title: Response rates and durability of chemotherapy among 62 patients with metastatic Merkel cell carcinoma.
abstract: Cytotoxic chemotherapy is commonly used to treat advanced Merkel cell carcinoma (MCC). However, its efficacy in distant metastatic MCC patients is unclear, in part because most prior reports aggregated these patients with those receiving adjuvant chemotherapy and combined chemoradiation for whom prognosis and outcomes may differ. In this retrospective study, we analyzed detailed records from 62 patients with distant metastatic MCC treated with cytotoxic chemotherapy. Efficacy outcomes including response rate (RR), durability of response (DOR), progression-free survival (PFS), and overall survival (OS) were evaluated. In this cohort, platinum plus etoposide was the most commonly used first-line regimen (69%). RR to first-line chemotherapy was 55% (34/62) with complete responses (CR) in 13% (8/62) and partial responses (PR) in 42% (26/62) while 6% (4/62) had stable disease and 39% (24/62) had progressive disease. Median PFS was 94 days and median OS was 9.5 months from start of chemotherapy. Among responding patients (n = 34), median PFS was 168 days and median DOR was 85 days. Among 30 of the 62 patients who received second-line chemotherapy, RR was 23% (7/30; 1 CR, 6 PR), median PFS was 61 days, and median DOR was 101 days. In summary, first-line chemotherapy is associated with a high RR in metastatic MCC, but responses are typically not durable, and the median PFS is only 3 months. These results suggest rapid emergence of chemoresistance in MCC tumors, and may serve as a useful comparator for immunotherapies currently being explored for metastatic MCC.
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Jayasri G
authors.initials: JG
authors.lastname: Iyer
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Astrid
authors.initials: A
authors.lastname: Blom
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Ryan
authors.initials: R
authors.lastname: Doumani
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Christopher
authors.initials: C
authors.lastname: Lewis
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Erica S
authors.initials: ES
authors.lastname: Tarabadkar
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Austin
authors.initials: A
authors.lastname: Anderson
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Christine
authors.initials: C
authors.lastname: Ma
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington.
authors.forename: Amy
authors.initials: A
authors.lastname: Bestick
authors.affiliation: Department of Radiation Oncology, University of Washington, Seattle, Washington.
authors.forename: Upendra
authors.initials: U
authors.lastname: Parvathaneni
authors.affiliation: Department of Medicine/Medical Oncology, University of Washington, Seattle, Washington.
authors.forename: Shailender
authors.initials: S
authors.lastname: Bhatia
authors.affiliation: Department of Medicine/Dermatology, University of Washington, Seattle, Washington. pnghiem@uw.edu.
authors.forename: Paul
authors.initials: P
authors.lastname: Nghiem
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000009:adverse effects / Q000627:therapeutic use*; D015266:Carcinoma, Merkel Cell / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009367:Neoplasm Staging; D019233:Retreatment; D016019:Survival Analysis; D016896:Treatment Outcome
keywords: Chemotherapy; Merkel cell carcinoma; durability of response; metastatic; neuroendocrine tumor; progression-free survival; response rate