老年癌症患者的鳥型分枝桿菌感染可能不需要治療
作者：Daniel M. Keller, PhD
出處：WebMD醫學新聞
November 11, 2009 （賓州費城）－一部分罹患固體器官惡性腫瘤的患者，感染鳥型分枝桿菌（MAC），如果接受治療的話，感染狀況可能變得更嚴重。這些病患經常無法耐受三種藥物合併療程，接著可以成功地接受嚴密追蹤與放射線攝影檢查，且可能在沒有治療感染的情況下存活較長的一段時間。
為了瞭解無法耐受抗分枝桿菌治療或是選擇不接受這些藥物治療的癌症病患，肺部MAC感染的自然史，休士頓德州大學安德森癌症中心的研究者們進行了一項回溯性研究，分析2004年到2009年之間，在他們機構中10位這樣的病患，這些病患都罹患經實驗室確認的MAC感染。
這些病患的平均年齡為70.8歲，其中90%為男性，他們都沒有發燒，且沒有MAC感染的症狀。其中4位病患接受抗腫瘤治療。10位病患有5位選擇不接受MAC的治療，3位病患在3~12週時因為無法耐受而停用標準三重藥物治療，2位病患完成18個月的治療，但細菌培養持續呈現陽性，且放射線攝影結果仍然異常。10位沒有接受MAC治療的病患，後續追蹤平均28個月（範圍從9~57個月）。三重藥物治療包括ethambutol與一項macrolides加上rifampin或moxifloxacin。
在美國感染醫學會第47屆年會上，安德森癌症中心的Coralia Mihu醫師以壁報發表指出，所有病患在沒有抗分枝桿菌治療下，仍然維持只有非常少的症狀或是沒有症狀，雖然這10位病患的肺部病灶部分有臘化或變小的現象，但沒有病患發生需要治療的肺部進展性感染。
Mihu醫師向Medscape感染疾病表示，雖然這些病患有4位接受癌症治療，但這麼做顯然不會讓他們處於MAC感染惡化的高風險中。
即使樣本數目非常有限，她表示她的觀察仍然是很重要的。在現實生活中，有許多病患有MAC感染的問題，而這些絕大多數是老年病患，且同時使用多種藥物。因此，將三種藥物加入他們原有的複雜療程中，在耐受性來說會變得更糟。因為他們的年齡較大、治療時間較長（12~18個月）、有許多並存疾病，包括他們所罹患的癌症，治療有MAC感染的癌症病患可能會變得更加困難。
Mihu醫師建議，因為病患罹患癌症，且可能接受化學治療，並不代表他或是她需要接受MAC治療，特別是如果這些病患沒有症狀的話。如果病患接受健康照護專家的照顧，且時常接受胸腔攝影檢查，嚴密地追蹤感染病程，則這項建議是恰當的。但是，如果病患們確實發生感染惡化的臨床病徵，例如輕度發燒、咳痰，這些在我們的病患身上並未見到，則是值得治療的。
紐約Bronx Montefiore醫學中心的感染疾病主治醫師Paul Riska向Medscape感染疾病表示，某些病患與Mihu醫師研究中的相似，但是那些病患的疾病更加嚴重，且需要治療。他解釋，那些病患有更多的全身症狀，例如發燒、體重降低、血中發炎標記變高。這些病患中許多被推定罹患肺結核（TB），且接受TB治療。我們學到的是，不是每個像TB的疾病就是TB，應該要考慮MAC，因為它經常與TB很相似。
Riska醫師繼續說道，MAC培養也可能遮蓋併存的TB感染。MAC培養速度較快，且在雙重感染下，通常會壓過TB。
這項研究並未接受外在贊助。Mihu醫師與Riska醫師表示已無資金上的往來。
Mycobacterium Avium-Complex Infections in Elderly Cancer Patients May Not Require Treatment
By Daniel M. Keller, PhD
Medscape Medical News
November 11, 2009 (Philadelphia, Pennsylvania) — A subset of patients with solid organ malignancies and pulmonary Mycobacterium avium–complex (MAC) infections might fare worse if the infection is treated. These patients, who are often intolerant of the 3-drug regimen, can be successfully followed with close clinical and radiographic monitoring and may survive for prolonged periods without treatment of the infection.
To characterize the natural history of pulmonary MAC infection in cancer patients who were intolerant of antimycobacterial therapy or elected not to receive it, researchers at the University of Texas M.D. Anderson Cancer Center in Houston did a retrospective review and analysis of the medical records of 10 such patients at their institution between 2004 and 2009. All had laboratory-confirmed MAC infection.
Patients had a median age of 70.8 years, 90% were female, and all were afebrile and asymptomatic for MAC. Four patients were receiving antineoplastic therapy. Five of the 10 patients elected not to receive therapy for MAC, and an additional 3 patients discontinued standard triple-drug therapy at 3 to 12 weeks because of intolerance. Two patients completed 18 months of therapy but had persistent positive cultures and radiographic changes. The 10 patients were followed for a median of 28 months (range, 9 to 57 months) without MAC therapy. Triple-drug therapy consisted of ethambutol and a macrolide plus either rifampin or moxifloxacin.
In a poster presentation here at the Infectious Diseases Society of America 47th Annual Meeting, Coralia Mihu, MD, an assistant professor at M.D. Anderson Cancer Center, reported that all the patients remained minimally symptomatic or asymptomatic without antimycobacterial therapy, although there was some waxing and waning of pulmonary opacities in all 10 patients. None developed progressive infection of the lung that required treatment.
Dr. Mihu told Medscape Infectious Diseases that although 4 of the patients were receiving active chemotherapy for their malignancies, "this did not appear to put them at higher risk for worsening of MAC infection."
Even though the sample size was limited, she noted the importance of her observations. "In real life, there are a lot of patients with MAC infection, and most of these patients tend to be old and to be on polypharmacy," she said. "Therefore, 3 drugs added to their already complicated medication regimen makes things worse in terms of tolerability." Treating cancer patients for MAC might be additionally difficult because of advanced patient age, duration of therapy (12 to 18 months), and comorbidities, including their underlying malignancies.
Dr. Mihu advised that just because a patient has active cancer and might be undergoing chemotherapy does not automatically indicate that he/she needs to be treated for MAC, especially if the patient is asymptomatic. This advice is especially pertinent if a patient is seen by healthcare professionals and receives chest imaging frequently so that the course of the infection can be followed closely. But "it is worth treating in patients who do have clinical signs of worsening infection?.?.?. like low-grade fevers, productive cough, which our patients did not," she said.
Paul Riska, MD, attending physician in infectious disease at Montefiore Medical Center in the Bronx, New York, told Medscape Infectious Diseases that some patients are similar to the ones in Dr. Mihu's study, but others have more aggressive disease and require treatment. "There would be more systemic symptoms, [such as] fever, weight loss, high inflammatory markers in the blood," he explained. "Many of these people are assumed to have TB [tuberculosis] and are treated for TB. The lesson is that not everything that looks like TB is TB, and MAC needs to be considered because it often can mimic TB."
MAC cultures can also mask a concomitant TB infection. "MAC grows faster and sometimes can overwhelm TB in dual infections," Dr. Riska cautioned.
The study did not receive any outside funding. Dr. Mihu and Dr. Riska have disclosed no relevant financial relationships.
Infectious Diseases Society of America (IDSA) 47th Annual Meeting: Abstract 1019. Presented October 31, 2009.
