Exponential decay nonlinear regression analysis of patient survival curves: Preliminary assessment in non-small cell lung cancer

BackgroundFor processes that follow first order kinetics, exponential decay nonlinear regression analysis (EDNRA) may delineate curve characteristics and suggest processes affecting curve shape. We conducted a preliminary feasibility assessment of EDNRA of patient survival curves.MethodsEDNRA was performed on Kaplan–Meier overall survival (OS) and time to relapse (TTR) curves for 323 patients with resected NSCLC and on OS and progression-free survival (PFS) curves from selected publications.Results and conclusionsIn our resected patients, TTR curves were triphasic with a “cured” fraction of 60.7% (half-life [t1/2] >100,000 months), a rapidly relapsing group (7.4%, t1/2 = 5.9 months) and a slowly relapsing group (31.9%, t1/2 = 23.6 months). OS was uniphasic (t1/2 = 74.3 months), suggesting an impact of co-morbidities; hence, tumor molecular characteristics would more likely predict TTR than OS. Of 172 published curves analyzed, 72 (42%) were uniphasic, 92 (53%) were biphasic, 8 (5%) were triphasic. With first-line chemotherapy in advanced NSCLC, 87.5% of curves from 2 to 3 drug regimens were uniphasic vs. only 20% of those with best supportive care or 1 drug (p < 0.001). 54% of curves from 2 to 3 drug regimens had convex rapid-decay phases vs. 0% with fewer agents (p < 0.001). Curve convexities suggest that discontinuing chemotherapy after 3–6 cycles “synchronizes” patient progression and death. With postoperative adjuvant chemotherapy, the PFS rapid-decay phase accounted for a smaller proportion of the population than in controls (p = 0.02) with no significant difference in rapid-decay t1/2, suggesting adju