Can FDG-PET/CT scanning predict treatment outcomes in diffuse large B-cell lymphoma?

This study evaluated whether FDG-PET/CT imaging during treatment helped predict outcomes for patients with diffuse large B-cell lymphoma (DLBCL). The authors concluded that mid-treatment imaging might help determine disease status rather than guide treatment decisions.

DLBCL is the most common type of non-Hodgkin's lymphoma. R-CHOP chemotherapy remains the standard treatment for patients with DLBCL. For patients who do not respond to this treatment, chemotherapy followed by a stem cell transplant (SCT) is recommended. However, SCT is effective for only 30 – 35% of patients. Tailoring therapy based on treatment response may be helpful for patients with a poor prognosis. 

Imaging techniques are one way to adapt treatments. These techniques are used during treatment to see how the tumor has responded. This result, obtained mid-treatment, could then guide further therapy. One such imaging technique is FDG-PET/CT. This type of imaging has been used at the end of treatment for patients with DLBCL. However, whether it can also be useful during treatment remains unclear.

This study included 80 patients with newly diagnosed DLBCL. All patients had FDG-PET/CT scanning before, during (interim), and after chemotherapy. Patients received 6 to 8 courses of either R-CHOP or R-THP-COP (R-CHOP plus pirarubicin).

During treatment, 82.5% of patients had negative interim scan results (no residual cancer). 17.5% had positive interim scan results (disease still present). At the end of treatment, 90% of patients had negative scan results, and 10% of patients had positive scan results.

57.1% of patients who had positive interim scan results showed negative scan results at the end of treatment. Only 3% of patients who had negative interim scan results showed positive scan results at the end of treatment. 

Significantly fewer patients with positive interim scans were still alive two years later without disease progression compared to patients with negative scans (50.0% vs. 86.4%). Significantly fewer patients with positive scans at the end of treatment were still alive two years later without disease progression compared to patients with negative scans (25.0% vs. 84.7%).

Interim scanning was 57.1% likely to predict relapse or disease progression. Scanning at the end of treatment was 75% likely to predict relapse or progression.

This study concluded that interim PET/CT imaging for patients with DLBCL might help determine disease status. The authors suggest that using interim imaging results to make treatment decisions may not be recommended for patients with DLBCL.

This study had a small number of patients and analyzed data retrospectively. Treatment regimens and courses were not identical for all patients. Larger studies are needed to confirm these results.