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significant difference in either PFS (P=0.3022) or OS (P=0.7842) between the patient groups with 0 and with 1- 3 FLs (Table 3 and Online Supplementary Figure S1).
Suppression of FL signal at serial time points and its relationship to outcome
We show that the suppression of FL signal following treatment is prognostically important. Patients achieving 100% suppression of FL signal following treatment at each time point studied (day 7, end of induction, post trans- plantation, and maintenance) have PFS and OS values that are not significantly different from cases with no FL pres- ent at baseline. Importantly, at each time point, patients with no detectable FL signal at that time point have a sig- nificantly superior outcome compared to patients with at least one detectable FL at that time point, irrespective of whether they had a FL at baseline (Table 4, Figure 2 and Online Supplementary Figure S2). Conversely, failure to sup- press the FL signal (i.e. continued positivity) was seen in 46.4% of patients at day 7, 23.6% at the end of induction, 11.4% post transplantation, and 7.3% at maintenance, and was associated with an impaired outcome.
Interaction of GEP70 risk status with PET-CT signal suppression and outcome
At presentation, 33.6% of GEP70 low-risk (LR) patients had more than 3 FLs and were associated with an adverse outcome (P=0.007 for PFS and P<0.001 for OS). A higher percentage of patients with FLs was seen in the GEP70 high-risk (HR) group at presentation (50.7%), and these cases also had an adverse outcome (P=0.04 for PFS and P=0.05 for OS) (Figure 1, Online Supplementary Table S1 and Online Supplementary Figure S3).
Following treatment, the suppression of FL signal had a similar impact in both risk strata with total suppression of signal being associated with outcomes that are not signif- icantly different from cases with no FLs at baseline. For LR patients, this was significant at all time points analyzed. In contrast, the differences in outcome were not as obvi- ous in HR patients due to the smaller number of cases and their adverse outcomes irrespective of FL status at base- line. Nonetheless, we observed a significant difference in OS and PFS between patients with no FL at baseline and day 7 compared to patients with at least one FL at day 7, and we observed a non-significant trend in OS and PFS
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Figure 2. Paired day 1, 7, and end of induction positron emission tomography with computed tomography (PET-CT). (A) Progression-free survival (PFS) and (B) over- all survival (OS) for patients entered into TT4-6 trials with paired day 1 and day 7 PET-CT studies. An overall difference in PFS and OS was noted. A significant differ- ence was observed for patients with no focal lesion(s) (FL) at baseline and no FL at day 7 compared to those with lesions present at day 7 in PFS (P=0.0002) and OS (P<0.0001). A significant difference was observed for patients with resolution of FL at day 7 compared to those with lesions present at day 7 in PFS (P=0.0001) and OS (P=0.0015). (C) PFS and (D) OS for patients entered into TT4-6 trials with paired day 1 and end of induction PET-CT studies. A significant difference was observed in PFS for patients with no FL at baseline and no FL at the end of induction compared to those with FL (P=0.0069). A significant difference was observed in PFS for patients with resolution of FL at this time point compared to those still with lesions (P=0.0064).
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