Postsurgical radiotherapy (RT) has been early proven to prevent local tumor recurrence, initially performed with whole brain radiotherapy. Subsequent to disadvantageous cognitive sequelae for the patient and the broad distribution of modern linear accelerators, focal irradiation of the tumor has omitted WBRT in most cases. In many studies, the effectiveness of local radiotherapy of the resection cavity, either as single-fraction stereotactic radiosurgery (SRS) or hypofractionated stereotactic radiotherapy (hFSRT), has been demonstrated to be effective and safe. However, whereas prospective high-level incidence is still lacking on which dose and fractionation scheme is the best choice for the patient, further ablative techniques have come into play. Neoadjuvant SRS (N-SRS) prior to resection combines straightforward target delineation with an accelerated post-surgical phase, allowing an earlier start of systemic treatment or rehabilitation as indicated. In addition, low-energy intraoperative radiotherapy (IORT) on the surgical bed has been introduced as another alternative to external beam radiotherapy, offering sterilization of the cavity surface with steep dose gradients towards the healthy brain 1)
see Stereotactic radiosurgery for brain metastases.
It is used when there are a limited number (usually 1 to 4) of smaller brain metastases. SRS/SRT allows for a higher dose of radiation to be delivered to the tumor while sparing nearby healthy brain tissue. This treatment is typically completed in a single session or a few sessions, and patients can often resume their normal activities shortly afterward. The choice between whole brain radiotherapy and stereotactic radiosurgery will depend on several factors, including the number and size of brain metastases, the location of the tumors, the patient's overall health, and any previous treatments received.
It's essential to consider that each case is unique, and treatment decisions should be made in collaboration with a multidisciplinary team of healthcare professionals, including neurosurgeons, radiation oncologists, and medical oncologists. They will take into account the specific characteristics of cancer and the individual's health to determine the most appropriate treatment approach.
In some cases, a combination of radiotherapy and other treatments, such as surgery or systemic therapies (chemotherapy, targeted therapies, immunotherapy), may be recommended to optimize the chances of controlling the brain metastases and improving the patient's quality of life.
Although adjuvant stereotactic radiotherapy after resection of brain metastases is considered standard of care treatment, there is a need for further prospective research to determine the optimal fractionation scheme. The SATURNUS study is the only randomized phase III study comparing different regimes of postoperative stereotactic radiotherapy to the resection cavity adequately powered to detect the superiority of hypofractionated stereotactic radiotherapy (HFSRT) regarding local control 2).
Hippocampal sparing whole brain radiotherapy.
The decline in cognitive function was more frequent with WBRT than with SRS and there was no difference in overall survival between the treatment groups. After resection of a brain metastases, Stereotactic radiosurgery should be considered one of the standards of care as a less toxic alternative to WBRT for this patient population 3).
With the development of therapies that improve extracranial disease control and increase long-term survival of patients with metastatic cancer, effective treatment of brain metastases while minimizing toxicities is becoming increasingly important. An expanding arsenal that includes surgical resection, whole brain radiation therapy, radiosurgery, and targeted systemic therapy provides multiple treatment options. However, significant controversies still exist surrounding appropriate use of each modality in various clinical scenarios and patient populations in the context of cancer care strategies that control systemic disease for increasingly longer periods of time. While whole brain radiotherapy alone is still a reasonable and standard option for patients with multiple metastases, several randomized trials have now revealed that survival is maintained in patients treated with radiosurgery or surgery alone, without upfront whole brain radiotherapy, for up to four brain metastases. Indeed, recent data even suggest that patients with up to 10 metastases can be treated with radiosurgery alone without a survival detriment. In an era of dramatic advances in targeted and immune therapies that control systemic disease and improve survival but may not penetrate the brain, more consideration should be given to brain metastases-directed treatments that minimize long-term neurocognitive deficits, while keeping in mind that salvage brain therapies will likely be more frequently required. Less toxic therapies now also allow for concurrent delivery of systemic therapy with radiosurgery to brain metastases, such that treatment of both extracranial and intracranial disease can be expedited, and potential synergies between radiotherapy and agents with central nervous system penetration can be harnessed 4).