Merkel-Cell Carcinoma: Local Recurrence Rate Versus Radiation Dose Study from a 949-Patient Database

TL;DR

This study finds that higher radiation doses reduce local recurrence in Merkel-cell carcinoma patients.

Contribution

The study uniquely stratifies recurrence rates by radiation dose and treatment settings in a large patient database.

Findings

A local recurrence rate of 23% was observed in irradiated patients without chemotherapy.

Radiation doses below 50 Gy2 showed significantly higher recurrence rates than doses of 50 Gy2 or more.

The study highlights the need for prospective research to determine optimal radiotherapy doses.

Abstract

(1) Background: Knowledge regarding the optimal radiotherapy dose for Merkel-cell carcinoma (MCC) remains limited. (2) Methods: Following a PubMed search, equivalent doses in 2 Gy fractions (Gy2) were compared. (3) Results: Of the 949 patients, 939 were evaluable, with 728 (77.5%) cases localized to the primary site and 171 irradiated without chemotherapy. The overall local recurrence rate (LRR) was 23% (40/171). After definitive radiotherapy with EQD2 < 50 Gy2 versus ≥50 Gy2, the LRRs were 23.1% (3/13) and 12.5% a(1/8), respectively (p = 0.0004). (4) Conclusions: For definitive radiotherapy, EQD2 < 50 Gy2 demonstrates a significantly higher LRR than ≥50 Gy2 (p = 0.0004). This study is clinically useful and unique with stratification by definitive/adjuvant settings and positive/negative resection margins. A future prospective multicenter study is needed to determine the optimal radiotherapy doses.