Subject Ph. D.

Context

In carcinological surgery, the main objective is to obtain sufficient surgical margins to minimize the risk of recurrence, while being as conservative as possible (Egloff-Juras et al, 2021). Although intraoperative histological evaluation is not always routine practice, it remains the most frequently performed examination, either by intraoperative frozen section analysis or by tactile impression cytology. This examination is performed immediately after surgery to check that all tumour tissue has been removed. Analysis of the surgical specimen is carried out during the operation, without the specimen being fixed. Thus, the pathologist can make thin sections and place them on a gel pad for freezing before studying them under the microscope with rapid hematoxylin, eosin and saffron (HES) staining (Girardi FM et al, 2021). However, sample analysis is time-consuming, requiring coordination between several specialties and thus increasing the duration of the procedure. The result of this analysis can be communicated in 20 to 40 minutes, depending on the sampling procedures and the organization of the care unit.

Consequently, there is a need for intraoperative techniques operating in real time and ex vivo with sufficient spatial resolution (< 1 mm), minimal interference in daily practice, offering ergonomic and practical instrumentation for the surgeon. In an ideal clinical scenario, an accurate diagnosis should be made in 5 to 10 minutes.

It is in this context that new non-invasive approaches using the properties of confocal imaging have been tested in oncology, and in particular on basal cell carcinomas (Cameron et al, 2019). One of the unique features of confocal imaging is that subsequent histopathological examinations, including immunohistochemistry, are not influenced by this technique, enabling direct and accurate correlation. Confocal imaging produces images of tissue directly in the focal plane of the objective. The sample under study is illuminated in the focal plane of the objective by a point source of light. In combination with fluorescent dyes, the contrast of different tissue structures can be enhanced and regions of interest highlighted (Grizzetti et al, 2022). This study, using fluorescence techniques, will benefit from the expertise of CRAN Laboratory in fluorescence and phototherapy (Marchal S et al, 2015; Leufflen L et al, 2018).

Synopsis

This thesis will be based on the HISTOBLOC protocol, whose principal investigator is Dr Gilles Dolivet. The study will be conducted at CRAN, on the site of the Institut de Cancérologie de Lorraine. 45 tumors measuring 2 to 4 cm will be treated intra-operatively with Histolog® scanners to determine the quality of the margins of excision of the lesions. The same tumors will be subjected to the reference protocol for determining tumor excision margins: extemporaneous histological analysis by a doctor specializing in pathological anatomy. The results of the two methods will be compared to assess the concordance of the intraoperative diagnosis of the condition of the resection margins. The primary objective of the thesis is to obtain sufficient arguments to establish a non-inferiority protocol for the use of confocal microscopy versus extemporaneous histological analysis, in order to assess the quality of peri-tumoral margins in resection surgery for cutaneous carcinomas and squamous cell carcinomas of the oral or oropharyngeal mucosa. The secondary objective is to build up a reference atlas of confocal imaging of squamous cell carcinoma sections, for use in future artificial intelligence software capable of identifying suspicious areas intraoperatively.

References

Cameron MC, Lee E, Hibler BP, Giordano CN, Barker CA, Mori S, Cordova M, Nehal KS, Rossi AM. Basal cell carcinoma: Contemporary approaches to diagnosis, treatment, and prevention. J Am Acad Dermatol. 2019 Feb;80(2):321-339.

Claire Egloff-Juras, Lina Bezdetnaya, Gilles Dolivet, Henri-Pierre Lassalle. NIR fluorescence-guided tumor surgery: new strategies for the use of indocyanine green. International Journal of Nanomedicine, 2019, 14, pp.7823-7838.

Girardi FM, Wagner VP, Martins MD, Abentroth AL, Hauth LA. Factors associated with incomplete surgical margins in basal cell carcinoma of the head and neck. Braz J Otorhinolaryngol. 2021 Nov-Dec;87(6):695- 701

Grizzetti L, Kuonen F. Ex vivo confocal microscopy for surgical margin assessment: A histology-compared study on 109 specimens. Skin Health Dis. 2022 Jan 10;2(2):e91

Léa Leufflen, Aurélie François, Julia Salleron, Catherine Barlier, Gilles Dolivet, et al.. Photodynamic diagnosis with methyl-5-aminolevulinate in squamous intraepithelial lesions of the vulva: Experimental research. PLoS ONE, 2018, 13 (5), pp.e0196753.

Sophie Marchal, Gilles Dolivet, Henri-Pierre Lassalle, François Guillemin, Lina Bezdetnaya. Targeted photodynamic therapy in head and neck squamous cell carcinoma: heading into the future. Lasers in Medical Science, 2015, 30 (9), pp.2381-2387.