喫煙者　乳癌焼けば　次肺癌　　川柳（８）

Ionizing Radiation and Tobacco Use Increases the Risk of a Subsequent Lung Carcinoma in Women With Breast Cancer: Case-Only Design 喫煙する乳癌患者に放射線治療をすると肺癌のリスクが高まる
Michaela Prochazka, Per Hall, Giovanna Gagliardi, Fredrik Granath, Bo N. Nilsson, Peter G. Shields, Meredith Tennis, Kamila Czene 
From the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet; Department of Hospital Physics, Radiumhemmet, and Department of Medicine, Clinical Epidemiology Unit, Karolinska University Hospital; Department of Medical Radiation Physics, Stockholm University, Stockholm, Sweden; and Lombardi Cancer Center, Georgetown University Medical Center, Washington, DC. 

Address reprint requests to Michaela Prochazka, RN, MPH, Department of Epidemiology and Biostatistics, Karolinska Institutet, PO Box 281, SE-171 77, Stockholm, Sweden; e-mail: Michaela.
PURPOSE: To analyze the risk of lung cancer in women treated with radiotherapy for breast cancer. We accessed the lung dose in relation to different radiotherapy techniques, provided the excess relative risk (ERR) estimate for radiation-associated lung cancer, and evaluated the influence of tobacco use. 目的：乳癌に対して放射線治療をした患者の肺癌のリスクを分析すること。いろいろな放射線治療法と肺での被爆量の関係を、肺癌発生と喫煙との影響を含めて解析した。

PATIENTS AND METHODS: The Swedish Cancer Registry was used to identify 182 women diagnosed with breast and subsequent lung cancers in Stockholm County during 1958 to 2000. Radiotherapy was administered to 116 patients. Radiation dose was estimated from the original treatment charts, and information on smoking history was searched for in case records and among relatives. The risk of lung cancer was assessed in a case-only approach, where each woman contributed a pair of lungs. 患者と方法：スエーデンの癌登録で182人の乳癌とのちに肺癌になった患者（1958ー2000年）。放射線量はもとの治療計画から推定し、喫煙歴は病歴と親戚から聴取。肺癌のリスクはそれぞれの患者が左右の肺にどう癌が生じるかという一症例アプローチ法で推定した。

RESULTS: The average mean lung dose to the ipsilateral lung was 17.2 Gy (range, 7.1 to 32.0 Gy). A significantly increased relative risk (RR) of a subsequent ipsilateral lung cancer was observed at 10 years of follow-up (RR = 2.04; 95% CI, 1.24 to 3.36). Squamous cell carcinoma (RR = 4.00; 95% CI, 1.50 to 10.66) was the histopathologic subgroup most closely related to ionizing radiation. The effect of radiotherapy was restricted to smokers only (RR = 3.08; 95% CI, 1.61 to 5.91). The ERR/Gy for women with latency 10 years after exposure was 0.11 (95% CI, 0.02 to 0.44). 結果：同側に肺癌を生じる平均放射線量は17.2Ｇｙ。１０年の追跡で2.04倍のリスク上昇が見られた。組織分類では扁平上皮癌が最も放射線と関連していた(4倍のリスク）。放射線治療の影響は喫煙者のみに限られていた（3.08倍）。ＥＲＲ（過剰リスク）／Ｇｙは10年の遅れをもって0.11倍であった。

CONCLUSION: Radiotherapy for breast cancer significantly increases the risk of lung carcinoma more than 10 years after exposure in women who smoked at time of breast cancer.結果：乳癌への放射線治療は、肺癌治療時に喫煙していた女性では１０年以上のちでの肺癌のリスクを高める。 

Authors' disclosures of potential conflicts of interest are found at the end of this article.