Hormone therapy and lung cancer mortality in women: Systematic review and meta-analysis
Introduction
Lung cancer presents some distinctive differences in both etiology and prognosis between the sexes. Women are more likely to develop adenocarcinoma than men [1]. The incidence of lung cancer in never smokers is significantly higher in women, and women are more susceptible to cigarette exposure in terms of lung cancer incidence [2]. This kind of gender-related difference also exists in lung cancer mortality, which is reflected by the observation that women with lung cancer present significantly better clinical outcomes than their male counterparts. This prognosis advantage retains after a full consideration of stages and histological subtypes [3]. The incidence and prognosis of lung cancer are thus suspected to be sex hormone related. More relevant studies emerged after the verification of the expression of estrogen and progesterone receptors in lung cancer tissue [4], [5].
Hormone therapy (HT) is the primary source of long-term exogenous estrogen and/or progestogen exposure in postmenopausal women. Although many studies have explored the association between HT and lung cancer incidence [6], limited studies explored the possible association between HT use and lung cancer mortality, while existing findings were highly inconsistent [7], [8]. The potential prognostic role of HT in lung cancer mortality remains elusive, given a small number of lung cancer cases in most studies that employed different designs and had some unique features in their study populations. We summarized present evidence to elucidate the association between HT use and mortality in female lung cancer patients by conducting a systematic review and meta-analysis.
Section snippets
Literature search strategy
We conducted a literature search in Pubmed and Embase. We completed all electronic search of the literature on February 22, 2016. The time range of publication search was set between 1985 and 2016. We only included publications written in English. We developed a search strategy which consists of: (1) hormone therapy, hormone replacement therapy, hormone use, menopausal hormone therapy, estrogen or progestogen; (2) lung cancer, lung carcinoma, lung tumor or lung neoplasm; (3) survival, mortality
Results
The literature screening process is shown in Fig. 1. After screening according to the preset inclusion criteria, 11 studies were eligible and included in the final meta-analysis [7], [8], [16], [17], [18], [19], [20], [21], [22], [23], [24]. We did not encounter significant discrepancies in judging eligibility and extracting data.
Discussion
In this systematic review and meta-analysis, we found that the pooled HRs of all included studies, post hoc analyses of RCTs, and cohorts with retrospective survival data were statistically insignificant. We only found a protective role of HT use in lung cancer mortality in prospective cohorts.
Lung cancer presents marked differences in prognosis between the sexes. In addition to established factors (e.g. smoking, occupational exposure, consumption of meat and vegetable/fruits), factors that may
Conflicts of interest and source of funding
This study was not supported by any fund. The authors declare no actual or potential competing financial interests.
Funding source
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
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