Adjuvant therapy is given in the post operative period to patients with both colon and rectal cancers.
There is little doubt that adjuvant chemotherapy is beneficial to patients with Duke's stage C disease. The data for the benefit of adjuvant chemotherpay in Duke's stage B is not convincing.
Most of the trials that have shown benefit use 5-FU as the cornerstone of their treatment.
Prior to 1987 there was little evidence for a beneficial effect of adjuvant chemotherpay in bowel cancer. The the Intergroup Study was published. This study used 5-FU and levamisole and showed benefit for patients with Dukes B2 and Dukes C lesions. The benefit in patients with Dukes B2 lesions was not replicated in other studies and it is no longer felt that there is a convincing role for adjuvant therapy in patients with stage Dukes B2 disease.
One of the main difficulties for the patients in this trial was the toxicity associated with the Levamisole. This was of sufficient severity that 40% of the patients did not complete the course.
The Intergroup Study 1993 looked at the combination of Folinic Acid with the 5-FU instead of the levamisole. They found that this was better tolerated and was at least as effective. Again there was a statisticl benefit for patients with Dukes B2 lesions as well as Dukes C. But the role of adjuvant chemotherapy in Dukes B2 lesions is not universally agreed upon because of no statistical benefit in other trials.
To clarify the whether Levamisole in addition to the folinic acid was of any benefit, and to investigate whether high dose or low dose folinic acid was best the quick and simple and reliable (QUASAR) study was performed in the UK on patients with Dukes B2 and C lesions; the levamisole contributed little if anything to the beneficial effect of folinic acid and there was not great difference between the effects of the high and low dose folinic acid regimens.
As a result of the QUASAR study most patients who are considered for adjuvant therpay receive 5-FU and Folinic acid (Leucovorin). This is the mainstay of adjuvant therpy for colon and rectal cancer at this point of time.