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© Oxford University Press 2007.
IN THIS ISSUE
Mammography Use, Hormone Therapy Use, and Breast Cancer IncidenceBreast cancer incidence in the United States had been rising for many years, but it has declined in the last several years. Changes in mammography screening patterns and in the use of hormone therapy during menopause may influence trends in breast cancer incidence. To investigate, Glass et al. (p. 1152) analyzed data from a single large health plan, Kaiser Permanente Northwest, for 1980–2006. Population-level data were used from more than 7,000 women diagnosed with incident invasive breast cancer. Overall breast cancer incidence rose from 1980 to 2001 and then dropped through 2004 before leveling off. Mammography screening rates increased substantially from 1980 to 1993, then leveled off. The percentage of women given menopausal hormone therapy by the Kaiser Permanente pharmacy increased through 2002 then declined dramatically. The authors suggest that the total rise and temporal trends in incidence rates that they observed through the early 1990s are consistent with the increase in mammography screening. The subsequent rise and decline in incidence are consistent with increased use of menopausal hormone therapy until a recent steep decline following release of data from the Women's Health Initiative showing its health risks.
In an editorial, Ravdin and Berry (p. 1139) suggest that the relative timing of the incidence and hormone therapy declines is inconsistent with the hypothesis that menopausal hormone therapy causes breast cancer. Instead, hormone therapy could promote tumor growth, and its withdrawal could slow or stop tumor growth. They note that the availability of individual-level, rather than population-level, data would further improve the understanding of the relationship between menopausal hormone therapy use and breast cancer development.
Technologist Double Reading of Screening Mammograms
Previous studies have suggested that more breast cancers might be detected if screening mammograms were reviewed by mammography technologists (i.e., nonradiologists) as well as by radiologists. Duijm et al. (p. 1162) examined the effects of independent double reading by technologists—in addition to the standard practice of double reading by radiologists—on screening performance in 61,251 screening mammograms. The mammograms were collected at two screening units in The Netherlands and read by both technologists and radiologists. Adding technologists increased the cancer detection rate from 5.27 to 5.63 cancers per 1,000 women screened while only slightly increasing the rate of referral for more imaging, from 1.48% to 1.61%. The authors conclude that an imaging referral strategy that includes readings from technologists in addition to standard readings by radiologists should be considered.
In an editorial, Elmore and Brenner (p. 1141) discuss several factors that limit the generalizability of the results, including variability in the recall rates among international screening programs, differences in the availability of experienced breast imaging radiologists, and discrepancies in the methods used for double reading of breast images.
Cancer Control and a Surgical Learning Curve after Prostatectomy
The idea that surgical outcomes improve with increased surgeon experience has rarely been tested directly using surgical outcome data. Vickers et al. (p. 1171) analyzed the association between a surgeon's prior experience at performing radical prostatectomy and the probability that a patient will be free of biochemical recurrence (as defined by serum prostate-specific antigen level) after prostatectomy. They examined data from 7,765 patients with clinically localized prostate cancer who were treated by one of 72 surgeons at four major U.S. medical centers between 1987 and 2003. The learning curve for prostate cancer recurrence after radical prostatectomy was steep and did not start to plateau until a surgeon had completed approximately 250 operations. The results were essentially the same in patients treated after 1995, when stage migration related to the advent of PSA screening was largely over. The authors conclude that as a surgeon's experience increases, cancer control after radical prostatectomy improves, presumably because of improved surgical technique.
Hormone Levels, Mammographic Density, and Breast Cancer Risk
Mammographic density and circulating sex hormone levels are two confirmed predictors of breast cancer risk, but the relationship between them is unclear. Tamimi et al. (p. 1178) investigated whether these predictors are independently associated with breast cancer risk in a prospective nested case–control study of postmenopausal women in the Nurses’ Health Study. Circulating sex steroid levels and mammographic density appeared to be strongly and independently associated with the risk of breast cancer in postmenopausal women. The authors conclude that mammographic density is independent of circulating sex steroid hormone levels when determining postmenopausal breast cancer risk.
Tumor Endothelium, Regulatory T Cells, and Pancreatic Cancer
Regulatory T (Treg) cells may be involved in preventing the rejection of cancer cells by the host's immune system. The tumor's endothelium may regulate whether these Treg cells infiltrate the tumor tissue. To find out, Nummer et al. (p. 1188) analyzed a xenotransplant mouse model and pancreatic cancer and adjacent nonmalignant pancreatic tissues and blood samples from pancreatic cancer patients. They also measured the expression of Treg homing receptors to determine how Treg cell infiltration is regulated. More Treg cells infiltrated tumors than nonmalignant tissues, and more blood-derived Treg cells than conventional T cells moved through tumor-derived endothelial cells. This infiltration was mediated by homing receptors that were overexpressed on tumor-derived endothelial cells and their ligands on Treg cells. The authors conclude that the expression of ligands to Treg cell homing receptors on the surface of tumor endothelial cells is important for the movement of Treg cells from peripheral blood to tumor tissues.
Fruit and Vegetable Intake and the Risk of Prostate Cancer
Associations between fruit and vegetable intake and a reduced risk of prostate cancer have been reported, but the findings are inconsistent, and clinically relevant data on advanced prostate cancer are limited. Kirsh et al. (p. 1200) investigated this association using data from a long-term prospective trial, the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. The overall risk of prostate cancer was not related to fruit and vegetable intake. However, a decreased risk of extraprostatic cancer was associated with increased intake of cruciferous vegetables, in particular broccoli and cauliflower. The authors conclude that further study is needed to determine whether fruit and vegetable intake is associated with a decreased risk of prostate cancer.
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J Natl Cancer Inst 2007 99: 1162-1170.
J Natl Cancer Inst 2007 99: 1152-1161.
J Natl Cancer Inst 2007 99: 1171-1177.
J Natl Cancer Inst 2007 99: 1178-1187.
J Natl Cancer Inst 2007 99: 1188-1199.
J Natl Cancer Inst 2007 99: 1200-1209.
J Natl Cancer Inst 2007 99: 1141-1143.
J Natl Cancer Inst 2007 99: 1139-1141.
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