Panniculitis does not predict clinical response in patients with advanced melanoma under targeted therapy.

Background: BRAF and MEK inhibitors have changed the landscape of treatment for advanced melanoma. Among their side effects, panniculitis has been hypothesized to be associated with better survival.

Objectives: In this study, we aimed to explore the association between the occurrence of panniculitis during targeted therapy and outcome of metastatic melanoma.

Materials & Methods: This was a retrospective single-centre comparative study from 2014 to 2019. An English literature review was also conducted to further our understanding of the mechanism(s) involved and identify characteristics of this association, in order to support better management.

Results: Ten patients who developed panniculitis during treatment were matched to 26 controls based on potential confounders at treatment introduction. The prevalence of panniculitis was 5.3%. Median progression-free survival (PFS) for all patients was 8.5 months (range: 3.0-94.0). The median PFS for the group with panniculitis was 10.5 months (7.0-undefined) and 7.0 months (6.0-32.0) for controls (p=0.39). According to the scientific literature, panniculitis occurring during targeted therapy affects mainly young people, predominantly women, with variable delay to onset (with half reported cases occurring in the first month). In addition, panniculitis usually only affects the lower limbs or is associated with other clinical signs (fever, arthralgia), without histological specificity. Discontinuation of targeted therapy is not required as spontaneous remission is usually experienced. Symptomatic treatment may be administered but systemic corticosteroids have not been proven to be effective.

Conclusion: In contrast to the belief that there is a link between panniculitis and clinical response to targeted therapy according to the literature, our results show that there is no significant association between the two.