E-4. Radiation therapy of lung cancer detected by screening

Abstract

Spiral CT scan screening for lung cancer may diagnose a large volume of patients with early stage cancers, potentially curable with local treatment alone. Surgery is likely to be the usually offered treatment. However, some patients present with surgically resectable disease have medical contraindications or refuse surgery [l]. For such patients, primary radiation therapy offers an alternative and potentially curative approach. The very good results reported with surgery for early stage disease may in part be due to the more favorable performance status of surgical patients and the fact that surgically treated patients are more rigorously staged and the results are reported by pathological stage rather than clinical stage. Most patients who receive primary radiation therapy are not surgically staged and may have occult N2 (mediastinal) disease, whereas such patients may be excluded or reported separately in surgical series. Results of radiation alone for medically inoperable early stage lung cancer: There are many series which document reasonable survival following radical radiation alone for stage I and II cancers. [2-61 While 5-year survival from all causes may be low, the cause specific survival is often substantially higher due to high rates of intercurrent illnesses. Cause specific survival ranges from 20-50% at 5 years.[7,8] Locoregional failure (using traditional radiologic and clinical criteria) is the dominant cause of failure ranging from approximately 40-50%. [8,9] This may underestimate of local failure as traditional clinical/radiologic assessment of local failure following radiation nderestimates the incidence in locally advanced cancer. In one series routine bronchoscopy was performed during follow-up, and local control was less than 20% at 1 year. [IO] There is clearly a need to improve the locoregional disease eradication rates to impact on survival. This could be achieved by better patient selection and improved radiation technology. Patient selection: PET is an expensive imaging technique which requires the availability of a cyclotron and is not, therefore, widely available. Reports have demonstrated accuracy rates of 80-100% in the detection of nodal metastases compared to approximately 65% for CT and MRI (151. PET also has the advantage of providing accurate whole body staging. PET can also e used in helping to refine the process of radiation target volume delineation. The advent of accurate non-invasive staging with PET could have as substantial impact on the use of radiation for this category of patients by removing advanced stage patients from the series of the future. Radiation pulmonary toxicity could contribute to increased morbidity and even mortality. It would be useful to exclude patients in whom the treatment would be more likely to cause damage than improve survival. There are no strict guidelines for such selection, however it may be possible to identify patients likely to have very poor pulmonary function post-radiation in a manner analogous to the preoperative selection of patients. Investigators at the NKI calculate the FEVl post-RT to be: