Impact of body surface area on survival in EGFR-mutant non-small cell lung cancer patients treated with gefitinib monotherapy: observational study of the Okayama Lung Cancer Study Group 0703

Background The approved dose of gefitinib is fixed, without adjustment for physical size. We demonstrated previously that its efficacy was affected by body surface area (BSA) in patients with EGFR-mutant non-small cell lung cancer (NSCLC). To validate these observations, we assessed the association between BSA and the efficacy of gefitinib using a different patient cohort. Methods Prospective cohort data from 115 NSCLC patients with EGFR-mutant tumours, who received gefitinib monotherapy between 2007 and 2012, were analysed. Results Gefitinib was less effective in individuals with a high BSA (>= 1.5 m(2)) in EGFR-mutant NSCLC compared with those with a low BSA (< 1.5 m(2)). The median progression-free survival (PFS) in the high- and low-BSA groups was 4.2 and 8.5 months, respectively, although there was no difference in survival among the whole NSCLC cohort. Multivariate analysis also showed a significant effect of BSA on PFS (hazard ratio 1.72; 95 % confidence interval 1.08-2.74; p = 0.021). Sensitivity analysis revealed that the use of the BSA cut-off level around 1.50 m(2) was robust for detecting subpopulations that would benefit less from gefitinib monotherapy. Conclusion We found in the prospective cohort data that BSA could affect the efficacy of gefitinib monotherapy in patients with EGFR-mutant NSCLC, suggesting that BSA-based dose setting of gefitinib monotherapy might be further investigated, despite the fact that no molecular-targeted agent described to date undergoes dose adjustment according to BSA.