If you look at the changing incidence of lung cancer in men, you can see that the United Kingdom is actually decreasing quite substantially from the earlier 1960s and '70s. In the United States, lung cancer has actually leveled off in the 1980s and it has started to decline in the last couple of years and in France it is still rising. So it really just depends on where you are and on your habits. In women, lung cancer in the United States is still going up.
If we look at the types of lung cancer, lung cancer is obviously not all one disease but there are two major types: non small cell and small cell. Approximately 75-80% of the tumors that we see are non small cell, while only 20-25% are small cell itself. If we look at the small cell subtypes, previously the vast majority of those particularly with the disease found in males was squamous cell cancer but more recently the majority of them are adenocarcinomas and 40% of all lung cancers are adenocarcinomas. So this has really shot up and changed the nature of the disease as well. Squamous cell is only 17% of all lung cancers at this point.
This is a complicated slide but if we look at males over here and females over here and the left one is smokers and the right one is nonsmokers, you see that the incidence of different subtypes is different. In smokers, particularly males, again squamous cell is a fairly predominant tumor type. But if we look at nonsmokers, adenocarcinoma is by far the most common subtype. The same is true of females even to a greater extent. In smokers, adenocarcinoma is more common in canser.
I am going start talking about stage 3-A and go down here and then come back to stage 1 and 2 because you will see some of the applications that have developed for advanced disease are now being applied to earlier stage disease. So, stage 1 and 2 are localized to the lung itself. Stage 3A is more advanced with neostile metastases in general or chest wall invasion and 3B is unfortunately your unresectable tumors. The change I have heard recently is this group here, T3N0 which is tumors that involve the parietal pleura either on the chest wall, the diaphragm or the mediastinum, now it is considered to be stage 2 as well since the survival is actually better. In these two groups up here, TI and T2, each one has been divided into A and B. Now, there is 1A, 1B, 2A, 2B and then T3 can be observed in 2B.
Well, the stages Y this goes from stage 1 and we will go over each stage separately, this is now over here T1N0 stage 1A. The tumors have to be less than 3 cm and it can't involve a major lobar bronchus and create lobar atelectasis or consolidation.
Stage 2 is the same two groups except for there is intrapulmonary lymph node involvement so that the criteria are the same. This is 2A, this is 2B but there is intrapulmonary lymph nodes either along the segmental bronchi or either the lobar bronchi.
This is 3A. This is locally advanced now. We are at T3N0 again goes to the 2B now but T3N1 and 2, T3 involves basically anything that has parietal pleura. That is the chest wall, the diaphragm or the mediastinum without involving major organs.
The other component of a 3A is N2 disease and that means now lymph nodes up in this area that are involved. So you can kind of get a feeling from the number of different subgroups in this phase that there are a lot of different patient populations in here. N2 disease is a lot different from T3 disease so implications in terms of survival and treatment are also different.
3B again is something that is unresectable in general which includes N3 disease which is either contralateral, if you have a tumor over here, contralateral lymph node involvement on the opposite side or a scalene lymph nodes in this particular area or you have a T4 lesion which is either a tumor growing into a major structure like an aorta, esophagus, left atrium or some major unresectable organ or a malignant pleural effusion. So those are the two criteria for 3B.
One of the things surgeons keep in mind is the spread of tumors along lymph node chains.
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