title: Optical coherence tomography imaging of non-melanoma skin cancer undergoing photodynamic therapy reveals subclinical residual lesions.
abstract: BACKGROUND
  Photodynamic therapy with methyl aminolaevulinate (MAL-PDT) is a widely used non-invasive treatment modality for non-melanoma skin cancer (NMSC). The outcome of MAL-PDT is usually primarily evaluated clinically. Optical coherence tomography (OCT) is a non-invasive imaging technology based on interferiometry. OCT has been proven to provide high accuracy in identifying NMSC lesions and performing thickness measurements of thin tumours.
  
  
  OBJECTIVE
  To describe the OCT morphology in in-vivo NMSC lesions during MAL-PDT treatment and to investigate the use of OCT in evaluating the response of MAL-PDT treated NMSC lesions.
  
  
  METHODS
  A total of 18 biopsy-proven basal cell carcinomas and actinic keratoses were monitored by OCT during 2 sessions of MAL-PDT treatment. At 3-months follow-up the patients were assessed both by OCT and clinically. If the clinical and OCT evaluation came to different conclusions on recurrence of the lesion, patients were followed more closely at clinical appointments for up to one year after the PDT treatment.
  
  
  RESULTS
  All lesions displayed at least one OCT characteristic before MAL-PDT treatment. At 3 months follow-up, recurrence was suspected clinically in 5/18 cases, with OCT in 7/18 cases. OCT correctly identified all of the partial responses also found by the clinical examinations. In both cases where recurrence was only found in OCT, this was subsequently confirmed by histology.
  
  
  CONCLUSIONS
  Our study suggests that OCT identified 29% more recurrences than clinical examination alone. OCT can detect subclinical residual NMSC lesions after MAL-PDT treatment and may therefore be an accurate tool for early detection of residual lesional tissue.
authors.affiliation: Department of Dermatology, Roskilde Hospital, Health Sciences Faculty, University of Copenhagen, Kogevej 7-13, 4000 Roskilde, Denmark. Electronic address: lotte.themstrup@gmail.com.
authors.forename: L
authors.initials: L
authors.lastname: Themstrup
authors.affiliation: Department of Dermatology, Roskilde Hospital, Health Sciences Faculty, University of Copenhagen, Kogevej 7-13, 4000 Roskilde, Denmark.
authors.forename: C A
authors.initials: CA
authors.lastname: Banzhaf
authors.affiliation: Department of Dermatology, Gentofte Hospital; Health Sciences Faculty, University of Copenhagen, Copenhagen , Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Mogensen
authors.affiliation: Department of Dermatology, Roskilde Hospital, Health Sciences Faculty, University of Copenhagen, Kogevej 7-13, 4000 Roskilde, Denmark.
authors.forename: G B E
authors.initials: GB
authors.lastname: Jemec
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000622:Aminolevulinic Acid / Q000031:analogs & derivatives* / Q000627:therapeutic use; D002280:Basal Cell Carcinoma / Q000188:drug therapy*; D005260:Female; D006801:Humans; D055623:Keratosis, Actinic / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D010778:Photochemotherapy / Q000379:methods*; D017319:Photosensitizing Agents / Q000627:therapeutic use*; D012878:Skin Neoplasms / Q000188:drug therapy*; D041623:Tomography, Optical Coherence / Q000379:methods*
chemical_list: D017319:Photosensitizing Agents; C475457:methyl 5-aminolevulinate; D000622:Aminolevulinic Acid
keywords: Actinic keratosis; Non-melanoma skin cancer; Optical coherence tomography; Photodynamic therapy