{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T13:08:46Z","timestamp":1788959326548,"version":"build-2803163510"},"reference-count":30,"publisher":"MDPI AG","issue":"18","license":[{"start":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T00:00:00Z","timestamp":1788912000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Cancers"],"abstract":"<jats:p>Background\/Objectives: Cutaneous squamous cell carcinoma (cSCC) treated with high-dose-rate (HDR) surface brachytherapy using patient-specific 3D-printed applicators lacks a validated non-invasive follow-up modality capable of resolving microscopic residual disease. Line-field confocal optical coherence tomography (LC-OCT) provides real-time, cellular resolution, three-dimensional imaging of the epidermis and superficial dermis and has been proposed as a candidate tool for post-radiotherapy monitoring. We evaluated the feasibility of LC-OCT for pre- and post-treatment imaging of cSCC and assessed whether an LC-OCT-defined remission phenotype, operationally defined a priori as the absence of all malignancy-associated LC-OCT criteria, can be documented after 3D-printed HDR surface brachytherapy. Methods: Eight consecutive patients with histologically confirmed cSCC, unsuitable for surgery, were treated with HDR surface brachytherapy delivered through patient-specific 3D-printed applicators. LC-OCT imaging was performed immediately before brachytherapy and at short-term follow-up (six months). Nineteen pre-treatment LC-OCT criteria derived from the Cinotti 2021 descriptive criterion set for cSCC were scored: seventeen malignancy-associated criteria, plus elastosis (scored as a background photodamage covariate, not counted towards remission) and fibrosis (scored post-treatment only). Presence\/absence of each criterion was rated by two blinded dermatologists; inter-assessor agreement was quantified using percentage agreement and Cohen\u2019s kappa. Results: Baseline LC-OCT showed a rich malignant signature: hyperkeratosis, parakeratosis, disarranged epidermal architecture, dyskeratotic keratinocytes, atypical and crowded nuclei, and dermoepidermal junction alterations were present in eight out of eight lesions (100%) under an inclusive two-reader rule. At short-term follow-up, six months after the final brachytherapy fraction, all seventeen malignancy-associated criteria constituting the pre-specified remission set were absent in all eight patients under the decision rule described in the article\u2014which classifies isolated dilated linear vessels occurring in an otherwise criterion-negative, fibrotic dermis as post-radiation telangiectasia rather than residual tumour, yielding an LC-OCT-defined remission phenotype rate of 100% (eight out of eight; 95% exact binomial [Clopper\u2013Pearson] CI 63.1\u2013100%). Post-radiation fibrosis was observed in 8\/8 patients (100%), and dilated linear vessels were observed in six out of eight patients (75%, evaluated under the same decision rule (Observer 1: 4\/8; Observer 2: 6\/8). Elastosis, a marker of background actinic photodamage present in eight out of eight lesions at baseline and excluded from the malignancy-associated criterion count, is distinct from post-treatment fibrosis, a radiation-induced dermal remodelling feature scored only at follow-up; the two should not be conflated. Conclusions: In this proof-of-concept cohort, LC-OCT was feasible for pre- and post-treatment imaging of cSCC after 3D-printed HDR surface brachytherapy, produced highly reproducible dual-observer readings (\u03ba = 0.903), and documented, at a single short-term time point six months after the final fraction, an LC-OCT-defined remission phenotype in every treated lesion, with a consistent fibrosis signature. Persistent dilated linear vessels in a fibrotic, otherwise criterion-negative dermis were classified as a non-specific post-radiation vascular change and did not preclude LC-OCT-defined complete remission. Because this remission phenotype rests on a pre-specified but not externally validated imaging definition and was not anchored to post-treatment histopathology or reflectance confocal microscopy, it constitutes an imaging surrogate rather than a confirmed complete remission, and microscopic residual disease below the resolution limit of LC-OCT cannot be excluded. These hypothesis-generating findings support LC-OCT as a candidate non-invasive monitoring modality, requiring confirmation in larger, biopsy-anchored prospective studies with longer follow-up.<\/jats:p>","DOI":"10.3390\/cancers18182922","type":"journal-article","created":{"date-parts":[[2026,9,9]],"date-time":"2026-09-09T12:26:11Z","timestamp":1788956771000},"page":"2922","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Line-Field Confocal Optical Coherence Tomography as a Follow-Up Tool for 3D-Printed HDR Surface Brachytherapy of Cutaneous Squamous Cell Carcinoma: A Proof-of-Concept Study at Short-Term (Six-Month) Follow-Up"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3775-8021","authenticated-orcid":false,"given":"Piotr","family":"Sobolewski","sequence":"first","affiliation":[{"name":"The National Medical Institute of the Ministry of the Interior and Administration, Woloska 137, 02-507 Warsaw, Poland"},{"name":"Chair and Clinic of Dermatology and Pediatric Dermatology, Centre of Postgraduate Medical Education, 02-507 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1048-2774","authenticated-orcid":false,"given":"Mateusz","family":"Koper","sequence":"additional","affiliation":[{"name":"The National Medical Institute of the Ministry of the Interior and Administration, Woloska 137, 02-507 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"given":"Michal","family":"Poltorak","sequence":"additional","affiliation":[{"name":"The National Medical Institute of the Ministry of the Interior and Administration, Woloska 137, 02-507 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"}]},{"given":"Pawel","family":"Banatkiewicz","sequence":"additional","affiliation":[{"name":"The National Medical Institute of the Ministry of the Interior and Administration, Woloska 137, 02-507 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"investigation","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"}]},{"given":"Malgorzata","family":"Kolos","sequence":"additional","affiliation":[{"name":"The National Medical Institute of the Ministry of the Interior and Administration, Woloska 137, 02-507 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8799-8461","authenticated-orcid":false,"given":"Lukasz","family":"Poltorak","sequence":"additional","affiliation":[{"name":"Electrochemistry at Soft Interfaces Team, Department of Inorganic and Analytical Chemistry, Faculty of Chemistry, University of Lodz, Tamka 12, 91-403 Lodz, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8414-7493","authenticated-orcid":false,"given":"Maciej","family":"Szwast","sequence":"additional","affiliation":[{"name":"Department of Chemical and Process Engineering, Warsaw University of Technology, Warynskiego 1, 00-645 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"}]},{"given":"Irena","family":"Walecka","sequence":"additional","affiliation":[{"name":"The National Medical Institute of the Ministry of the Interior and Administration, Woloska 137, 02-507 Warsaw, Poland"},{"name":"Chair and Clinic of Dermatology and Pediatric Dermatology, Centre of Postgraduate Medical Education, 02-507 Warsaw, Poland"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,9]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Fahradyan, A., Howell, A.C., Wolfswinkel, E.M., Tsuha, M., Sheth, P., and Wong, A.K. 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