Colon cancer: when should chemotherapy follow surgery?
Some patients with stage 2 colon cancer will recur after surgery. Our Chief Medical Officer provides detail on when post-surgery chemotherapy is likely to help treatment.
It is estimated that more than 1.3 million people will be diagnosed with colon cancer worldwide this year. Almost half of the patients will be older than 70 years, and 40% of them will have stage 2 colon cancer. While adjuvant chemotherapy (chemotherapy after surgery) has proven beneficial in stage 3 colon cancer, its role for stage 2 disease remains unclear.
About 75% of patients with stage 2 colon cancer will be cured by surgery alone.
The remaining 25% will recur. A small percentage of this group will benefit from chemotherapy following surgery (adjuvant chemotherapy). However, the criteria used for considering patients for adjuvant chemotherapy are not clear. For this reason, selection is based on risk for recurrence, which is determined by clinical, histological and molecular factors.
Clinical and Histological factors
Clinical factors are obstruction, perforation of the large bowel at presentation.
Histological factors are:
- tumor size
- stages 2B, 2C
- poorly differentiated tumors
- lymphovascular invasion, as well as
- the number of examined lymph nodes (≤12 means worse prognosis).
Clinical and histological factors are mostly prognostic, and not predictive of the benefit from chemotherapy. Such prediction is more feasible with molecular factors.
Molecular factors (markers) have lately entered the daily practice in an effort to predict the benefit of chemotherapy. Such a marker is the defective mismatch repair status (called "dMMR") which is related to resistance to chemotherapy with Fluorouracil, but also with better natural evolution of the cancer.
Recently, a set of 12-gene recurrence score was explored and patients were grouped in low, intermediate and high risk.
In general, patients with tumor spread characterized as “T3”, and with dMMR status, have very good prognosis and do not require adjuvant chemotherapy. On the contrary, patients with spread “T4” and proficient (i.e. not defective) MMR have poorer prognosis and need adjuvant chemotherapy. For patients with T3 and proficient MMR status, the 12-gene recurrence score may be required to support the chemotherapy decision.