The use of circulating tumor cells in predicting survival in chemotherapy patients

The aim of this study was to investigate if circulating tumor cells (CTC) levels in the blood could be used to determine the outcome for metastatic castration resistant prostate cancer patients.

This study concluded that CTC levels could be used to predict survival in these patients. 

Treatment for metastatic prostate cancer (cancer that has spread to other areas) often involves hormone therapy. Hormone therapy lowers male hormones, such as testosterone, active in cancer growth. Over time, however, many men become resistant to standard hormone therapy. This is known as metastatic castration-resistant prostate cancer (mCRPC).

Docetaxel (Taxotere) is a common chemotherapy (drugs used to treat cancer) used in prostate cancer. It works to stop the cancer growing and spreading to other parts of the body. Lenalidomide (Revlimid) is also used to treat prostate cancer. This treatment blocks the growth of blood vessels the tumor needs to survive.

CTCs are cells that the tumor has shed and that are now travelling around the body in the blood. CTC levels have been shown to be a predictor of survival rates in prostate cancer. It is unknown whether CTC counts could be used in mCRPC patients who were treated with docetaxel with or without lenalidomide.

208 men with mCRPC were involved in the study. There were two groups of patients and they were treated for 21 day cycles. One group was treated with 75 mg/m² docetaxel on day 1, 5 mg of prednisone twice a day every day and 25 mg of lenalidomide daily for the first 14 days. The other group received the same treatment except they received placebo (drug that has no effect) instead of lenalidomide.

Patients with a CTC count of 5 cells/7.5 ml of blood or more were 3.23 times more likely to have a worse overall survival (OS; time from treatment until death from any cause) compared to those with fewer CTCs.

CTCs that increased from less than 5 cells/7.5ml to 5 cells/7.5ml or more after 3 cycles of treatment were associated with 5.24 times the risk of a shorter OS.

CTCs that reduced from 5 cells/7.5ml or more to less than 5 cells/7.5ml had the best OS. 

In mCRPC patients treated with docetaxel with or without lenalidomide, patient survival could be predicted by CTC at the start of treatment. A rise in CTC during therapy indicated decreased OS and a decrease in CTC indicated increased OS. 

This study was carried out in a small group. A larger group is needed to validate results. 

Talk to your physician about CTC count if receiving docetaxel with or without lenalidomide.