Forty-one patients with locally advanced non-small cell lung cancer (Stage III = 38, Stage II = 3) were treated with definitive radiotherapy using conventional fractions of 1.8 or 2 Gy. Doses ranged from 54 to 70 Gy with a median dose of 66 Gy. All patients were previously enrolled on imaging protocols and underwent multiple 4D fan beam CT scans during radiotherapy. Thirty-six patients also received chemotherapy (29 concurrent, 5 sequential). The primary tumor was contoured on fan beam CT scans acquired pre-treatment, during treatment, and up to 3 months following treatment. A competing risk model was used to determine if there was a relationship between the primary tumor recurrence and percent reduction in tumor size per day.

Results

The median overall survival for all patients was 1.74 years. The median follow-up time for living patients was 6.45 years (range: 3.41 to 6.96 years). Median initial primary tumor size was 75.7cc (range: 4.7cc to 622.0cc). Twenty patients (49%) had LR at the primary tumor site, and 23 patients (56%) had distant metastases. During radiotherapy, the average percent reduction of tumor per day was 1.34% (range: -0.25% to 2.72%). Tumors that decreased in size less than 1.4% a day had a hazard ratio of 2.15 for local recurrence compared to those that decreased in size more than 1.4% a day (p = 0.0075). Although larger initial tumor size was associated with an increased risk of primary tumor recurrence (p = 0.0064), there was no relationship between initial tumor size and daily percentage change in tumor size (Pearson correlation coefficient of -0.29). The change in tumor size was not associated with the rates of distant metastases (p = 0.45). Scans taken at 3 months follow-up were also analyzed as tumors continued to shrink in size after treatment, albeit slower at an average rate of 0.81% per day (range: 0.08% to 1.28%). The average volume at 3 months was 21.5cc (range: 0.53cc to 188.3cc). There was no relationship between the change in tumor size at 3 months following treatment and local control (p = 0.18).