Better outcomes for patients with brain metastases

Brain metastases most commonly arise from lung and breast cancers. Others common causes of brain metastases are renal cell carcinoma and malignant melanoma. The impact of brain metastases cannot be overstated, in view of the risk of losing functional independence, mental abilities as well as a patient’s sense of self.

With improvement in imaging methods, especially magnetic resonance imaging ( MRI) scanning of the brain, the chances of identifying brain metastases in asymptomatic patients has increased, at the same time resulting in improvement of results of treatment due to the detection of smaller metastases.

MRI Image demonstarting 2 brain metastases.

Identification of certain molecular subtypes of lung cancer, and the development for drugs targeting  abnormal pathways such as Her 2 neu gene in breast cancer and EGFR or Alk pathway in  non small cell lung cancer has also resulted in an improvement of outcome for patients suffering from tumours carrying these pathways.

Radiotherapy is the treatment of tumours using high energy X rays or charged particles. It is an essential component of the treatment of brain metastases. Traditionally, the treatment of brain metastases has been giving radiotherapy to the whole brain.

A sophisticated, high precision form of radiotherapy called stereotactic radiosurgery (SRS) is the administration of a very high dose of radiotherapy in a single session, the dose ranging from 15 Gy to 24 Gy versus the usual conventional daily dose of radiotherapy, 1.8 – 2 Gy. When added to whole brain radiotherapy, this method of treatment improves the survival of patients and also decreases the chances of the treated brain lesion regrowing.

Stereotactic Radiosurgery plan of a patient with 2 brain metastases.

 One of the concerns of whole brain radiotherapy is its impact on the mental abilities of the patient receiving this form of treatment. In view of this, there is a school of thought that advocates treating patients with SRS alone, omitting whole brain radiotherapy. Patients who receive SRS alone have a better chance of preserving their cognition; though with the caveat they also have a higher chance of requiring treatment for brain metastases in other parts of the brain. This treatment can be in the form of repeat SRS or also whole brain radiotherapy.

Another way of preserving cognition is administering radiation to the whole brain while avoiding high doses to the hippocampus, a structure in the brain, responsible for creating new memories. Though it is quite possible that the hippocampus is not the only structure responsible for cognition, studies have proven that patients treated with techniques that avoid dose to the hippocampus can reduce the chance of deterioration in memory due to radiotherapy.

Hippocampal avoidance whole brain radiotherapy to prevent cognitive decline.  

     

While this is still under investigation, in certain situations, hippocampal avoidance radiotherapy may be combined with a simultaneous high dose to the metastatic lesions in the brain.

Whole brain radiotherapy with hippocampal avoidance & simultaneous boost to brain metastases.

 

These sophisticated technqiues, SRS and hippocampal avoidance radiotherapy add quality to life of cancer patients suffering from brain metastases. This is due to better control of metastases as well as reduction in side effects of radiotherapy.