Does high intake of fruit and vegetables improve lung cancer survival?

The objective of the study was to examine the prognostic effect of dietary intake of fruit and vegetables on lung cancer patients. We used data on 57,053 participants in the Danish prospective cohort study, 'Diet, Cancer and Health'. Patients in whom lung cancer was diagnosed constituted the final study cohort and were followed from the date of diagnosis until the date of death or 11 March 2004. A total of 353 participants had lung cancer. Increasing levels of intake of fruit and vegetables show a tendency toward decreased hazard of dying: the Cox proportional hazard model estimated a hazard ratio (HR) of 0.84 (95% confidence interval [CI], 0.59-1.21) for high intake of vegetables by current smokers and an HR of 0.81 (95% CI, 0.58-1.15) for high intake of fruits with low intake as the reference. In contrast, high intake of potatoes increased the hazard of dying (HR, 1.51; 95% CI, 1.12-2.23). Our study suggests that high intake of fruit and vegetables might have a favourable effect on the prognosis of lung cancer patients, but a high intake of potatoes appears to increase the hazard of dying.

Polymorphisms in genes involved in xenobiotic metabolism and lung cancer risk under the age of 60 years. A pooled study of lung cancer patients in Denmark and Norway.

The genetic susceptibility hypothesis has been used to explain why only a minority of smokers develop lung cancer. Only few studies have studied the role of polymorphisms in phase-I and II metabolizing genes, among young lung cancer patients. We have pooled the individual data of three studies from Denmark and Norway, including 320 patients diagnosed with non-small cell lung cancer at age 59 or below, and 618 age and gender matched controls. A questionnaire was used to determine relevant demographic and lifestyle characteristics, and polymorphisms in following genotypes were determined GSTM1, GSTM3, GSTP1, GSTT1, GPX1, MPO, NQO1 and NAT2. Based on the literature, the alleles of the genotypes were categorised as high- or low-risk alleles. No individual effect of the genotypes was found on the risk of lung cancer. Given a smoking exposure, the presence of high-risk alleles (or phenotypes) was generally found to increase the risk of lung cancer, although the effect modification did not reach statistical significance. A pattern of stronger protective effect was observed in carriers of more than one allele associated with lower risk of lung cancer, and a higher risk of lung cancer in carriers of one or more alleles associated with higher risk of lung cancer, but the results did not reach statistical significance. The effect modification was generally strongest at lower levels of smoking.

Does insufficient adjustment for smoking explain the preventive effects of fruit and vegetables on lung cancer?

Recent reports have raised the question, whether the previously observed protective effects of high intake of fruit and vegetables on the risk of lung cancer were due to insufficient adjustment for smoking leading to residual confounding. Association of intake of fruit and vegetables on lung cancer risk was examined, using the Danish prospective cohort study, "Diet, Cancer and Health". Participants completed a food-frequency and lifestyle questionnaire, and age-standardized incidence rates and rate ratios were estimated for quartiles of dietary exposure. In 1993-2001, 247 out of the 54158 participants were diagnosed with lung cancer. The incidence rate of lung cancer was highest in the lowest quartile of intake of plant food (fruit, vegetables, legumes and potatoes) and the age-standardized rate ratio of lung cancer decreased significantly with increasing intake of plant food to 0.35 (95% CI, 0.27-0.45) but after control for smoking it was attenuated to 0.65 (95% CI, 0.45-0.93). The incidence rate differences of current smokers with high (> or = 400 g per day) and low (< 400 g per day) daily intake of plant food were independent of smoking intensity; assuming a true biological protective effect, 80-90 lung cancer cases per 100000 current smokers could be prevented in our cohort if all smokers had a high intake of plant food. The observed inverse association between high intakes of plant food seems chiefly to be a real protective effect, and not solely due to residual confounding.