Prophylactic cranial irradiation: advantages and disadvantages

Anaplastic small cell carcinoma of the lung is a disease that responds to multiagent systemic therapy. Unfortunately, a high incidence of central nervous system (CNS) relapse has been observed by many investigators. Cranial irradiation has been successfully used in acute lymphoblastic leukemia to reduce CNS relapse and improve survival. A similar application of prophylactic cranial irradiation in patients undergoing therapy for small cell anaplastic carcinoma of the lung has been noted to decrease CNS relapse from approximately 25% to approximately 5%. However, CNS toxicity has been noted to occur with CNS prophylaxis. We can reduce the incidence of CNS toxicity by using modern treatment schedules and avoiding the use of doxorubicin with irradiation. Prophylactic cranial irradiation delivered to those patients who obtain a complete remission in response to induction chemotherapy can reduce the incidence of CNS relapse and can usually be delivered with minimal CNS toxicity. Unfortunately, long-term disease control with systemic agents is poor. Until more effective systemic agents are developed, the role of prophylactic cranial irradiation is one of palliation rather than improving survival.