Liquid Biopsy Marks The Progression Of Colorectal Cancer

Liquid biopsy assessing the blood or urine samples may help monitor the effectiveness of cancer therapy for the initial phase of colorectal cancer metastasis (oligometastatic) as per a study from Washington University School of Medicine in St. Louis, published in the Journal of Clinical Oncology Precision Oncology, a journal of the American Society of Clinical Oncology. Oligometastatic colorectal cancer requires initial chemotherapy to shrink and remove the remains of the primary tumor before having surgery. Food and Drug Administration (FDA) has approved a few liquid biopsies for lung, breast, ovarian, and prostate cancers, but none has been approved for colorectal cancer.

Limited data on predicting the patients’ response to early chemotherapy and no access to cancer genome sequencing to identify the DNA mutations in their original tumors contribute to the existing problem.

"Being able to measure the response to early chemotherapy without prior knowledge of the tumor's mutations is a novel idea and important for being able to determine whether the patient responded well to the therapy. This can provide guidance on how to treat oligometastatic disease. For example, if the liquid biopsy indicates that a patient responded well to the early chemotherapy, perhaps they should be offered the possibility of more surgery, which could potentially cure their disease. But if they didn't respond well, it's likely the cancer is too widespread and can't be eradicated with surgery, so those patients should receive more chemotherapy to control their disease", says senior author Aadel A. Chaudhuri, MD, Ph.D., an assistant professor of radiation oncology.

Uniqueness of Liquid Biopsy

The free and broken tumor DNA of cancer that is circulating in the blood and, to a lesser extent, has been collected in the urine is usually detected by the liquid biopsies. The uniqueness of the biopsies described in this study, compared with other liquid biopsies are following:

• Most of the traditional biopsies have been developed to track metastatic cancers or to ensure that local cancers have not started to spread.
• Knowledge of the original tumor's mutations is required by several liquid biopsies, to verify the presence of such mutations in the blood after therapy. However original tumor sequencing is not possible by all the patients.
• The new biopsies rely on detecting DNA mutations in the blood or urine and comparing them with DNA mutations measured in the treated primary tumor after it's surgically removed.
• Also, most of the urine biopsies have been limited to use in cancers of the genitourinary system – bladder cancer and hence the urine biopsy is unique for colorectal cancer.

Liquid Biopsy and its Role in Colorectal Cancer

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"The levels of circulating tumor DNA that we were able to measure in urine were lower than what we measured in blood, but this is still a proof of concept that it is possible to measure residual disease in non-urinary cancer in this non-invasive way. We will need to develop more sensitive techniques to detect colorectal tumor DNA in urine to make this a useful clinical test. But this is a promising start", says Chaudhuri.

The team demonstrated that lower circulating tumor DNA levels correlated with better responses to early chemotherapy. Undetectable levels of tumor DNA in blood samples showed no measurable cancer in patient’s surgical specimens.

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Residual cancer measured by liquid biopsies was also more predictive of outcomes than residual disease found in the surgical specimens.

The present study thereby highlights the options of liquid biopsies in personalizing treatment for oligometastatic colorectal cancer, identifying patients at high risk of recurrence, and helping guide the opt traditional/ new targeted/ immune therapies to be given.

Source-Medindia