Conservative management of < 3cm anterior mediastinal lesions in lung cancer screening is safe

To determine if a pragmatic, conservative approach to managing < 3 cm anterior mediastinal lesions in lung cancer screening (LCS) is safe.

55- to 77-year-old current or former smokers underwent low-dose computed tomography (LDCT) screening. Anterior mediastinal lesions < 3 cm at baseline were managed conservatively with annual LDCT follow-up for up to 2 years. Lesions ≥ 3 cm at baseline, growing during follow-up (based on visual assessment), or demonstrating concerning radiological characteristics were referred for further assessment. Outcomes for all anterior mediastinal lesions were assessed using follow-up LDCT images, electronic health records and the national cancer registry. Descriptive frequencies were calculated for all reported outcomes.

The baseline prevalence of anterior mediastinal lesions was 0.7% (n = 91/12,961). Among 54 participants with < 3 cm lesions who underwent annual LDCT follow-up, 74.1% (n = 40/54) completed 2 years of surveillance, while 26.9% (n = 14/54) required further assessment due to interval growth. Four participants with growing lesions were diagnosed with thymoma following surgery, and one required adjuvant radiotherapy for an R1 resection margin. Among all participants with anterior mediastinal lesions, 16 underwent surgical resection, resulting in eight thymoma diagnoses. The benign resection rate was 50%. No thymic or anterior mediastinal malignancies have subsequently been diagnosed among participants with < 3 cm lesions who completed surveillance within the study over a median follow-up of 1997.5 days.

Screen-detected anterior mediastinal lesions < 3 cm at baseline without concerning radiological characteristics can be managed conservatively with annual LDCT follow-up. Referral for further assessment only in the event of interval growth does not appear to compromise clinical outcomes.

Question No standardised approach for managing anterior mediastinal lesions identified incidentally through lung cancer screening currently exists. We aimed to determine if utilising a 3 cm baseline diameter referral threshold for screen-detected anterior mediastinal lesions is safe. Findings 74% of < 3 cm anterior mediastinal lesions remained stable over two annual screening rounds and did not require a secondary care referral. Four (out of 14) individuals with growing lesions during follow-up were diagnosed with thymoma, and one required adjuvant radiotherapy for an incomplete resection. Clinical relevance Utilising a 3 cm baseline referral threshold is safe and may improve the efficiency of large-scale, population-based LCS by reducing referrals to secondary care.