Abstract
2024 Background: The high response rates observed in recent trials of GBM patients (pts) treated with VEGF inhibitors, and the ongoing search for early endpoints which facilitate the efficient evaluation of new agents, have renewed the focus on tumor response as a potential surrogate for survival. Methods: In newly diagnosed (N=1,359) and recurrent (N=357) GBM pts treated prospectively on NCCTG phase II or III trials, we correlated best response (BR) category (responder or non-responder) with survival endpoints (PFS, TTP and OS). A responder was defined by standard NCCTG criteria as CR, PR or REGR (regression), and non-responder defined as STAB (stable) or PROG (progression) following treatment. Log-rank tests and Cox proportional hazard models were used to compare differences between survival and progression for each category. Landmark analyses at different cut-points were used for OS (newly diagnosed: 26 wks; recurrent: 9 and 13 wks) and TTP/PFS (newly diagnosed: 13 wks; recurrent: 6 and 9 wks). Results: For newly diagnosed GBM, best response was CR (n=9), PR (n=17) and REGR (n=150) (176 pts, 13%). For recurrent GBM, BR was CR (n=1) and REGR (n=26) (27 pts, 7.6%). For responders, median time to response for newly diagnosed and recurrent pts were 14 and 7 wks. For newly diagnosed pts, 988 pts were alive (176 responders, 812 non-responders) at wk 26. Median OS for responders and non-responders were 36 and 28 wks, respectively (p=0.01). At week 13, 1173 pts were alive without PROG (189 responders, 984 non-responders). Median TTP for responders and non-responders were 47 and 34 wks, respectively (p=0.0002). For recurrent pts, 251 were alive at wk 9 (227 non-responders, 24 responders), with median OS of 18 and 31 wks respectively (p=0.13); 195 pts were alive at wk 6 without PROG (171 non-responders, 24 responders), and median TTP were 7 and 21 wks (p=0.02). Results were not significantly altered after adjustment for age, gender and ECOG status. Conclusions: In newly diagnosed GBM, tumor response correlated significantly with TTP, but the predictive effect for OS was less robust, albeit reaching significance. For recurrent pts, response was an acceptable surrogate for TTP/PFS, but not OS. No significant financial relationships to disclose.
Published Version
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