Purpose
KIT-directed tyrosine kinase inhibitors (TKIs), such as imatinib, have demonstrated benefit in KIT mutant (KIT+) mucosal, acral, vulvovaginal, and chronically sun damaged (CSD) melanoma. Dasatinib has superior pre-clinical activity to other TKIs against cells with the most common KIT mutation, exon 11L576P. E2607 assessed dasatinib in patients (pts) with these melanoma subtypes.
Patients and Methods
Pts received dasatinib 70 mg orally twice daily. The primary objective for this two-stage phase II trial was response. Stage I was open to KIT+ and wild type (KIT-) mucosal, acral, and CSD melanoma (n=57). Stage II accrued only KIT+ tumors (n=30). To enrich for KIT+ tumors, vulvovaginal melanoma were added and CSD melanoma removed from eligibility. Secondary objectives included progression-free survival (PFS), overall survival (OS), and safety.
Results
From 5/09-12/10, the first stage enrolled 57 pts. Of the evaluable pts, 3/51 (5.9%) achieved a partial response (PR): all KIT-. Stage II closed early due to slow accrual (11/11-12/15). In stage II, 4/22 evaluable pts had a partial response (PR: 18.2%), median duration of 4.2 months. The median PFS was 2.1 months (n=73), 95% confidence interval (CI): 1.5-2.9 months. The median OS was 7.5 months (CI: 6.0-11.9 months). In exploratory analyses, no differences were seen in PFS or OS by KIT status or subtype. Dasatinib was discontinued due to adverse events in 9/75 pts (12%).
Conclusions
Dasatinib response among KIT+ melanoma pts was low. In view of its clinical activity, we recommend that imatinib remain the KIT TKI of choice for unresectable KIT+ melanoma.