Correlation between overall survival and growth modulation index in pre-treated sarcoma patients: a study from the French Sarcoma Group

Growth modulation index (GMI), the ratio of two times to progression measured in patients receiving two successive treatments (GMI = TTP2/TTP1), has been proposed as a criterion of phase II clinical trials. Nevertheless, its use has been limited until now. We carried out a retrospective multicentre study in soft tissue sarcoma patients receiving a second-line treatment after doxorubicin-based regimens to evaluate the link between overall survival and GMI. Second-line treatments were classified as 'active' according to the EORTC-STBSG criteria (3-month progression-free rate > 40% or 6-month PFR > 14%). Comparisons used chi-squared and log-rank tests. The population consisted in 106 men and 121 women, 110 patients (48%) received 'active drugs'. Median OS from the second-line start was 317 days. Sixty-nine patients experienced GMI > 1.33 (30.4%). Treatments with 'active drug' were not associated with OS improvement: 490 versus 407 days (P = 0.524). Median OS was highly correlated with GMI: 324, 302 and 710 days with GMI < 1, GMI = [1.00-1.33], and GMI > 1.33, respectively (P < 0.0001). In logistic regression analysis, the sole predictive factor was the number of doxorubicin-based chemotherapy cycles. GMI seems to be an interesting end point that provides additional information compared with classical criteria. GMI > 1.33 is associated with significant OS improvement.