The Mayo Lung Project: preliminary report of "early cancer detection" phase

Volunteer effect and compromised randomization in the Mayo Project of screening for lung cancer

It has been confirmed recently that the volunteer effect in lung cancer screening is characterized by higher lung cancer mortality risk in self-selected screening participants. The Mayo Lung Project, the most influential trial of screening for lung cancer ever completed, was conducted in nonvolunteer Mayo Clinic outpatients, with a peculiar study design that rendered the randomization vulnerable to the volunteer effect. Of all nonvolunteers randomized in the Mayo Lung Project, only those allocated in the screened group were asked consent to participate in the trial. The final Mayo Lung Project report stated that 655 randomized nonvolunteers refused screening and were excluded from the study, thus documenting violation of the rule that no selection should occur after randomization. The long-term follow-up of the Mayo Lung Project showed an enigmatic result which has never been explained: the lung cancer mortality was 13% higher in the screening intervention group than in the control group [4.4 (95% CI 3.9-4.9) vs. 3.9 (95% CI 3.5-4.4) per 1,000 person-years; P = 0.09]. Such overrepresented mortality is consistent with the volunteer effect and supports the concept that the Mayo Lung Project randomization was compromised by the post-randomization self-selection of participant nonvolunteers.

Screening for lung cancer

PURPOSE OF REVIEW

With the development of newer forms of technology such as low-dose spiral computed tomography, there has been a resurgent interest in screening for lung cancer. The purpose of this review is to highlight recent advances in screening for lung cancer. Articles published since September 2002 are reviewed here.

RECENT FINDINGS

More frequent screenings (every 4 or 6 months) showed increased mortality from lung cancer, compared with annual screening. A mass screening conducted in 1990 was effective in a case-control study. The results of lung cancer screening by low-dose spiral computed tomography were reported from the Milan group and the Mayo Clinic. Computed tomography depicted peripheral early lung cancer, especially adenocarcinoma. These results are consistent with previous reports from other groups. Screening with imaging becomes more sensitive with automated computerized methods.

SUMMARY

A high percentage of stage IA lung cancers were detected by screening with low-dose helical computed tomography. The characteristics of the nodules detected by low-dose spiral computed tomography have been clarified. There have been many controversial discussions about cost effectiveness and overdiagnosis. There is still no evidence that screening tests reduce the rate of cancer-specific mortality. Several studies of screening for lung cancer are under way.

Diagnosis of peripheral lung cancer using a new type of endoscope

A new fiberoptic bronchoscope, the BF-2.2T, has been designed to go through the 2.6-mm channel of the conventional fiberoptic bronchoscope (Olympus BF-1T20). It measures 2.2 mm in outer diameter; it has a visual angle of 75 degrees, a range of observation of 3 to 50 mm, an effective length of 1,150 mm, and a total length of 1,400 mm. It bends at 120 degrees in an upward direction and at 120 degrees in a downward direction. The 2.2-mm tip of the BF-2.2T bends like a conventional fiberoptic bronchoscope, and this is the main characteristic of this instrument. The BF-2.2T facilitates clinically satisfactory observation and photography, as a method for detecting peripheral lung cancer.

Lung cancer detection. Results of a randomized prospective study in Czechoslovakia

A randomized prospective study of lung cancer detection was begun in 1976 to evaluate semiannual screening by radiologic and sputum cytologic study in comparison to screening at a 3-year interval, and to no screening. In a high-risk population of 6364 men (aged 40 to 64 years), the initial prevalence of lung cancer was 0.28% (18 cases), the annual incidence was 0.35% per year (66 cases during 3 years), the proportion of Stage I cases was 31% (26/84), and Stage II was 17% (14/84), "curative" resections were 27% (23/84), and 5-year survival was 23% (19/84). The study confirmed the ability of radiologic screening to detect lung cancer at an earlier stage when treatment by resection can be accomplished. The fate of a high-risk population submitted to screening was better than that of a population with no screening where lung cancer was discovered by symptoms, accidental x-rays, or at autopsy. A matter of lesser importance was the frequency of screening. The absolute numbers of 5-year survivors detected by screening were practically the same for either compared screening frequency.

Cytologic diagnosis of lung cancer. Principles and problems

This diagnostic seminar discusses the current status of the principles and problems of cytology as it is applied to the diagnosis of lung cancer. This discussion is divided into four major parts. Part I presents a discussion of cytopreparatory techniques and cytology of the lung in the absence of cancer. The cytology of benign proliferations which may mimic cancer is emphasized. The role of cytology in the diagnosis of pulmonary infectious organisms is noted. Part II discusses lung cancer as manifested in specimens of sputum, bronchial washings, and bronchial brushings. Part III presents some data on the validity of cytology with respect to role of specimen number and type in lung cancer diagnosis and cell typing in lung cancer. The continued usefulness and importance of multiple specimens of sputum for lung cancer diagnosis are documented. Part IV presents a brief synopsis of fine needle aspiration biopsy of lung cancer.

Detection of true pathologic stage I lung cancer in a screening program and the effect on survival

One-hundred-sixty-nine lung cancers have occurred to date among 10,040 cigarette smoking men who participated in the New York Lung Cancer Detection Program. Almost 40% of the cases, 65, were still Stage I when their disease was diagnosed; 62 had thoracotomy and resection, and in 57, mediastinal node dissection confirmed that the mediastinum was free of metastases ("true pathologic" Stage I). Fifty-four of the 62 (87%) are still alive at this time, while only 15 of 104 (14%) of those with Stage II and III lung cancers are alive. Only two patients of the 62 in Stage I who were treated by resection died of lung cancer, both with T2 tumors. Two others are alive with metastases, one died postoperatively, and five died of other causes without evidence of lung cancer. The estimated probability of survival for true Stage I lung cancer is over 90% at five years, and close to 40% of all lung cancers can be detected in this favorable stage by present radiologic and cytologic screening techniques.

Environmental carcinogens in the city air and lung cancer incidence

Possible contribution of polycyclic hydrocarbons, trace metals, and gaseous pollutants to the incidence of lung cancer in the urban populations has been considered, including the role of carcinogens in the cigarette smoke. A long-term plan has been proposed for the epidemiological studies and control of urban lung cancer incidence. A comparative assessment of lung cancer mortality rate for occupational, urban, and rural exposure to levels of benzo(a)pyrene typical of these environments is presented.

Preliminary report of the lung cancer detection program in New York

The early lung cancer detection program in New York is described, and preliminary prevalence rate data are reported. Cigarette-smoking men over the age of 45, who are considered at high risk, are encouraged to enroll in the program and, to date, 6,612 have done so. These men receive PA and lateral chest x-rays annually, while a randomly selected sub-population of about half also have sputum cytology every four months. A controlled study of sputum cytology as an adjunct to the chest x-ray is now in progress. There were 15 cases of late lung cancer (pathologic stages II and III) detected at the initial examination, and 11 early cases (pathologic stages O and I). In the population of 3,387 men who had x-rays alone there were three early lung cancers detected; in the population of 3,225 men who had both examinations four early cancers were detected by x-ray and four by cytology. In addition, three cases of larynx cancer were detected by cytology. The early lung cancers detected by x-ray were peripheral and most were bronchiolar or adenocarcinoma; the early cancers detected by cytology were central epidermoid carcinoma of major bronchi. No early carcinomas were detected by both techniques. These findings suggest that a combination of chest x-rays and sputum cytology can be more effective than either one alone in detecting early lung cancer.

Diagnostic and therapeutic challenges following the cytologic diagnosis of in situ carcinoma of the lung

Clinical challenges associated with the cytologic detection of eight cases of occult pulmonary carcinoma are presented. The pulmonary lesions were successfully localized and resected in three of six cases encountered since the availability of flexible fiberoptic bronchoscopy and selective bronchial brushing. Two of the resected neoplasms were unequivocally in situ, while preoperative radiotherapy precluded accurate pathologic determination of invasiveness in the third. The reported experience with unequivocal in situ bronchogenic carcinoma localized and treated surgically prior to invasion through the basement membrane now totals 17 cases (15 previously reported). Forty-four additional cases (43 previously reported) have been localized and resected following early invasion. From this group totaling 61 occult carcinomas, only two patients (3 percent) are known to have died of pulmonary carcinoma during a followup ranging from 2 to 20 years.

Early lung cancer detection and localization

The Mayo Lung Project was established to develop and evaluate a screening program for early lung cancer in high-risk subjects. Men who are more than 45 years of age and who smoke one package of cigarettes or more daily are screened by the use of thoracic roentgenograms, three-day pooled sputum cytology, and lung health questionnaires at four-month intervals. These data are compared with data from similar subjects screened only on entry into the project. During the past three years, 34 patients who had no roentgenoraphic evidence of lung cancer were identified and examined because of carcinoma cells in sputum. Of these 34 patients, 27 have had bronchoscopic localization of their tumors and definitive treatment and 3 had upper respiratory tract neoplasms and also have been treated. Of the remaining four, one patient died suddenly after myocardial infarction and three patients have not had localization or treatment because of other severe complicating medical problems. Localization of roentgenographically occult lung cancer is reliable by the use of bronchofiberoscopy and meticulous, thorough sampling from the tracheobronchial tree. A search must be made for upper airway cancers in the same high-risk population, and the possibility of second primary bronchogenic tumors also must be considered. Although follow-up is short, 22 of the 27 treated lung cancer patients were found with stage I disease. The outlook for 19 of these 27 is encouraging an average of 16 months after surgical resection.

The Mayo Lung Project for early detection and localization of bronchogenic carcinoma: a status report

The Mayo Lung Project (MLP) is a screening program designed to detect bronchogenic carcinoma at a curable stage. Screening tests include chest roentgenograms, three-day "pooled" sputum cytology studies, and lung-health questionnaires. These are being applied every four months to a study population of outpatients who have a high probability of developing lung cancer. Initial patient acceptance of the screening program has been excellent. Small asymptomatic lung cancers have been detected both roentgenographically and cytologically. The two procedures have complemented each other with little overlap. Chest roentgenography has proved most useful in diagnosing peripherally situated cancers, whereas sputum cytology studies have been most effective in identifying early squamous cancer involving major airways. At present, more cancers have been detected roentgenographically than cytologically, but the cytologically detected cases appear to have a better prognosis. Roentgenographically occult cancers have been localized with regularity, although the localization process is complicated. Theoretically, vigorous application of radiologic and cytologic screening, combined with optimum use of localizing procedures and treatment, could increase the five-year survival rate among lung cancer patients to nearly 50 percent. However, the actual survivorship attained will ultimately be determined by currently imponderable factors such as patient acceptance of longterm screening, frequency of multicentric respiratory cancers, and incidence of noncancerous smoking-related diseases, especially chronic obstructive pulmonary disease and ischemic heart disease.

Anesthesia for prolonged bronchoscopy

At the Mayo Clinic, experience with 22 patients undergoing bronchoscopy on 29 occasions has shown that prolonged operative manipulation in the airway can be carried out safely and satisfactorily using general anesthesia. Requisites for this procedure include a period of apneic oxygenation, an adequate-sized endotracheal tube, hyperventilation of the patient during operative manipulation, and careful attention to management of postoperative bronchospasm. Prolonged bronchoscopy under general anesthesia has permitted localization of occult bronchogenic carcinoma at an earlier stage than has been possible up to this point.

Use of a Pulsed-Flow Lavage Unit for Bronchial Washing

A pulsating lavage irrigation system was employed during diagnostic bronchoscopy in patients with suspected bronchogenic carcinoma to facilitate collection of specimens for cytologic examination. No untoward effects were observed, and good quality samples of exfoliated cells were recovered. This method also might have application in the management of patients with suppurative lung disease or retained secretions and in situations in which a large volume of lavage solution is desired.