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contradictory infor from CT & PET

Guest shaoyun

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Guest shaoyun


My dad (in China) started coughing in Feb. In mid March. he did a CT and they found a tumor 2.5cm x 3.2 cm in his right lung. CT also shows some tiny little ones in both lungs, with biggest diameter at about 2mm. He later on did a biopsy on the primary tumor and was diagnosed as non-small cell adenocarcinoma and was staged IV because of the metastases in both lungs.

One week later, he followed up with a full body PET scan and PET reveals two primary tumors in his right lung, 2.6x2.6x1.8cm and 2.8x3.3x2.2cm with MAX SUV4.0. However, PET did not ditect any other abnormality anywhere in the body. Not even the left lung or the mediastinum.

I've read some articles about PET. It's supposed to able to detect extremely small cancerous tumors and very subtle changes of function in the brain and heart. However, some other articles say that PET has limitation on resolution for tumor < 1cm.

I've talked to the person who performed the PET and she said those tiny little ones are benign if they're not picked up by PET. Since PET is a pretty new technology in China and not many doctors are familiar with it. I would like to hear about your comments. My questions are:

Is it possible that PET might miss some small tumors that were caught by CT?

How accurate is PET in dictecting tumors smaller than 1cm even if they don't show on the film. Can the SUV tell us the existance of them?

How accurate is PET in dictecting mediastinal lymph-node metastases?

Should I obtain a copy of the PET results and have a second interpretation here in the USA?

If so, what kind of information do I need from my dad's doctor. Right now all he has is the scan and a very brief report. I believe the PET scan machine should be able to automatically capture some information during the process. What kind of data would that be?

Is there any other non-invasive preoperative method to stage non-small cell lung cancer?

I appreciate your input.

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PET sensitivity. I believe the PET scan is around 85%-90% sensitve.

They may be able to do a helical CT scan. This is much more sensitive than a CT scan. Get someone like Dr Henschke to do the scans.

Maybe they can determine if the left side is just a result of inflammation

Best of luck

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My mom had a PET scan and it did not show any lymph node involvement. When they sent the nodes to a pathologist, they found cancer cells. So as I said before the PET scan won't catch everything.

Find out the grade of the cancer (1-4) 1 is a worse grade. They can cell based on the biopsy how fast the cells are dividing (mitotic rate)

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  • 2 months later...

I had a bone scan done and it showed that my NSCLC had not gone into me ribs, but 4 weeks and one chemo later I had a PET scan done and it showed 'uptake' in my rib. Now it wasn't much uptake (1.5 compared to the tumor at 3.5), but could the uptake be from a previous break in this rib (car accident 1979)?

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What did the doctor say about that SUV level?

I'm not a Dr but this is what I found on the net. generally, SUV > 3 are malignant. So 1.5 *probably* isnt bad. Talk to the Dr. I dont know if the sequential pet scans after waiting a period of time. That way there is a baseline and they can compare the different scans.

" ....

The role of semiquantitative analysis for lesion characterization is limited, since there is an overlap of SUVs between benign and malignant lesions. Avril, using receiver operator characteristics (ROC) analysis and partial volume correction, found that an SUV of 2.5 offered the best diagnostic criterion.3 In general, lesions with an SUV greater than 3 are malignant. It should be noted that most studies of primary breast cancer have been performed with full-ring PET scanners. With such devices, sensitivity for lesions smaller than 1 cm has been suboptimal.

.... "

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Im not posting this to shake anyones faith but I have to put it out there. Right after my father's stem cell transplant for lymphoma, 4months later, a nodule appeared on his CT scan. They decided to wait. It grew a little in June so they did a PET. It was negative. It didnt grow again till January and then again in March. In April his PET showed it was indeed cancer and had gone to a node. I never knew about these levels Ive just read about in these posts so I cant comment on that, but I had to share his story.

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  • 4 weeks later...

I didn't mean to discourage you, I just want to share some info. My fahter's PET before any treatment shows SUV of 4 on the primary tumor. After two rounds of chemo SUV goes down to 1.1. However, when they did the biopsy during the surgery, cancers were still there on the primary tumor.

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Dear Shaoyun,

I am sorry that your Father has lung cancer. I wanted to let you know that there are several subtypes that fall under the catagory of Adenocarcinoma, and one of those is called Bronchioloalveolar Carcinoma, or BAC for short. Some tumors are pure BAC, others are Adenocarcinoma with Bronchioloalveolar Features, where the tumor(s) have mixed cell types with both aggressive cancer cells and indolent cancer cells. BAC is broken up further into non mucinous, mucinous, single nodular form, multi-focal nodular form, part solid, or non solid diffuse form... And it doesn't always show up on PET scans, especially if it is in the indolent state.

Perhaps this may be something that is applicable to your Father's case. I'm not a physician, but I do have the multifocal and mucinous, mixed cell type of cancer. (Or rather "had". My lung was removed almost 2 months ago.)

I hope that this information proves helpful.

Best Wishes,

Fay A.

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