Discovering lung abnormalities after surviving breast cancer can bring about feelings of anxiety and uncertainty. It is natural to feel overwhelmed when faced with new health concerns, especially after navigating a previous cancer journey. This article aims to provide clear information about why a lung diagnosis might occur after breast cancer and what it means for your health.
Differentiating Metastatic Breast Cancer from Primary Lung Cancer
When a lung mass is discovered in someone with a history of breast cancer, doctors first determine if it is metastatic breast cancer or a new primary lung cancer. Metastatic breast cancer in the lung means that cells from the original breast tumor have traveled to and grown in the lung. These cells are still breast cancer cells, not lung cells, and the condition is treated as advanced breast cancer. Think of it as the original plant spreading its seeds to a new part of the garden, but the new growth is still the same type of plant.
Conversely, primary lung cancer is a distinct, new cancer that originates directly in the lung tissue. The cells in a primary lung cancer are abnormal lung cells, unrelated to any previous breast cancer. Differentiating between these two possibilities is an important step because their treatments differ significantly. Pathologists use specialized tests to analyze tissue samples to pinpoint the exact origin of the cancer cells.
Causes and Risk Factors
Several factors can contribute to a lung cancer diagnosis following breast cancer, ranging from treatment effects to shared genetic predispositions. Previous radiation therapy for breast cancer can slightly increase the long-term risk of developing a new primary lung cancer in the irradiated lung. This increased risk typically becomes more noticeable 10 to 15 years or more after the radiation treatment.
Certain chemotherapy drugs used in breast cancer treatment may also contribute to the risk of a subsequent primary lung cancer. Patients who received chemotherapy for breast cancer had a higher risk of developing a new primary lung cancer compared to those who received radiation or endocrine therapies.
Beyond treatment, shared risk factors also play a role. Smoking is the most significant risk factor for primary lung cancer, and this risk is amplified in individuals with a history of breast cancer. Some genetic mutations, such as specific variants in the BRCA2 gene, have been linked to an elevated risk of squamous cell lung cancer.
The Diagnostic Process
Determining whether a lung abnormality is metastatic breast cancer or a new primary lung cancer involves a diagnostic process. It begins with imaging tests, such as computed tomography (CT) scans or positron emission tomography (PET) scans, which can identify suspicious nodules or masses in the lungs. These scans help oncologists visualize the location and characteristics of the lung lesion. However, imaging alone cannot definitively distinguish between the two types of cancer.
The most conclusive step is a biopsy, where a small tissue sample is taken from the lung lesion. This sample is then sent to a pathology laboratory for microscopic examination. Pathologists use specialized immunohistochemical (IHC) stains, which are laboratory tests that react with specific proteins within the cells, to determine the cancer’s origin.
By observing which specific markers are present, pathologists can accurately identify whether the cells originated from the breast or the lung, providing a clear diagnosis that guides subsequent treatment decisions.
Treatment Implications
The specific diagnosis—whether metastatic breast cancer or primary lung cancer—significantly influences the treatment approach. When breast cancer has spread to the lungs, it is still treated as breast cancer. Systemic treatments are generally the main strategy for metastatic breast cancer in the lungs. These include hormone therapy for hormone receptor-positive tumors, which aims to block the hormones that fuel cancer growth.
Chemotherapy is another systemic option, often tailored based on the patient’s previous treatment history and the specific characteristics of the breast cancer. For HER2-positive breast cancers, targeted therapies are employed to specifically block the HER2 protein that drives cancer cell growth. In select cases, if there are only a few, localized lung lesions, stereotactic body radiation therapy (SABR) or surgery may be considered to manage symptoms or reduce the tumor burden, though these are typically complementary to systemic therapy.
If the diagnosis is a new primary lung cancer, it is treated as an entirely separate malignancy. Treatment plans are determined by its specific type (e.g., non-small cell lung cancer, small cell lung cancer), stage, and molecular characteristics. Options include surgery, radiation therapy, or chemotherapy. Many primary lung cancers are also treated with targeted therapies that block specific genetic mutations, or with immunotherapy, which harnesses the body’s immune system to fight cancer. The medical team considers the patient’s breast cancer history and treatments when devising the most appropriate plan for the new lung cancer diagnosis.