Do small lung adenocarcinomas need subclassifying?




CHICAGO– Five-year survival rates are nearly identical for small lung carcinomas classified as adenocarcinoma in situ or minimally invasive adenocarcinoma, a systematic review shows.

At 5 years, disease-free survival was 97% for patients with lung adenocarcinoma in situ (AIS) and 96.7% in those with minimally invasive adenocarcinoma (MIA) (P = .34).

Overall survival rates were 97.5% and 96% (P = .58).

“Our findings raise questions regarding the necessity of classifying these types of tumors into two separate categories when it may not provide any additional prognostic information,” lead author Madhusmita Behera, Ph.D., said during a briefing at the 2014 Chicago Multidisciplinary Symposium in Thoracic Oncology.

The review included 18 clinical studies involving 863 patients with tumors 3 cm or less in size that were classified as AIS (no tumor invasion) or MIA (≤ 0.5 cm foci of invasion), according to the 2011 International Association for the Study of Lung Cancer (IASLC)/American Thoracic Society (ATS)/European Respiratory Society (ERS) international lung adenocarcinoma classification (J. Thor. Oncol. 2011;6:244-85).

Part of the rationale for separating AIS and MIS was that it was believed patients with minimal invasion would have worse prognosis, Dr. Behera, a researcher at the Winship Cancer Institute of Emory University, Atlanta, explained.

Instead, “Patients who have minimal invasion have equally great survival outcomes as those with adenocarcinoma in situ,” she said. “That’s the message we wanted to give out, that patients have excellent outcomes regardless of what category they belong to.”

The studies were published between 2011 and 2014 and included 451 AIS patients and 344 MIA patients. One study reported survival data on 68 patients with AIS and MIA grouped together.

All patients underwent surgical resection. There was no evidence that patients with MIA tumors received more treatment, Dr. Behera said.

Press briefing moderator Dr. Laurie E. Gaspar, professor and chair of radiation oncology at the University of Colorado, Denver, said oncologists usually think of invasive cancers as being more serious than adenocarcinoma in situ and possibly needing more intensive treatment. The outcomes in both groups, however, were excellent and treatment, usually surgical resection, should be the same in both groups.

Dr. Gaspar went on to say that too often the public and physicians think of lung cancer as a male gender cancer occurring in current or former smokers, but that Dr. Behera’s study reminds us that lung cancer is increasingly common in nonsmokers and women.

Of the 863 patients, 61% were female and 43% were smokers. The median age was 67.5 years and median tumor size 1.3 cm.

For the whole population, the 5-year disease-free survival rate was 97.7% and overall survival rate 97.3%.

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