Lugano 2013: PET-guided Radiation Therapy Improves Survival in Patients with Advanced Diffuse Large B-cell Lymphoma
Residual masses are often detected on post-therapy computed tomography (CT) scans in patients with diffuse large B-cell lymphoma, and the potential role of consolidative radiation therapy in such cases remains undefined. An analysis of the use of PET-guided radiation therapy presented by Laurie H. Sehn, MD, and colleagues from the British Columbia Cancer Agency at the 12th International Conference on Malignant Lymphoma in Lugano, Switzerland, indicated favorable outcomes with PET-guided radiation therapy in select patients (Abstract 123).
BC Cancer Agency Strategy
A policy has been in place in British Columbia (BC) since 2005 that recommends post-therapy PET evaluation for patients with advanced-stage diffuse large B-cell lymphoma who have residual masses > 2 cm on CT, with radiation therapy being administered to PET-positive sites when feasible. Patients with a negative PET scan are observed irrespective of initial or residual bulk, and patients who are PET-positive but not suitable for radiation therapy are treated according to physician discretion.
Study Details
The BC Cancer Agency Lymphoid Cancer Database was used to identify all newly diagnosed patients with advanced-stage diffuse large B-cell lymphoma between January 2005 and February 2012 treated with curative-intent R-CHOP (rituximab [Rituxan] plus cyclophosphamide, doxorubicin, vincristine, and prednisone) who underwent a post-therapy PET scan. Patients in complete remission on CT, HIV-infected patients, and patients with primary progressive disease, primary mediastinal large B-cell lymphoma, or transformed lymphoma were not included in the analysis.
A total of 262 patients were included in the analysis. Patients had a median age of 65 years, 60% were male, 69% had stage III/IV disease, 42% had a bulky site > 10 cm, and 48% had International Prognostic Index scores of 3 to 5. Of these patients, 167 (64%) were PET-negative, 82 (31%) were PET-positive, and 13 (5%) had indeterminate PET findings. Of the PET-positive patients, 60 (73%) received radiation therapy (30-45 Gy, 56 in single and four in multiple fields); of the 21 not receiving radiation therapy, 13 were not amenable to treatment, physicians decided against treatment in 7, and 2 had negative biopsy. One PET-negative patient received radiation therapy.
Outcomes
The median follow-up for living patients was 45 months. Relapse occurred in 10 of 60 PET-positive patients receiving radiation therapy, with in-field relapse occurring in 6. Four-year rates of freedom from progression and overall survival in PET-positive patients receiving radiation therapy (81% and 85%) were similar to those in PET-negative patients (74% and 83%) and better than those in PET-positive patients not receiving radiation therapy (33% and 30%).
The investigators concluded, “Patients with advanced-stage diffuse large B-cell lymphoma with residual CT abnormalities after R-CHOP who receive consolidative radiation therapy to sites of PET positivity have an unexpectedly favorable outcome, strongly supporting the rationale for the use of PET-guided radiation therapy. Patients with PET-negative residual CT abnormalities also have a favorable outcome and should be spared unnecessary toxicity.”
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