Abstract 633P
Background
PCNSL response assessments rely upon contrast enhanced magnetic resonance imaging (MRI) for the evaluation of response. EOT MRI is not fully accurate in anticipating cure or relapse as patients (pts) in complete response (CR) will recur while some patients in partial response (PR) will not. We aimed to determine the prognostic value of EOT 18F-choline PET as novel adjunctive study at the RMH for pts with PR and CR at EOT MRI following first line (1L) treatment.
Methods
Clinical data was collected from pts treated at RMH for PCNSL between August 2009 and March 2020. Kaplan Meier survival analysis for progression free survival (PFS) and overall survival (OS) was performed for pts who were in PR (residual contrast visible) or CR (no residual contrast) on their EOT MRI. PFS and OS was also calculated for pts with residual choline (PET-PR) vs no residual choline uptake (PET-CR) on PET. PFS is calculated from time from 1st treatment to progression/death. OS is calculated from time from 1st treatment to death of any cause.
Results
70 pts were treated for PCNSL. 40/70 pts completed all intended induction treatment. The majority that did not complete treatment was due to progression/death. 7 pts that completed intended treatment were excluded from evaluation as 3 had progressive disease (PD) on their EOT MRI and EOT MRI was not available for 4. All 3 patients with PD had choline uptake on their EOT scan. For the remaining 33 evaluable pts the table below summarises their outcomes. After this EOT timepoint, 17 of these 33 patients proceeded to consolidation with either whole brain radiotherapy or autologous stem cell transplant following 1L chemotherapy. Table: 633P
| (n)= Number of pts. (*)=Omitting pts where no PET performed. (+)= Unable to calculate upper bound due to insufficient number of events | |||||||
| Response category | n | Median PFS (years) (95% CI) | p-value | Median OS (years) (95% CI) | p-value | n receiving consolidation after 1L therapy | |
| All pts | 33 | 2.2 (1.2, 7.0) | 5.0 (2.0, +) | 17 | |||
| EOT MRI outcome | CR | 17 | 1.6 (0.6, 5.7) | 0.08 | 5.0 (1.2, +) | 0.40 | 6 |
| PR | 16 | 5.2 (1.6, +) | 6.0 (1.8, +) | 11 | |||
| EOT PET outcome* | CR | 19 | 1.9 (0.8, 7.0) | 0.98 | 5.0 (1.8, +) | 0.73 | 7 |
| PR | 5 | 2.2 (0.8, +) | 4.8 (1.5, +) | 3 |
Conclusions
Patients achieving PR on MR or PET had similar OS to those with CR. This could be attributed to higher proportion of pts with PR receiving consolidation therapy.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.