Update of a Prospective Study of Stereotactic Body Radiation Therapy for Post-Chemoradiation Residual Disease in Stage II/III Non-Small Cell Lung Cancer.

Purpose: To report long-term outcomes (risk of late toxicities, local control, and survival) of dose escalation by stereotactic radiation therapy boost to residual fluorodeoxyglucose positron emission tomography-positive residual disease after chemoradiation (CRT) in stage III non-small cell lung cancer (NSCLC).

Methods And Materials: Patients with stage IIB/III NSCLC underwent computed tomography or positron emission tomography-computed tomography screening approximately 1 month after completion of CRT. Limited residual disease (≤5 cm) within the site of the primary tumor received a stereotactic radiation therapy boost of either 10 Gy × 2 fractions or 6.5 Gy × 3 fractions to the primary tumor, to achieve a total Biologically Equivalent Dose >100 Gy.

Results: Thirty-seven patients received protocol therapy. With a median follow-up of 25.2 months, the crude local control rate for the entire group was 78% (n=29), but 10 patients (29%) and 24 patients (65%) developed regional and metastatic disease, respectively. At last follow-up, 5 patients (13.5%) remain alive, all with no evidence of disease, whereas 27 (73%) died of disease and the remaining 5 (13.5%) died of other causes. Median overall survival (OS) for the entire group was 25.2 months. Predictors for grade 3 pneumonitis included age and mean lung dose. Poorer median OS was associated with histology: median OS 15.6 months for squamous cell versus 34.8 months for other histologies (large cell neuroendocrine tumors excluded) (P=.04). The median progression-free survival was 6 months, with IIIB disease having significantly worse median progression-free survival (stages IIB/IIA being 9.4 months, vs 4.7 months for stage IIIB [P=.03]).

Conclusions: Stereotactic radiation therapy boost after CRT is a safe treatment resulting in improvements in local control for locally advanced NSCLC. No additional late toxicities were seen. Possible improvement in OS was found, but further study in a larger prospective trial is needed.