Do All Patients Diagnosed With Cancer Deserve Germline Testing?

Tucatinib in the treatment of HER2-overexpressing gastrointestinal cancers: current insights and future prospects

INTRODUCTION

Over the past 20 years, the treatment landscape of HER2-amplified tumors has considerably evolved. Until now, no approved targeted therapies were available for patients with HER2-amplified metastatic colorectal cancer (mCRC). Tucatinib, a highly selective tyrosine kinase inhibitor, demonstrated significant efficacy in combination with trastuzumab in patients with refractory mCRC, leading to its approval by the Food and Drug Administration (FDA).

AREAS COVERED

This review dives into the efficacy of tucatinib-based regimens in gastrointestinal malignancies, with a focus on the pivotal MOUNTAINEER trial, which led to the FDA approval of tucatinib plus trastuzumab in chemo-refractory HER2-amplified mCRC. Additionally, ongoing trials are exploring tucatinib in earlier treatment lines and across other gastrointestinal cancers, including biliary tract, gastric, and pancreatic malignancies. The mechanistic basis of dual HER2 inhibition and its implications for clinical practice are discussed.

EXPERT COMMENTARY

The future of tucatinib-based therapeutic strategies in GI malignancies depends on their integration into different treatment lines. Addressing acquired resistance using liquid biopsy-guided strategies and other TKIs like lapatinib will be paramount to improve outcomes.

Molecular diagnostics tailoring personalized cancer therapy-an oncologist's view

Medical oncology is rapidly evolving with the implementation of personalized, targeted therapies. Advances in molecular diagnostics and the biologic understanding of cancer pathophysiology led to the identification of specific genetic alterations as drivers of cancer progression. Further, improvements in drug development enable the direct interference with these pathways, which allow tailoring personalized treatments based on a distinct molecular characterization of tumors. Thereby, we are currently experiencing a paradigm-shift in the treatment of cancers towards cancer-type agnostic, molecularly targeted, personalized therapies. However, this concept has several important hurdles and limitations to overcome to ultimately increase the proportion of patients benefitting from the precision oncology approach. These include the assessment of clinical relevancy of identified alterations, capturing and interpreting levels of heterogeneity based on intra-tumoral or time-dependent molecular evolution, and challenges in the practical implementation of precision oncology in routine clinical care. In the present review, we summarize the current state of cancer-agnostic precision oncology, discuss the concept of molecular tumor boards, and consider current limitations of personalized cancer therapy. Further, we provide an outlook towards potential future developments including the implementation of functionality assessments of identified genetic alterations and the broader use of liquid biopsies in order to obtain more comprehensive and longitudinal genetic information that might guide personalized cancer therapy in the future.

Impact of genetic counseling strategy on diagnostic yield and workload for genome-sequencing-based tumor diagnostics

PURPOSE

Genome sequencing (GS) enables comprehensive molecular analysis of tumors and identification of hereditary cancer predisposition. According to guidelines, directly determining pathogenic germline variants (PGVs) requires pretest genetic counseling, which is cost-ineffective. Referral for genetic counseling based on tumor variants alone could miss relevant PGVs and/or result in unnecessary referrals.

METHODS

We validated GS for detection of germline variants and simulated 3 strategies using paired tumor-normal GS data of 937 metastatic patients. In strategy-1, genetic counseling before tumor testing allowed direct PGV analysis. In strategy-2 and -3, germline testing and referral for post-test genetic counseling is based on tumor variants using Dutch (strategy-2) or Europen Society for Medical Oncology (ESMO) Precision Medicine Working Group (strategy-3) guidelines.

RESULTS

In strategy-1, PGVs would be detected in 50 patients (number-needed-to counsel; NTC = 18.7). In strategy-2, 86 patients would have been referred for genetic counseling and 43 would have PGVs (NTC = 2). In strategy-3, 94 patients would have been referred for genetic counseling and 32 would have PGVs (NTC = 2.9). Hence, 43 and 62 patients, respectively, were unnecessarily referred based on a somatic variant.

CONCLUSION

Both post-tumor test counseling strategies (2 and 3) had significantly lower NTC, and strategy-2 had the highest PGV yield. Combining pre-tumor test mainstreaming and post-tumor test counseling may maximize the clinically relevant PGV yield and minimize unnecessary referrals.