Atlanta, GA—A positron emission tomography (PET)-directed approach after standard chemotherapy can guide the need for consolidation radiation therapy in patients with diffuse large B-cell lymphoma (DLBCL). This approach can spare patients from further treatments, such as salvage chemotherapy and stem-cell transplant, as well as unnecessary radiation therapy, according to a study presented at ASH 2017.
“Our experience shows that 18-F-fluorodeoxyglucose [FDG]-PET can be used to guide the administration of consolidative radiation therapy. This approach limits toxicity associated with radiation to those at greatest risk,” said lead investigator Ciara Louise Freeman, MD, MRCP, Lymphoma Fellow, Medical Oncology and Centre for Lymphoid Cancer, British Columbia Cancer Agency, Vancouver, Canada, who presented the results.
“We found that patients with bulky DLBCL who become PET-negative at end of therapy have excellent outcomes without radiation therapy. PET-positive patients who did not progress…have favorable outcomes and appear to benefit from this approach,” she told listeners. “Almost 60% of those with bulky disease at diagnosis can be safely spared radiation therapy.”
To determine the benefit of FDG-PET in selecting patients for radiation therapy after chemotherapy, this retrospective analysis included 723 patients with newly diagnosed advanced DLBCL who were listed in the British Columbia Cancer and Lymphoid Imaging databases between 2015 and 2017. Patients received treatment with curative intent using 6 cycles of the R-CHOP regimen, and then underwent posttreatment FDG-PET scans.
Patients with PET-negative results went on to observation. Nonprogressing PET-positive patients had consolidative radiation therapy, when feasible.
Patients enrolled in the study had stage III or IV (74%) or stage I or II disease, with B-cell symptoms and/or bulky disease (ie, ≥10 cm). At the end of chemo-immunotherapy, 72% were PET-negative and went on to observation. The remaining 206 (28%) patients were PET-positive.
At a median of 3.3 years of follow-up from diagnosis, PET-negative patients were less likely to have disease progression: 83% of the PET-negative group and 57% of the PET-positive group had not progressed, relapsed, or died from lymphoma.
Of the 206 PET-positive patients, 47% did not receive radiation therapy and 109 received radiation. More than three-quarters (78%) of those with PET-positive disease who received radiation were free of disease progression at 3 years compared with 83% of the PET-negative patients, and 34% of the PET-positive patients who did not get radiation therapy.
The 3-year overall survival was similar (86% and 84%) for the PET-negative and PET-positive cohorts of patients who received radiation therapy, respectively, compared with 44% of PET-positive patients who did not have radiation.
The presence of bulky disease at baseline did not affect time to disease progression. The 3-year time to disease progression was 84% in the nonbulky PET-negative disease cohort and 82% in the bulky PET-negative disease cohort.
