A test that looks for tumor cells in the blood may make doctors better able to check whether chemotherapy is helping a prostate cancer patient, researchers reported on Tuesday.

The CellSearch test, made by Johnson & Johnson unit Veridex, works better than standard tests for men whose prostate cancer has spread, the researchers said in the medical journal Lancet Oncology.

The test counts the number of cancer cells that have broken away from the tumor and are circulating in the blood.

In a study involving 164 men, the researchers found that the CellSearch test helped them monitor the response to chemotherapy in patients who had prostate cancer that had spread and were not being helped by hormone therapy.

Hormone therapy aims to stop the body’s production of testosterone or block hormones from getting into tumor cells.

They said it worked better than a standard test that looks at prostate specific antigen, or PSA, levels. PSA is a protein produced by the prostate, and levels may shoot up when prostate tumors grow or spread.

“It shows that the CTC (circulating tumor cells) counts can be used to help determine an individual’s prognosis, particularly when the counts are high,” Dr. Howard Scher of Memorial Sloan Kettering Cancer Center in New York, one of the researchers, said in a telephone interview.

“And it also helps in terms of understanding if the treatment is working,” Scher added.

Once prostate cancer has advanced to the point that chemotherapy may be used - at a late stage, unlike in many other cancers - doctors often struggle to determine how well the treatment is working, said John Neate of the Prostate Cancer Charity, a London-based advocacy group.

“Measuring circulating tumor cells seems to be more finely attuned to the effects of the chemotherapy than previously thought,” Neate said in a statement.

“There are, therefore, circumstances where some men will benefit from further courses of chemotherapy treatment when at present they may not be offered it,” Neate added.

The findings in the study have led to a larger one to confirm them involving more than 1,100 men, Scher said.

By Will Dunham
WASHINGTON (Reuters)