The first genomic test to predict whether or not stage II colon cancer will recur has been developed and validated in a large number of tumor tissue samples from patients in the United States and the United Kingdom. The 12 gene assay can reliably predict whether an individual patient has a low, intermediate, or high risk of having their cancer return.
Doctors and patients will be able to use the Recurrence Score, along with other clinical indicators, to decide whether further chemotherapy treatment after surgery should be considered or whether they can safely skip chemo and its risks.
However, the study was not able to link recurrence scores with benefits from 5-FU and leucovorin chemotherapy.
Researchers from the National Surgical Adjuvant Breast and Bowel Project (NSABP) and the Cleveland Clinic analyzed tumor samples saved from 1,850 patients enrolled in clinical trials for 761 different genes. They found 18 that were likely to predict whether or not cancer would recur or whether the patient would benefit from 5-FU chemotherapy. The 18 gene assay was then validated by testing tumor tissue from more than 1,400 patients who were part of the QUASAR (Quick And Simple And Reliable) clinical trial. QUASAR had randomized patients to either receive chemotherapy with 5-FU and leucovorin or further treatment surgery.
The QUASAR validation showed that recurrence scores could accurately predict who had a low, intermediate, or high risk of recurrence. The score also reliably predicted disease-free and overall survival. Scores were ranked from 0 to 100 with the lowest scores having an 8 to 10 percent risk of recurring and the highest scores a 20 to 25 percent chance of coming back.
About 25 to 30 percent of patients with colon cancer are diagnosed with stage II cancer where the tumor has gone to the outermost layers of the colon or through the colon wall but has not yet spread to nearby lymph nodes. Chemotherapy has only a modest benefit for stage II patients, reducing the absolute risk of recurrence for the whole group by about 3 percent.
Being able to decide which patients will have cancer come back, usually as a spread to a distant organ (metastasis), and might benefit from chemotherapy has been a challenging decision for doctors and patients alike.
David Kerr, MD, DSc, professor of cancer medicine at the University of Oxford and lead author of the QUASAR validation study, which will be presented at the upcoming meeting of the American Society of Clinical Oncology in Orlando, explained yesterday:
Having this well-validated molecular signature to predict risk of colon cancer recurrence will have a significant impact on the way we treat patients with this disease.This assay gives physicians important clinical information that will enable them to better select the right patients for the right treatment at the right time.” Scientists have validated the accuracy of a 12 gene test to estimate the risk that stage II colon cancer will return within three years. Using the test, stage II patients can be identified as having low, intermediate, or high risk of recurrence.
Two clinical factors — T4 stage and mismatch repair status — remained independent predictors of recurrence. In the QUASAR study T4 tumors, which have grown through the wall of the colon and into nearby tissues, had a poor prognosis nearly doubled the risk of recurrence. On the other hand, patients whose tumors showed deficient mismatch repair or microsatellite instability (MSI) had a 70 percent reduction in the risk of their cancer coming back.
T4 tumors and those with deficient mismatch repair genes account for only about 25 percent of stage II colon cancers. For other tumors, the recurrence score can be valuable in clinical decision-making, according to Dr. Kerr.
Carlea Bauman, President of C3:Colorectal Cancer Coalition, reflected on possibilities of the new test.
Patients with stage II colon cancer are often faced with tough decisions about treatment. These findings will help patients and their physicians make decisions based on each patient’s potential risk. This is critically important to patients facing treatment options that can be life-altering. Patients want the assurance that they are receiving the most appropriate course of treatment for their individual disease.
SOURCE: Kerr et al., Abstract #4000, A quantitative multigene RT-PCR assay for prediction of recurrence in stage II colon cancer: Selection of the genes in four large studies and results of the independent, prospectively designed QUASAR validation study, ASCO 2009 Annual Meeting Abstracts.