6. Needle-free electronically-controlled jet injector treatment with bleomycin and lidocaine is effective and welltolerated in patients with recalcitrant keloids. 158 In our study we observed a relatively modest decrease in total POSAS patient- and observer scores after three treatments with EPI-assisted bleomycin and lidocaine, with respectively 15% and 18%. This reduction was substantially smaller compared to EPIassisted TCA in Bik et al. (POSAS reduction of resp. 27% and 34%) and spring loaded jet injector-assisted bleomycin in Saray et al. (complete flattening in 73.3%).16, 27 These discrepancies could be related to the characteristics of the keloids in our patient population. The patients analyzed in this retrospective study had recalcitrant keloids with a more extensive treatment history, and more severe pain and pruritus at baseline compared with the patients in the studies by Bik et al. and Saray et al. Importantly, some of the patients who were challenging to treat with EPI-assisted TCA, did show good clinical improvement in this study. Moreover, although there is no clear difference between the median total POSAS patient scores before and after treatment in our study, it is important to note the relevant shift in the spread of the interquartile range before and after treatment (Figure 3). However, in our clinic, for safety reasons, patients are treated with a bleomycin and lidocaine solution of 1 USPE/mL, with a maximum dose of 3 mL. This concentration is lower than 1.5 IU/mL, the concentration that is commonly used in clinical studies with bleomycin, for example, in the study of Saray et al.27 While increasing the bleomycin concentration could potentially improve efficacy, caution must be exercised due to the high rate of necrosis and ulceration associated with higher doses of bleomycin.28 In addition, treating physicians regularly observed a considerable amount of spilled volume, noticeable as a residue of the medication on the treated skin. This unintended spill may have led to a lower administered dose than intended, potentially impacting treatment outcomes. Remarkably, four out of 15 patients did not show any improvement post-treatment. In retrospect, these non-responders had considerably thicker, stiffer and larger keloids than the other patients. Furthermore, all of the non-responders had previously undergone a minimum of five different types of treatments. Presumably, larger and thicker keloids are
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