Metastatic colorectal cancer patients tend to live longer when they respond to the first line of chemotherapy their doctors recommend. To better predict how patients will respond to chemotherapy drugs before they begin treatment, researchers conducted a proof-of-principle study with a small group of metastatic colorectal cancer patients. The results, published in PLOS ONE, revealed two genes that could help physicians make more informed treatment decisions for patients with this disease.
Metastatic colorectal cancer, the third deadliest cancer in the Unites States, is typically treated with two chemotherapy drugs, 5-Fluorouracil in combination with either oxaliplatin or irinotecan.
The researchers used a commercially available test to analyze levels of the genes ERCC1 and TS in 41 patients with metastatic colorectal cancer. These genes encode proteins involved in building and repairing DNA.
The researchers found that 33 of their 41 patients had low ERCC1 levels. These same patients also had significantly longer average survival times (36 months) compared to patients with high ERCC1 levels (10 months). Similarly, 29 patients had low TS levels and significantly longer average survival times (36 months) than patients with high TS levels (15 months).
Twenty-two of the 41 patients had low levels of both ERCC1 and TS. Of that group, 20 - 91 percent - responded to oxaliplatin, suggesting that this should be the first treatment choice for patients with low ERCC1 and TS. Patients responded to irinotecan at the same rate whether they had low or high levels of these genes. This finding suggests that physicians might want to select irinotecan as the first-choice chemotherapy for patients with high ERCC1 or TS levels. These results are consistent with other studies evaluating the roles of ERCC1 and TS in metastatic colorectal cancer.
According to the authors, ERCC1 and TS profiling could help physicians better manage patients with metastatic colorectal cancer, individualizing and optimizing therapy for subsequent interventions such as surgical removal of metastatic tumors.
While the study is small, retrospective and all of the patients were located at a single medical center, it demonstrates that it's possible to use molecular diagnostics to identify subgroups of patients more likely to respond to a given treatment.
Based on material originally posted by University of California - San Diego.