Here’s a second article from C3 research advocate, Pam McAllister, based on information she learned at the 2010 GI Cancers Symposium in Orlando.
Pam’s experience with colorectal cancer research advocacy goes back more than a decade. She has been a patient advocate with several cancer cooperative groups and now chairs the Radiation Therapy Oncology Group (RTOG) Patient Advocacy Committee.
While most patients with stage II colon cancer are at low risk of recurrence, there are patients in this group who are at increased risk and who may need chemotherapy to reduce their risk.
The average stage II patient has an absolute benefit of only 1 or 2 percent from chemotherapy. In other words, the average Stage II patient will decrease risk of recurrence by only 1 or 2 percent it they have chemotherapy. And since chemotherapy has its own risks, it is important to identify those at increased risk whose potential benefit would be greater than average.
Currently a variety of factors are used to try to identify which stage II patients are at increased risk of recurrence.
- One is the number of lymph nodes examined. Not only is examination of at least 8 to 12 nodes essential to accurate staging but the number of nodes removed is a strong prognostic indicator. In other words, people with more nodes removed do better than people with fewer. At the 2010 Gastrointestinal Cancer Symposium it was again confirmed that patients with 12 or more lymph nodes examined had a recurrence risk at 3 years about 5% lower than those with examined fewer nodes. It was further noted that the prognostic value of lymph node number was independent of the 12 gene recurrence score.
- The 12 gene recurrence score (Oncotype DX Colon recently released by Genomic Health) reports patients as at high, medium or low risk of recurrence at 3 years. The recurrence scores range from an average risk of 12 % for low risk, 18% for medium risk to 22% for high risk.
- Also frequently used to evaluate stage II tumors is lymphovascular invasion (the visualization of cancer cells in small vessels within the tumor), T stage (T3 versus T4), and the markers 18qLOH and MSI (microsatellite instability).
- Microsatellite status has been shown to be a prognostic indicator in stage II colon cancer. Patients with pMMR (proficient mismatched repair) have worse outcomes than those who are deficient in mismatch repair (dMMR or MSI-H). The 5 year survival for patients who have pMMR is less than 75% in comparison with those who have dMMR (MSI-H) whose 5 year survival is greater than 90%. About 15% of patients have deficient mismatch repair (are MSI) and are a reduced risk of recurrence. A presentation at the ASCO Gastrointestinal Symposium indicated a need for physician education on the value of mismatch repair testing and use in treatment planning.
- Those who have loss of heterozygosity at 18q, a place on a chromosome, (18qLOH) are at increased risk of recurrence.
Examination of these factors and others can assist patients and their physicians to decide whether or not to have chemotherapy. At this point, no single factor is adequate to guide treatment decisions. When many factors available are used together, though, sufficient information is available to assist physicians and their patients decide whether or not chemotherapy is warranted.
Since patients vary widely in the amount of decreased risk is necessary to justify the toxicity and expense of chemotherapy, the decision must be made on an individual basis. This will require better education of physicians so they can better inform their patients.