Purpose: Tumor shrinkage categorized as complete response (CR) or partial response (PR) is a fundamental efficacy measure for new cancer treatments and often considered a surrogate for overall survival. However, for any given treatment, many more patients typically achieve stable disease (SD) or have progressive disease (PD) than achieve response. We hypothesized that PD (or its converse, disease control rate [DCR], consisting of CR, PR, SD) is a stronger predictor of survival than response alone in advanced non-small-cell lung cancer (NSCLC), and that this determination might be assessable early on during therapy.
Patients and methods: Data from 984 NSCLC patients entered onto three randomized Southwest Oncology Group trials of platinum-based chemotherapy were pooled and subjected to Landmark survival analysis. Patients were categorized according to proportions alive at weeks 8, 14, and 20 after registration, as well as response status. Elements were fitted into a Cox proportional hazards model.
Results: Tumor response (CR, PR) was seen in 260 patients (27%). Median time to response, time to progression, and survival time were 2.0, 4.3 and 8.9 months, respectively. Median survival times among patients with CR/PR, SD, or PD were 13.5, 8.4, and 3.1 months, respectively. Of 892 patients alive at week 8, DCR was 62%. Although CR/PR at week 8 was associated with longer survival (hazard ratio [HR] = 0.61; P < .001), DCR was superior in predicting survival (HR = 0.45; P < .0001).
Conclusion: DCR at week 8 is a more powerful predictor of subsequent survival than is the traditional tumor response rate in advanced NSCLC and provides an early assessment of subsequent outcome.