Abstract
This work is devoted to a first exploration of Mueller polarimetric imaging for the detection of residual cancer after neoadjuvant treatment for the rectum. Three samples of colorectal carcinomas treated by radiochemotherapy together with one untreated sample are analyzed ex vivo before fixation in formalin by using a multispectral Mueller polarimetric imaging system operated from 500 to 700 nm. The Mueller images, analyzed using the Lu-Chipmann decomposition, show negligible diattenuation and retardation. The nonirradiated rectum exhibits a variation of depolarization with cancer evolution stage. At all wavelengths on irradiated samples, the contrast between the footprint of the initial tumor and surrounding healthy tissue is found to be much smaller for complete tumor regression than when a residual tumor is present, even at volume fractions of the order of 5%. This high sensitivity is attributed to the modification of stromal collagen induced by the cancer. The depolarization contrast between treated cancer and healthy tissue is found to increase monotonously with the volume fraction of residual cancer in the red part of the spectrum. Polarimetric imaging is a promising technique for detecting short-time small residual cancers, which is valuable information for pathological diagnosis and patient management by clinicians.
Highlights
Gastrointestinal malignancies are among the most important causes of cancer-related deaths
The light backscattered by the sample was analyzed with a polarization state analyzer (PSA), a “mirror image” of the polarization state generator (PSG), composed by the same PSG optical elements but placed in reverse order
We first show the polarimetric response of a colorectal adenocarcinoma without any neoadjuvant treatment
Summary
Gastrointestinal malignancies are among the most important causes of cancer-related deaths. It is often difficult for pathologists to detect residual cancer when the response to the treatment is good but not complete. Sometimes they can miss small residual cancers while making histopathological cuts. Any fast and easy-to-use method able to provide relevant information on the surgical specimen such as the localization of the zones, where residual cancer may be present, or a preliminary mapping of the degree of cancer penetration can make the pathologist life easier.
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