Bronchology – Past, Present and Future Diagnostic Procedures 15 The general observation and agreement was: Within the trials there was no advantage in terms of mortality reduction to the groups offered intensive screening in the Mayo Clinic Study (MLP) with sputum cytology and chest radiology every four months, while in the JHLP and MSKLP studies there was no advantage to the group with sputum cytology   in   addition   to   annual   chest   radiography   examination.   The Czechoslovak Trial patients underwent radiology and sputum cytology every six months. This led to the adoption of policies discouraging routine X-ray and sputum screening for early detection of lung cancer. The search for other avenues for early detection continues. Molecular Markers in Screening An intensive search for genetic markers is in progress. The markers should be detectable at a very early stage of the carcinogenic process and be specific for malignancy. Other criteria include reproducible detectability, inexpensive, auto- mated or semi-automated techniques. The Ras (Rous avian sarcoma) oncogene meets some of these criteria. Both healthy individuals and cancer patients show small amounts of soluble DNA fragments in the blood stream permitting the development of a PCR (polymerase chain reaction) assay to look for Ras muta- tions (in codon 12). The methodology is under study for high-risk individuals. With respect to circulating tumor markers, blood levels of carcinoembryonic antigen and neurospecific enolase are commonly elevated in histologic lung cancer and SCLC, respectively. However early stages of disease and relapse after  treatment  are  not  clearly  detected.  Bronchial  lavage  levels  are  high, whereas serum levels are not. Immunostaining of Sputum Specimens In the John Hopkins Lung Project, Tockman reported 20 months early detection of lung cancer prior to the development of invasive carcinoma. This result was obtained by analysis of immunostained, cytologically atypical sputum speci- mens from exfoliated cells. The process is under study for evaluation. A  new  quantitative,  solid-state  microscopy  system  has  been  developed  at Columbia Cancer Research Center. The system features different DNA distribu- tion patterns which permit to differentiate between cancerous and normal cells. The location of the site of malignancy has to be determined by bronchoscopy even when the system has proved efficacious. There is a misconception that radiologically occult lung cancer detected by sputum cytology with negative chest film represents an early stage of the disease. The number of in-situ carci- nomas in such cases is reported to be very low. The tumors detected by cyto- logy are not small. Back –––––––Table of Contents–––––––Next Back –––––––Table of Contents–––––––Next