Is involved-field radiotherapy based on CT safe for patients with limited-stage small-cell lung cancer?

To examine the pattern of failures in patients with limited-stage small-cell lung cancer (LS-SCLC) treated with involved-field radiotherapy (IFRT) and chemotherapy, with the aim of investigating the safety of IFRT.

Two consecutive clinical phase II trials in patients with LS-SCLC conducted in our center from 1997 to 2010 were reviewed retrospectively. Both trials had the same inclusion criteria. All patients (n=108) received combined chemotherapy and thoracic radiotherapy. Only the primary tumor and involved lymphatic regions based on computed tomography (CT) scan were irradiated. Isolated nodal failure (INF) was defined as a failure in an initially uninvolved lymph node region in the absence of local recurrence or distant metastasis.

With a median follow-up of 21 months, 78 patients experienced treatment failures. Out of 28 patients with local-regional recurrences, 16 in-field, 10 out-of-field, and 2 both in-field and out-of-field recurrences were observed. INF occurred in 5 patients (4.6%), all in the ipsilateral supraclavicular area. Four patients developed simultaneously supraclavicular nodal failures and distant metastases. The median overall survival was 27 months (95% confidence interval, 24-30 months) and the median progression-free survival was 16 months (95% confidence interval, 12-21 months). For the 5 patients with INF, the median time to INF from the end of thoracic radiotherapy was 5 months (range, 1-18 months).

IFRT based on CT scan in our patients resulted in a low rate of INF (4.6%), all in the ipsilateral supraclavicular area; but another four supraclavicular nodal failures with simultaneously distant metastases were also observed. The modern imaging with higher diagnostic capabilities of lymph node especially for supraclavicular area should be incorporated in the assessment of LS-SCLC when IFRT is being contemplated.