"Detecting colon cancers is just the first step", stated Dr. Contag. He predicted similar techniques will eventually be able to find a wide range of cancers, monitor cancer treatment, and deliver chemotherapies directly to cancerous cells in the colon, stomach, mouth and skin. The study is being published on-line March 16 in Nature Medicine.
Colon cancer is the third most common cancer in men and women, with about 150.000 people diagnosed each year. Although colonoscopy isn't perfect, it's currently the best way of finding colon cancers when they are still at the most treatable stage.
If doctors find suspicious growths during a routine colonoscopy, they take a sample, called a biopsy, and send it to a pathology lab to screen for cancer. That step takes time and not all people have ready access to a nearby pathologist. What's more, doctors biopsy only the cancers that form easily visible growths called polyps. Early stage cancers that remain flat aren't detected.
The trick to picking up cancer without a biopsy is to find a way of seeing which cells are cancerous while they are still in the body. That's what Dr. Contag and his group succeeded in doing.
The group found a short protein that sticks to colon cells in the early stages of cancer. Before screening a person, they spray that short protein attached to a fluorescent beacon into the colon. The protein then gloms on to any cancerous cells and creates an easily visible fluorescent patch. They then used a miniaturized microscope called CellVisio, developed by Pennsylvania-based Mauna Kea Technologies and loaned to Dr. Contag, to peer inside the colon and look for those telltale spots.
Not only did the researchers see fluorescent patches, they could make out the individual cancerous cells. That fine resolution could allow doctors to pick up the earliest possible cancers. Dr. Contag said it could also become a useful research tool for studying the small number of cancer stem cells that are thought to establish the eventual tumour.
In the initial trial with 15 patients, the technique detected 82 percent of the polyps that were considered cancerous by a pathologist. Dr. Contag said the next step is to work with some of the additional small proteins they've found that also attach to cancerous cells. He thinks that a combination of those proteins will make the technique highly accurate.
Once the screen is ready for widespread use, Dr. Contag said it could bring accurate cancer detection to people in remote locations who otherwise don't have access to pathology labs. "A doctor could send a video in real time via the Internet to someone trained to analyse the living cell images", Dr. Contag stated. This could help people begin the appropriate therapy when the cancer is still at an early stage.
Dr. Contag thinks this technique, developed in part through the cancer imaging programme at the Stanford Cancer Center, could also be adapted to detect cancers in the mouth, esophagus and stomach. In addition, real-time screening could be used as a way of assessing whether a chemotherapy regimen is working. Dr. Contag said that if a tumour responds to a given chemotherapy, changes in the cells might be visible immediately. That response could allow doctors to switch patients to a new, more effective treatment if the first one results in no improvement. Currently people go through several rounds of chemotherapy before the first screen to find out if the treatment is working, a delay that prevents people from moving on to an effective treatment as soon as possible.
The work was funded by the National Institutes of Health, the Doris Duke Charitable Foundation, the Stanford School of Medicine Dean's Fellowship and the John and Cynthia Fry Gunn Research Fund. Additional Stanford researchers who contributed to the study include postdoctoral scholar Pei Pei-Lei Hsiung, PhD; Jonathan Hardy, PhD, research associate; assistant professors of medicine Shai Friedland, MD, and Roy Soetikno, MD; Christine Du, research assistant; Amy Wu, MD, medical student at that time; Peyman Sahbaie, MD, scientist at the Molecular Research Institute in Palo Alto; Anson Lowe, MD, associate professor of medicine, and Thomas Wang, MD, PhD, former clinical instructor of medicine, now at the University of Michigan.
Stanford University Medical Center integrates research, medical education and patient care at its three institutions - Stanford University School of Medicine, Stanford Hospital & Clinics and Lucile Packard Children's Hospital at Stanford.