163: Cumulative Incidence of Brain Metastasis after Diagnosis of Non-Small Cell Lung Cancer: Estimates from a Regional Cancer Centre Cohort
Radiotherapy and Oncology
Purpose: Tumour volumetric changes can be observed during radical chemo-radiotherapy (CRT) for locally advanced non-small cell lung cancer (NSCLC); but it is unclear whether these changes are predictive of outcomes. This study aims to a) examine whether the magnitude of tumour regression is correlated with disease control and survival; b) explore the potential difference between adenocarcinoma (AC) and non-adenocarcinoma (non-AC) NSCLC subtypes. Methods and Materials: Primary tumour volumes
... tumour volumes were recorded and analyzed on weekly serial cone beam computed tomography (CBCT) images of NSCLC patients treated with CRT from January 2006 to June 2007 at our institution 1 . Tumour volume regression was divided into three categories: < 10%, 10-30%, and ≥ 30%. Outcome measures included locoregional failure-free survival (LRFFS), distant failure-free survival (DFFS), and overall survival (OS), which were calculated using the Kaplan-Meier method. Univariate analysis (UVA) and multivariate analysis (MVA) of LRFFS, DFFS and OS were performed using the Cox regression model. Further analysis was performed comparing AC and non-AC subgroups. Results: Forty-five patients with Stage II-III NSCLC were included. Median age was 64 years (range: 43 -79 years). Median follow up was 22.1 months for all patients, and 90 months for alive patients (range: 0.9-108 months). The distribution of 7th Ed. AJCC stage was as follows: Stage IIB (T3N0) 8.9%; IIIA 66.7%; IIIB 24.4%. Twenty patients (44.4%) had AC, while 25 patients (55.6%) had non-AC histologies. All patients received concurrent chemotherapy. Twenty-eight patients (62.3%) received a total radiation dose of ≥ 60 Gy, 15 patients (33.3%) received 45 Gy as part of trimodality therapy determined upfront, and two patients (4.4%) received 58-59 Gy due to missed fractions. Among all 45 patients, 23 patients (51.1%) had ≥ 30% regression by fraction 15 and 32 patients (71.1%) by treatment completion. In UVA for all patients, young age (p = 0.02) and AC histology (p = 0.03) were significantly associated with better LRFFS; young age was significantly associated with better DFFS (p = 0.048) and OS (p = 0.04). For patients with AC histology, MVA showed that ≥ 30% regression by fraction 15 and younger age were significantly associated with better LRFFS (p = 0.007, 0.006 respectively), DFFS (p = 0.007, 0.004), and OS (p = 0.02, 0.004). For patients with non-AC histology, ≥30% regression by treatment completion was significantly associated with better LRFFS (p = 0.02), but none of the factors had any significant correlation with DFFS or OS. Conclusions: Evaluation of primary tumour regression on CBCT images during CRT may be predictive of treatment response. Early tumour regression, as indicated by ≥30% regression by fraction 15, was shown to be associated with better outcomes for adenocarcinoma histologic subtype in our study. This observation may provide insight into when, how and in which patients to best utilize adaptive radiotherapy. 1. J Thorac Oncol. 2011; 6: 531-6.