MOPP combination chemotherapy for Hodgkin's disease

In the early 1960s, advanced Hodgkin's disease was a death sentence. Radiation therapy could cure localized disease, but patients presenting with stage III or IV involvement had no treatment that reliably produced lasting remission. Single-agent chemotherapy with nitrogen mustard or vinblastine generated responses, sometimes impressive ones, but the tumor almost always returned. The oncology community had not yet established whether curing a disseminated human malignancy with drugs alone was biologically possible.

What changed this was a new way of thinking about drug resistance. If a cancer could develop resistance to one drug, exposing a residual clone to a second agent with a different mechanism might kill it before it could repopulate. Vincent DeVita and colleagues at the National Cancer Institute reasoned that combining agents with non-overlapping toxicity profiles would allow each drug to be given near its full therapeutic dose, maximizing cell kill while avoiding cumulative organ-specific injury. They assembled four drugs, mechlorethamine, vincristine (Oncovin), procarbazine, and prednisone, into the MOPP regimen and began treating patients with advanced Hodgkin's disease in 1964.

The 1970 report in Annals of Internal Medicine summarized the NCI series: 81 percent of patients with advanced disease achieved complete remission, and approximately half remained disease-free at ten years. Those figures represented an entirely different order of magnitude from anything prior single-agent therapy had achieved. Patients who had been expected to die within one to two years were alive and well a decade later. The results received wide attention but also some skepticism, in part because the NCI series was not a randomized controlled trial, and the patient selection criteria were scrutinized carefully.

MOPP also had serious long-term toxicity. Male patients had high rates of permanent azoospermia, and both sexes faced an elevated risk of treatment-related myelodysplastic syndrome and acute leukemia in the years following therapy, estimated at several percent over ten years. These complications, along with the emergence of ABVD (doxorubicin, bleomycin, vinblastine, dacarbazine) as an equally effective regimen with a more favorable toxicity profile, led to ABVD largely replacing MOPP as first-line therapy for advanced Hodgkin's disease by the 1990s.

The conceptual contribution of MOPP extended beyond Hodgkin's disease. The demonstration that cycling multiple cytotoxic agents at full therapeutic doses could cure a disseminated human malignancy became the template for curative regimens in acute leukemia, testicular cancer, and other hematologic malignancies. Emil Frei III and Emil Freireich had earlier demonstrated combination chemotherapy in acute lymphoblastic leukemia at the NCI. MOPP confirmed the same principle in a solid lymphoma, and rational combination design became a standard approach across cancer treatment.