The Unique Spatial-Temporal Treatment Failure Patterns of Adjuvant Gefitinib Therapy: A Post Hoc Analysis of the ADJUVANT Trial (CTONG 1104)

Adjuvant gefitinib therapy prolonged disease-free survival in patients with resected early-stage EGFR-mutation positive NSCLC in the ADJUVANT study (CTONG 1104). However, treatment failure patterns after gefitinib therapy are less well characterized.Overall, 222 stage N1-N2, EGFR-mutant NSCLC patients received gefitinib or vinorelbine plus cisplatin (VP) treatment. Tumor recurrences or metastases occurring during follow-up were defined as treatment failure; sites and data of first treatment failure were recorded. A post hoc analysis of treatment failure patterns which was estimated by Kaplan-Meier and hazard rate curves in modified intention-to-treat patients was conducted.There were 114 recurrences and 10 deaths before recurrence across 124 progression events. Spatial distribution analysis showed that the first metastasis site was most frequently the central nervous system in the gefitinib group (29 of 106 [27.4%]), extracranial metastases were most frequent in the VP group (32 of 87 [36.8%]). Temporal distribution analysis showed lower tumor recurrence with gefitinib than with VP 0 to 21 months post-surgery. However, recurrence with gefitinib showed a constant rate of increase 12 months post-surgery. The first peak of extracranial metastasis appeared during 9 to 15 months with VP and 24 to 30 months with gefitinib. The highest peak for central nervous system metastases post-surgery occurred after 12 to 18 months with VP and 24 to 36 months with gefitinib.Adjuvant gefitinib showed advantages over VP chemotherapy in treatment failure patterns especially in extracranial metastasis. Adjuvant tyrosine kinas inhibitors may be considered as a treatment option in resected stage N1-N2 EGFR-mutant NSCLC but longer duration should be explored.