Dr. Judith Balogh
MSc, MD, FRCP(C)Radiation Oncologist, Toronto Ontario
Lung Cancer Canada Volunteer Writer
What is the Role of Radiation in Lung Cancer Treatment?
External beam therapy is the most commonly used form of radiation therapy. It describes treatment with a machine using photon or x-ray beams to deliver dose to the tumour. These are most commonly from the front and back of the patient but may require treatment from more than two beams to minimize the dose to lung and maximize the dose to tumour within a tight margin. Other forms of radiation therapy may include brachytherapy and stereotactic radiosurgery (see below).
The role of radiation is quite widespread. Radiation, alone, may be offered in very early (stage I and stage II non-small cell carcinoma of the lung) disease, considered unsuitable for surgery in patients who either refuse or are unable to have the surgery for medical reasons. Radiation can be given to the tumour with good effect, which approximates the outcomes with surgery.
Radiation can also be used in the adjuvant setting after surgery has been completed. In some patients surgery removes all visible disease but, follow-up by the Pathologist identifies either that the margins are involved or very close to tumour. Under these circumstances, sometimes chemotherapy and radiation therapy is given to the area at risk of containing small amounts of disease. The dose is moderate and given over a five to six week period.
The major role of radiation, however, is in treating those patients who are considered unsuitable for surgery because of loco-regionally advanced disease. In the majority of cases, where the patient is felt to be a suitable candidate, chemotherapy is given together with the radiation therapy, called concurrent chemo-radiation therapy. Radical, or high doses of radiation are used to treat both the tumour and the central structures of the chest, the mediastinum and, as well, adjuvant radiation is given to areas where potential risk of spread is perceived to be high. This treatment generally takes six and a half to seven weeks to deliver. In addition, it may be followed by two to four further courses of chemotherapy.
The palliative role of radiation therapy is extensive. The most common palliative role is local treatment in advanced disease where the tumour is considered incurable but symptoms, such as cough, spitting of blood, chest pain or potential risk of airway collapse exist. Short courses of high dose radiation, can be delivered to the tumour and lymph nodes.
Other palliative roles of radiation may include treatment of selected metastases considered suitable in bones, either because of tumour spread or potential risk of fracture. Existing pathologic fractures are stabilized before radiation is safe to deliver. Skin nodules can also be treated as well as brain metastases.
The palliative role of radiation has been expanded with the use of radiation delivered through the use of radioactive sources within the airways called brachytherapy, in patients who have already received high dose radical treatment but have had relapse in an airway, and cannot have further external beam treatment.
The patients who have been treated initially with external beam for brain metastases, who are in good general condition with no metastatic disease and only minimal local lung disease, may also be considered for further palliative radiation using stereotactic radiation surgery. This is a technique to deliver very limited volume treatment to the tumour and requires very complex technical preparation and head frames to ensure high accuracy.
What are the Side Effects of Radiation Therapy?
The side effects of radiation treatment are numerous, both minor and potentially severe, and may be related to both the chemotherapy and the radiation therapy. Dr. Verma's previous article addressed the nature of the side effects of chemotherapy (see Fall 2005 edition of Lung Cancer Connection). Depending on the drugs that are offered, the general side effects of chemotherapy may include fatigue, changes in the blood counts which can lead to an increased risk of infection, as well as increased side effects in the radiation treatment area to the lining surfaces of the esophagus and the trachea. The former can lead to swallowing difficulties and pain on swallowing, the latter can lead to cough and occasionally spitting of small amounts of blood during the treatment.
The side effects of radiation are related to the area that is treated. The overwhelming side effect that most patients are aware of is fatigue. There may also be taste changes which can be attributed either to the chemotherapy and, more infrequently, to the radiation therapy during the phase of treatment with the two modalities.
Generally the skin, in the treatment area, becomes red like a moderate sunburn, more marked on the back than on the front. For men, there may be hair loss in the treatment area only. As treatment progresses, swallowing difficulties may develop. This is more frequent with chemotherapy given together with the radiation as opposed to radiation alone. There may also be irritation of the lining of the trachea and airways. Once short term and intermediate term side effects have settled, the long term side effects include some pigmentation changes in the skin, more commonly on the back. In selected cases, there may be some thickening of the tissues underneath the skin which is called fibrosis and there may be dilated blood vessels, called telangectasia in the treated area.
There may be narrowing of the esophagus, called stenosis which happens in approximately 10% of patients. The risk to the lung of chronic scarring, which is called fibrosis happens in almost all patients. In over 90% it is a silent event that is noted only on x-rays as a "ground glass” appearance in the x-ray corresponding to the radiation field. This can sometimes be quite difficult to sort out, and CT's may be used to rule out a possibility of recurrent tumour.
Extremely rarely, patients may get numbness and tingling down their legs which is usually temporary. It can occur from the three to the six months after treatment completion and resolves gradually over the following three months. This phenomenon is called L'Hermitte's Syndrome.