Progress in refining the clinical management of cancer of unknown primary in the molecular era

Cancer of unknown primary stem-like cells model multi-organ metastasis and unveil liability to MEK inhibition

Cancers of unknown primary (CUPs), featuring metastatic dissemination in the absence of a primary tumor, are a biological enigma and a fatal disease. We propose that CUPs are a distinct, yet unrecognized, pathological entity originating from stem-like cells endowed with peculiar and shared properties. These cells can be isolated in vitro (agnospheres) and propagated in vivo by serial transplantation, displaying high tumorigenicity. After subcutaneous engraftment, agnospheres recapitulate the CUP phenotype, by spontaneously and quickly disseminating, and forming widespread established metastases. Regardless of different genetic backgrounds, agnospheres invariably display cell-autonomous proliferation and self-renewal, mostly relying on unrestrained activation of the MAP kinase/MYC axis, which confers sensitivity to MEK inhibitors in vitro and in vivo. Such sensitivity is associated with a transcriptomic signature predicting that more than 70% of CUP patients could be eligible to MEK inhibition. These data shed light on CUP biology and unveil an opportunity for therapeutic intervention.

Cancer of unknown primary (CUP) is a mysterious malignancy featuring metastatic dissemination in the absence of a recognizable primary tumor. By characterizing CUP cancer stem cells we show that self-sustained long-term propagation and sensitivity to MEK inhibition are CUP common features.

Comparative genomic characterization of melanoma of known and unknown primary

BACKGROUND

This study aims to genomically characterize melanoma of unknown primary (MUP) in comparison to melanomas of cutaneous primary (MCP).

METHODS

Eligible cases were collected from the MSK-IMPACT™ Clinical Sequencing Cohort published in the cBioPortal database. Genomic analysis was performed using a hybridization-capture-based next-generation sequencing assay designed to detect mutations, small insertions and deletions, copy number alterations, and genomic rearrangements.

RESULTS

Among 462 patients of whom 18.4% had MUP, brain metastasis was more common among patients with MUP (23% vs 7.1%). The differences in genomic profiling between MCP and MUP did not reach statistical significance. The 187 MCP and 44 MUP patients treated with immune checkpoint inhibitors had a median overall survival of 49 and 44 months, respectively (p = 0.705).

CONCLUSIONS

The differences in somatic mutation patterns and survival outcomes were not statistically significant. These findings may allude to similar carcinogenic processes but should be considered exploratory and interpreted with caution.

The management of patients with cancer of unknown primary in middle-income countries: an ESO-AROME survey

Aim: To report on the management strategies in patients with cancer of unknown primary (CUP) in middle-income countries. Methods: We conceived a survey of 20 items concerning the management of patients with CUP in daily clinical practice. Only participants from lower- and higher-middle-income countries, as per the World Bank Classification, were eligible for this study. Results: The indications for the first-line treatment did not differ between the two economic regions, whereas those for second-line treatment were more prevalent in higher-middle-income countries. The use of targeted therapy based on immunohistochemistry alone was higher in lower-middle-income countries, although the access to CUP classifiers was similar between the two regions. Conclusions: Proper recommendations must ensure that the economic burden is minimized and that other benefits outweigh the limited survival benefit achieved in patients with CUP.

Site-Specific and Targeted Therapy Based on Molecular Profiling by Next-Generation Sequencing for Cancer of Unknown Primary Site: A Nonrandomized Phase 2 Clinical Trial

Importance

Although profiling of gene expression and gene alterations by next-generation sequencing (NGS) to predict the primary tumor site and guide molecularly targeted therapy might be expected to improve clinical outcomes for cancer of unknown primary site (CUP), to our knowledge, no clinical trial has previously evaluated this approach.

Objective

To assess the clinical use of site-specific treatment, including molecularly targeted therapy based on NGS results, for patients with CUP.

Design, Setting, and Participants

This phase 2 clinical trial was conducted at 19 institutions in Japan and enrolled 111 previously untreated patients with the unfavorable subset of CUP between March 2015 and January 2018, with 97 patients being included in the efficacy analysis. Eligibility criteria included a diagnosis of unfavorable CUP after mandatory examinations, including pathological evaluation by immunohistochemistry, chest-abdomen-pelvis computed tomography scans, and a positron emission tomography scan.

Interventions

RNA and DNA sequencing for selected genes was performed simultaneously to evaluate gene expression and gene alterations, respectively. A newly established algorithm was applied to predict tumor origin based on these data. Patients received site-specific therapy, including molecularly targeted therapy, according to the predicted site and detected gene alterations.

Main Outcomes And Measures

The primary end point was 1-year survival probability. Secondary end points included progression-free survival (PFS), overall survival (OS), objective response rate, safety, efficacy according to predicted site, and frequency of gene alterations.

Results

Of 97 participants, 49 (50.5%) were women and the median (range) age was 64 (21-81) years. The cancer types most commonly predicted were lung (21 [21%]), liver (15 [15%]), kidney (15 [15%]), and colorectal (12 [12%]) cancer. The most frequent gene alterations were in TP53 (45 [46.4%]), KRAS (19 [19.6%]), and CDKN2A (18 [18.6%]). The 1-year survival probability, median OS, and median PFS were 53.1% (95% CI, 42.6%-62.5%), 13.7 months (95% CI, 9.3-19.7 months), and 5.2 months (95% CI, 3.3-7.1 months), respectively. Targetable EGFR mutations in tumor specimens were detected in 5 patients with predicted non-small-cell lung cancer (5.2%), 4 of whom were treated with afatinib; 2 of these patients achieved a durable PFS of longer than 6 months.

Conclusions and Relevance

This study's findings suggest that site-specific treatment, including molecularly targeted therapy based on profiling gene expression and gene alterations by NGS, can contribute to treating patients with the unfavorable subset of CUP.

Trial Registration

UMIN Identifier: UMIN000016794.

The spectrum of pathological diagnoses in non-sentinel axillary lymph node biopsy: A single institution's experience

Although axillary lymphadenopathy is a common clinical encounter, systemic evaluation of non-sentinel lymph node biopsy is sparse. We reviewed our institution's 15-year experience to delineate the spectrum of diagnoses in non-sentinel axillary lymph nodes. 1165 non-sentinel axillary lymph node biopsies were retrieved and the diagnosis and relevant clinical information was reviewed. This spectrum of diagnoses was further stratified by gender, age, and oncologic history. The spectrum of diagnoses included: breast carcinoma (27.6%), lymphoma (29.2%), melanoma (3.5%), other carcinoma (2.9%), sarcoma (0.4%), and benign changes (36.3%). The most common diagnoses in men were lymphoma (61.8%) and benign changes (23.6%); while in women they were benign change (41.2%), breast carcinoma (37.8%) and lymphoma (16.7%). Besides benign changes, lymphoma and breast carcinoma were most common in women younger and older than 30 years, respectively. In patients with a history of malignancy, the most common diagnoses were metastasis from the known tumor and benign change; while in patients with a negative oncologic history and female patients without a history of breast cancer, the diagnosis was generally either lymphoma or benign change. Anaplastic large cell lymphoma was rare but may be mistaken as metastatic carcinoma thus a high index of suspicion is warranted. Thus through retrospective review of a large cohort of non-sentinel axillary lymph node biopsies, we described the spectrum of pathological entities based on the gender, age, and clinical history, which could provide valuable information for further work-up of axillary lymph node biopsy.

Insights from the genetic and transcriptional characterization of a cancer of unknown primary (CUP)

Cancer of unknown primary (CUP) defines a heterogeneous group of metastatic tumors that lack an identifiable primary tumor, despite a standardized diagnostic work‐up (Fizazi et al, 2015). CUPs are characterized by an aggressive clinical course, unusual metastatic pattern, and poor prognosis. Research in this field has been encouraged to unravel the complexity of this enigmatic entity and improve clinical management and survival of CUP patients. In this issue of EMBO Molecular Medicine, Benvenuti et al (2020) describe the molecular characterization of multiple synchronous and spatially distinct metastases from a CUP patient, shedding light on the evolutionary dynamic and distinctive features of CUP.

What can we learn from cancer of unknown primary in canine oncology?

Cancer of unknown primary (CUP) represents a heterogeneous group of metastatic tumors that lack an identifiable primary site despite an extensive diagnostic work-up. It is a well-recognized entity that is characterized by early dissemination, aggressive clinical course, unpredictable metastatic pattern, intrinsic treatment resistance, and a dismal prognosis. Despite the molecular diagnostic workup and personalized therapy, the expected improvements in the diagnosis and treatment of CUP have not been achieved. Comparative oncology has a promising role in the exchange of knowledge and practices between humans and canines. Therefore, we intended to review the literature reporting on CUP in dogs in order to identify some interesting parallels and unique results that could be transposed to in-human research.