Assessing treatment in Hodgkin Lymphoma with PET-CT

3 Apr 2016

Positron emission tomography-computed tomography (PET-CT) has been confirmed as the new standard for staging patients with Hodgkin lymphoma (HL) as well as for assessment of treatment response and should replace contrast-enhanced CT (ceCT) for most patients, results from an analysis of a prospective trial have shown.

Among the 1,214 patients with advanced HL enrolled in the Response-Adapted Therapy in Advanced Hodgkin Lymphoma (RATHL) study, 14% of patients were upstaged following PET-CT while 6% were down staged from their staging status arrived at by using clinical examination, ceCT, and bone marrow biopsy (RATHL stage), reported Sally Barrington, King's College London, U.K. and multi-center colleagues. Importantly, there was also agreement between the PET-CT-derived stage and RATHL stage in 80% of patients overall.

Barrington and colleagues also assessed early response after two cycles of ABVD chemotherapy (doxorubicin, bleomycin, vinblastine, and dacarbazine) with repeat PET-CT (PET2).  "Our study is the first to compare PET-CT staging with the established standard of clinical assessment, contrast-enhanced CT, and bone marrow biopsy stage in a large cohort of patients with advanced HL in an international trial, [and showed] that PET-CT altered staging in 20% of patients compared with the standard approach," Barrington and colleagues wrote.

Clinical trial details

RATHL included Hodgkin lymphoma patients with stage IIB to IV disease as well as those with stage IIA provided they had adverse features. Patients whose PET2 scans were deemed negative continued to receive four cycles of ABVD or even four cycles of a slightly de-escalated treatment with doxorubicin, vinblastine, and dacarbazine.

In contrast, those whose PET2 scan was positive had their treatment cycle escalated to a combination of bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone (BEACOPP) or a slightly modified version of BEACOPP.

"The main reason for upstaging was detection of extranodal disease, most commonly in bone marrow," Barrington observed. The main reason for downstaging was for enlarged nodes or an enlarged spleen when FDG-avid uptake was not avid.


Had PET-CT influenced patients’ treatment choices?

The study authors pointed out that they could not tell whether stage by PET-CT affected the treatment decisions of trial participants, but they speculated that upstaging by PET-CT probably did not affect management as trial investigators had already determined that all patients needed a full course of chemotherapy. It was also unlikely that downstaging from stage 4, which denoted a positive scan, to stage 3, which was a negative scan, would have affected treatment either.

However, as the study authors also noted, PET-CT did downstage 56 patients to stage 2 and one patient to stage 1 -- "and this could potentially influence treatment choices. The authors also pointed out that use of PET-CT is actually recommended as a good strategy by which to assess lymphoma patients' response to treatment using the 5-PS. As the team observed in the paper, the 5-PS actually predicts outcomes, especially in advanced Hodgkin lymphoma.

Study limitations

Limitations of the study include not being able to re-review ceCT scans alongside PET-CT scans and the fact that the researchers could not assess how the PET-CT scans affected patient management. "These findings support the move to a modern standard using PET-CT for staging and suggest that, in the vast majority of cases, ceCT is not required." Barrington concluded.

Josée Zijlstra, MD, VU University Medical Center, Amsterdam, the Netherlands, pointed out in an accompanying commentary that accurate staging is of "utmost importance' to help clinicians arrive at the best treatment option for patients with HL. "[To use] PET-CT as the modality to distinguish good and poor responders, and to de-escalate or to intensity chemotherapy, it is critical that this assessment is reliable and reproducible," he wrote.

Source: MedPage Today

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