Is Interim/Mid-Treatment PET (interim PET, i-PET) Scan Predictive of Outcome in Diffuse Large B-Cell Lymphoma?.

Initial treatment of diffuse large B-cell lymphoma (DLBCL) involves 6–8 cycles of chemo-immunotherapy and may be curative in 60–65% of patients. However, in the remaining patients, subsequent therapies appear inadequate for long lasting remission. A strategy to improve patient outcomes could involve early identification of patients who do not respond to treatment as expected and then employing different/aggressive treatment modalities in these patients. PET scan done during mid-treatment (interim PET, i-PET) may help identify these patients early. However, the value of i-PET in DLBCL is not established as there is controversy about its prognostic value and studies are ongoing to evaluate its benefit.

To determine predictive value of i-PET on progression-free survival (PFS), overall survival (OS) in DLBCL patients.

We performed retrospective analysis of DLBCL patients treated at LSU Health Shreveport, LA, between Jan 2002 – July 2012. All patients were treated with R-CHOP chemotherapy. PET-CT was performed at baseline at time of diagnosis, after 2 to 4 courses (i-PET) and at the end of therapy (final PET, f-PET).

Forty-four patients were evaluable for analysis. The median age was 55 years (range 21–84), 32 (73%) were males. Ann-arbor staging showed 5 patients each in stage I and II, 11 patients in stage III, 23 in stage IV, and the median IPI score was 3. Median time to i-PET was after 3 cycles of chemotherapy, and median days to i-PET after chemotherapy were 16. The median follow-up duration from start of chemotherapy was 23 months (range 4 – 89). The PET results were as follows: i-PET negative 30 (68%), i-PET positive 14 (32%) patients. Final PET results were: f-PET negative 33 (75%), f-PET positive 11 (25%) patients. The 3-year PFS was 96.3% and 35.7% for i-PET negative versus positive patients respectively (p<0.001), and the 3-year PFS for f-PET negative versus positive patients was 78.9%% versus 30.0% respectively (p<0.001). The 3-year OS was 79.4% and 62.6% for i-PET negative versus positive patients respectively (p=0.3306). The 3-year OS was 79.9% and 58.7% for f-PET negative versus positive patients respectively (p=0.021).

Interim/mid-treatment PET (i-PET) scan is predictive of progression free survival but not overall survival for DLBCL patients. A final PET (f-PET) scan is predictive of progression free survival as well as overall survival for DLBCL patients. Larger prospective studies are needed to confirm these findings and could also look into the biology of i-PET positive patients by gene expressing profiling (GEP) and evaluate the role of novel agents in modifying the disease course.

No relevant conflicts of interest to declare.