February 26, 2015
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PET scans improve response assessment in peripheral T-cell lymphoma

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Use of 18fluoro-deoxyglucose PET scans more accurately predicted response durability than conventional radiology in patients with relapsed or refractory peripheral T-cell lymphoma who achieved stable disease or a partial response with Istodax, according to phase 2 study results.

“For patients with peripheral T-cell lymphoma — a rare and aggressive type of non-Hodgkin’s lymphoma — the utility of 18fluoro-deoxyglucose [FDG]-PET for assessing response to treatment and prognosis is unclear,” Barbara Pro, MD, director of the Cutaneous Lymphoma Center at Jefferson University Hospitals, told HemOnc Today. “This study evaluated the role of FDG-PET, in addition to conventional imaging studies, in patients with relapsed or refractory peripheral T-cell lymphoma treated with romidepsin.”

Barbara Pro, MD

Barbara Pro

Pro and colleagues evaluated data from 110 patients who received 14 mg/m2 romidepsin (Istodax, Celgene) on days 1, 8 and 15 of 28-day cycles. A majority of patients (95%) had PET-positive disease at baseline.

According to International Workshop Criteria — or conventional CT/MRI radiology — 26% of patients achieved an objective response to therapy. Sixteen patients (15%) achieved a complete response.

When researchers evaluated response with conventional radiology plus FDG-PET, the objective response rate increased to 30% (n = 33) and the complete response rate increased to 20% (n = 22).

After a median follow-up of 22.6 months, the median duration of response among the 33 responders was 28 months (range, ˂1-48+ months). The duration of response was well differentiated by complete vs. partial conventional radiology response criteria (P = .0001) and negative vs. positive PET status (P ˂ .0001).

Patients who achieved a complete response by International Workshop Criteria demonstrated a median PFS of 25.9 months, which was significantly longer than that achieved by patients with a partial response or stable disease (P = .0007).

The median PFS was not yet reached in 13 of the patients who achieved a complete response and who were also PET negative, whereas the median PFS was 9.2 months in the other three patients who achieved a complete response but were PET positive.

Among patients who achieved a partial response or stable disease, those who were PET negative had a longer median PFS than those with PET-positive disease, although the difference did not reach statistical significance (18.2 months vs. 7.1 months; P = .09).

“For patients who achieve stable disease or partial response, the study showed that interim FDG-PET status better predicted durability of response than conventional criteria,” Pro said. “Patients who achieved PET-negative status had a prolonged PFS compared with patients who remained PET-positive. Routine use of PET maybe very useful for treatment decisions in patients with T-cell lymphoma.” – by Alexandra Todak

Barbara Pro, MD, can be reached at Jefferson University Hospital, 925 Chestnut St., Suite 420A, Philadelphia, PA 19107.

Disclosure: Pro reports honoraria from Celgene. See the full study for a list of all other researchers’ relevant financial disclosures.