There are two main types of research studies - qualitative and quantitative. Each type is used to answer different research questions. Dr Col, from Brown Medical School, USA, and colleagues found that all of the qualitative studies on the recurrence of breast cancer in patients taking HRT they looked at have "serious design features that could introduce selection, reporting and/or publication biases".
These qualitative studies have concluded that there is no increased risk of the recurrence of breast cancer in patients taking HRT, but the authors of today's study feel that this is not a reliable conclusion. Meanwhile, evidence from randomized controlled trials - a type of quantitative study - suggests the opposite - that there is an increased risk of the recurrence of breast cancer in patients taking HRT.
Patients and doctors, the authors conclude, should base their decision on randomised controlled trials, as these "provide the only reliable estimates of recurrence risk".
The authors scrutinized 10 studies on the recurrence of breast cancer in a total of 1,316 breast cancer survivors who used HRT and 2,839 who didn't. Out of the ten studies, the eight qualitative studies were positive and suggested that HRT decreases the risk of breast cancer recurrence by 0.64. The two randomised controlled trials found the opposite and concluded that HRT increases the risk of recurrence by 3.41.
The positive studies were all said to have methodological limitations that could not be controlled using statistical methods. For example, they selected healthier women to take HRT and followed them for only a very short time. The authors also speculated that 'publication bias' played a role - this is where researchers and journals are more likely to publish positive results, which suggests that negative results have not been published. Overall, this bias in the reporting of results has propagated the idea of a protective effect of HRT.
Overall, the authors conclude that these qualitative studies "should be considered essentially uninformative with respect to HRT use in breast cancer survivors."
Women who have been treated for breast cancer are usually menopausal, either because of age, the cancer itself or because of therapy. HRT offers the hope of overcoming symptoms of the menopause such as hot flushes, mood swings and increased risk of developing osteoporosis. The link between HRT and breast cancer is controversial. The present study highlights the need for extreme caution and critical judgment when looking at the evidence for or against HRT use in breast cancer survivors.
This press release is based on the article:
Menopausal hormone therapy after breast cancer: a meta-analysis and critical appraisal of the evidence
Nananda F. Col, Jung A Kim, Rowan T. Chlebowski
Breast Cancer Research 2005, 7:R535-R540 (19 May 2005)
This article is available free of charge, according to Breast Cancer Research 's Open Access policy at http://breast-cancer-research.