Abstract

OBJECTIVES:

• To review all prospective studies which provided data about total fruits or vegetables, their subgroups, and specific types of vegetables and fruits, in relationship with esophageal cancer risk, disease progression and mortality/survival.
• To define the amount of consumption found to be related with the described effects on cancer.
• To define possible effect modification by confounders.

DATA SOURCE: The Pubmed database was searched (No start date - Sep 11, 2009) for relevant articles using the keywords "cancer, neoplasm, or neoplasms" combined with "vegetables, vegetable, fruit, or fruits" and a fair amount of other keywords. The exact search term is described in the methods.
Prospective studies published in the English language were included. Reference lists were searched for additional articles.
RESULTS: 12 articles were found which provided information about 10 different cohorts.
Of these, 0 articles were excluded.
Results are described when any evidence for an association - as defined in the Methods - was found. In addition, data about total vegetables or fruits is described.

• Total disease risk.
  -Data about total vegetables was provided by 5 cohorts, including a total of 2,865 cases. No evidence was found for an association between total vegetables and esophageal cancer risk.
  -Data about total fruits was provided by 5 cohorts, including a total of 2,865 cases. Total fruit possibly protects against esophageal cancer risk. No level of consumption could be defined for this effect. The effect may be restricted to Asian populations.
  -Data about green (leafy) vegetables was provided by 3 cohorts, including a total of 507 cases. Suggestive evidence was found for a protective effect of green (leafy) vegetables against esophageal cancer risk. No level of consumption could be defined for this effect.
• Advanced stage/metastatic disease risk or disease progression.
  No data was found.
• Mortality risk.
  -No data was found about the relation between total vegetables and esophageal cancer death.
  -Data about total fruits was provided by 1 cohort, including 80 cases. No evidence was found for an association between total fruits and esophageal cancer death.

CONCLUSION: Total fruit possibly protects against esophageal cancer risk, and this effect may be restricted to Asian populations. Suggestive evidence was found for a protective effect of green (leafy) vegetables. No level of consumption could be defined for these associations, because few articles presented risks in grams, servings, or cups. No evidence was found for an association with any specific vegetable or fruit item. In addition, little data is available about disease progression or mortality end points.

Total vegetables and esophageal cancer.

Esophageal cancer risk: Data about the relation with total vegetables was provided by 5 cohorts, including a total of 2,865 cases. Two articles about The EPIC Study were found, and since the articles published data about different histologic types of cancer, they were both included.
A nonsignificant trend of a protective effect was found in one cohort (8). No (non)significant associations were found in any other cohort.

Inclusion of intermediate levels of consumption:
Data about results published in grams, servings, or cups was restricted to findings from 2 cohorts. A significantly increased risk among women was found at the level of consumption of 320-440 g/day in one cohort (George SM). No other (non)significant effects were found in any cohort at any level of consumption.

Esophageal cancer mortality: No data was found.

Conclusion: A nonsignificant trend of a protective effect was found in one cohort, but no other (non)significant associations were found with esophageal cancer risk. No data was found about cancer mortality. No evidence was found for an association between total vegetables and esophageal cancer risk.

Total fruit and esophageal cancer.

Esophageal cancer risk: Data about the relation with total fruit was provided by 5 cohorts, including a total of 2,865 cases. Two articles about The EPIC Study were found, and since the articles published data about different histologic types of cancer, they were both included.
Significant protective effects were found in 2 cohorts, including 2,059 cases (2, 9). In addition, nonsignificant trends of a protective effect were found in 1 cohort (9), and in one cohort among men only (7), including another 579 cases.

Inclusion of intermediate levels of consumption:
Data about results published in grams, servings, or cups was restricted to findings from 2 cohorts. Though nonsignificant trends were found in both cohorts among men, no (non)significant effects were related to any level of consumption.

Effect modification: (Non)significant protective associations were found in all 3 Asian cohorts (2, 8, 9), but protective effects among the Western cohorts (5, 7) were restricted to a nonsignificant trend of a protective effect in only one of these cohorts, among men only.

Esophageal cancer mortality: Data about the relation with total fruit was provided by 1 cohort, including 80 cases (4). A nonsignificant trend of a protective effect was found.

Conclusion: Significant protective effects of total fruit against esophageal cancer risk were found in 2 cohorts of moderate size, including 72% of all cases. In addition, nonsignificant protective associations were found in 2 other cohorts, including another 20% of all cases. Total fruit possibly protects against esophageal cancer risk. No level of consumption could be defined for this effect. The effect may be restricted to Asian populations. Data about cancer mortality was restricted to findings from one cohort. No evidence was found for an association between total fruits and esophageal cancer mortality.