Forgive me, but I have another question for Dr. Joe

[Elaine]

As you may have read, I am writing a feature article on the stealth of many lung cancers and arguing for early screening.

I just read a study that reads in part:

The seven-year baseline study was led by Claudia I. Henschke, MD, who organized the Early Lung Cancer Action Project in 1992. Henschke’s goal was to see whether chest X-rays or low-dose CT scans were better at detecting early lung cancers. In all, 1,000 symptom-free volunteers who were at least 60 years old and who were at high risk of lung cancer were enrolled. All patients had a history of cigarette smoking. Each received a chest X-ray as well as a low-dose CT scan.

Among the 1,000 participants, 233 patients had a positive result (one or more nodules present) and 767 had a negative result (no nodules or cancer detected) using the CT scan. The chest X-ray was significantly less reliable. Using a chest X-ray for screening, only 68 of the same patients had a positive result (compared with 233) and only seven cases of cancer were detected, compared to 27 by CT scan.

I also have read that early lc is especially difficult to detect in women by chest xray.

My questions are:

Besides the smallness of some tumors, what are other reasons that chest xrays don't pick up as many tumors? I do know that chest xrays can't really see tumors/nodules when they are confined in a bronchus or in the rather unique instances where the tumors are confined to the trachea.

What other places can lc tumors be hiding from xray? And why in women, especially, are they hard to pick up on chest xray?

LOL, I think I had another related question and I can't think of it!

thanks again!

Elaine

[kdaru]

With a chest xray, you are looking at a thick three-dimensional object (your body) projected onto two dimensions (the film). Thus, things overlap. The rib cage, clavicles, shoulder blades, sternum, heart, great vessels, trachea, esophagus, and diaphragm (and in women, breasts) all partially obscure the lungs, giving tumors lots of things to hide behind. Add to this technical factors (films overexposed, underexposed, poor inspiration or patient positioning) and a little tumor can easily be missed.

With CT, you are projecting thin slices of your torso onto a 2D film, one at a time (as opposed to the whole thing, all at once). Thus the overlapping structures are taken out of the equation, and you can look at the lungs straight on.

HTH, Katie

ETA: whoopsie, I didn't realize this was addressed to Dr. Joe.

[kimblanchard]

Exactly what Katie said! Xrays are too insensitive (don't catch things early enough) and too inaccurate (miss things too often). To have a major impact on survival, it would be ideal to catch lung cancers when they are less than 1cm in size. Xrays are just not capable of doing so.

[kimblanchard]

But oncdoc, if ct is the superior tool will it catch the cancer in an early stage. I know that I have seen comments that the false negatives are too high but we are talking about a disease where our success has not been great. We are proud of treatments that work with low percentages. From my personal perspective, (2years and looking forward with Stage IV cancer - 46woman non-smoker) a false negative would have been emotionally easier and far less costly. Most days I feel like I becoming the 6 billion dollar woman with the costs that we are incurring now.

[john]

The Low dose or spiral CT scan has higher resolution than a regular CT scanner. I think Henschke proposed serial spiral CT scans to do away with false positives

[Bill]

But oncdoc, if ct is the superior tool will it catch the cancer in an early stage. I know that I have seen comments that the false negatives are too high but we are talking about a disease where our success has not been great. We are proud of treatments that work with low percentages. From my personal perspective, (2years and looking forward with Stage IV cancer - 46woman non-smoker) a false negative would have been emotionally easier and far less costly. Most days I feel like I becoming the 6 billion dollar woman with the costs that we are incurring now.

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In my wife's case, her treating physicians keep ordering CT scans but end up largely ignoring the results in favor of other findings and factors. Most of their comments seem to be about what CT scans miss or don't show. For instance, those small nodules that suddenly appeared in the other lung on my wife's latest chest CT scan are now thought to have been there since the start. They were just missed up till now. Recently my wife's neurosurgeon had access to a fresh batch of brain and full spine plain film x-rays, CT scans and MRIs. He didn't even request to see the x-rays and CT scans. He was interested in the MRIs only. In a past discussion on this board regarding discrepancies in tumor measurements with CT scans someone even commented that both the size and number of tumors identified by pathology after their lung surgery differed significantly from the CT scan commentary of that area leading up to surgery. Lastly, my wife's latest chest CT scan indicates that her lung cancer has worsened. Her med onc scoffed at the results and told us that in his opinion she was getting better. Since then her respiratory symptoms ( i.e. gagging with blood-tinged sputum & involuntary gasping ) have disappeared. She currently has NO identifiable respiratory symptoms. Go figure !