PET Scan Reports: Interpreting SUV Values and Their Implications

Interpretation of Positron Emission Tomography (PET) Report

Hello Doctor, the report from the PET scan I had last time has come out, and I have some questions.
The report states:
"The whole body study revealed increased uptake of radioactivity involving the right nasopharynx (SUV 3.1, score 1-2) and a right upper neck node (SUV 2.7, score 1-2).
There were no other abnormal measurable lesions in other parts of the body.
In addition, a subpleural nodule was found by coregistered CT in the right middle lung (low-dose, free breathing) without measurable FDG uptake (score 1-2).

Impression:
1.
Mild focal uptake over the right nasopharynx and small upper neck node, more in favor of inflammation or benign lymphoid hyperplasia.
2.
Right middle lung subpleural nodule without measurable uptake.
Post-inflammatory change may show this picture.
3.
No other abnormal focal uptake lesions in the scanned range.
Comment:
1.
FDG PET scan might demonstrate a false negative result if the tumor size is below 0.6 cm or non-FDG-avid.
2.
Score 0 = normal; score 1 = benign lesion; score 2 = equivocal lesion; score 3 = possible malignancy; score 4 = high probability of malignancy.
After reviewing the report, I feel quite positive about it, but I am more concerned about the nasopharynx (SUV 3.1, score 1-2) and the right upper neck node (SUV 2.7, score 1-2).
The SUV values seem a bit high; I found that an SUV < 2 is mostly associated with benign inflammation, while an SUV > 2.5 is more commonly associated with malignancy.
Most sources I checked use 2.5 as a benchmark.
I asked the doctor who performed the PET scan, and he said that these values are still considered low.
I'm not sure if I'm being too pessimistic, or if the doctor is being too optimistic, or if the 2.5 benchmark is not really a valuable reference (though almost all sources mention 2.5).
Sorry for the lengthy message, and thank you for your help.

Xiao Chen, 30~39 year old female. Ask Date: 2021/08/25

Dr. Zheng Xiaoyi reply Nuclear Medicine

Hello Mr.
Chen, I apologize for the confusion.
Although I recall responding to your question about a month ago, the system indicates that I have not yet addressed your inquiry.
It may be a technical error.
Regardless, it is more important to answer your question.

As mentioned last time, the principle of positron emission tomography (PET) imaging involves injecting a glucose-like tracer into the body.
The uptake of this tracer by cellular tissues is quantified, resulting in a value known as the Standardized Uptake Value (SUV).
Cancer cells typically exhibit a higher metabolic rate and thus absorb more glucose, which is reflected as a higher SUV on the PET scan.
However, there are exceptions to this principle, as some benign conditions can also show elevated glucose uptake.
For example, inflamed tissues in the body may have increased glucose absorption, and in severe cases of inflammation, the imaging may resemble that of cancer cells.

Therefore, the interpretation of PET imaging is not solely based on SUV values.
We also consider the computed tomography (CT) scans performed alongside the PET scan and other clinical information.
We do not make a definitive diagnosis of cancer based solely on an SUV greater than 2.5.
Thus, you need not worry excessively about this.

Ultimately, the physician who is most familiar with your clinical condition is the best person to assess your situation.
I cannot determine whether it is cancer based solely on fragmented information.
If you have further questions regarding your report, I recommend discussing them with your physician to avoid unnecessary concerns.

Wishing you good health and all the best.

Reply Date: 2021/08/25

More Info

Interpreting PET scan reports, particularly the Standardized Uptake Values (SUVs), can indeed be a complex process, especially when considering the implications for potential malignancies. In your case, the report indicates increased uptake of radioactivity in the right nasopharynx (SUV 3.1) and a right upper neck node (SUV 2.7). Understanding these values in the context of your overall health and any symptoms you may be experiencing is crucial.

Firstly, it's important to clarify what SUV means. The SUV is a measure of how much of the radioactive tracer (in this case, FDG, or fluorodeoxyglucose) is taken up by tissues in the body. Higher SUV values can indicate higher metabolic activity, which is often associated with cancerous tissues. However, it is not a definitive measure of malignancy. The thresholds you mentioned (SUV < 2 indicating benign processes and SUV > 2.5 suggesting malignancy) are general guidelines, but they can vary based on individual circumstances and the specific characteristics of the tissues being examined.

In your report, the SUV values of 3.1 and 2.7 are indeed above the 2.5 threshold, which may raise concerns. However, the interpretation of these values is nuanced. The report suggests that the findings in the nasopharynx and neck node are more consistent with inflammation or benign lymphoid hyperplasia rather than malignancy. This is a crucial point because inflammatory processes can also lead to increased FDG uptake, mimicking the patterns seen in cancer.

The report also notes that there were no other abnormal measurable lesions in the body, which is a positive sign. Additionally, the subpleural nodule in the right middle lung without measurable FDG uptake (score 1-2) further supports the idea that there may not be significant malignancy present, as non-FDG avid lesions are often less concerning.

It's understandable to feel anxious about these findings, especially given the context of your health history and the potential implications of increased SUV values. However, it's essential to remember that PET scans are just one part of the diagnostic puzzle. They should be interpreted in conjunction with clinical findings, other imaging studies (like CT scans), and, if necessary, biopsy results.

Your physician's reassurance that the SUV values are still considered low is important. They have the context of your overall health and any symptoms you may be experiencing, which is critical in making a comprehensive assessment. If there is still uncertainty or if your symptoms persist, further evaluation or follow-up imaging may be warranted.

In summary, while the SUV values you mentioned are above the typical benign threshold, the overall impression from your PET scan report leans towards benign conditions rather than malignancy. Continuous communication with your healthcare provider is essential to address your concerns, discuss potential next steps, and ensure that you receive the most appropriate care based on your individual situation.

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