Survival in Colorectal Cancer

Over many years at Royal Melbourne Hospital, I have been fortunate to have had a strong research collaboration with medical oncologist Prof Peter Gibbs. Back in 2003, we established a comprehensive database on all of our Colorectal Cancer (CRC) patients treated at RMH and Melbourne Private Hospital and now have data on several thousand patients including treatment received and long term follow up.

We have also stored fresh tumour samples and serum on 80% of these patients which allows us to match the genetic make up of these tumours with their actual outcomes  potentially leading to the discovery of tumour markers to predict recurrence and to the development of  new treatments.

For example, we know that recurrence after surgery for Stage III (Dukes C) colon cancer (where regional lymph nodes are involved) approaches 50%, but when post operative chemotherapy is given, the overall survival improves by an impressive 25%.  However, even in the better prognosis group of Stage II (Dukes B) colon cancer (without lymph node involvement), recurrence occurs in up to 20% of patients. The dilemma until now has been how to predict which of the Stage II patients should also receive chemotherapy.

To a very large extent, this has been answered by recently published work from our group, where Dr Jeanne Tie has measured circulating tumour DNA (ctDNA)  in patients with Stage II colon cancer. ctDNA is made up of fragments of cancer genes released from naturally dying cancer cells but its significance has been uncertain. What this study shows is that:

  • ctDNA was found in the serum of 8% of Stage II patients and 80% of these patients developed metastatic disease
  • in those patients without detectable ctDNA, only 10% developed metastases

 

This means that those Stage II patients with ctDNA can be offered the benefit of post operative chemotherapy in the same way as Stage III patients are – and importantly we can advise the 92% of Stage II patients without detectable ctDNA that chemotherapy is not necessary. This might seem a modest outcome but this research has had a direct impact on how CRC patients benefit from “tailored” treatment that gives them the best possible outcome.