Bronchioloalveolar carcinoma, or BAC, is a unique subtype of non-small cell lung cancer (NSCLC) that has unique features in terms of the demographics of who gets it, how it appears on scans, how it often behaves, and potentially in how it responds to treatment. It is a subset of lung cancer for which most of what we know emerged in the last 10 years, with our understanding of this entity, and even the definition of BAC, still evolving.
What is BAC?
BAC was first identified and defined as a separate subtype of lung cancer by Dr. Averill Liebow in 1960. At that time, he highlighted it as a form of well differentiated adenocarcinoma of the lung that appeared to not be able to invade the surrounding lung scaffolding and spread within the lung(s), presumably aerogenously and/or through lymphatic channels.
This is the first part of a case presentation I did with two great colleagues: Dr. Anne Tsao, who is a medical oncologist and lung cancer expert at MD Anderson Cancer Center in Houston, and Dr. Alex Farivar, who is a terrific thoracic surgeon at my own institution, Swedish Cancer Institute in Seattle.
This case is an elderly gentleman who has a very indolent but growing lung lesion. His story brings up questions of how concerned to be in following a nodule in a patient of advanced age and with competing medical issues, whether surgery that is less than a lobectomy might be considered, as well as the systemic therapy options for bronchioloalveolar carcinoma.
Here are the audio and video versions of the podcast, along with the transcript and figures.
This is a continuation of my discussion with Dr. Matthew Horton, a pathologist with a special training and a great expertise in lung pathology who works here in Seattle at a company called CellNetix.
This portion of our discussion covers the spectrum of neuroendocrine lung tumors, ranging from carcinoids to small cell lung cancer and large cell neuroendocrine carcinomas; we then turn to a discussion of bronchioloalveolar carcinoma (BAC), including everything from a little history to a look forward at a new interpretation of BAC. Below you’ll find the audio and video versions of our discussion (the video with a few images of what we’re talking about), and the associated transcript and figures.
The most expert lung cancer pathologists in the world are planning a revision of the classification of lung adenocarcinomas that is expected to be approved and implemented next year, and it’s going to make some big changes. Specifically, it’s planning to eliminate the diagnosis of bronchioloalveolar carcinoma (BAC), reflecting our evolving understanding of this disease.
BAC with lesions less than 2 cm is now being designated as a pre-cancerous adenocarcinoma in situ (AIS), which essentially means it’s a pre-invasive condition with a favorable prognosis. In fact, the available literature, largely from Japan but also including evidence from other parts of the world, shows a 100% 5-year survival for a <2 cm AIS, which is far more commonly the non-mucinous BAC sybtype. The size limit is significant, however, because larger lesions are felt far more likely to have at least some area of invasive disease.
The invasive portion of what is now in the spectrum of BAC with focal invasion to adenocarcinoma with BAC features has a major impact on prognosis. In fact, the size of that invasive component is what drives prognosis, not the invasive part:
So a largely pre-invasive (adenocarcinoma in situ) lesion with a small area of invasiveness will now be designated as minimally invasive adenocarcinoma, and it also has a 100% cancer-specific survival at 5 years.