Background: Precision medicine trials disrupted the paradigm of randomized controlled trials in large populations. Patient selection may be based on molecular alterations rather than on primary tumor location. In small patient populations, the growth modulation index (GMI) has been developed to evaluate treatment efficacy by using each patient as its own control. The FFCD 0307 randomized phase III trial compared two sequences of chemotherapy in advanced gastric cancer, which represents a unique opportunity to evaluate the relevance of the GMI.
Patients and methods: In the FFCD 0307 trial, patients with advanced gastric cancer were randomized between two chemotherapy sequences [ECX followed by FOLFIRI at disease progression (arm A) versus FOLFIRI followed by ECX (arm B)]. GMI was defined as the ratio of the progression-free survival on second treatment (PFS2) to the time to progression on first treatment (TTP1). Sequence benefit was defined as a GMI exceeding 1.3 (GMI-high). GMI was correlated with overall survival (OS). OS1 and OS2 were measured from first randomization and second-line failure to death.
Results: Four hundred and sixteen patients were randomized (209 in arm A, 207 in arm B). One hundred and seventy-five patients (42%) received the two sequences and were assessable for GMI (97 in arm A, 79 in arm B). The median GMI was higher in arm A than in arm B (0.62 versus 0.47, P = 0.04). Patients with a high GMI had a longer OS1 (median 14.9 versus 11.5 months, NS). Median OS2 was doubled in the GMI-high group (3.4 versus 1.6 months, NS).
Conclusion: GMI analyses suggest that ECX followed by FOLFIRI might represent a better therapeutic strategy than FOLFIRI followed by ECX. High GMI was associated with prolonged survival.
Keywords: growth modulation index; precision medicine; progression-free survival ratio; survival endpoints; therapeutic sequence.
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