Regional nodal relapse in surgically staged Merkel cell carcinoma

The nodal relapse pattern of surgically staged Merkel cell carcinoma (MCC) with/without elective nodal radiotherapy (RT) was studied in a single institution.

A total of 51 patients with MCC, 33% UICC stage I, 14% II, 53% III (4 lymph node metastases of unknown primary) were eligible. All patients had surgical staging: 23 patients sentinel node biopsy (SNB), 22 patients SNB followed by lymphadenectomy (LAD) and 6 patients LAD. In all, 94% of the primary tumors (PT) were completely resected; 57% of patients received RT, 51% of known PT sites, 33% (8/24 patients) regional RT to snN0 nodes and 68% (17/27 patients) to pN+ nodes, mean reference dose 51.5 and 50 Gy, respectively. Mean follow-up was 6 years (range 2-14 years).

A total of 22% (11/51) patients developed regional relapses (RR); the 5-year RR rate was 27%. In snN0 sites (stage I/II), relapse occurred in 5 of 14 nonirradiated vs. none of 8 irradiated sites (p = 0.054), resulting in a 5-year RR rate of 33% versus 0% (p = 0.16). The crude RR rate was lower in stage I (12%, 2/17 patients) than for stage II (43%, 3/7 patients). In stage III (pN+), RR appeared to be less frequent in irradiated sites (18%, 3/14 patients) compared with nonirradiated sites (33%, 3/10 patients, p = 0.45) with 5-year RR rates of 23% vs. 34%, respectively.

Our data suggest that adjuvant nodal RT plays a major role even if the sentinel nodes were negative.

Adjuvant RT of the lymph nodes in patients with stage IIa tumors and RT after LAD in stage III tumors is proposed and should be evaluated prospectively.