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© Oxford University Press 2007.
IN THIS ISSUE
Lymph Node Evaluation, Colon Cancer Surgery, and SurvivalThe number of lymph nodes evaluated during surgery appears to be inadequate in most patients treated for colon cancer. The number of nodes examined may be a measure of quality for colon cancer care. To investigate the association between lymph node evaluation and survival among colon cancer patients, Chang et al. (p. 433) performed a systematic review of 17 studies that included more than 60,000 patients. An increased number of lymph nodes evaluated was associated with improved survival among patients with stage II and stage III colon cancer. The authors conclude that the number of lymph nodes should be considered as a measure of the quality of colon cancer care.
In an accompanying editorial, Ricciardi and Baxter (p. 414) note that simple solutions to improve the quality of care are attractive to policy makers and health care payers. However, unless these solutions are based on sound evidence, they are not likely to improve patient outcomes. Worse, they may divert both attention and resources away from more effective strategies.
Surgery versus Radiotherapy for Late-Stage NSCLC Patients
The survival rate of patients with stage IIIA-N2 non–small-cell lung cancer (NSCLC) who undergo chemotherapy before surgical resection is higher than that of patients treated with surgery alone. Van Meerbeeck et al. (p. 442) performed a randomized controlled trial of 579 patients to determine whether patients who respond to initial chemotherapy would have a better outcome after subsequent surgery or thoracic radiotherapy. The median and overall survival times were similar in both groups of patients, as were rates of progression-free survival. However, the authors conclude that radiotherapy is the preferred treatment due to its lower morbidity and mortality rates among patients who respond to initial chemotherapy.
In an editorial, Johnson et al. (p. 415) describe the procedures currently used to detect stage IIIA-N2 NSCLC and treatment options. They write that the results of this study reinforce the importance of patient selection to treatment decisions.
Dietary Fat and Postmenopausal Invasive Breast Cancer
Although environmental and animal studies support a direct effect of dietary fat on breast cancer development, epidemiologic studies have been inconclusive. Thiébaut et al. (p. 451) prospectively examined the association between fat intake and the incidence of invasive breast cancer among 188,736 postmenopausal U.S. women who completed a food-frequency questionnaire in 1995–1996. A doubling of reported fat intake—from 20% to 40% of energy from total fat—was associated with a 15% greater risk of breast cancer. The excess risk increased to 32% after correction for dietary measurement error. Positive associations were also identified for several fat subtypes. Associations between intake of some fat types and breast cancer risk were restricted to women who were not using menopausal hormone therapy. The authors conclude that dietary fat was associated with the risk of postmenopausal invasive breast cancer in this group.
In an editorial, Smith-Warner and Stampfer (p. 418) review previous evidence for the association between fat intake and breast cancer risk. Given the modest size of the reported associations, interventions to control the amount of body fat are likely to have a greater impact on breast cancer incidence than interventions aimed at reducing fat intake.
Progression-Free Survival and Interval Censoring
Many cancer trials, especially phase II trials, use progression-free survival (PFS) as an endpoint. This outcome is available earlier than overall survival and is not affected by second-line treatment. However, measuring disease progression is not as straightforward as measuring survival. First, progression may be defined differently by different investigators. Moreover, it is often not known exactly when progression occurred. Panageas et al. (p. 428) note that a true progression event that occurs between two scheduled assessments results in data that are interval censored; however, the event is typically recorded as having occurred on the date of the second assessment. they show how the timing of the assessment schedule may affect the estimation of PFS. Interval censoring leads to biased estimation of median PFS, with the degree of bias depending on the timing of the assessment interval relative to the true median. The authors note that comparing median PFS times between two studies with different assessment intervals can lead to erroneous conclusions, and they suggest that investigators use appropriate statistical methods to analyze interval-censored data.
DNA Mismatch Repair and Colorectal Cancer Risk
To investigate whether changes in DNA mismatch repair genes are associated with colorectal cancer risk, Raptis et al. (p. 463) genotyped patients with colorectal cancer and control subjects from Ontario and Newfoundland for selected polymorphisms in the mismatch repair genes MLH1 and MSH2. The polymorphism –93G>A in the MLH1 gene was strongly associated with colorectal tumors with high microsatellite instability in both patient populations. Homozygosity for this allele was associated with a higher risk of colorectal cancer than was heterozygosity. The authors conclude that the MLH1 –93G>A polymorphism is associated with an increased risk of colorectal cancer in these patient populations.
Lignan Intake and Risk of Postmenopausal Breast Cancer
High consumption of soy-based foods rich in isoflavone phytoestrogens is associated with a reduced risk of breast cancer in Asian populations. However, the potential associations between other dietary phytoestrogens, that is, lignans, and breast cancer risk are unclear, particularly among women with the lower soy consumption levels typical of Western diets. Touillaud et al. (p. 475) prospectively examined associations between the risk of postmenopausal invasive breast cancer and consumption of four plant lignans among 58,049 postmenopausal French women who completed a diet history questionnaire and who were not taking soy isoflavone supplements. Women with the highest intakes of total lignans or of the lignan lariciresinol had a reduced risk of breast cancer compared with women with the lowest intakes. The inverse associations were limited to ER- and PR-positive disease.
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J Natl Cancer Inst 2007 99: 414-415.
J Natl Cancer Inst 2007 99: 415-418.
J Natl Cancer Inst 2007 99: 418-419.
J Natl Cancer Inst 2007 99: 428-432.
J Natl Cancer Inst 2007 99: 433-441.
J Natl Cancer Inst 2007 99: 442-450.
J Natl Cancer Inst 2007 99: 451-462.
J Natl Cancer Inst 2007 99: 463-474.
J Natl Cancer Inst 2007 99: 475-486.
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