Concordance of folate receptor-α expression between biopsy, primary tumor and metastasis in breast cancer and lung cancer patients

Abstract

Folate receptor alpha (FRα) is known to be upregulated in a variety of cancers, including non-small cell lung cancer (NSCLC) and breast cancer. To ensure reliable implementation of diagnostic- and therapeutic agents, concordance of FRα expression between biopsy, primary tumor and metastases is important. Using immunohistochemistry (Mab 26B3.F2) these concordances were investigated in 60 NSCLC and 40 breast cancer patients. False positivity of FRα expression on breast and lung cancer biopsies was limited to less than 5%. In NSCLC, FRα expression was shown in 21/34 adenocarcinomas and 4/26 squamous cell carcinomas (SCC). Concordance of FRα expression between biopsy and primary tumor was achieved in respectively 83% and 91% of adenocarcinomas and SCCs. Approximately 80% of all local and distant metastases of NSCLC patients showed concordant FRα expression as their corresponding primary tumor. In breast cancer, FRα positivity was shown in 12/40 biopsies, 20/40 lumpectomies and 6/20 LN metastases, with concordance of 68% between biopsy and primary tumor and 60% between primary tumor and LN metastases. In conclusion, this study shows high concordance rates of FRα expression between biopsies and metastases compared to primary NSCLC and breast cancers, underscoring the applicability of FRα-targeted agents in these patients.

Keywords: Pathology Section; biomarker; diagnosis; oncology; personalized medicine; targeting.

Figure 1. Staining intensities of FRα in NSCLC and breast cancer samples using immunohistochemistry (IHC)

The staining score (0 to 3+) was obtained by assessment of membrane intensity. A score of 0 equals no membrane staining, a score of 1+ a faint apical membrane staining, a score of 2+ a moderate apical and occasional lateral membrane staining and a score of 3+ equals a strong circumferential membrane staining. 1a-1d: staining intensity of respectively 0, 1+, 2+ and 3+ in adenocarcinoma samples of NSCLC patients (40x) 2a-d: staining intensity of respectively 0, 1+, 2+ and 3+ in breast cancer samples (40x).

Figure 2. Examples of (dis)concordance in FRα staining in biopsy-, primary tumor-, and metastatic LN tissue in NSCLC and breast cancer patients

1a-1c: example of concordance between positive FRα expression on biopsy (1a), primary tumor (1b) and metastatic LN tissue (1c) in a NSCLC patient, containing adenocarcinoma (20x). 2a-2c: example of disconcordance between FRα expression on biopsy (2a), primary tumor (2b) and metastatic LN tissue (2c) in a NSCLC patient, containing SCC (20x). 3a-3c: example of concordance between positive FRα expression on biopsy (3a), primary tumor (3b) and metastatic LN tissue (3c) in a breast cancer patient (20x).

Figure 3. FRα expression in NSCLC and corresponding distant metastases

1a: primary tumor containing adenocarcinoma without FRα expression (20x). 1b: corresponding distant metastasis of the bone with positive FRα expression (20x). 2a: primary tumor containing adenocarcinoma with positive FRα expression (20x). 2b: corresponding distant metastasis of the brain with positive FRα expression (20x).

Figure 4. Example of FRα-targeted detection of an adenocarcinoma using EC-17, i.e

fluorescent FRα-targeted molecular agent, in a patient suffering from NSCLC. In vivo fluorescence imaging was performed using the Artemis imaging system [34]. a: Prior to pulmonary resection, a tumor of 3 cm in the upper lobe of the left lung is detected by CT-and PET-scan. b: In vivo fluorescence imaging shows clear tumor delineation. c: Ex vivo fluorescence imaging of the tumor in the resected specimen. d: After resection, the wound bed was inspected with λex 490 nm and demonstrated no residual fluorescence at the surgical margins. e: FRα upregulation was confirmed by fluorescence microscopy and immunohistochemical staining.

Figure 5. Examples of FRα staining in normal lung and breast tissue

a: staining of FRα at the luminal border of normal lung tissue in an adenocarcinoma patient (10x). b: staining of FRα at the luminal border of normal lung tissue in a SCC patient (10x). c: staining of FRα in normal breast tissue: staining at the luminal border of secretory cells (10x).