Prognosis and Follow-Up Recommendations for Subcutaneous and Dermal Leiomyosarcoma: Local Recurrence, Metastasis, and Overall Survival in a Danish Nationwide Cohort of 661 Patients

BACKGROUND AND OBJECTIVES: The prognostic differences between subcutaneous leiomyosarcoma and dermal leiomyosarcoma are not well defined due to limited cohort sizes and insufficient follow-up in prior studies. This study aimed to investigate the clinicopathological features of subcutaneous and dermal leiomyosarcoma and estimate their 10-year rates of metastasis, local recurrence, and overall survival. Additionally, we propose standardized follow-up recommendations.

METHODS: All patients diagnosed with cutaneous leiomyosarcoma in Denmark from 1980 to 2022 were included. The prognosis was estimated using age- and sex-standardized stratified cause-specific Cox-regression with all-cause mortality as competing risk.

RESULTS: We included 196 patients with subcutaneous leiomyosarcoma and 465 with dermal leiomyosarcoma. The 10-year local recurrence rate was similar in patients with subcutaneous leiomyosarcoma (15%) and dermal leiomyosarcoma (11%, p = 0.13). However, patients with subcutaneous leiomyosarcoma had a significantly higher 10-year risk of metastasis (25%), primarily observed in grade 2 and 3 tumors, compared with dermal leiomyosarcoma (2.7%), p < 0.001, and a lower 10-year-overall survival (56% vs. 64%), p = 0.02.

CONCLUSIONS: Grade 2 and 3 subcutaneous leiomyosarcoma should be classified as a high-risk sarcoma with a substantial risk of metastasis and poor overall survival, necessitating follow-up that includes both clinical examinations and PET/CT or CT of the thorax for 5 years to detect both locoregional and distant metastases. Dermal leiomyosarcoma should be considered a low-risk sarcoma due to its low risk of metastasis and moderate risk of local recurrence, suggesting that the follow-up can focus on clinical examinations for 4 years as the 10-year risk of local recurrence is < 1% after this time point.