The three major treatment modalities for lung cancer are surgery, radiation therapy, and chemotherapy. The preferred treatment(s) for a specific patient depend on several factors, including cell type (histology) of the tumor, its location in the lungs, the extent of tumor spread to lymph nodes in the immediate area, and the presence or absence of distant metastases (that is, spread to other parts of the body).
Radiation Therapy for Lung Cancer – An Overview in English
Lung cancers are generally divided into two major histologic categories, small cell and non-small cell carcinomas. The latter can be further subdivided into squamous cell carcinomas and adenocarcinomas. Several other less common histologies as well as several subtypes of adenocarcinomas also exist.
Radiation Therapy for Lung Cancer – An Overview in Spanish
In general, early-stage non-small cell carcinomas are best treated by surgery, followed in some cases (but not all) by radiation therapy, with or without chemotherapy. In contrast, patients with more advanced non-small cell carcinomas may be best treated by a combination of radiation therapy and chemotherapy, or sometimes radiotherapy alone. Patients having other medical problems that might make surgery too risky are also often treated with radiation therapy, possibly in conjunction with chemotherapy.
On the other hand, small cell carcinomas are virtually always treated with chemotherapy, often in conjunction with radiotherapy to the chest and possibly also to the brain. This will be explained more fully in the following sections.
Before any treatment is started, the recommended treatment, the reasons it is recommended, the procedures to be carried out, the expected or possible side effects or complications, and the expected benefits are all explained to the patient and family. The patient must give permission for treatment, based on this knowledge (“informed consent”), before treatment is given.
Radiation treatments can vary widely from one institution to the next, depending on the training and expertise of the physicians and staff, as well as the treatment planning and treatment technology or capabilities available at any given center. New computer-generated treatment calculation programs enable precise administration of radiation to specific areas of concern, while limiting the dose to other, healthy tissues.
Non-small cell carcinomas
The two most common types of non-small cell carcinomas are adenocarcinomas and squamous cell carcinomas. Several less common types and subtypes are also occasionally seen. Surgery is the mainstay of treatment for early-stage patients who are medically fit to have an operation. If lymph nodes are involved, the margins of the surgical resection are very close to the tumor or involved by tumor, or extensive tumor is found at surgery, radiation therapy with or without chemotherapy may be recommend postoperatively.
Surgery is the accepted standard in the early stages of lung cancer, but stereotactic body radiation therapy, or SBRT, and stereotactic ablative radiotherapy, or SABR, are good options for patients who may not tolerate surgery. These methods, which rely on detailed 3-D imaging and exact treatment planning, focus highly accurate, high-dose radiation beams for short periods on well-defined tumors. Typically, they are advantageous for the patient as they completed in one to five treatments and minimize the adverse effects to healthy tissue.
However, SBRT and SABR are used only for small, well-defined tumors that can be seen on CT (computed tomography, or CAT) or MR (magnetic resonance or MRI) scans, so they are not helpful in treating all cancers. In addition, if the cancer is located close to sensitive structures such as blood forming organs and some areas of the gastrointestinal and nervous systems, the radiation dose may be limited.
The primary drainage pathways from the lungs are to the lymph nodes in the center of the chest around the breathing tubes (bronchi) and heart. As a result, cancers in the lung will frequently spread to these areas. CT scans and chest x-rays before surgery are often, but not always, successful in identifying this type of spread.
Patients who are found preoperatively to have extensive lymph node involvement or extension of tumor to critical structures in the chest (classified as Stage III) are usually best treated with radiotherapy in conjunction with chemotherapy. Radiation therapy is usually given once or twice per day, five days a week, for approximately 6 weeks. Sometimes shorter treatment courses (of 2 to 3 weeks) are used, depending on the situation. Each treatment session lasts only several minutes, although setup times and treatment planning may occasionally cause some sessions to last longer.
Small cell carcinomas have a tendency to spread early and are very sensitive to chemotherapy and radiation therapy. For these reasons, surgery is not routinely used in their treatment. Early (“limited”) stage patients are those who have no evidence on x-rays, bone scans, and CT scans of any spread outside of the chest. Treatment usually consists of multiple cycles of chemotherapy in conjunction with radiation therapy to the chest (to include the primary tumor as well as potential lymph node drainage pathways). Radiation treatments are usually given once or twice per day, five days a week, for approximately 4 to 6 weeks. On occasion, preventive (elective or “prophylactic”) radiation therapy to the brain will also be recommended, since small cell carcinomas often spread to this area and chemotherapy may not infiltrate the brain as well as other sites. In general, to prevent growth of any small, undetectable cancer sites in the brain, a lower dose of radiation is given than would be used to treat actual known sites of metastatic disease. Radiation therapy can also be given to sites of distant spread (metastases) to alleviate pain or tumor impingement on vital structures, such as the spinal cord. In general, small cell lung cancer can be cured in approximately 20% – 50% of patients who have disease confined to the chest, using multimodality (chemotherapy and radiotherapy) treatment.