Clinical Characteristics and Prognosis of Subcutaneous Panniculitis-like T-Cell Lymphoma Based on the SEER Database
Authors: Zhang Lijuan , Lin Qiaochu , Qi Lin , Ji Jie , Niu Ting , Xiang Bing 
Published: December 2024

Background: Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare type of T-cell lymphoma that primarily affects the skin. However, it is not uncommon for patients to experience systemic involvement and life-threatening conditions. To date, SPTCL still lacks standardized treatment, and clinical outcomes show significant variability. Therefore, we will further explore the clinical characteristics and prognostic factors of SPTCL to provide research information for subsequent treatment strategies.
Methods: Patients diagnosed with SPTCL from 2000 to 2021 were identified from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database. The Kaplan-Meier (KM) method was used to plot survival curves, and differences in survival rates were compared using the Log-Rank test. Univariate and multivariate analyses were conducted using the COX proportional hazards model to identify prognostic factors for SPTCL.
Results: In the study, 205 patients with SPTCL were included, with the majority being women and the vast majority under the age of 50. The most common race was Caucasian, accounting for approximately 59%. Clinical staging is usually seen in the early stages (Stages I-II) (33.2%). About 29.3% of patients present with systemic involvement (Stages III-IV). Fewer patients concurrently present with fatal complications such as hemophagocytic lymphohistiocytosis (HLH). The primary sites of SPTCL were mostly in the skin (96.1%). In terms of treatment, chemotherapy remains the most common method. In the study, 53.2% of patients received chemotherapy, while only a small number of patients underwent radiotherapy (5.95%). The 1-year, 3-year, and 5-year Overall Survival (OS) rates for the 205 SPTCL patients, as analyzed by Kaplan-Meier, were 78.3%, 75.7%, and 66.4%, respectively. In multivariate Cox regression analysis, age, race, year of diagnosis, and treatment modality were identified as independent prognostic factors for overall survival in SPTCL patients. Patients aged 50-65 (p=0.008; HR=3.23; 95% CI=1.36-7.65), &gt;65 years (p=0.000; HR=5.07; 95% CI=2.35-10.98), and Caucasians (p=0.032; HR=4.90; 95% CI=1.14-20.96) were independently associated with poor OS. Patients diagnosed after 2008 (the gamma-delta subtype is likely to be excluded) (p=0.000; HR=0.20; 95% CI=0.11-0.36) had a better OS compared to those diagnosed before 2008. The group that received radiotherapy alone had a lower risk compared to those who received chemoradiotherapy (p=0.036; HR=0.17; 95% CI=0.03-0.90), chemotherapy (p=0.022, HR=0.17; 95%CI=0.04-0.78), and no treatment (p=0.048; HR=0.22; 95% CI=0.05-0.99). To our surprise, the Ann Arbor clinical stage was not an independent risk factor for prognosis of SPTCL patients. However, previous studies using the TNM (Tumor Node Metastasis) staging method showed significant differences in survival outcomes among patients with different stages. For SPTCL, the practical value of the Ann Arbor staging is limited, and the TNM staging system may be a more appropriate choice.
Conclusion: SPTCL is a rare disease that is comparatively more prevalent in young women. Radiotherapy was found to be associated with favorable survival outcomes, while older patients, Caucasians, and those diagnosed before 2008 were associated with a poor prognosis. The benefit of radiotherapy on survival outcomes may be due to the fact that these patients are at an early stage of the disease. Thus, radiotherapy is a good option for patients with single or localized skin lesions. Chemotherapy and chemoradiotherapy did not show significant associations with OS. This discrepancy may arise from the inability of the Ann Arbor staging to accurately assess the condition, while the use of the TNM staging may provide more personalized information for treatment. In general, for patients with SPTCL, we will still need to seek more effective treatment methods in the future.