Mucocutaneous Adverse Events in Patients With Cancer Treated with the Highly Selective RET Kinase Inhibitor Selpercatinib (LOXO-292).

INTRODUCTION

Selective RET inhibitors are approved for the treatment of RET-dependent cancers. A comprehensive characterization of mucocutaneous adverse events (MAEs) has not been performed; therefore, we characterized MAEs associated with the selective RET inhibitor, selpercatinib.

METHODS

We assessed 133 patients with altered cancers treated with selpercatinib. The type, grade, cumulative incidence, and time to onset of MAEs were determined. Therapy interruptions, clinicopathologic findings, and management were described. Laboratory values were compared between patients with and without MAEs.

RESULTS

A total of 73 patients with mostly NSCLC (n = 46, 63%), medullary thyroid (n = 19, 26%), and papillary thyroid (n = 6, 8%) cancers had 126 predominantly grade 1/2 (n = 124, 98%) MAEs, with 48% reporting greater than one MAE. Xerostomia (n = 49, 37%), rash (n = 24, 18%), periorbital edema (n = 16, 12%), and xerosis (n = 12, 9%) were the most common MAEs. The yearly cumulative incidence of all-grade MAEs was 55%, with a median time to onset of 57 (interquartile range: 15-166) days after initiation. Those with MAEs had a significantly higher percentage of lymphocytes (mean = 21.8, SD = 11.3,  = 0.005) compared with those without MAEs (16.9, SD = 10.0) and elevated immunoglobulin E (mean = 275, SD = 294.5 IU/mL). There were 18 (14%) MAE-related therapy interruptions, including the following: three (2%) rechallenged with dose maintained, 10 (7%) with a 50% dose reduction, 5 (4%) with a 25% dose reduction, and no drug discontinuations. A treatment algorithm was created for the most common MAEs: xerostomia managed with saliva and lubricants; mucositis with steroid rinses; rashes with topical steroids with or without topical ammonium lactate; periorbital edema with cold or caffeine compresses; and xerosis and pruritus with emollients.

CONCLUSIONS

Selective RET inhibition is associated with a unique MAE profile. Early recognition and management of MAEs may improve quality of life, minimize interruptions, and maximize therapeutic benefit.