Image from Jens Langner
PET scan
In the PETAL trial, treatment intensification based on results of an interim positron emission tomography (PET) scan did not improve survival outcomes for patients with aggressive lymphomas.
PET-positive patients did not benefit by switching from R-CHOP to a more intensive chemotherapy regimen.
PET-negative patients did not benefit from 2 additional cycles of rituximab after R-CHOP.
These results were published in the Journal of Clinical Oncology.
PETAL was a randomized trial of patients with newly diagnosed T- or B-cell lymphomas.
Patients received 2 cycles of CHOP (cyclophosphamide, doxorubicin, vincristine, prednisone)—plus rituximab (R-CHOP) in CD20-positive lymphomas—followed by a PET scan.
PET-positive patients were randomized to receive 6 additional cycles of R-CHOP or 6 blocks of an intensive protocol used to treat Burkitt lymphoma. This protocol consisted of high-dose methotrexate, cytarabine, hyperfractionated cyclophosphamide and ifosfamide, split-dose doxorubicin and etoposide, vincristine, vindesine, and dexamethasone.
PET-negative patients with CD20-positive lymphomas were randomized to receive 4 additional cycles of R-CHOP or 4 additional cycles of R-CHOP followed by 2 more doses of rituximab.
Among patients with T-cell lymphomas, only PET-positive individuals underwent randomization. PET-negative patients received CHOP. Patients with CD20-positive T-cell lymphomas also received rituximab.
PET-positive results
Of the PET-positive patients (108/862), 52 were randomized to receive 6 additional cycles of R-CHOP, and 56 were randomized to 6 cycles of the Burkitt protocol.
In general, survival rates were similar regardless of treatment. The 2-year overall survival (OS) rate was 63.6% for patients who received R-CHOP and 55.4% for those who received the more intensive protocol.
Two-year progression-free survival (PFS) rates were 49.4% and 43.1%, respectively. Two-year event-free survival (EFS) rates were 42.0% and 31.6%, respectively.
Among patients with diffuse large B-cell lymphoma (DLBCL), the OS rate was 64.8% for patients who received R-CHOP and 47.1% for those on the Burkitt protocol. PFS rates were 55.5% and 41.4%, respectively.
There was a significant difference in EFS rates among the DLBCL patients—52.4% in the R-CHOP arm and 28.3% in the intensive arm (P=0.0186).
Among T-cell lymphoma patients, the OS rate was 22.2% in the R-CHOP arm and 30.0% in the intensive arm. The PFS rates were 12.7% and 30%, respectively. The EFS rates were the same as the PFS rates.
Overall, patients who received the Burkitt protocol had significantly higher rates of grade 3/4 hematologic toxicities, infection, and mucositis.
PET-negative results
Of 754 PET-negative patients, 697 had CD20-positive lymphomas, and 255 of those patients (all with B-cell lymphomas) underwent randomization.
There were 129 patients who were randomized to receive 6 cycles of R-CHOP (2 before and 4 after randomization) and 126 who were randomized to receive 6 cycles of R-CHOP plus 2 additional cycles of rituximab.
Again, survival rates were similar regardless of treatment.
The 2-year OS was 88.2% for patients who received only R-CHOP and 87.2% for those with additional rituximab exposure. PFS rates were 82.0% and 77.5%, respectively. EFS rates were 76.4% and 73.5%, respectively.
In the DLBCL patients, the OS rate was 88.5% in the R-CHOP arm and 85.8% in the intensive arm. PFS rates were 82.3% and 77.7%, respectively. EFS rates were 72.6% and 78.9%, respectively.
As increasing the dose of rituximab did not improve outcomes, the investigators concluded that 6 cycles of R-CHOP should be the standard of care for these patients.
The team also said interim PET scanning is “a powerful tool” for identifying chemotherapy-resistant lymphomas, and PET-positive patients may be candidates for immunologic treatment approaches.