The incidence of symptomatic brain metastases from extra-pulmonary small cell carcinoma: Is there a role for prophylactic cranial irradiation in a clinically relevant population cohort?

BACKGROUND AND PURPOSE: To examine the incidence and outcomes of patients with brain metastases from extra-pulmonary small cell carcinoma (EPSCC) and assess the indication for prophylactic cranial irradiation (PCI).

MATERIALS AND METHODS: A Provincial cancer registry was used to conduct a retrospective, population-based study of patients diagnosed with EPSCC between January 1997 and December 2011. The primary end point was the incidence of brain metastases. The secondary endpoint was overall survival. A "PCI Eligible" cohort was defined to provide an estimation of the incidence of brain metastases in clinically relevant patients.

RESULTS: In 287 patients, the primary sites were 21% gastrointestinal, 34% genito-urinary, 14% gynecologic, 5% head/neck and 25% unknown primary. Thirty-five (12.5%) patients had brain metastases: 12 (4.2%) at initial diagnosis and 23 (8%) later in the disease course. In PCI Eligible patients, the 3-year cumulative incidence of new brain metastases was 5.5% for M0 stage disease and 26.3% for M1 disease. There was no significant difference in the incidence of brain metastases between primary sites.

CONCLUSIONS: The incidence of brain metastases in patients with EPSCC is comparatively low, even in a cohort of patients that were suitable for PCI. Based on our analysis, we cannot recommend PCI for patients with EPSCC.