Clinical implication of genetic intratumor heterogeneity for targeted therapy in head and neck cancer

Separating distant recurrences from second primaries in head and neck squamous cell carcinomas - A DAHANCA group analysis on paired tumor samples

BACKGROUND

In head and neck squamous cell carcinomas (HNSCC), there is no clinically available method to separate distant metastases (DMs) from SCC secondary primary tumors. The study aimed to assess the genetic relationship in paired tumor samples.

METHODS

Patients with pairs of solid biopsies from the primary HNSCC and suspected DMs were identified (2007-2017). Targeted next-generation sequencing of 22 genes was applied, including TP53, supplemented with human papillomavirus (HPV) genotyping.

RESULTS

Of 55 pairs obtained, 33 were successfully analyzed. Distant biopsies included lung, liver, and bone. A genetic match was found in 23/33 (70%) patients, primarily with identical TP53 mutations or HPV genotypes. In 10/33 patients (30%), the genetic relationship was absent, all with lung involvement. In patients with no lung involvement, 8/8 had a match.

CONCLUSIONS

One-third of patients with DMs in HNSCC lack a genetic relationship with the primary tumors. The risk of misclassification is most prominent for patients with lung involvement.

Genomic alterations in the stepwise progression from normal mucosa to metastasizing oral squamous cell carcinoma

Introduction

The aim of this study was to investigate the genomic changes that occur in the development from dysplasia, cancer and to regional metastases in patients with oral cavity squamous cell carcinoma (OSCC).

Material and methods

We included OSCC patients with lymph node metastases at diagnosis, treated with primary surgery at Rigshospitalet, University of Copenhagen in the period 2007-2014. The resected tumor specimens were evaluated by a pathologist, who marked areas of morphologically normal tissue and dysplasia surrounding the cancer, two areas from the cancer tissue, and one area within the lymph node metastases. From these areas a punch biopsy was taken, and DNA from each sample was extracted and sequenced using Illumina's TSO500 HT cancer panel.

Results

From 51 OSCC patients, 255 samples were included, comprising a wide variety of genomic alterations. Substantial intratumor heterogeneity was found. The most commonly mutated gene was TP53, mutated in 65% of all samples. Only two patients had no TP53 mutation in any samples. We found that morphologically normal appearing mucosa as well as surrounding dysplasia also contained malignant mutations, supporting the theory of field cancerization. There was a significant lower average tumor mutational burden (TMB) in the lymph node metastases compared to the primary tumors, supporting the theory of clonal selection.

Conclusion

Substantial inter- and intratumor genomic heterogeneity was found. Mutation of TP53 was the most common and was present in all but two patients. Our data strongly supports the theory of clonal selection and the theory of field cancerization.

De-Escalation Strategies in HPV-Associated Oropharynx Cancer: A Historical Perspective with Future Direction

The incidence of HPV-related oropharyngeal cancers has increased in recent decades. While cure rates exceed those of HPV-negative head and neck cancers, both acute and long-term sequelae of chemotherapy, radiation and surgery have led to clinical investigation into de-escalation of treatment. De-escalation trials have sought to reduce long-term treatment-related morbidity by altering or omitting chemotherapy, reducing radiation, or incorporating less invasive surgical resection through transoral surgery. More recent approaches include the use of novel agents such as immunotherapy in place of cisplatin. With the advent of tumor-tissue-modified HPV DNA detection and monitoring in blood, new strategies incorporating this biomarker are being developed.