancer, and opt for either very focused treatment or the watchful-waiting approach," said Sedelaar. "In this environment, the need for an accurate imaging tool is paramount."

Sedelaar and colleagues designed two imaging drugs: a PSMA and a PSA-activated pro-drug. These agents are therapeutic drugs that are modified by adding a tyrosine ring for imaging.

After the drugs were given to laboratory mice, the researchers noted a measurable reduction in prostate cancer cells.

Experiments also showed that the imaging pro-drugs were cleaved and activated by PSMA or PSA, suggesting their viability as a prostate cancer imaging modality.

"Unfortunately, next to clear tumor uptake, there was also uptake into liver and kidney organs," Sedelaar said. "Further experiments will have to address that problem."

More information

The U.S. National Cancer Institute has more on prostate cancer.

SOURCE: American Association for Cancer Research, news release, April 21, 2009