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Lung Cancer in Nonsmoking Individuals: A Review

Author/s: 
Cian Murphy, Tej Pandya, Charles Swanton

Importance: Lung cancer in nonsmoking individuals (defined as people who have smoked fewer than 100 cigarettes in their lifetime) accounts for 15% to 20% of all lung cancer cases worldwide. In the US, the annual incidence of lung cancer in nonsmoking individuals is 14.4 to 20.8 per 100 000 person-years in females and 4.8 to 12.7 per 100 000 person-years in males.

Observations: Most lung cancers in nonsmoking individuals are histologically adenocarcinomas (60%-80%) with the remainder being squamous or adenosquamous (10%-20%) and rarely small cell lung cancer (<10%). Risk factors include exposure to passive smoking, radon exposure, air pollution, asbestos, and history of lung cancer in a first-degree family member. Therapeutically targetable genomic variants, such as EGFR mutations or ALK gene rearrangements, are more common in tumors from nonsmoking individuals compared with those with a smoking history (defined as people who currently or formerly smoked) (43% vs 11% for EGFR and 12% vs 2% for ALK). In contrast, tumor mutation burden, the number of somatic mutations in a tumor cell, is lower in lung cancer among nonsmoking individuals (0-3 mutations/megabase [Mb] vs 0-30 mutations/Mb). Similar to individuals with a history of smoking, nonsmoking individuals with lung cancer may present with wheeze, chest pain, dyspnea, hemoptysis, or symptoms attributable to metastatic disease (eg, bone pain and headache) or be diagnosed with incidentally detected disease. The US Preventive Services Task Force does not currently recommend lung cancer screening with low-dose computed tomographic scans for nonsmoking individuals, although screening guidelines vary globally. Treatment typically involves a combination of surgery, radiotherapy, and systemic therapies depending on stage, performance status, and molecular features of the tumor. Comprehensive next-generation sequencing should be performed on stage Ib to IIIa lung cancer tumor tissue from nonsmoking individuals because actionable genomic alterations, such as EGFR mutations or ALK gene rearrangements, are treated with targeted therapy such as the tyrosine kinase inhibitors osimertinib or lorlatinib, respectively. Median survival among nonsmoking individuals with advanced non-small cell lung cancer (stage IIIb or higher) and actionable genomic alterations can exceed 3 to 5 years, while survival without these genomic alterations is similar to lung cancer in people with a history of smoking (1-2 years).

Conclusions: Lung cancer in nonsmoking individuals accounts for 15% to 20% of lung cancer cases worldwide. Among patients with lung cancer, nonsmoking individuals are more likely to have genomic alterations such as EGFR mutations or ALK gene rearrangements, and these patients have improved survival when treated with tyrosine kinase inhibitors compared with chemotherapy.

Keywords 
adenocarcinoma Carcinoma Squamous Cell tobacco Smokers smoking Early Detection of Cancer

Long QT Syndrome

Author/s: 
Peter J. Schwartz, Lia Crotti

To assess a physician’s expertise on the basis of whether the doctor checks a patient’s QT interval would be excessive, but the fact remains that in many cases, checking it saves lives. The author of a respected textbook on electrocardiography1 wrote, “The measurement of the QT interval has little usefulness” in 1957 — the same year in which Jervell and Lange-Nielsen published their first report on the association between QT-interval prolongation and sudden death in a family with congenital deafness,2 which was soon followed by similar findings reported by Romano and colleagues3 and by Ward4 in patients with normal hearing. In 1975, Romano–Ward syndrome and Jervell–Lange-Nielsen syndrome were grouped under the name long QT syndrome.5
Long QT syndrome is an uncommon disease of genetic origin with a documented prevalence of 1 in 2000 live births6; however, the actual prevalence is probably higher because the original prospective study, which involved 44,000 infants,6 did not include genotype-positive–phenotype-negative persons. The syndrome is characterized by prolongation of the QT interval on an electrocardiogram (ECG) obtained when the patient was at rest and by a propensity for life-threatening arrhythmias that occur mostly under conditions of physical or emotional stress.5,7 The clinical importance of the timely diagnosis of the syndrome stems from the fact that sudden cardiac death is often the first symptom, which makes remedying diagnostic or therapeutic errors impossible. As stated 50 years ago,5 given the high efficacy of current therapies, the existence of patients with undiagnosed — and therefore untreated — long QT syndrome is nowadays inexcusable; unfortunately, missed diagnosis is still too often the case.

Keywords 
Long QT Syndrome Adrenergic beta-Antagonists DNA Mutation Mutation Genetic Therapy

Risk Assessment, Genetic Counseling, and Genetic Testing for BRCA-Related Cancer: US Preventive Services Task Force Recommendation Statement.

Author/s: 
US Preventive Services Task Force

IMPORTANCE:

Potentially harmful mutations of the breast cancer susceptibility 1 and 2 genes (BRCA1/2) are associated with increased riskfor breast, ovarian, fallopian tube, and peritoneal cancer. For women in the United States, breast cancer is the most common cancer after nonmelanoma skin cancer and the second leading cause of cancer death. In the general population, BRCA1/2 mutations occur in an estimated 1 in 300 to 500 women and account for 5% to 10% of breast cancer cases and 15% of ovarian cancer cases.

OBJECTIVE:

To update the 2013 US Preventive Services Task Force (USPSTF) recommendation on risk assessment, genetic counseling, and genetic testing for BRCA-related cancer.

EVIDENCE REVIEW:

The USPSTF reviewed the evidence on risk assessment, genetic counseling, and genetic testing for potentially harmful BRCA1/2 mutations in asymptomatic women who have never been diagnosed with BRCA-related cancer, as well as those with a previous diagnosis of breast, ovarian, tubal, or peritoneal cancer who have completed treatment and are considered cancer free. In addition, the USPSTF reviewed interventions to reduce the risk for breast, ovarian, tubal, or peritoneal cancer in women with potentially harmful BRCA1/2 mutations, including intensive cancer screening, medications, and risk-reducing surgery.

FINDINGS:

For women whose family or personal history is associated with an increased risk for harmful mutations in the BRCA1/2 genes, or who have an ancestry associated with BRCA1/2 gene mutations, there is adequate evidence that the benefits of risk assessment, genetic counseling, genetic testing, and interventions are moderate. For women whose personal or family history or ancestry is not associated with an increased risk for harmful mutations in the BRCA1/2 genes, there is adequate evidence that the benefits of risk assessment, genetic counseling, genetic testing, and interventions are small to none. Regardless of family or personal history, the USPSTF found adequate evidence that the overall harms of risk assessment, genetic counseling, genetic testing, and interventions are small to moderate.

CONCLUSIONS AND RECOMMENDATION:

The USPSTF recommends that primary care clinicians assess women with a personal or family history of breast, ovarian, tubal, or peritoneal cancer or who have an ancestry associated with BRCA1/2 gene mutations with an appropriate brief familial risk assessment tool. Women with a positive result on the risk assessment tool should receive genetic counseling and, if indicated after counseling, genetic testing. (B recommendation) The USPSTF recommends against routine risk assessment, genetic counseling, or genetic testing for women whose personal or family history or ancestry is not associated with potentially harmful BRCA1/2 gene mutations. (D recommendation).

Keywords 
breast cancer genetics risk ovarian cancer
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