Trial Information

Evaluation of Rectal Tumor Margin Using Confocal Endomicroscopy and Comparison to Histopathology

Defining the limits of resection of rectal tumors is often imprecise. The identification of
the banks of a tumor becomes critical when it comes to the decision to potentially sacrifice
the sphincter during the surgical resection. Currently tumor margins are identified by
direct examination by the surgeon, or using flexible endoscopy. Endoscopy and confocal
microscopy could provide precise images of tumor enabling the reliable definition of
resection margins.

There would be a direct benefit for the patient, whom sphincter could be preserved. pCLE
(probe-based Confocal Laser Endomicroscopy) has already been widely used for colorectal
lesions, and its value proposition has been demonstrated and validated in several studies.
This study is the first using pCLE intraoperatively. Study results may lead the use of pCLE
to validate surgical procedure decision (resection margin) and to a revision of patient
management for colorectal cancer, by adapting neoadjuvant radiochemotherapy to the patient's
responder status.

The goal is to identify tumor margin (lower pole) to optimize the resection margin, and to
limit resection of healthy rectal tissue for optimal anal sphincter preservation. Moreover,
determining the optimal date of surgery following neoadjuvant radiochemotherapy in rectal
cancer is being discussed and no consensus has been reached. Therefore, to date, there is no
formal evaluation of tumor response. This is partly due to the lack of information on tumor
state and tumor evolution over time, between the end of radiochemotherapy and surgery.
Histological follow up of tumor would provide supporting information to fill this gap.
However, frequent tumor biopsies are not possible. Alternatively, probe-based confocal laser
endomicroscopy (pCLE) could allow for a sequential analysis of tumor response. Response to
treatment could be assessed and used to define optimal date of surgical resection, depending
on patient responding status to treatment. Responding patients would undergo surgery at a
later date than non-responders, in whom surgery could be performed earlier.

Benefits of the study lay in the more accurate definition of resection margins, with its
associated potential therapeutic impact of the anal sphincter preservation and in the
definition of the optimal date of rectal tumor resection, based on response status to
radiochemotherapy.

Study interests are :

- Microscopic structure of tumor will be analyzed at the cellular and microvascular
levels and compared to healthy mucosa.

- Evolution of response during and following radiochemotherapy will be assessed, and will
help classify patients as responders/non responders.

- pCLE results will be compared to histopathology results on pre-treatment and resection
biopsies.

- Images gathered through the imaging modalities (WLE, pCLE, EUS) along with
histopathology results will be combined to create an atlas and database of rectal
tumors.