PET and Prognosis in Hodgkin Lymphoma: Retrospective Analysis

Summary and Comment |
September 18, 2007

PET and Prognosis in Hodgkin Lymphoma: Retrospective Analysis

  1. Michael E. Williams, MD

Posttreatment PET positivity predicts progression in patients with Hodgkin lymphoma.

  1. Michael E. Williams, MD

Current therapeutic approaches for Hodgkin lymphoma (HL) provide durable remissions and cure most patients. However, identifying the subset of patients at greatest risk for relapse or progression would permit early intervention with second-line therapies, including stem-cell transplantation.

Investigators at Stanford University retrospectively analyzed data from 81 HL patients who had been treated with the Stanford V regimen, which includes multiagent chemotherapy and involved-field radiation therapy (RT; 30 Gy to the pretreatment involved field and 36 Gy for nodal sites with original bulk >5 cm or for macroscopic splenic disease). Patients with nonbulky stage I or II disease and favorable risk received 8-week courses of chemotherapy, whereas those with bulky stage II disease or stage III or IV disease received chemotherapy for 12 weeks. All patients had positive pretreatment [18F]fluoro-2-deoxy-d-glucose positron emission tomography (PET) scans and underwent repeat PET imaging after completion of chemotherapy but prior to administration of RT. All patients received protocol-defined RT regardless of PET findings (6 patients with favorable low-stage disease received only 20 Gy after a protocol modification).

After a median follow-up of 4 years, 4 of 6 patients with postchemotherapy PET positivity (67%) had relapsed, versus only 3 of 75 (4%) of those with negative scans (P<0.0004). Overall survival was 100%, because salvage therapies were employed. Time to relapse was similar for the two groups: 14 months for PET-positive patients and 16 months for PET-negative patients. Interestingly, all posttreatment PET-positive sites were in the mediastinum, and all relapses occurred in these sites or at the margins, despite RT; two patients also had concomitant distant relapse. Thus, the RT doses and fields employed in this regimen did not reliably control residual disease identified by PET. No association was noted between residual PET-positive sites and pretreatment bulky mediastinal disease or higher International Prognostic Scores (IPS; based on 7 clinical and laboratory parameters [N Engl J Med 1998; 339:1506]).

Comment

To date, risk-adapted treatment of HL has focused on disease stage, presence of favorable versus unfavorable clinical features (variously defined by HL study groups), and IPS. These findings confirm PET scanning as a predictor of treatment outcome for patients with HL. Other investigators have prospectively demonstrated a prognostic role for PET scanning that was performed after only 2 to 4 cycles of combination chemotherapy (Journal Watch Oncology and Hematology Sep 18 2007). RT in the doses used in the Stanford V regimen was not reliable salvage therapy for these patients, suggesting that future studies should focus on alternative radiation and chemotherapy strategies, including dose-intensive approaches with stem-cell transplantation. Furthermore, although current criteria do not result in many false-positive PET scans, core or excisional biopsies of residual PET-positive sites should be obtained before recommending salvage therapy.

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