Lung cancer and cigarette smoking in women: a case-control study in Barcelona (Spain)

Systematic review with meta-analysis of the epidemiological evidence in the 1900s relating smoking to lung cancer

BACKGROUND

Smoking is a known lung cancer cause, but no detailed quantitative systematic review exists. We summarize evidence for various indices.

METHODS

Papers published before 2000 describing epidemiological studies involving 100+ lung cancer cases were obtained from Medline and other sources. Studies were classified as principal, or subsidiary where cases overlapped with principal studies. Data were extracted on design, exposures, histological types and confounder adjustment. RRs/ORs and 95% CIs were extracted for ever, current and ex smoking of cigarettes, pipes and cigars and indices of cigarette type and dose-response. Meta-analyses and meta-regressions investigated how relationships varied by study and RR characteristics, mainly for outcomes exactly or closely equivalent to all lung cancer, squamous cell carcinoma ("squamous") and adenocarcinoma ("adeno").

RESULTS

287 studies (20 subsidiary) were identified. Although RR estimates were markedly heterogeneous, the meta-analyses demonstrated a relationship of smoking with lung cancer risk, clearly seen for ever smoking (random-effects RR 5.50, CI 5.07-5.96) current smoking (8.43, 7.63-9.31), ex smoking (4.30, 3.93-4.71) and pipe/cigar only smoking (2.92, 2.38-3.57). It was stronger for squamous (current smoking RR 16.91, 13.14-21.76) than adeno (4.21, 3.32-5.34), and evident in both sexes (RRs somewhat higher in males), all continents (RRs highest for North America and lowest for Asia, particularly China), and both study types (RRs higher for prospective studies). Relationships were somewhat stronger in later starting and larger studies. RR estimates were similar in cigarette only and mixed smokers, and similar in smokers of pipes/cigars only, pipes only and cigars only. Exceptionally no increase in adeno risk was seen for pipe/cigar only smokers (0.93, 0.62-1.40). RRs were unrelated to mentholation, and higher for non-filter and handrolled cigarettes. RRs increased with amount smoked, duration, earlier starting age, tar level and fraction smoked and decreased with time quit. Relationships were strongest for small and squamous cell, intermediate for large cell and weakest for adenocarcinoma. Covariate-adjustment little affected RR estimates.

CONCLUSIONS

The association of lung cancer with smoking is strong, evident for all lung cancer types, dose-related and insensitive to covariate-adjustment. This emphasises the causal nature of the relationship. Our results quantify the relationships more precisely than previously.

[Endoscopic techniques in bronchogenic carcinoma. Changes in recent decades]

A 57-year old woman with arterial hypertension under treatment. She has smoked since she was 18 years old with an accumulated index of 70 years/pack. She was studied in our Respiratory Department due to constitutional syndrome, the X-ray showing an image of focal pulmonary lesion in the right upper lobe of more than 3cm of peripheral location. The computed tomography (CT) scan confirmed the existence of a 3.3cm mass in the upper right lobe and detected paratracheal and subcarinal mediastinal abnormal lymph nodes. A subsequent Positron Emission Tomography (PET) confirmed pathological uptake of the mass and both lymph node locations. Which additional studies do you consider to be indicated for a correct diagnosis and mediastinal staging? Do bronchoscopy techniques alone establish the final diagnosis and staging of this patient?

Does increased cigarette consumption nullify any reduction in lung cancer risk associated with low-tar filter cigarettes?

Epidemiological data suggest that smoking filter and lower tar cigarettes is associated with less lung cancer risk than is smoking plain and higher tar cigarettes. A recent National Cancer Institute monograph claimed these apparent benefits of lower delivery products may be illusory if relative risks are adjusted for daily consumption, and switching leads to "compensation" for reduced nicotine intake by increasing numbers of cigarettes smoked. To investigate this, we compared relative risks unadjusted and adjusted for daily cigarette consumption. Overall estimates of the filter/plain relative risk, using random-effects meta-analysis, were 0.61 (95%confidence interval 0.54 to 0.70) for unadjusted data and 0.66 (0.58 to 0.76) for adjusted data. The lower tar/higher tar relative risk was estimated as 0.60 (0.45 to 0.81) for unadjusted data and 0.73 (0.64 to 0.83) for adjusted data. The risk reductions were clearly seen regardless of gender, study location, period, or design, and when only studies providing both unadjusted and adjusted estimates were considered. Whether or not relative risk estimates are adjusted for cigarette consumption is not crucial to the conclusion of a clear advantage to filter cigarettes and tar reduction. Data on "compensation" for amount smoked were reviewed and any increase following switching to reduced-tar-yield cigarettes was shown to be quite small. Other biases in the epidemiology are also discussed, and we conclude that the apparent advantage to reduced-tar-delivery products is real and likely to be a marked underestimate of the reduction in lung cancer risk from lifetime smoking of low-tar cigarettes.

Cigarette tar yields in relation to mortality from lung cancer in the cancer prevention study II prospective cohort, 1982-8

OBJECTIVE

To assess the risk of lung cancer in smokers of medium tar filter cigarettes compared with smokers of low tar and very low tar filter cigarettes.

DESIGN

Analysis of the association between the tar rating of the brand of cigarette smoked in 1982 and mortality from lung cancer over the next six years. Multivariate proportional hazards analyses used to assess hazard ratios, with adjustment for age at enrollment, race, educational level, marital status, blue collar employment, occupational exposure to asbestos, intake of vegetables, citrus fruits, and vitamins, and, in analyses of current and former smokers, for age when they started to smoke and number of cigarettes smoked per day.

SETTING

Cancer prevention study II (CPS-II).

PARTICIPANTS

364 239 men and 576 535 women, aged > or = 30 years, who had either never smoked, were former smokers, or were currently smoking a specific brand of cigarette when they were enrolled in the cancer prevention study.

MAIN OUTCOME MEASURE

Death from primary cancer of the lung among participants who had never smoked, former smokers, smokers of very low tar (< or = 7 mg tar/cigarette) filter, low tar (8-14 mg) filter, high tar (> or = 22 mg) non-filter brands and medium tar conventional filter brands (15-21 mg).

RESULTS

Irrespective of the tar level of their current brand, all current smokers had a far greater risk of lung cancer than people who had stopped smoking or had never smoked. Compared with smokers of medium tar (15-21 mg) filter cigarettes, risk was higher among men and women who smoked high tar (> or = 22 mg) non-filter brands (hazard ratio 1.44, 95% confidence interval 1.20 to 1.73, and 1.64, 1.26 to 2.15, respectively). There was no difference in risk among men who smoked brands rated as very low tar (1.17, 0.95 to 1.45) or low tar (1.02, 0.90 to 1.16) compared with those who smoked medium tar brands. The same was seen for women (0.98, 0.80 to 1.21, and 0.95, 0.82 to 1.11, respectively).

CONCLUSION

The increase in lung cancer risk is similar in people who smoke medium tar cigarettes (15-21 mg), low tar cigarettes (8-14 mg), or very low tar cigarettes (< or = 7 mg). Men and women who smoke non-filtered cigarettes with tar ratings > or = 22 mg have an even higher risk of lung cancer.

[Lung cancer and smoking in Asturias, Spain. A case-control study]

OBJECTIVE

Lung cancer in Asturias is 1.4-fold greater than the Spanish average, while the proportion of smokers is similar. The objective of this study was to examine the relationship between lung cancer and smoking in Asturias.

MATERIAL AND METHODS

We performed a hospital-based, incident case control study. The cases were newly diagnosed lung cancer patients and controls were patients from the surgical wards. Information was sought on smoking, occupational exposures, and demographic variables. The analysis was performed by means of odds ratios (OR).

RESULTS

One hundred ninety-seven cases and 196 controls were included in the analysis. The adjusted OR of cigarette smoking was 5.77 (95% CI, 2.96-11.22). The risk increased with the number of cigarettes smoked per day (chi 2 = 56.3), the number of packs/year (chi 2 = 48.4), and the age at which smoking started (chi 2 = 76.5). The OR diminished with the number of years of cessation (chi 2 = 39.9).

CONCLUSIONS

The relationship between smoking and lung cancer in Asturias is similar to that found in other studies carried out in other parts of the western world. The magnitude of the OR may explain the frequency of lung cancer in Asturias. Greater efforts should be devoted to controlling this problem.

Health impact of "reduced yield" cigarettes: a critical assessment of the epidemiological evidence

Cigarettes with lower machine measured "tar" and nicotine yields have been marketed as "safer" than high tar products over the last four decades, but there is conflicting evidence about the impact of these products on the disease burden caused by smoking. This paper critically examines the epidemiological evidence relevant to the health consequences of "reduced yield" cigarettes. Some epidemiological studies have found attenuated risk of lung cancer but not other diseases, among people who smoke "reduced yield" cigarettes compared to smokers of unfiltered, high yield products. These studies probably overestimate the magnitude of any association with lung cancer by over adjusting for the number of cigarettes smoked per day (one aspect of compensatory smoking), and by not fully considering other differences between smokers of "high yield" and "low yield" cigarettes. Selected cohort studies in the USA and UK show that lung cancer risk continued to increase among older smokers from the 1950s to the 1980s, despite the widespread adoption of lower yield cigarettes. The change to filter tip products did not prevent a progressive increase in lung cancer risk among male smokers who began smoking during and after the second world war compared to the first world war era smokers. National trends in vital statistics data show declining lung cancer death rates in young adults, especially males, in many countries, but the extent to which this is attributable to "reduced yield" cigarettes remains unclear. No studies have adequately assessed whether health claims used to market "reduced yield" cigarettes delay cessation among smokers who might otherwise quit, or increase initiation among non-smokers. There is no convincing evidence that past changes in cigarette design have resulted in an important health benefit to either smokers or the whole population. Tobacco control policies should not allow changes in cigarette design to subvert or distract from interventions proven to reduce the prevalence, intensity, and duration of smoking.

Errors and biases in the diagnosis of cancer of the lung and their influence on risk estimates

When diagnosed as primary lung cancer, metastases from the abdomen, plus false negative cases have little effect on epidemiology studies of male smokers, but may result in a severe dilution of the lung cancers among women and nonsmokers. We have attempted to quantitate this handicap for epidemiological studies using two approaches. The relative frequency of diagnosed primary lung and abdominal cancer among males, women, and nonsmokers differs substantially and is used here to calculate magnitude. The second approach postulates that the ratio of nonsmokers among persons with squamous cell lung cancer and primary adenocarcinoma of the lung would be constant by sex if there were no distortion by abdominal metastases. These two approaches indicate that the much higher ratio of metastatic disease diagnosed as primary lung cancer among nonsmoking women (factor of 15 to 20), makes it more difficult to identify an environmental carcinogen among women or nonsmokers than among male smokers in case-control studies.

Intake of specific carotenoids and flavonoids and the risk of lung cancer in women in Barcelona, Spain

Newly available data of a case-control study of lung cancer in women in Spain were analyzed to assess the relationship with the intake of specific carotenoids (alpha-carotene, beta-carotene, lutein, and lycopene) and flavonoids (quercetin, kaempferol, myricetin, and luteolin). The study included 103 cases and 206 hospital controls, matched by age and residence. Usual food intake was estimated through a food-frequency questionnaire. With adjustment for smoking habit and vitamin E, vitamin C, and total flavonoid intake, no association was found for the intake of alpha-carotene, beta-carotene, or lutein. The odds ratio (95% confidence interval) for women in the highest tertile of lycopene intake with respect to the lowest was 0.56 (0.26-1.24), with p for trend = 0.15. A nonsignificant association was observed for the highest vs. lowest tertile intake of kaempferol (odds ratio = 0.51, 95% confidence interval = 0.22-1.17), with p for trend = 0.10, after adjustment for smoking and vitamin E, vitamin C, and total carotenoid intake. No protective effect was observed for quercetin or luteolin or for total flavonoid intake.

What happened to life expectancy in Spain in the 1980s?

BACKGROUND

Life expectancy at birth in Spain improved between 1972 and 1982, by 2.5 years for males and 3.2 years for females. This slowed considerably in the following decade, with increases of only 0.5 and 1.7 years respectively.

OBJECTIVE

To determine the causes of death that have been responsible for the failure by Spain to maintain in the 1980s and 1990s the rate of improvement in life expectancy seen during the 1970s.

DESIGN

Data from WHO mortality tapes grouped in a series of clinically meaningful categories were used to calculate the contribution of each category, in five year age groups, to the changing life expectancy at birth in the two periods.

SETTING

Spain.

RESULTS

The trend in life expectancy at birth in Spain over this 20 year period can be considered to have two components, both with important consequences for public health policy. Underlying trends include a steady negative contribution from respiratory cancer in men and a reduction in cardiovascular disease. More recent trends include a considerable deterioration in deaths among young adults, most notably from accidents and, possibly, AIDS.

CONCLUSION

The failure to maintain the rate of earlier gains in life expectancy in Spain can be attributed largely to a few conditions, although these may indicate less obvious underlying problems. These findings have important consequences for prioritising public health policies.

Vegetable and fruit intake and the risk of lung cancer in women in Barcelona, Spain

A case-control study on women was carried out in Barcelona, Spain, to investigate the relationship of lung cancer with the intake of vegetables, fruits and some foods of animal origin. The study included 103 cases and 206 controls matched by age and residence. Diet intake was assessed by means of a food frequency questionnaire. A reduction in risk, adjusted for smoking habit, was found for the intake of yellow/orange vegetables (mainly carrots) and tomatoes. The odds ratio (OR) and 95% confidence interval (CI) for the highest versus lowest tertile of intake were 0.37 (0.19-0.74) for yellow/orange vegetables and 0.45 (0.22-0.91) for tomatoes; both had a significant inverse trend. A tendency to a reduction in risk of lung cancer with increased intake was observed for all vegetables, leafy green vegetables, dark green vegetables and cruciferous, but these associations did not reach statistical significance. No association with lung cancer was found for the intake of fruits or foods of animal origin rich in retinol. Similar patterns were observed for women who never smoked and when the analysis was restricted to adenocarcinoma.