Long-term survival and failure patterns in unresectable early-stage non-small cell lung cancer after stereotactic body irradiation: a single-institution retrospective study

Patient characteristics

215 eligible patients with 224 lesions were included in the study. Overall, 153 (71%) were male and 62 (29%) female, with a median age of 76 years (range 43–90 years). The breakdown of target lesion size by AJCC 8th edition T stage was as follows: T1 (81%), T2 (18%), and T3 (1%). Detailed patient and treatment characteristics are summarized in Table 1.

Error patterns

Of the 215 patients, 76 (35.3%) patients showed local, regional and/or distant progression. The overall patterns of failure are as follows: local recurrence 16 cases, regional recurrence 4 cases, distant metastasis 44 cases, local-regional (local recurrence combined with regional recurrence) 1 case, local-distant 7 cases, regional-distant 2 cases, local-regional-distant 2 cases. A total of 55 patients (25.6%) developed distant metastases in the study. The most common site of initial distant metastasis was intrathoracic (43.6%). The failure patterns are shown in Fig. 1 and Table 2. The 1-, 3-, and 5-year recurrence rates were 1.4%, 6.5%, and 9.5%, respectively. The 1-, 3-, and 5-year local recurrence rates were 1.4%, 6.5%, and 9.3%, respectively, and the 1-, 3-, and 5-year distant metastasis rates were 8.8%, 15, 3% and 19.5% respectively.

The progression patterns of 55 patients.

Survive

The median follow-up time for all patients was 50.8 months (range: 1.0-117.9 months). At 1, 3, and 5 years, the OS rates were 97.1%, 80.9%, and 63.8%, respectively, as shown in Fig. 2A. Median OS was 92.2 months (95% CI: 61.5-122.9 months). The 1-, 3-, and 5-year PFS rates were 87.5%, 65.9%, and 50.8%, respectively, with a median PFS of 62.2 months (95% CI: 45.0-59.4 months ). At 1, 3, and 5 years, LRFS rates were 97.1%, 80.9%, and 50.9%, respectively. The 1-, 3-, and 5-year LRFS rates were 95.7%, 75.5%, and 58.8%, respectively. The RRFS rates at 1, 3, and 5 years were 96.1%, 78.0%, and 61.9%, respectively. The 1-, 3-, and 5-year DMFS rates were 88.5%, 69.8%, and 55.4%, respectively. The survival curves are shown in Figures 2B–E.

Survival curves for 215 patients in different categories.

Of 80 (37.2%) patients who died, causes of death were available for 63 cases. Twenty (25%) patients had noncancer deaths, including pulmonary infection, chronic obstructive pulmonary disease (COPD), heart failure, cerebral infarction, cerebral hemorrhage, chronic liver failure, and accident.

Pathology versus non-pathology

In this study, 67 patients had no pathology, among which patients refused puncture biopsy or it was difficult to obtain enough samples from the tumor location. When comparing patients with and without pathology, it was found that there was no significant difference in overall survival (P= 0.832) and progression-free survival (P= 0.672) between the two groups, as shown in Fig. 3.

Survival curves for patients with and without pathological results.

Prognostic factors

Gender, age, tumor diameter, smoking index, CCI, KPS, BED, histological subtype and T stage were included as variables in the univariable Cox analysis. The results showed that BED, smoking index and age were correlated with OS, while BED, smoking index, age and pathological type were correlated with PFS. Multivariate analysis showed that BED and age were independent prognostic factors affecting survival of lung cancer patients, while BED was an independent factor for PFS, as shown in Table 3.

There was a significant difference in OS and PFS between the two groups depending on whether the BED was 100 Gy or less, as shown in Fig. 4. The progression rate was 42.3% in patients with a BED of 100 Gy or less and 16.9% in patients with a BED of 100 Gy or less. Patients with a BED of 100 Gy or more (P<0.001). The distant metastasis rates of the two groups were 32.6 and 11.9%, respectively (P= 0.002), but there was no statistically significant difference in recurrence rates between the two groups.

Survival curves for patients with BED ≥ 100 Gy and < 100 Gy.