過敏降低神經膠質細胞瘤風險


  【24drs.com】根據一項收納超過400位神經膠質細胞瘤患者與600位醫院為主控制組患者的分析結果,過敏顯然可以保護免於罹患神經膠質細胞瘤,然而,使用抗組織胺藥物可能不會影響神經膠質細胞瘤風險。
  
  來自芝加哥伊利諾大學的Bridget J. McCarthy博士與同事們在二月號的癌症流行病學、生物標記與預防期刊上報告這些發現。
  
  根據研究人員表示,許多研究指出過敏史與神經膠質細胞瘤風險之間的關係,而抗組織胺類藥物可能透過對過敏的效應影響神經膠質細胞瘤風險,此外,抗組織胺類藥物diphenhydramine hydrochloride被認為與鼠類神經致癌性有關。
  
  在目前這項研究中,總共有419位神經膠質細胞瘤患者(其中344位為高度病例,75位為低度病例),以及612位醫院為主的控制組患者,這些患者沒有神經退化疾病、腦瘤、或任何癌症病史,他們接受電話或網路為主的訪查。
  
  這些問卷著重於過敏型態(例如季節性、藥物性、寵物、食物與其他),以及過敏次數、幾年前的診斷、診斷時的年紀。相較於其他類似研究,這些受訪者被要求只通報經醫療診斷確認過敏的事件。研究人員也收集使用抗組織胺類藥物的資訊,包括種類、時間長短、以及使用次數等等。
  
  相較於控制組患者,罹患神經膠質細胞瘤的患者,有過敏的機率顯著較低(勝算比[OR]為0.60;95%信賴區間[CI]為0.46-0.79)。進一步來看,相較於控制組,高度與低度病例通報過敏的次數也顯著較少(高度患者的OR為0.66;95% CI為0.49-0.87;低度患者的OR為0.44;95% CI為0.25-0.76)。
  
  神經膠質細胞瘤的風險也與不同過敏型式的總數、每一種過敏型式的過敏次數成反比,且都有劑量依賴性關係(趨勢P值小於0.05)。相反的,第一次診斷過敏時的年齡、過敏時間長短並未顯著與神經膠質細胞瘤風險有關。
  
  除此之外,使用抗組織胺類藥物與神經膠質細胞瘤風險成反比,不論使用的時間長短與使用頻率。然而,當患者以過敏史分組時,口服diphenhydramine hydrochloride只有在未經醫療診斷過敏的患者身上才有較低神經膠質細胞瘤風險的顯著關係。
  
  這項研究限制包括可能的回憶及選擇性誤差。舉例來說,相較於控制組患者,認知功能受損可能影響罹患神經膠質細胞瘤患者回憶的能力,罹患神經膠質細胞瘤可能導致他們對於可能成因更加注意。除此之外,受試者大都年紀較輕。另一個可能的限制是,這項研究統計力量不足。
  
  McCarthy與同事們的結論是,其研究結果確認了過敏與較低神經膠質細胞瘤風險之間的關係,且隨著過敏次數增加,風險下降。作者們表示,與異位性疾病有關的高度活化免疫監視系統可能限制了異常細胞生長,且降低那些過敏患者發生神經膠質細胞瘤的風險。然而,因為生物機轉目前仍然未知,我們無法排除這些主要效應可能肇因於環境、或其他在這項研究中沒有測量到且與過敏有關的因子。
  
  他們提到,一項以罹患與未罹患腦瘤患者,使用標準化問題與生物標記,針對過敏與異位性疾病、以及抗組織胺藥物使用的整合性研究,是未來要進一步釐清可能牽涉到腦部腫瘤發展的生物機轉所必需的。
  
  這項研究由國家衛生研究院卓越研究專門計畫經費、美國腦部腫瘤組織贊助。作者們表示沒有相關資金上的往來。

Allergies Reduce Risk for Glioma

By Emma Hitt, PhD
Medscape Medical News

February 7, 2011 — Allergies appear to protect against glioma, whereas antihistamine use may not influence glioma risk, according to an analysis of more than 400 patients with glioma and 600 hospital-based control patients.

Bridget J. McCarthy, PhD, from the University of Illinois at Chicago, and colleagues reported their findings in the February issue of Cancer Epidemiology, Biomarkers & Prevention.

According to the researchers, a number of studies have indicated an inverse association between history of allergies and risk for glioma. Furthermore, antihistamines may influence glioma risk via their effects on allergic conditions, and the antihistamine diphenhydramine hydrochloride has been associated with neurocarcinogenicity in rats.

In the current study, a total of 419 patients with glioma (344 high-grade cases and 75 low-grade cases) and 612 hospital-based control patients, with no history of neurodegenerative disease, brain tumors, or any cancers, were surveyed via telephone or Web-based strategies.

Questions focused on types of allergies (ie, seasonal, medication, pet, food, and other), as well as number of allergies, years since diagnosis, and age at diagnosis. In contrast to other similar studies, participants were asked to report only on allergies that had been medically diagnosed. Information on antihistamine use was also gathered, including type, duration, and frequency of exposure.

Patients with glioma were significantly less likely to report an allergy compared with control patients (odds ratio [OR], 0.60; 95% confidence interval [CI], 0.46 - 0.79). Specifically, high- and low-grade cases reported having significantly fewer allergies than controls (OR, 0.66; 95% CI, 0.49 - 0.87; and OR, 0.44; 95% CI, 0.25 - 0.76, respectively).

The risk for glioma was also inversely associated with the total number of different allergy types and with the number of allergies for each allergy type, both in a dose-dependent manner (P values for trends < .05). In contrast, age at diagnosis of first allergy and duration of allergic condition were not significantly associated with glioma risk.

In addition, antihistamine use was inversely associated with glioma risk, irrespective of its duration and frequency of use. However, when patients were stratified by allergy history, oral diphenhydramine hydrochloride use was significantly associated with a reduced risk for glioma only in patients with no medically diagnosed allergy.

Study limitations include possible recall and selection biases. For example, cognitive impairment may influence ability for those with glioma to recall details, yet having a glioma could lead to more attention to possible causes compared with the recall of control patients. In addition, case participants tended to be younger. Another potential limitation is that the study may have been underpowered.

"Our results confirm the overall association with allergies and the trend of decreased glioma risk with increasing number of allergies," McCarthy and colleagues conclude. The authors suggest that hyperactive immune surveillance related to atopic disease may limit abnormal cell growth and result in reduced glioma risk in those patients with allergies. However, "as the biological mechanism is still unknown, we cannot rule out the possibility that the primary effect is due to environmental or other factors related to allergies that are unmeasured in this study," they add.

"A comprehensive study of all aspects of allergies and atopic disease, as well as antihistamine use, in those with and without brain tumors using standardized questions and biological markers will be essential to further delineate the biological mechanism that may be involved in brain tumor development," they add.

The study was supported by a National Institutes of Health Specialized Programs of Research Excellence grant and by the American Brain Tumor Association. The authors have disclosed no relevant financial relationships.

Cancer Epidemiol Biomarkers Prev. 2011;20:370-378.

    
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