Surgery has long been the only way to cure lung cancer. If the tumor was discovered early – a rare occurrence in the past – then resection could remove it totally. Recently it has been shown that radiation can be used successfully for early stage disease. And new approaches to radiation therapy result in the ability to give higher doses to the tumor, limit damage to surrounding normal lung and do so with relatively few sessions under the machine.
Thus far in this five part series has been a general discussion of lung cancer facts and figures followed by controlled enthusiasm about early diagnosis using CT scanning. The treatment of lung cancer has also progressed dramatically and with early diagnosis as a result of CT scanning high risk individuals, it is now possible to cure a larger proportion of patients.
Today an increasing number of individuals are having their cancer detected early so curative approaches will become more common. But many if not most lung cancer patients are older and have either chronic lung disease, heart disease or both, rendering them at higher risk for surgery. At a minimum the surgeon wants to do as limited a procedure as possible, using the least invasive approach. Still, not all patients are good surgical risks.
Despite finding the cancer when it is still small and with no apparent evidence of spread, many patients still relapse in a few months or years after surgery. The addition of chemotherapy to treat microscopic but undetected disease has a resulted in improved cure rates. The same approach is being used for those treated with radiation of early stage lung cancer.
Until recently, it was assumed that only surgical resection could cure small early stage lung cancer. But many patients are poor surgical candidates due to age, chronic lung disease, heart disease or other concomitant conditions. The question thus arises, could these newer approaches to radiation therapy be as effective. Multicenter trials have now demonstrated that stereotactic body radiation treatment (SBRT) appears equivalent to surgery in terms of the local control of the tumor in small (
It is important to understand that radiation can destroy any cancer if sufficient radiation can be applied. For many cancers, however, the risk of damage to adjacent normal tissues that are essential for life (e.g., normal lung) makes it impossible to give the desired dose. That said, radiation oncology has advanced dramatically in the past decade and the rate of progress is increasing rapidly. Innovations as a result of engineering and computer advances along with conceptual advances are making a dramatic difference. Major advances in radiation therapy mean greater effectiveness, fewer side effects and less time in treatment.
Newer devices allow stereotactic treatment not only for stationary tumors but also lung cancers– overcoming the problem of motion caused by breathing or even heartbeat and blood flow. The combination of continuous imaging, motion detection and robotic guidance combine to allow much more effective treatment than in just the very recent past.
Stereotactic body radiation treatment appears to be a very useful new approach to many otherwise difficult to treat cancers such as in the lung. It begins with the use of earlier techniques where the cancer is treated from multiple angles such that the tumor receives a large dose but the adjacent normal tissues receive much less. Stereotactic means that the tumor is imaged and the radiation adjusted to directly attack the cancer and not the normal tissue. A related innovation is to link actual delivery of radiation with the patient’s breathing parameters (gating). This is done with an infrared device that observes motion and turns the radiation beam on and off during the breathing cycle. This can be of great value in lung cancer because the target is constantly moving. This greatly reduces normal tissue damage occurring as the lungs move with respiration. It also means that the cancer gets a higher dose because the physician is less encumbered by a concern for damaging adjacent normal lung. This is a real improvement as in the past it was necessary to curtail the ideal dose with the realization that that dose would cause unacceptable side effects on adjacent normal tissue.
Hypofractionation, that is giving a much higher dose of radiation per session, with the much greater accuracy of the stereotaxic approach, means many fewer sessions yet with high effectiveness. Much SBRT is now done in 3-5 fractions rather than the more typical approach of multiple, perhaps as many as 45, fractions over as many days or more. Add robotic guidance based on motion detection and the combination becomes very powerful. With robotic control of the equipment from outside the treatment room, this means less time is wasted by the staff moving back and forth to make adjustments and less time on the table for the patient.
Most radiation today is delivered by X-rays or electrons (photons). Another approach is to use protons. Proton beam therapy has the advantage that the proton gives up its energy only when it hits its intended target – in this case the tumor. It does not continue through the tumor and damage normal cells on the far side. So it allows for the delivery of very high doses of radiation to the tumor with minimal side effects. It follows that proton beam might prove very useful because one can give a much higher dose without as much fear of adjacent normal tissue damage. But it is critical to keep in mind that there are no controlled studies showing superiority of protons over photons and certainly none in lung cancer as of yet. As a result it is important that the clinical value of proton beam therapy not be over inflated. The cost of one center runs into the hundreds of millions of dollars — which would purchase 20 or more photon linear accelerators.
What is clear is there is a steady and rapid, advance in the ability to deliver radiation therapy to those with lung cancers in a more effective and more safe manner, often in much less time than in the past. The realization that radiation can actually be used to cure early stage lung cancer is a stunning advance, allowing effective treatment for those not able to undergo surgery.
In the next of this series will be a discussion of the dramatic advances in lung cancer treatment with drug therapy.