Blood cancers

PET scans identify poor responders in follicular lymphoma

A/Professor Judith Trotman

Australian research has confirmed the prognostic value of PET scans in patients with follicular lymphoma, with new long term data showing good prediction of overall survival as well as progression free survival.

Analysis of six year outcomes for patients enrolled in the GALLIUM trial showed that complete metabolic response (CMR) status with an end-of-induction PET-CT scan following first-line immunochemotherapy for advanced-stage symptomatic follicular lymphoma was highly predictive of PFS and OS.

The additional PET study, led by Associate Professor Judith Trotman, Director of the Haematology Clinical Research Unit in Haematology at Concord Hospital showed an almost 12% difference in overall survival at six year follow up between patients who had CMR on a PET scan and those who did not (91.3% vs 79.6%)

Differences in PFS from end of induction PET scan results were 62.6% for CMR patients compared with 23.4% for non-CMR patients.

The GALLIUM phase 3 study compared the anti-CD20 monoclonal antibody obinutuzumab with rituximab (each combined with a chemotherapy backbone) in patients with previously untreated follicular lymphoma.

Presented at the European Haematology Association virtual meeting (EHA 25), the analysis of more than 500 evaluable PET scans from patients in the study showed that CMR status was highly prognostic for longer OS (Hazard Ratio 3.34)  and also PFS (non-CMR vs CMR: HR 3.40).

Professor Trotman said the 12% difference in survival was a substantial difference in survival at only five to six years after induction in a patient population with indolent lymphoma who would usually be expected to live on average a further20 years after diagnosis.

“It’s really important to identify the poor players, the patients who are going to need something more than just standard antibody-chemotherapy for treating their lymphoma,” she told a Lymphoma Australia webinar.

However she noted that while PFS was better in patients treated with obinutuzumab  in the GALLIUM study, there was no difference in overall survival compared to rituximab in patients with CMR, with both groups of patients showing OS of 92%. In addition, patients treated with obinutuzumab had higher rates of grade 3 and higher adverse effects compared to rituximab

“So we’re not seeing that overall survival advantage with the more powerful, more toxic antibody and it’s really important now that we don’t just focus on progression free survival which is an earlier and easier endpoint,” she said

“We need to start thinking about what are the other endpoints that are really important to our patients: the toxicity of treatments, the number of times they have to come into hospital, the number of times they get recurrent bronchitis and sinusitis … which can really severely impact on their quality of life.”

“And we need to tease out the patient population whom we really do need to give more powerful, more toxic therapies form those who are destined to do every well – and that’s where the PET scanning is going to be really valuable.”

Professor Trotman said the Australasian Leukaemia & Lymphoma Group (ALLG) is now sponsoring the PETReA (PET-Response-Adapted therapy) study adapted response to answer further questions in this area.

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