A standard dose of radiation for "microscopic disease" is not appropriate

Article Abstract:

Generally speaking, the treatment of cancer patients is an empirical art, and patients are treated according to experience. Clinical data represent averages, and it is not always possible to test every single variation of treatment that might be thought to be desirable or to warrant further investigation, simply because the numbers of patients do not permit. One way around this problem is the development of theoretical models. While theoretical models in biology are often far from satisfying, on occasion they may be the only source of guidance for the clinician when substantive data are lacking. One such circumstance is the use of radiotherapy after surgical removal of a cancer. There is no question that, on the average, radiotherapy will help to eliminate microscopically small regions of tumor which were not removed at surgery. But what is the proper dose of radiation? Many clinicians use doses that are known to be effective, and there is little or no data to indicate if smaller doses might be equally effective. Indeed, the dose is usually chosen on the basis of the tolerance of the particular tissue for radiation, rather than on the basis of what dose is effective. For this reason, the author has developed a mathematical model of the treatment of residual cancer with radiotherapy. The model is based on an analysis of the several probabilities involved. What is the range of tumor cells that are likely to be left behind after surgery? What is the probability of sterilizing a site with a given dose of radiation? The results of the mathematical analysis indicate that lower doses of radiation may be more effective in tumor control than previously suspected. The optimal dose, however, strongly depends upon the type of tumor and its location. The author suggests that when circumstances do not permit the use of the maximum radiation dosage, a smaller dosage may well be equally effective. (Consumer Summary produced by Reliance Medical Information, Inc.)

Models, Cancer, Cancer treatment, Dosage and administration

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Primary tumors of the trachea: results of radiation therapy

Article Abstract:

Patients with primary tumors of the trachea often have respiratory symptoms and hemoptysis (coughing up blood). Unfortunately, the tumors are frequently in an advanced stage at the time of diagnosis. Surgery is the primary treatment for tumors of the trachea which results in a 20 to 40 percent 5-year survival rate for epidermoid cancers (from epidermal cells), and a 60 to 100 percent 5-year survival for adenoid (gland-like) cystic cancers. However, recent advances in radiotherapy have improved the chances of achieving good control and possible cure for cancer of the trachea. Over a 27-year period, 24 patients with primary cancer of the trachea were treated with either radiation alone or in conjunction with surgery. Overall survival was 25 percent at 5 years and 13 percent at 10 years after treatment. Control of local tumor was achieved in 10 of the 24 patients, and was more likely in patients receiving both surgery and radiation. For those receiving radiotherapy alone, local control was related to the dose. Six out of seven patients receiving greater than 6,000 cGy achieved complete remission, compared with 1 out of 11 remissions in patients who received a lower dose. Five patients developed complications from the radiotherapy; three patients died of these complications, although these deaths were at least partially attributable to surgery. The results of these cases suggest that surgery is the recommended treatment, and that radiotherapy should be used in cases where surgery is impossible or the risk of recurrence is high. When radiotherapy is indicated, the dose should be between 6,000 and 6,600 cGy. Lower doses are not completely effective, and higher doses create an unacceptable risk of complications. (Consumer Summary produced by Reliance Medical Information, Inc.)

Care and treatment, Thoracic cancer

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