Glioblastoma is most common in older adults. Peak incidence occurs in the 75-84 age group, and most patients at this age have at least one other health condition. When a newly diagnosed parent or spouse faces treatment discussions, it can feel like too much to handle - especially when their heart doctor, kidney specialist, and cancer doctor each talk about different risks to the body.
Comorbidities (other health problems that exist alongside cancer) directly affect what treatment can safely be given and how well a patient will tolerate it. In older people with glioblastoma, the most common comorbidities are high blood pressure, diabetes, and heart disease. A study of elderly glioblastoma patients found high blood pressure in about 29.4% of cases, diabetes in 11.8%, and heart disease in 7.4%. Chronic kidney disease is also common, especially in patients who have had diabetes or high blood pressure for many years.
This article explains how each of these conditions works with standard glioblastoma treatments and what your team should consider. For more on how age affects overall treatment strategy, see how age shapes glioblastoma treatment in older versus younger adults.
Why Do Comorbidities Change a Glioblastoma Treatment Plan?
Standard glioblastoma treatment involves surgery to remove as much tumor as possible, six weeks of daily radiation with daily chemotherapy (temozolomide), then six months of monthly chemotherapy cycles. This demands a lot from the body. In older patients who also have heart disease, diabetes, or kidney problems, the cancer team must decide whether full-intensity treatment is safe, or whether a modified plan will work better while protecting quality of life. There is no one right answer for everyone.
Research shows that older patients who receive active treatment do better than those who receive no treatment. The real question is how to change the plan to keep the survival benefit while staying safe.
How Doctors Measure Fitness Before Making Recommendations
Most neuro-oncology teams no longer use age alone to decide treatment. Formal fitness assessment tools give a fuller picture of what the patient can tolerate.
The two most widely used tools are the Karnofsky Performance Status (KPS) scale, which scores daily function and independence on a 0-100 scale, and the Comprehensive Geriatric Assessment (CGA), a broader review that looks at thinking ability, nutrition, fall risk, social support, medications, and comorbidities alongside physical function. Research on CGA use in older glioblastoma patients shows it helps sort patients into three groups: fit elderly (can tolerate standard or near-standard treatment), vulnerable (need modified treatment intensity), and frail (need gentler approaches). Where your relative falls in this classification drives most decisions about how intense the treatment is, how long it lasts, and which drugs to use.
If your relative's team has not specifically talked about a fitness classification, ask them directly. The answer will explain why certain treatments are being proposed and others are not.
Heart Disease and Glioblastoma Treatment: What Changes
Heart disease takes many forms. Atrial fibrillation, coronary artery disease, heart failure, and high blood pressure each create different challenges during glioblastoma treatment.
Surgery: Brain surgery under general anesthesia carries higher risk in patients with active heart disease. The neurosurgery team will typically ask for a heart doctor's approval before scheduling. Sometimes, brief pre-surgery work to adjust heart medications or blood pressure is needed first. For patients with severe heart problems, the team may recommend a less invasive biopsy instead of maximal tumor removal - still enough to confirm the diagnosis and get tissue for molecular testing, but with shorter procedure time and lower risk.
Bevacizumab: This drug (an anti-VEGF agent sold as Avastin) is sometimes used at recurrence to reduce brain swelling from the tumor and slow progression. It raises blood pressure in some patients. A review of bevacizumab side effects in glioblastoma found that pre-existing heart disease significantly increases the risk of serious high blood pressure complications during treatment. For patients with already-weakened heart function, the cancer doctor will weigh this risk carefully before recommending it.
Anticoagulation: Patients taking blood thinners for atrial fibrillation or prior clots face added complexity around surgery and procedures. The neurosurgery and cancer teams need to coordinate timing and planning before any procedure.
Radiation scheduling: Brain radiation itself does not strain the heart. However, patients with significant heart disease may have less energy and stamina. A 30-session daily radiation schedule across six weeks can be physically tiring. Short-course radiation can cut that burden significantly for patients whose daily function is already limited.
How Diabetes Affects Glioblastoma Treatment in Older Patients
Diabetes is the second most common comorbidity in older glioblastoma patients, and its impact extends far beyond blood sugar management. A study of comorbidity burden in older high-grade glioma patients getting radiotherapy found that diabetes without complications independently predicted worse overall survival and worse progression-free survival. The reasons are unclear, but weakened immune response and reduced cellular repair are thought to play a role.
The biggest clinical challenge for diabetic patients is dexamethasone. This steroid is used in nearly all glioblastoma patients to reduce brain swelling around the tumor. It works well, but it raises blood sugar - sometimes a lot. A review of research found that dexamethasone use was tied to lower overall survival in glioblastoma patients, partly from its effects on metabolism and immunity during long-term use. In patients with diabetes, this can make blood sugar control much harder.
This means the cancer doctor and the doctor managing your relative's diabetes need to talk before treatment starts. The steroid dose should be kept as low as possible to control symptoms and cut back as quickly as safety allows. For details on how dexamethasone is used throughout glioblastoma treatment, see this guide on dexamethasone side effects and safe tapering.
Blood sugar checks are usually more frequent for diabetic patients during radiation and chemotherapy. If your relative takes insulin, the team should adjust doses when steroid doses change. Nutrition planning also needs more care in this group - steroids change appetite and metabolism, adding to the complexity of diet management. Patients wanting structured vitamin and mineral support during long treatment, especially to address deficiencies that develop with long-term steroid use, can discuss vitamin and mineral options at Ayurnomics with their dietitian before starting.
Kidney Problems and Glioblastoma: What the Team Monitors
Chronic kidney disease often occurs with diabetes and high blood pressure in older adults, so it appears alongside glioblastoma in this age group more often than families expect. It affects treatment in several specific ways.
Temozolomide: A study of temozolomide safety in patients with reduced kidney function found that blood-count side effects were similar to those in patients with normal kidney function, meaning kidney disease alone does not prevent receiving temozolomide. The team will still check blood counts and kidney function regularly throughout treatment.
Contrast brain MRI scans: Glioblastoma patients get frequent brain MRIs with gadolinium contrast to track treatment response. In patients with significantly reduced kidney function, gadolinium carries a small risk of a rare complication called nephrogenic systemic fibrosis. The imaging team will check kidney function before each contrast scan. For patients with severe kidney disease, alternative imaging protocols or safer gadolinium forms may be used.
Anti-seizure medications: Seizures are common in glioblastoma, and most patients take anti-seizure drugs. Several of these drugs clear through the kidneys, and doses must be adjusted in kidney disease to prevent under-dosing - which leaves the patient at seizure risk - or toxic buildup. For more on seizure management during glioblastoma treatment, see this overview of seizures in glioblastoma.
Short-Course Radiation: The Most Common Treatment Adaptation
The biggest practical change most older glioblastoma patients with comorbidities will face is a modified radiation schedule. Standard glioblastoma radiation delivers 60 Gy (Gray, the unit of radiation dose) over 30 daily sessions across six weeks. For many older patients - especially those with multiple comorbidities that limit stamina or daily travel capacity - finishing this schedule is genuinely difficult.
Two shorter, well-tested alternatives exist:
- 40 Gy in 15 daily sessions (three weeks)
- 25 Gy in 5 daily sessions (one week)
A trial published in the New England Journal of Medicine found that adding temozolomide to short-course radiotherapy gave significantly better survival in older glioblastoma patients compared to short-course radiation alone, with the biggest benefit in patients whose tumor had MGMT promoter methylation. MGMT methylation is a molecular marker tested from the tumor biopsy that shows how well temozolomide will work. Every older patient's diagnostic workup should include this test, because it directly affects whether adding chemotherapy alongside a shortened radiation course makes sense.
Short-course radiation is not a compromise for patients who cannot manage the standard schedule. It is a separate, evidence-backed approach with its own clinical trial data for older patients. For details on hypofractionated radiation options, see this guide to short-course radiation for older glioblastoma patients.
When Multiple Conditions Make the Picture Complex
When comorbidities add up - poorly controlled type 2 diabetes plus stage 3 kidney disease and mild heart failure, for example - the treatment decision becomes harder for everyone, including the oncologists. That patient has a very different risk profile from a healthy 70-year-old with the same tumor. The plan for one is not the right plan for the other.
In these situations, a formal tumor board or multidisciplinary team meeting - where neurosurgery, neuro-oncology, radiation oncology, cardiology, and nephrology review the case together - gives the best basis for a treatment decision. If your relative's hospital does not offer this full multidisciplinary review, ask who else has reviewed the case. A remote second opinion from a specialist center provides the same expert input without requiring travel.
If you feel the proposed plan has not fully accounted for the complete medical picture, consider asking the Art of Healing Cancer team about your case - they work with families navigating this kind of multi-system complexity and can help clarify which options are genuinely available given your relative's medical conditions.
When to Talk to Your Doctor
Before treatment starts, ask the cancer team to address these points directly:
- Has a formal fitness assessment - KPS score or CGA - been completed? What category does the patient fall into?
- Has MGMT promoter methylation been tested from the biopsy? The result directly affects whether adding temozolomide is likely to help.
- If there is a heart condition, has a heart doctor reviewed and approved the surgical and treatment plan?
- Is there a coordinated plan for managing blood sugar during dexamethasone use, developed with the doctor managing the diabetes?
- Has kidney function been checked in relation to gadolinium contrast timing and anti-seizure drug dosing?
- Is the proposed radiation schedule the full 30-session course or a short-course alternative, and what is the clinical reason for that choice?
These are not confrontational questions. A complete multidisciplinary assessment should already be answering them. If you do not have clear responses, those are gaps worth filling before treatment begins. You can also upload your relative's full records for a remote expert review through the Glioblastoma Center team at glioblastoma.center/patient-journey.
This article is for general information and is not a substitute for medical advice. Always consult your oncologist or care team about your specific situation.