The study included 132 patients treated between 2021 and 2024, all of whom had at least two brain metastases and underwent microsurgical resection of one or more selected lesions. In this population, surgery is rarely curative in the conventional sense. Surgeons operate either to relieve symptoms caused by a mass pressing on critical brain structures, or to obtain tissue for histopathologic diagnosis when the primary cancer or its molecular profile remains uncertain. Because most of the tumor burden remains elsewhere in the brain, the operation is a calculated intervention whose value depends entirely on whether the patient lives long enough, and recovers well enough, to benefit from it.

The headline finding is stark: the ninety-day mortality rate was 28 percent, with 37 of the 132 patients dying within three months of surgery. That figure alone reframes the conversation around surgery for multiple metastases, a field where much of the historical literature has focused on carefully selected single-lesion patients. The median age of the cohort was 63 years, roughly 41 percent were women, and about two-thirds of patients had between two and four metastases while nearly a third had five or more. The median resected tumor volume was 15.4 cubic centimeters, quantified through volumetric assessment of magnetic resonance imaging rather than the crude diameter measurements used in many older studies.

What elevates the work beyond a simple outcome audit is its systematic search for preoperative predictors. Four factors emerged as significantly associated with increased ninety-day mortality: advanced age, a lower preoperative Karnofsky Performance Status, the absence of adjuvant treatment after surgery, and a higher score on the five-item modified frailty index. Each of these captures a different dimension of physiological reserve. Age reflects cumulative biological wear; the Karnofsky score, a scale from 0 to 100 that grades a patient’s functional independence, measures how much the disease has already eroded daily functioning; the frailty index aggregates comorbidities such as diabetes, cardiac disease and functional dependence into a compact vulnerability score; and adjuvant therapy, whether radiotherapy or systemic treatment, addresses the residual disease that surgery cannot touch.

The statistical relationships were strong. Age and lack of adjuvant treatment each reached p-values below 0.001, meaning the probability that these associations arose by chance is vanishingly small. The frailty index was associated with mortality at p = 0.008, and Karnofsky status at p = 0.048. Notably, the sheer number of metastases and the volume of the resected tumor did not predict early death. This is a counterintuitive and clinically important result: it suggests that the decision to operate should hinge less on how many lesions a patient carries, and more on who the patient is physiologically when they arrive in the operating room.

Survival was not the only endpoint. The researchers also examined where patients went after discharge, how long they stayed in the hospital, and whether they were allocated to adjuvant treatment. Here, two variables dominated. Patients with lower preoperative Karnofsky scores and higher frailty index scores were significantly more likely to be discharged to institutional care rather than to their own homes, with both associations reaching p-values below 0.001. For patients and families weighing surgery against symptom-directed care, this is a concrete and often underappreciated consideration: the operation may relieve pressure and clarify diagnosis, but in frail or functionally compromised patients it may also mark the transition from independent living to a nursing facility.

Length of postoperative hospital stay told a similar story through correlation analysis. Stay duration correlated inversely with Karnofsky status, with a Spearman rank correlation coefficient of rs = -0.29 and p = 0.001, meaning weaker patients stayed longer. It correlated positively with the frailty index at rs = 0.26 and p = 0.003. Once again, age, tumor volume and the number of lesions showed no significant relationship with recovery time. The pattern is consistent and mechanistically plausible: functional reserve and frailty govern how quickly a brain recovers from surgery, how well wounds heal, and how quickly complications such as confusion, weakness or infection can be overcome, whereas the anatomical extent of metastatic disease matters less for the perioperative trajectory.

The findings arrive at a moment when the treatment landscape for brain metastases is shifting rapidly. Stereotactic radiosurgery, which delivers precisely focused radiation to multiple lesions in a single session without opening the skull, has become the default for many patients with limited metastatic burden, supported by large prospective studies such as the JLGK0901 trial. Meanwhile, targeted therapies and immunotherapies increasingly penetrate the blood-brain barrier, allowing systemic treatment to control intracranial disease in ways that were unimaginable two decades ago. Surgery has retained a defined but narrower role: large symptomatic lesions threatening herniation or severe neurological deficit, and diagnostic uncertainty that blocks access to molecularly matched treatment. Within that narrowed role, knowing who benefits and who is harmed becomes paramount, which is precisely the gap this study addresses.

The authors are careful about the implications. They do not argue that frail, elderly or functionally impaired patients should be denied surgery outright; rather, they state that resection for symptom relief or tissue diagnosis in patients with multiple metastases may be performed with these precautions in mind. In practice, that means the four risk factors should be part of the preoperative conversation. A 78-year-old with a Karnofsky score of 50, a frailty index of three out of five, and no realistic prospect of adjuvant therapy carries a fundamentally different risk profile from a 58-year-old who is functionally independent, robust, and eligible for radiosurgery or targeted drugs afterward. Quantifying that difference before consent is obtained is the essence of risk stratification, and it converts a vague warning about being a poor candidate into a structured, evidence-based assessment.

There are limits worth keeping in view. The study is retrospective and bicentric, drawing on two academic centers in Germany and Austria, so selection biases in who was offered surgery cannot be fully excluded, and the ninety-day window captures early perioperative harm but not longer-term survival or quality of life. The frailty index, while practical, is a coarse instrument compared with comprehensive geriatric assessment. Still, the message for oncology teams is actionable and timely: in the era of powerful non-surgical options for multiple brain metastases, the bar for operative intervention is set not by the tumor map alone, but by age, frailty, functional status and the availability of subsequent therapy. Patients with multiple brain metastases and their families should expect those four factors to be weighed explicitly, and documented, before anyone is wheeled into the operating theater.

Subject of Research: Risk stratification for surgical outcomes in patients with multiple brain metastases

Article Title: Risk stratification for unfavorable outcome after resection of selected brain metastases in patients with multiple brain metastases

Article References: Eibl, T., Mercea, P. A., Liebert, A., Ritter, L., Rossmann, J., Rezai, A., Moskwa, M., Hurtig, H., Stadler, C., Wunderlich, S., Feldheim, J., Liman, J., Schwartz, C., Griessenauer, C. J., & Schebesch, K.-M. (2026). Risk stratification for unfavorable outcome after resection of selected brain metastases in patients with multiple brain metastases. Journal of Neuro-Oncology, 180(1), Article 9. https://doi.org/10.1007/s11060-026-05819-6

Image Credits: AI Generated

DOI: 10.1007/s11060-026-05819-6

Keywords: brain metastases, neurosurgery, risk stratification, Karnofsky Performance Status, frailty index, 90-day mortality, tumor resection, adjuvant therapy, stereotactic radiosurgery, Journal of Neuro-Oncology, prognostic factors, cancer surgery