Post-Surgery Considerations for Residual Meningioma: Is Radiation Necessary?

Residual tumor after brain surgery?

I have been diagnosed with a meningioma, approximately 3 cm in size, located on the right side of the brain, specifically a sphenoid wing meningioma.
The tumor envelops the internal carotid artery and compresses the optic nerve, extending to the optic chiasm.
A month ago, I underwent craniotomy, but the tumor could not be completely removed, leaving a residual mass of about 2 cm.
The remaining portion tightly surrounds the internal carotid artery and the optic chiasm.
The excised tumor was analyzed and confirmed to be a benign meningioma, classified as WHO Grade 1.
The doctor mentioned that I will need to undergo low-dose radiation therapy, specifically stereotactic radiosurgery, in 30 sessions.
After the surgery, my visual field and vision have improved significantly, and I can see clearly, with a good recovery overall.

Is it necessary to undergo radiation therapy for this slow-growing Grade 1 benign meningioma? If radiation therapy is required, considering that the residual tumor is located on the optic chiasm, will it lead to a decrease in my visual field or vision, or even blindness? After completing radiation therapy, is there a possibility that the benign tumor could become malignant in the future?

Xiao Yu, 40~49 year old female. Ask Date: 2016/12/11

Dr. Chen Sirong reply Oncology

Xiao Yu / 42 years old / Male
1.
Is it necessary to undergo radiation therapy for a slowly growing grade I benign meningioma?
A: Yes, it can delay the time to recurrence and may even prevent it from growing further, maintaining the current status.
2.
If radiation therapy is necessary, since the residual tumor is located on the optic chiasm, will it lead to decreased visual fields or vision loss after treatment?
A: The physician will keep the radiation dose within a safe range.
However, the term "safe dose" means that there is less than a 5% risk of vision loss within five years.
No physician can guarantee a zero probability of vision loss, and future vision loss could be due to tumor recurrence or radiation treatment, which may be difficult to determine.
The low risk of vision loss should not deter you from receiving radiation therapy, similar to how patients are still given contrast agents or medications despite a low risk of anaphylactic shock.
3.
After radiation therapy, is there a possibility that the benign tumor could become malignant in the future?
A: Recurrence is possible, and regardless of whether radiation therapy is received, there is a chance that the tumor could become more malignant.
However, undergoing radiation therapy reduces the chance of recurrence.
If recurrence occurs, the malignancy grade may potentially increase.
Your consideration should be to take all possible measures to delay recurrence, which also means delaying vision loss.
Doing nothing essentially means waiting for recurrence, at which point a neurosurgeon may not be able to completely remove a tumor that is adhered to the nerves.
Therefore, I recommend that you proceed with radiation therapy at Taoyuan Hospital.
- Dr.
Chen Si-Rong

Reply Date: 2016/12/11

More Info

When considering post-surgery treatment options for residual meningioma, particularly in your case of a sphenoid wing meningioma, there are several important factors to weigh. Given that your tumor was classified as a WHO Grade 1 benign meningioma and that a portion remains after surgery, the decision to pursue radiation therapy is often based on the potential benefits versus the risks involved.

Is Radiation Necessary?
In cases where a meningioma cannot be completely resected, radiation therapy is frequently recommended to reduce the risk of tumor recurrence. Even though your tumor is classified as benign and has a slow growth rate, the presence of residual tumor tissue—especially in a location that is in close proximity to critical structures like the internal carotid artery and the optic chiasm—can pose a risk for future complications. Radiation therapy, such as stereotactic radiosurgery (often referred to as "Gamma Knife" or "X-knife"), is designed to target the remaining tumor cells while minimizing exposure to surrounding healthy tissue.
The primary goal of radiation in this context is to delay or prevent tumor regrowth. Studies have shown that radiation can significantly extend the time before recurrence, and in some cases, it may even stabilize the tumor, preventing it from growing further. Therefore, in your situation, undergoing radiation therapy could be a prudent choice to maintain your current health status and visual function.

Risks of Radiation Therapy
You raised a valid concern regarding the potential impact of radiation on your vision, especially since the residual tumor is located near the optic chiasm. While radiation therapy is generally safe, there is a small risk of complications, including vision changes. According to medical literature, less than 5% of patients may experience significant vision loss within five years following radiation treatment, particularly when the treatment area is near critical structures like the optic nerves. However, it is important to note that the risk of vision loss can be mitigated by careful planning and dose management by your radiation oncologist.

Your medical team will aim to deliver the radiation dose within a "safe" range to minimize the risk of adverse effects. They will monitor your vision closely throughout the treatment process to identify any changes early on.

Potential for Malignancy
Regarding your concern about the possibility of the benign meningioma transforming into a malignant tumor after radiation therapy, it is essential to understand that while recurrence is possible, the likelihood of a benign meningioma becoming malignant is relatively low. The risk of malignant transformation is more associated with higher-grade tumors rather than Grade 1 meningiomas. However, if a recurrence does occur, there is a chance that it could present with a higher grade than the original tumor. Radiation therapy can help reduce the likelihood of recurrence, thus indirectly lowering the risk of any potential malignant transformation.

Conclusion
In summary, while the decision to proceed with radiation therapy after incomplete resection of a benign meningioma involves weighing the benefits against the risks, the consensus in the medical community supports its use in such scenarios. The primary aim is to prevent recurrence and maintain your quality of life, particularly your vision. It is crucial to have an open dialogue with your healthcare team, including your neurosurgeon and radiation oncologist, to discuss your specific case, treatment plan, and any concerns you may have. They can provide tailored advice based on your unique circumstances and help ensure that you receive the best possible care moving forward.

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