STM: Imaging circulating tumor cells could direct therapy in prostate cancer

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A quantitative automated imaging system for analyzing prostate circulating tumor cells present in the blood of patients can direct targeted therapies in advanced prostate cancer, according to a study published March 31 in the Science Translational Medicine.

Rare circulating tumor cells (CTCs) are present in the blood of patients with metastatic epithelial cancers and could help in monitoring cancer treatment, but have been difficult to measure. In a pilot analysis, Shyamala Maheswaran, PhD, associate professor of surgery at Massachusetts General Hospital, Harvard Medical School in Boston and colleagues tested an automated imaging system in prostate cancer patients which could be used to analyze the cancer cells at different points--before and after tumor removal surgery and during hormone-based therapy.

The new system uses a microfluidic chip containing microscopic posts coated with an antibody to a protein found on tumor cells to capture tumor cells from a drop of blood. The cells were then stained with an antibody for prostate-specific antigen (PSA), specific to prostate tumor cells, and imaged with a fluorescent marker. Though they used PSA, the system is "completely universal," and the researchers have begun testing it with antibodies for other types of cancer cells as well, said Shannon Stott, PhD, research fellow in the department of surgery at Massachusetts General Hospital, Harvard Medical School in Boston.

Maheswaran and colleagues detected CTCs in eight of 19 (42 percent) prostate cancer patients with localized disease before surgical tumor removal. For six of the eight patients with preoperative CTCs, a steep postoperative decline (less than 24 hours) was observed by the researchers suggesting a short half-life for CTCs in the blood circulation.

“Other patients had persistent CTCs for up to 3 months after prostate removal, suggesting early but transient disseminated tumor deposits. In patients with metastatic prostate cancer, CTCs were detected in 23 of 36 (64 percent) cases,” wrote Maheswaran and colleagues.

The researchers also noted that in previously untreated patients followed longitudinally, the numbers of CTCs declined after the initiation of effective therapy.

One diagnostic assay called CellSearch, which measures circulating tumor cells, is already on the market. But the Harvard system is more likely to detect tumor cells in patients before their tumor has metastasized, when there are far fewer circulating in the blood, said Alison Allan, PhD, oncology scientist at the University of Western Ontario, Canada, who uses the CellSearch system. "It's actually these patients that have the most chance of benefiting" from the technology, she noted, because it could allow them to get earlier treatment.