Interim PET Scan may Define Prognosis and Provide Treatment Guidance for Patients with Advanced Hodgkin Lymphoma

SUMMARY: The American Cancer Society estimates that in the United States for 2016, about 8500 new cases of Hodgkin lymphoma will be diagnosed and over 1100 patients will die of the disease. Hodgkin lymphoma is classified into two main groups – Classical Hodgkin lymphomas and Nodular Lymphocyte Predominant type, by the World Health Organization. The Classical Hodgkin lymphomas include Nodular sclerosing, Mixed cellularity, Lymphocyte rich, Lymphocyte depleted, subtypes and accounts for approximately 10% of all malignant lymphomas. Nodular sclerosis Hodgkin lymphoma histology, accounts for approximately 80% of Hodgkin lymphoma cases in older children and adolescents in the United States. Classical Hodgkin Lymphoma is a malignancy of primarily B lymphocytes and is characterized by the presence of large mononucleated Hodgkin and giant multinucleated Reed-Sternberg (RS) cells collectively known as Hodgkin and Reed-Sternberg cells (HRS).

Advanced-stage (stage III to stage IV) Classical Hodgkin lymphoma has a cure rate of approximately 70-80% when treated in the first-line setting with a combination of Doxorubicin, Bleomycin, Vinblastine, and Dacarbazine (ABVD regimen). This regimen which was developed more than 40 years ago is less expensive, easy to administer, is generally well tolerated and is often used in first line setting. Nonetheless, this regimen which contains Bleomycin can cause pulmonary toxicity, the incidence of which is higher in older patients and in those who receive consolidation radiotherapy to the thorax. The second most often used regimen in the first-line setting, e-BEACOPP (escalated doses of Bleomycin, Etoposide, Doxorubicin, Cyclophosphamide, Vincristine, Procarbazine, and Prednisone) has been associated with a higher Progression Free Survival as well as higher 5-year Overall Survival (approximately 90%). This regimen however is associated with short and long term toxicities such as prolonged fatigue, permanent fertility, Myelodysplasia and secondary malignancies.

A retrospective study by Gallamini and co-workers in 2007 had shown that a PET scan after two cycles of ABVD chemotherapy was an independent prognostic factor, with a 2-year Progression Free Survival rate of 95%, for those patients with negative interim PET scan, compared to only 12.8% for those with persistently positive PET scan. Based on these observations, the authors in this prospective trial evaluated the benefit of a “response-adapted” approach, by performing a PET scan following 2 cycles of ABVD treatment and modifying therapy based on the interim PET scan findings.

In this randomized controlled trial, 1203 eligible patients with newly diagnosed advanced Classical Hodgkin lymphoma were registered. The median age was 33 years. Following 2 cycles of chemotherapy with ABVD regimen, 1119 patients had an interim PET-CT scan and patients with negative PET findings (83.7%) were randomly assigned in a 1:1 ratio to continue ABVD regimen (ABVD group) or receive ABVD omitting Bleomycin (AVD group), for cycles 3 through 6. Radiotherapy was not recommended for patients with negative findings on interim PET scans. Patients with positive interim PET scan findings following two cycles of ABVD (16%), received 4-6 cycles of BEACOPP regimen. The primary outcome was the difference in the 3-year Progression Free Survival rate between randomized groups.

With a median follow up of 41 months, the 3-year Progression Free Survival was 85.7% with ABVD and 84.4% with AVD and 3 year Overall Survival was 97.2% and 97.6% in these two respective groups. Pulmonary toxicities were more severe in the ABVD group than in the AVD group and deleting Bleomycin following 2 cycles of ABVD, in patients with negative interim PET scan, did not compromise outcomes. Patients who received BEACOPP regimen based on a positive interim PET scan after the first 2 cycles of ABVD (N=172), had a 3-year Progression Free Survival of 67.5% and Overall Survival rate of 87.8%.

The authors concluded that following 2 cycles of ABVD regimen, omitting Bleomycin from the ABVD regimen, based on a negative interim PET scan (response-adapted therapy), resulted in lower incidence of pulmonary toxicities, compared with continued treatment with ABVD, without compromising efficacy. Adapted Treatment Guided by Interim PET-CT Scan in Advanced Hodgkin’s Lymphoma. Johnson P, Federico M, Kirkwood A, et al. N Engl J Med 2016; 374:2419-2429