Refining Surveillance Guidelines after SBRT for Early-Stage Lung Cancer

Abstract

Stereotactic Body Radiation Therapy (SBRT) is a popular treatment for patients with early-stage non-small cell lung cancer (NSCLC). After treatment, NCCN guidelines suggest 3-6-month imaging surveillance up to year 3, every 6 months in years 3-5, and yearly after 5 years. The Delphi Consensus Study recommends annual screening in years 2-5. While patients are more likely to locally recur up to two years after treatment there remains a paucity of data on the benefit of long-term surveillance. We therefore evaluated a cohort of NSCLC patients to evaluate the utility and frequency of both short- and long-term surveillance. A total of 224 patients with early-stage NSCLC treated with SBRT between 2014-2019 at a single institution were retrospectively evaluated. Patients with nodal disease, treated with >8 fractions, or metastatic disease at time of SBRT were excluded. Any cross-sectional imaging of the chest for each patient after SBRT was reviewed for evidence of recurrence or new malignancy. Recurrence or new malignancy was defined radiographically and/or pathologically. The median scan interval (MSI) was calculated using the time between surveillance scans. The MSI between patients with or without new disease was compared by t-test. Frequency of recurrence between patients with <T2 or > = T2 disease was compared using chi squared analysis. A total of 224 patients were reviewed and 168 were included in the analysis. 919 scans were performed, 800 as scheduled surveillance scans and 119 for other indications. Median number of scans per patient was 5 (IQR 3-13), with a max of 15 scans. The MSI was 5 months (IQR 3-6) for up to 3 years after treatment, 8 months (IQR 6-12) between 3-5 years after treatment, and 12 months (IQR 11-13) ≥5 years after treatment. There was no significant difference in MSI between patients that did or did not develop new/recurrent disease. 47% of patients with <T2 had new disease compared to 63% with > = T2 tumors (p = 0.10). All 3 patients with T3 disease recurred or had new malignancy identified on 2, 7, and, 36-month scans. 67 instances of new disease were found on 521 scans (13%) during years 1-3, 12 instances on 70 scans (17%) years 3-4, and 5 found on 11 scans (45%) after 5 years. Of 84 total instances of new disease, representing 50% evaluable patients, 75 were discovered on surveillance scans compared to 9 on non-surveillance scans. The MSI for patients in this cohort aligns with published guidelines. Half of the patients developed new disease with the vast majority discovered on surveillance scans. Higher chance of new disease in larger tumors would suggest not all patients benefit from the same scan interval with some patients receiving up to 15 diagnostic scans during follow up. With patients continuing to recur >5 years after treatment, scan frequency, radiation exposure, and probability of recurrence should all be considered in comprehensive surveillance guidelines.