Adjusting Treatment Strategies Using Circulating Tumor Cells: Preliminary Results on Metastatic Colorectal Cancer

To assess the effectiveness of circulating tumor cells (CTCs) in proposing second-line treatments for metastatic colorectal cancer (mCRC).

We analyzed CTCs from 21 patients (first group) with mCRC, for whom first-line treatment regimens were ineffective. CTCs were isolated and used for chemo-sensitivity/viability assays on several chemotherapeutic drugs. Based on these assays, a second-line treatment was recommended for each patient. Using overall survival (OS) as primary endpoint, statistical analysis was performed, comparing the survival of a group of 21 mCRC patients (first group) with the survival of 12 mCRC patients treated only with best supportive care (BSC) (second group), as well as with the survival estimated by meta-analysis of the BSC summary statistics (medians) published in various papers and clinical trials. Furthermore, the statistical significance of the difference between the two groups was examined by applying statistical tests that can deal efficiently with small datasets, non-proportional hazard patterns, and crossing curves, such as K-sample omnibus, MaxCombo, multiple-direction, and weighted log-rank tests.

The median OS (mOS) for the first group (9 months) was found longer than the mOS of the BSC group (about 5 months). This result was further verified since the weighted mOS, estimated by meta-analysis, was found at 5.15 months. This difference was found statistically significant for central and late hazards.

The preliminary results indicate that treatment based on CTCs' response in vitro prolongs mOS of mCRC patients compared with BSC patients, whereas a beneficial effect is gained for the prediction of treatment response in mCRC.