PHOTODYNAMIC THERAPY OF TYPICAL AND ATYPICAL KERATOACANTHOMA

Background:  Photodynamic  therapy  (PDT) has  shown  its  clinical  efcacy  in  the  treatment of  keratoacanthoma.  However,  the  published data  is  scarce  and  contradictory.  Methods  of a photosensitizer administration and irradiation doses  depending  on  the  type  of  keratoacanthoma have not been defned. Aim: To develop the  diferentiated  approached  to  PDT  for  typical  and  atypical  keratoacanthoma  by  variation of  the  light  density  while  using  of  a  chlorine photosensitizer.  Materials  and  methods:  We assessed and treated 36 patients with cytologically and/or histologically confrmed solitary keratoacanthomas,  among  them  22  patients  with typical  and  14  patients  with  atypical  ones.  In 12  patients,  persistent  keratoacanthomas  were diagnosed,  in  1,  a  gigantic  one  and  in  1,  a  centripetal one. Each patient was administered one session of PDT with an intralesional administration  of  a  photosensitizer  Radachlorin  at  a  dose of  0.75  mL/cm3.  The  source  of  laser  irradiation was a medical laser device LAMI (with the wave- length of 662 ± 3 nm, the power of irradiation at the edge of the light guide, 2 Wt). The absorbed light  density  was  50  J/cm2  for  typical  keratoacanthomas  and  300  J/cm2  for  atypical  ones. 70 Results: After the treatment, in 32 (89%) of patients  the  tumor  completely  regressed  within one month (26 ± 1.3 days). In 4 patients (all with atypical  keratoacanthomas)  the  tumors  did  not regress within one month and was removed surgically with the 3 mm margins of obviously normal skin. At the site of former tumors, there were areas of atrophic scarring (26 cases, in 4 patients, with  hyperpigmentation)  or  with  normotrophic scarring (10 patients) that were cosmetically acceptable. Within the next 2 years of the follow-up no  relapses  were  observed.  Conclusion:  Thus, we  proposed  an  efective  method  of  diferentiated approach to PDT of typical and atypical keratoacanthomas  based  on  one  PDT  session  with an  intralesional  administration  of  Radachlorin at a dose of 0.75 mg/cm3 of the tumor, with the intensity of irradiation of 0.39 Wt/cm2. The light dose  density  for  typical  keratoacanthomas  is 50 J/cm2 and for atypical ones, 300 J/cm2.