Uncertainties in contemporary treatment of aggressive lymphomas.

Contemporary treatment of malignant lymphomas relies on systemic chemotherapy. The role of radiation therapy is often debated. Randomized clinical trials have shown that the addition of radiation therapy, following complete response (CR) to several cycles of combination chemotherapy for early stage diffuse large B-cell and immunoblastic lymphoma, increases disease-free survival. The dose required to achieve consistent control after complete response is uncertain, but the available data suggest a dose-response for tumor control after CR. The role of radiation therapy after partial response (PR) is uncertain as many such patients are advised to undergo high dose chemotherapy followed by bone marrow reconstitution. Involved field radiation therapy after PR is able to achieve durable freedom-from-relapse. The role of radiation therapy for peripheral T-cell lymphomas and mediastinal T-cell lymphoblastic lymphomas is also uncertain. Finally, in the era of combination chemotherapy and conformal irradiation, a uniform understanding of what constitutes "involved field" treatment volume is lacking. This issue is even more complex now that intensity-modulated irradiation has become widely available. It is unlikely that these questions will be addressed in randomized clinical trials.