Even with effective early treatment, about 30% of breast cancers will develop distant metastases. If the metastases are metastatic, why do we need to re-biopsy the metastatic lesions to check the characteristics of the metastatic lesions when we can just treat them the same as the original ones?
The reason: the characteristics of metastatic cancer may change compared to the primary lesion
In the past, it was commonly believed that recurrent or metastatic lesions originated from the primary tumor in the breast, so treatment after recurrent metastasis could be guided by the primary tumor. However, studies have shown that the expression of hormone receptor (HR) and human epidermal growth factor receptor (HER-2) may be altered between the primary and metastatic foci of breast cancer. Compared to the primary site, 30% of patients had a change in ER status and 39.3% had a change in PR in the metastases. In another study, changes in ER, PR, and HER-2 expression in liver metastases amounted to 16.0%, 29.8%, and 13.1%, respectively, resulting in a change in treatment strategy in 18.8% of patients.
Why is this the case? On the one hand, it is because the biology of different cancer cells is inherently inconsistent during tumor growth, that is, the heterogeneity of the tumor. On the other hand, although still controversial, some medical experts believe that antitumor therapy may also have an impact on the expression profile of receptors in breast cancer tissue. One study, for example, found the highest rate of ER-positive to negative conversion in those who received endocrine therapy alone, the next highest rate of ER-negative conversion in those who received endocrine therapy combined with chemotherapy and chemotherapy alone, and the lowest rate of ER-negative conversion in patients who did not receive therapy.
What to do: re-biopsy to detect metastasis characteristics for targeted treatment
The choice of treatment for breast cancer relies heavily on molecular typing, that is, the expression of receptors on the tumor as detected by biopsy. Since the molecular typing of metastases may change compared with the primary site, treatment of metastatic cancer that relies exclusively on the molecular diagnosis of the primary site may lead to bias in treatment decisions. How can this bias be avoided?
Re-biopsy is important!
Considering the possibility of altered molecular staging after metastasis, in recurrent or post-metastatic breast cancer, physicians will perform another biopsy to clarify HR and HER-2 expression in the metastases. Re-biopsy has become a routine test after breast cancer recurrence or metastasis and is necessary to develop a treatment plan.
Take into account the characteristics of primary and metastatic sites to implement multiple treatments
When choosing a treatment plan, physicians will primarily refer to the molecular typing of the recurrent or metastatic lesion, but will also evaluate the primary site in a comprehensive manner to provide as diverse a treatment as possible. In other words, even if the HR of the metastatic lesion turns from positive to negative and HER-2 turns from positive to negative, the doctor will not completely discard the opportunity of endocrine therapy and anti-HER-2 targeted therapy in the follow-up treatment. The doctor will usually combine the characteristics of the disease and give individualized treatment.
Summary
In conclusion, the molecular typing of primary and metastatic foci in breast cancer may be inconsistent, and physicians will usually re-biopsy the recurrent metastatic lesion after detection of recurrence or metastasis, or even reexamine it at the same time as the sections of the primary lesion, so as to develop a more rational and diversified treatment plan for the patient and bring survival benefit. (Shanghai Tenth People’s Hospital, Department of Medical Oncology, Yuan Min contributed)