A blood test will be enough to determine if patients with stage II colon cancer will need to undergo chemotherapy after surgery. This is the hope that comes from Chicago, where the American Society of Clinical Oncology congress is underway and where researchers from the Johns Hopkins Kimmel Cancer Center and WEHI in Melbourne presented their study on the predictive power of circulating tumor DNA. In fact, the genetic material that tumors release into the blood can be measured and based on this score it can be decided which patient needs chemotherapy and which does not. Thus avoiding unnecessary aggressive treatments, unwanted side effects and ultimately also a cost. The findings were published concurrently with the presentation in the New England Journal of Medicine.
“Previous studies have terrified that the measurement of circulating tumor DNA could be useful in patient management and this study shows with real data that those assumptions were correct,” said Bert Vogelstein, co-director of the Ludwig Center at Johns Hopkins and author of the study. Vogelstein and his research team were the first to show that colon cancer is caused by a sequence of genetic mutations and that the DNA released by the tumor can be found in the blood, stool and body fluids.
Currently, the use of chemotherapy for patients with stage II colon cancer – defined as a cancer that has infiltrated the colon wall but has not spread to the lymph nodes or other organs – is controversial. There is no consensus among experts as to its effectiveness. In fact, if at stage I chemo is not necessary, given that the prognosis is very favorable, and at stage III it is substantially discounted because the risk of recurrence is very high, at stage II it is much less evident what is the right thing to do. The study therefore aims to help solve this dilemma by measuring circulating tumor DNA, which could be an accurate measure of the likelihood of tumor recurrence.
The study involved 455 patients, with stage II colon cancer and who had undergone the removal surgery, dividing them into two groups: the first received the standard treatment, which consists of a monitoring of the situation or chemotherapy, the second did the circulating DNA test and based on the results either had chemo or not. The use of the test reduced the use of therapy compared to the standard (15.3% against 27.9%) without risking the life of the patients: survival after 2 and 3 years is similar in the two groups.
The goal of chemotherapy is to eliminate micrometastases, cancerous cells not yet visible with radiological images which however travel in the bloodstream and from there move to other organs. Being able to identify them with a simple blood test would really be an important change of gear in clinical practice. The researchers hope that these findings will spur further research into circulating tumor DNA in other subgroups of patients, such as those with stage III cancer for whom it may be possible to understand how to modulate chemotherapy.