5
Recommendation 8.1
➤ Clinicians may test for NTRK fusions in patients with metastatic cancer
who are candidates for a treatment regimen that includes a tyrosine
receptor kinase (TRK) inhibitor to determine eligibility for larotrectinib
or entrectinib. (Moderate recommendation; IC-L)
Recommendation 9.1
➤ There are insufficient data to recommend routine testing of tumors for
TROP2 expression to guide therapy with an anti-TROP2 antibody-drug
conjugate for hormone receptor-negative, HER2-negative metastatic
breast cancer. (Moderate recommendation; IC-L)
Recommendation 10.1
➤ There are insufficient data to recommend routine use of ctDNA to
monitor response to therapy among patients with metastatic breast
cancer. (Moderate recommendation; IC-L)
Recommendation 11.1
➤ There are insufficient data to recommend routine use of CTCs to monitor
response to therapy among patients with metastatic breast cancer.
(Moderate recommendation; IC-I)
Recommendations Unchanged From 2015 Guideline
➤ At initial presentation of metastasis from breast cancer, it is standard
of care to biopsy an accessible lesion to confirm metastatic breast
cancer. When evaluating the metastatic site(s), it is important to note
that the results of estrogren receptor (ER), progesterone receptor (PR),
and/or HER2 status may have changed from the primary tumor, and
these results may inform treatment decisions. Therefore, this Panel
recommends retesting for ER, PR, and HER2 on ≥ one metastasis with
careful attention to assay performance, particularly for bone metastases.
However, for patients with documented changes in these biomarkers,
data are lacking to determine whether outcomes from systemic therapy
are altered when guided by biomarker test results from the metastases.
The Panel informal consensus for the management of care when there is
discordance of ER, PR, or HER2 results between primary and metastatic
tissues is to use the ER, PR, or HER2 status from the metastasis to direct
therapy, if supported by the clinical scenario and the patient's goals for
care. (Moderate recommendation; EB-Ins for biomarker change from
primary to metastasis, but no evidence to demonstrate that systemic
therapy choices affect health outcomes when biomarker change occurs.)
