Therapeutic Effectiveness of Radiotherapy for Lymph Node Metastases of Cutaneous Squamous Cell Carcinoma: A Single‐Center Retrospective Analysis

ABSTRACT

Cutaneous squamous cell carcinoma (cSCC) frequently affects older adults, and regional lymph node (LN) metastasis is associated with poor prognosis. Lymph node dissection (LND) is the standard treatment for LN metastasis; however, radiotherapy (RT) may represent an alternative option when surgery is not feasible. Although the effectiveness of RT for primary cSCC is well established, its effectiveness for LN metastases remains insufficiently evaluated. We conducted a single‐center retrospective analysis of patients with cSCC and LN metastases treated between 2007 and 2024. Two cohorts were examined: (1) the RT cohort, comprising 21 patients treated with RT, in which objective response rate (ORR) and local progression‐free survival (LPFS) were assessed; and (2) the LND versus RT cohort, comprising 24 patients with initial regional LN metastases treated with either LND or RT, in which LPFS, distant metastasis‐free survival (DMFS), and disease‐specific survival (DSS) were evaluated. In the RT cohort, ORR was 81% (complete response 52%, partial response 29%), and the median LPFS was 40.0 months. Patients with a sum of the diameters of the target lymph node (SDLN) of < 40 mm demonstrated significantly better local control than those with an SDLN of ≥ 40 mm (median LPFS, 40.0 vs. 6.6 months; p  = 0.029). In the LND versus RT cohort, no significant differences were observed between the LND and RT groups in LPFS, DMFS, or DSS. In exploratory multivariable analyses, a larger SDLN was consistently associated with poorer outcomes, whereas other covariates showed inconsistent associations and wide confidence intervals, reflecting model instability due to the limited sample size. These findings indicate that RT provides favorable local control of LN metastases of cSCC, particularly in smaller LN metastasis, and demonstrates survival outcomes comparable to those of LND. RT may be considered a reasonable alternative to surgery in selected patients who are ineligible for LND.