CERVICAL CANCER SCREENING
Cervical cancer continues to be a significant global health burden as the fourth most frequently diagnosed and fatal cancer globally. Although there is an effective vaccine (HPV vaccines) which is being used to reduce the future impact of cervical cancers, screening programs remain a key part of cervical cancer prevention and treatment.
One of the key tools we use to fight cervical cancer is regular screening. Screening helps catch cancers earlier when they are small (or even precancerous, before they progress to cancer), allowing for gentler treatments. Standard screening includes Papanicolaou (Pap) tests to check for abnormalities in the cervical tissue. In BC, if you have a cervix and are between the ages of 25–69, it is recommended that you get a Pap test every 3 years.
If an abnormality is found by the Pap test, the patient is brought in for further testing where a doctor or nurse will examine the cervix with a regular whitelight microscope (colposcope) and take a tissue sample from the suspicious area.
The cervix is shaped like a donut – and while we get a good top view of that donut with a regular whitelight microscope, the hole in the centre (or the endocervical canal) can be harder to see. The endocervical canal is lined with a different type of tissue than the surface of the cervix. The area where the tissue type changes is where some of the earliest cancers are thought to form, making it an important area for the healthcare providers to assess.
In addition to the regular whitelight microscope, we need special tools to screen the endocervical canal. That is why the Optical Cancer Imaging Lab has developed an imaging device that uses two types of imaging to look for early cancers, precancers, and other areas of concern.
NEW IMAGING TOOLS FOR CERVICAL CANAL SCREENING
The Optical Cancer Imaging Lab at the BC Cancer Research Institute develops imaging tools for early detection and management of cancer. We use light to generate images, rather than sound waves (ultrasound), ionizing radiation (x-rays, CT scans), or contrast dyes. Because light waves are so small, they allow for very high-resolution imaging, making it possible to see structures less than a tenth of a millimeter in size. These tools let clinicians look at tiny changes — and potentially detect some of the earliest cancers.
Our lab uses two main imaging technologies: optical coherence tomography (OCT) and autofluorescence imaging. OCT makes a 3D map of the tissue structure, which tells the story of what is happening below the tissue surface: density, layers, ducts, glands, vessels, and more. As cancers progress, the tissue around them changes and looks different than healthy tissue. Using OCT, we can look for areas that are more dense, have increased blood vessel activity, or have blurriness between tissue layers.
Autofluorescence provides a new angle of information: where OCT is a form of ‘structural’ imaging, which shows the shape of the tissue, autofluorescence is ‘functional’ and provides a snapshot into the chemistry within the tissue. We use a blue laser to excite the chemicals within the tissue, and they release back green light through a process called fluorescence. This green light is mostly from collagen, a structural protein. Cancer breaks down the organized structure of collagen, and so we look for dark regions as areas of potential cancers.
Unfortunately, it isn’t that straight forward: cancer isn’t the only thing that looks dark in an autofluorescence image. Gaps in tissue — like glands, ducts, folds, or even inflammation — also look dark, and might be mistaken for cancer. This is where OCT comes in agan, providing a look at what is happening below the surface. We believe that by using these two cancer detection techniques together, we will be able to achieve better accuracy than either on its own — and right now, we are putting that to the test.
CLINICAL STUDIES UNDERWAY
We have developed a tiny (<1mm diameter) imaging probe capable of simultaneous OCT and autofluorescence imaging and are conducting a clinical study to see if this device can detect early cancers in the endocervical canal. This is the first step to examine whether this technology can be used in the clinic and can provide useful information. If successful, this work has the potential to affect clinical practice and decrease the burden of disease of cervical cancer.
You can read more about our work at http://biophotonics.bccrc.ca/.