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Tracking and Treating Metastatic Breast Cancer: Simplifying Complex Medicine

With the diversification of treatment options and advancements in drug response, the treatment outcomes for breast cancer patients have significantly improved. Even those with metastatic breast cancer can delay disease progression and extend their actual survival time. Hello everyone! I am a radiologist on the AHI team, and today I will take on the role of an AHI editor, focusing on women's health topics, particularly breast health. I will discuss the treatment, tracking, and assessment of treatment efficacy after breast cancer metastasis.

What is "Metastatic Breast Cancer"?

Breast cancer staging is based on clinical imaging or pathological findings, distinguishing stages zero to four according to tumor size, lymph node involvement, and the presence of distant organ metastasis. Once cancer cells spread to distant organs, such as the bones, liver, or lungs, it is classified as metastatic breast cancer, which is stage four breast cancer. Metastatic breast cancer may develop after a period of recurrence following curative treatment or may be discovered at the time of initial diagnosis with concurrent distant organ metastasis.

Treatment Options After Breast Cancer Metastasis

For patients with metastatic breast cancer, systemic treatment is the preferred option. Systemic therapy fights cancer cells throughout the body and effectively controls disease progression. In contrast, surgery alone can only target local tumors and cannot prevent or treat distant metastases. These methods include:

Chemotherapy: Medications are used to kill cancer cells. Although chemotherapy drugs may have some side effects, they are very effective in controlling cancer.
Endocrine Therapy: If the cancer is hormone receptor-positive, endocrine therapy is chosen. This method inhibits cancer cell growth by blocking hormone actions.
Targeted Therapy: New medications target specific molecules in cancer cells, resulting in fewer side effects and significant effectiveness.

Tracking Metastatic Breast Cancer—Imaging Exams

Tracking after metastasis is critical, as it determines whether treatment plans need to be adjusted. After systemic treatment, we can monitor the metastatic lesions of breast cancer through imaging examinations. Common methods include MRI (Magnetic Resonance Imaging), CT (Computed Tomography), and PET (Positron Emission Tomography). These exams provide detailed information about the location and size changes of tumors.

>> RECIST Criteria for Solid Tumor Efficacy Evaluation

Through imaging examinations, we can visually measure changes in tumor size to assess treatment effectiveness. There is an internationally recognized efficacy evaluation standard known as RECIST (Response Evaluation Criteria in Solid Tumors), which assesses tumor response to treatment. In simple terms, RECIST helps doctors evaluate whether tumors have shrunk or grown.

>> Interpretation Mechanism of RECIST

RECIST determines treatment effectiveness by measuring changes in tumor size. The main criteria include:

Complete Response (CR): All target lesions have completely disappeared, with no new lesions.
Partial Response (PR): The total diameter of target lesions has decreased by at least 30%, with no new lesions.
Progressive Disease (PD): The total diameter of target lesions has increased by at least 20% or one or more new lesions have appeared.
Stable Disease (SD): The changes in target lesions do not meet the criteria for PR or PD, meaning the tumor size changes are minimal.

What is the Total Diameter of Target Lesions?

Target lesions refer to specific tumor sites selected for assessing treatment effectiveness during imaging examinations. The total diameter of target lesions is the sum of the maximum diameters of these lesions. For example, if three tumor sites are chosen as target lesions with maximum diameters of 3 cm, 2 cm, and 1 cm, the total diameter of the target lesions would be 6 cm.

RECIST and iRECIST

The most commonly used version is RECIST 1.1, released in 2009, which added assessment criteria for lymph nodes; it reduced the number of target lesions from a maximum of 10 to 5 and detailed the requirements for imaging examinations. As immunotherapy is applied in cancer treatment, traditional RECIST criteria may sometimes fail to accurately assess the efficacy of immunotherapy. iRECIST (immune RECIST) was introduced in 2017, considering a phenomenon known as "pseudoprogression," where tumors temporarily enlarge before shrinking. This does not signify disease progression but is part of the immune response. iRECIST aims to distinguish between "true progression" and "pseudoprogression," thus avoiding the premature termination of treatment in patients who are responding well.

Immunotherapy

Immunotherapy is a treatment method that harnesses the body’s immune system to fight cancer. The immune system is designed to protect the body from infections and diseases, but it sometimes fails to recognize and attack cancer cells. Immunotherapy enhances or modifies immune function, enabling it to more effectively detect and destroy cancer cells.

However, immunotherapy is not effective for all patients, and its side effects need to be managed carefully. Therefore, treatment plans often need to be personalized based on the patient’s specific condition and cancer type. Patients should discuss potential risks and benefits in detail with their medical teams before starting any new therapies.

Case Analysis

Let’s better understand RECIST and iRECIST through a case study. Suppose a breast cancer patient underwent imaging examinations before and after chemotherapy. In the initial exam, the physician found that her total diameter of target lesions was 10 cm. After three months of treatment, the second exam showed the total diameter of target lesions reduced to 7 cm. According to RECIST criteria, this patient achieved partial response (PR) because her tumor shrank by 30%.

If this patient received immunotherapy, we would need to use iRECIST for evaluation. During the initial imaging examination, the tumor may appear temporarily enlarged. If we were still using RECIST 1.1, we might incorrectly assess the condition as progressive disease (PD) and stop treatment. Using iRECIST, after a period of observation, if the tumor begins to shrink, this represents pseudoprogression during immunotherapy. Through iRECIST assessment, this patient can ultimately complete the entire treatment course.

Conclusion

The severity of metastatic breast cancer varies, and the treatment options are complex, with different physical states among patients. Current experts still recommend systemic drug therapy as the primary approach. Through a comprehensive multidisciplinary oncology team, patient treatment responses can be reviewed, and a suitable treatment strategy can be developed. We hope that with the advancement of treatment technologies, humanity will ultimately overcome the challenges posed by cancer.

AHI is an organization focused on enhancing healthcare quality through advanced technology. We are committed to improving patients' health through precise diagnosis and personalized treatment. If you have any questions about breast health, feel free to consult us.

Through this article, we hope to provide you with a deeper understanding of RECIST and the tracking and treatment of metastatic breast cancer. Protecting health begins with understanding, and we wish every reader a healthy and fulfilling life.