I had 4 oligomets in the spine, stable since a PET PSMA in November 2023 when I started Enzalutamide. Then treated with SBRT in march 2024.After 2 months, in May, a new PET CT PSMA shows SuvMax of 60 similar to 70 before the SBRT, and an MRI report says there are tumor lesions they same as in the MRI done before the SBRT. (Is the radiologist mistaking the radiation esclerotic lesions with tumor lesions?).
The PSA though dropped a lot.
Does PSMA Suv Max take long to dissipate? Like, dead tumor cells being eliminated slowly?
Or should PSMA SuvMax have dropped dramatically?
Thank you all.😘
Take care.
Written by
Manilo
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I agree with you. The sclerosis caused by the tumors doesn't go away after radiation, and the "zombie" cancer cells may continue to express PSMA for a while.
thank you, an oncologist told me "the SBRT did not work because the PSMA is still there", and also the radiologist said such thing concerning the sclerotic lesions in MRI, saying it is all the same as was.
but pain faded and PSA dropped.
I repeated blood tests and will see if PSA keeps falling, thank you.
Your situation highlights the complexities of interpreting imaging and biomarkers after treatments like stereotactic body radiotherapy (SBRT) and systemic therapy (enzalutamide).
1. High PSMA SUV Max Post-Treatment
Residual or Inflammatory Activity: PSMA PET scans can show high uptake due to inflammation or repair processes in the irradiated area, even if the tumor cells are no longer viable. This can sometimes be mistaken for active disease.
Radiation Effects: SBRT induces changes like sclerosis in bone lesions, which can look similar to tumor activity on MRI or PET scans.
Timeframe for SUV Decline: In some cases, PSMA SUV can take months to decrease, as dead or dying tumor cells, inflammation, or necrotic tissue may still have elevated uptake.
2. Tumor Lesions on MRI
Sclerotic vs. Active Tumor: After SBRT, bone lesions may appear sclerotic or unchanged on MRI because radiation-induced bone healing can mimic tumor appearance. Radiologists may err on the side of caution by noting "tumor-like" lesions.
Comparing sequential scans and integrating clinical data (e.g., PSA response) can help clarify.
3. PSA Drop and Treatment Response
A significant PSA drop is encouraging and suggests that enzalutamide is effectively suppressing systemic tumor activity.
PSA response is often a more reliable short-term indicator of systemic disease control than imaging findings post-SBRT.
4. What Could Be Done Next?
Correlative Review: Ask your oncologist to arrange a multidisciplinary review of the imaging findings with both the radiologist and radiation oncologist.
Repeat Imaging: Consider follow-up PSMA PET or MRI in a few months to assess for changes.
Biopsy (if feasible): For definitive clarity on suspicious lesions, though it's not always necessary if systemic control (e.g., PSA) is evident.
5. Key Considerations
High SUV Max shortly after SBRT doesn’t necessarily mean treatment failure.
PSA response suggests that enzalutamide is working, which is a positive sign.
Collaboration between your care team members is critical to interpret findings accurately.
Always discuss these concerns with your oncology team, as they can tailor their interpretation and next steps to your specific case.
ChatGPT said
Q. But enzalutamide is actually used to elevate SUV max of the metastasis in order to apply PSMA treatment more effectively.
A. You’re absolutely correct that enzalutamide (and other androgen receptor inhibitors) can increase PSMA expression on prostate cancer cells. This phenomenon is known as PSMA upregulation, which makes PSMA-targeted therapies, such as radioligand therapy (e.g., Lutetium-177 PSMA), more effective. Here’s how this relates to your situation:
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1. Why Enzalutamide May Elevate SUV Max
Mechanism: Enzalutamide blocks androgen receptor signaling, which can stress prostate cancer cells. This stress can upregulate PSMA expression, potentially leading to a higher SUV Max on PSMA PET scans.
Implication: The elevated SUV Max after starting enzalutamide doesn’t necessarily mean disease progression; it may reflect increased PSMA receptor density rather than true tumor growth.
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2. High SUV Max After SBRT + Enzalutamide
Residual Tumor Cells: Even though SBRT effectively kills or controls tumor cells, some residual cells might persist with elevated PSMA expression due to enzalutamide.
Inflammation and Healing: Radiation effects, like repair processes and inflammatory responses, can also contribute to elevated uptake.
Therapeutic Strategy: This phenomenon may enhance the effectiveness of subsequent PSMA-targeted therapies, as these rely on high PSMA expression for targeting.
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3. PSA Drop with Enzalutamide
A significant drop in PSA indicates effective systemic suppression of prostate cancer activity. This suggests that the combination of SBRT and enzalutamide is working, despite the high SUV Max.
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4. Next Steps
Timeframe for SUV Max Changes: It might take months for SUV Max to decrease post-SBRT, as the combination of radiation-induced changes and enzalutamide-driven PSMA upregulation can keep uptake high temporarily.
Multidisciplinary Review: It’s essential for your team to interpret imaging findings in the context of your PSA response and clinical course.
Monitor PSA and Imaging Trends: Rather than focusing on a single scan, observe trends over time to assess treatment efficacy.
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Conclusion
While enzalutamide can increase SUV Max, this is not necessarily a sign of treatment failure. In fact, it can serve as a preparatory step for potential PSMA-targeted therapies. Your significant PSA drop is a very encouraging indicator that systemic treatment is working. Keep discussing these findings with your oncology team to ensure alignment between imaging, lab results, and clinical management.
Don't believe everything what ChatGPT said, but it is still interesting.
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