Brain metastases (BM) are an ominous complication of cancer that develop in up to 30% of patients with solid tumors. Lately we have seen an increase in the incidence of BM, this might be due to an increased overall survival among patients with some types of solid tumors, as well as the increased use of surveillance imaging and increased awareness by oncologists.
Lung cancer (LC) and breast cancer (BC) are the tumors that most frequently develop brain metastases. (1). Up to 50% of patients with lung cancer and 15% of patients with breast cancer will develop BM at some point of their disease; due to the high incidence of the aforementioned malignancies, brain metastasis associated with either lung or breast cancer account for half of the cases of brain metastases. (2) Furthermore, the Surveillance, Epidemiology and End Results Program reported that patients with lung cancer present the highest rates of brain metastases at diagnosis. (3)
Whole brain radiation therapy (WBRT) has been a corner-stone tool for the management of BM; this therapy is primarily used for patients with BMs that are not suitable for surgical resection, and therefore this therapy is mainly used it the palliative setting (4). Although WBRT is associated with adverse effects, the effectiveness of this therapy has been validated by multiple clinical-trials, and when used in the appropriate setting the benefits outweigh the potential unwanted effects.(5) Concomitant treatment of solid tumors with WBRT along with systemic therapy has been studied elsewhere, albeit, to our current knowledge, there is no convincing evidence that simultaneous treatment with systemic therapy and WBRT significantly improves outcomes. Furthermore, it has been reported that unwanted effects increase while using both therapies at the same time(3). Therefore, WBRT alone is currently used in many centers as the palliative treatment of choice for patients with BM (4).
Most patients that develop BM generally present with more than one BM, and the location of these metastases vary in every patient. According to their location, brain metastases are widely sub-diveded as either: supratentorial metastases, which are located above the tentorium cerebelli (affecting the cerebrum); and infratentorial metastases, which are located between tentorium cerebelli and foramen magnum (affecting cerebellum and brainstem), the osseous boundaries of the infratentorial region include the clivus anteriorly, the temporal bones anterolaterally, and the occipital bone posteriorly-inferiorly, because of these osseous boundaries, the infratentorial region is considered a protective sanctuary that confers a resistance to radiation therapy is some patients, preventing them from getting the appropriate dose of radiation.
In adults most BM (80%) are located in the supratentorial compartment, however, lung and breast cancers have shown to have an increased tendency to metastasize to the infratentorial compartment (6). Owing to the cumbersome properties of this compartment , it has been proposed that patients with infratentorial metastases have worse outcome due to the fragile structures localized in this region, mainly brainstem and cerebellum, and the decreased effectiveness of radiation in this compartment(6).
The aim of the present study was to determine if WBRT is equally effective for palliating supratentorial and infratentorial BMs in patients with lung or breast cancer.