Single-Institution Experience of Larotrectinib Therapy for Patients With Fusion-Positive Thyroid Carcinoma.

CONTEXT

The real world efficacy and tolerabiltiy of NTRK inhibitor larotrectinib has not yet been reported in the literature although trial data has shown promising results.

OBJECTIVE

We report a retrospective analysis of patients with thyroid cancer harboring fusions who underwent treatment with larotrectinib.

METHODS

A single-institution, retrospective case series of patients with fusion-positive thyroid cancers treated with neurotrophic tyrosine receptor kinase ( inhibitors from January 1, 2007, to January 1, 2023, was performed. This study was conducted at a single academic tertiary referral center. Patients with confirmed -fusion thyroid cancer who received larotrectinib were included. Larotrectinib was administered in accordance with clinical judgment from oncology providers. The primary end point was progression-free survival (PFS).

RESULTS

Eight patients with fusion-positive thyroid cancer treated with larotrectinib were identified: 4 with papillary thyroid cancer (PTC) (50%), 3 with poorly differentiated thyroid cancer (PDTC) (38%), and 1 with anaplastic thyroid cancer (ATC) (12%). The median PFS (mPFS) for all patients was 24.7 months (95% CI, 11.3-38.1). mPFS in PTC was higher than PDTC (34.6 months [24.7-48.7 months] vs 17.5 [7.1-21.1 months]; = .017). The median overall survival (OS) was 43.8 months (29.8-56.8 months) overall. The single patient with ATC had a PFS and OS of 23 months. Two patients remained on treatment/alive at data cutoff, with a duration of response of 33.5 months and a median follow-up of 52 months. Patients achieved 1 complete response (12%), 6 partial responses (75%), and 1 stable disease (12%).

CONCLUSION

In this single-institution cohort of patients with fusion-positive thyroid cancer, inhibition led to an mPFS of 25 months, with survival surpassing historic benchmarks for ATC and PDTC.