Quicksilver II Pilot Study

Quicksilver II Non-inferiority Randomized Controlled Trial: Direct-to-surgery or Neoadjuvant Chemotherapy and Surgery in Margin-clear Stage II or III Rectal Cancer

This pilot study is being done to answer the following question: Will patients with margin-clear Stage 2 or 3 rectal cancer who don't require a colostomy agree to be randomized to 'surgery only' or 'chemotherapy and then surgery'? Study participants will be randomized to receive either 12 weeks of chemotherapy before rectal cancer surgery or they will proceed directly to surgery. The researchers hypothesize that patients with margin-clear clinical Stage II or III rectal cancer can avoid neo-adjuvant (i.e., pre-operative) radiation and chemotherapy treatments and go directly to surgery. A positive pilot study will support funding requests for a related large efficacy trial; this larger trial, if positive, should lead to an important de-escalation innovation - avoiding use of neo-adjuvant chemoradiation and associated toxicity risks for patients with margin-clear Stage II or III rectal cancer.

Before patients with rectal cancer go for surgery, tests determine tumour stage and if there are cancer cells near the edge of the rectum - if there are no cancer cells near the edge the tumour is called 'margin-clear'. Surgeons operate just outside the 'margin' to best remove all cancer cells. In Canada, patients with stage 2 or 3 cancer are almost always given radiation and chemotherapy before surgery to lower the risk the cancer will return. However, these treatments can cause life-long side effects like poor bowel function or nerve damage in the hands. A small study of patients with margin-clear stage 2 and 3 rectal cancer showed that radiation and chemotherapy is likely not needed before surgery. However, researchers would like to test these findings in a larger trial called "Quicksilver II". Before applying for Quicksilver II funding, the researchers have to show the trial steps are possible. This will be accomplished through a feasibility/pilot trial at several high-volume rectal cancer centres. Patients with margin-clear stage 2 or 3 rectal cancer will be randomized to 'surgery' or 'chemotherapy and surgery'. If the pilot study works and if Quicksilver II is positive, it may change the way patients with margin-clear tumours are treated around the world.

Inclusion Criteria:

• 18+ years of age
• able to provide written consent
• MRI confirmed margin-clear Stage II or III rectal cancer

Exclusion Criteria:

• patients with tumour criteria that encourage neoadjuvant treatments regardless of margin-status (e.g. need for a permanent colostomy, T4 category, and one or more pelvic sidewall lymph nodes with a short axis diameter >7 mm).
• Unable to provide consent (e.g., language barrier, cognitive issues).