Relapsing high grade mucoepidermoid carcinoma: Long-lasting complete response following reirradiation and EGFR blockade

Oral Cancer Stem Cells: Therapeutic Implications and Challenges

Head and neck squamous cell carcinoma (HNSCC) is currently one of the 10 most common malignancies worldwide, characterized by a biologically highly diverse group of tumors with non-specific biomarkers and poor prognosis. The incidence rate of HNSCC varies widely throughout the world, with an evident prevalence in developing countries such as those in Southeast Asia and Southern Africa. Tumor relapse and metastasis following traditional treatment remain major clinical problems in oral cancer management. Current evidence suggests that therapeutic resistance and metastasis of cancer are mainly driven by a unique subpopulation of tumor cells, termed cancer stem cells (CSCs), or cancer-initiating cells (CICs), which are characterized by their capacity for self-renewal, maintenance of stemness and increased tumorigenicity. Thus, more understanding of the molecular mechanisms of CSCs and their behavior may help in developing effective therapeutic interventions that inhibit tumor growth and progression. This review provides an overview of the main signaling cascades in CSCs that drive tumor repropagation and metastasis in oral cancer, with a focus on squamous cell carcinoma. Other oral non-SCC tumors, including melanoma and malignant salivary gland tumors, will also be considered. In addition, this review discusses some of the CSC-targeted therapeutic strategies that have been employed to combat disease progression, and the challenges of targeting CSCs, with the aim of improving the clinical outcomes for patients with oral malignancies. Targeting of CSCs in head and neck cancer (HNC) represents a promising approach to improve disease outcome. Some CSC-targeted therapies have already been proven to be successful in pre-clinical studies and they are now being tested in clinical trials, mainly in combination with conventional treatment regimens. However, some studies revealed that CSCs may not be the only players that control disease relapse and progression of HNC. Further, clinical research studying a combination of therapies targeted against head and neck CSCs may provide significant advances.

Advances and challenges in precision medicine in salivary gland cancer

Salivary gland cancer (SGC) is a rare malignancy consisting of 22 subtypes with different genetic, histological and clinical characteristics. This rarity and heterogeneity makes systemic treatment of recurrent or metastatic (R/M) disease challenging. Use of chemotherapy is scarcely studied and chemotherapy at best has moderate effects. New therapeutic strategies are therefore warranted, but advances made in SGC are lagging behind on advances made in more common cancers. By unraveling tumor characteristics of SGC, such as genetic alterations and protein expression profiles, therapeutic strategies tailored to the patient's tumor can be rationalized. This genomic profiling and mapping of immunohistochemical expression profiles is essential in the search for a suitable treatment approach. Thereby, it alleviates the paucity in systemic treatment options and can significantly alter the prognosis of patients with R/M SGC. This review aims to give a comprehensive overview of known genetic alterations and expression profiles amenable for targeted therapy in every histological subtype of SGC. We discuss the remaining knowledge gaps and the implications of these targets for future studies and personalized treatments, thereby aiding clinicians faced with this rare and heterogeneous type of cancer.

New concepts of personalized therapy in salivary gland carcinomas

Salivary gland carcinomas are rare tumours and therapy strategies are less standardized than in lung, gastric or breast cancer. Therapy is based on surgery, but not all carcinomas are completely resectable, e.g. because carcinomas often show infiltration of nerves. For further therapy decision pathology is recommended, but evaluation of potential targets for personalized therapy is not part of the routine panel. Many salivary gland carcinomas can be resistant to radio- and/or chemotherapy, which limits therapeutic options. This review summarizes new concepts for personalized therapy in salivary gland carcinoma patients. Targeting growth receptors HER2, EGFR, AR and ER is possible but, in some studies, potential target molecules were not adequately tested before therapy. In addition, approximately 20-25% of carcinomas have RAS mutation (mainly H-RAS), which could explain resistance to therapy. Possible therapy options in the future could be immunomodulation (inhibition of PDL1/PD1 signalling), nanoparticles (gold nanoparticles conjugated to cetuximab can increase radiosensitivity) and drug delivery systems (trastuzumab emtansine/T-DM1).

Cytogenetic and immunohistochemical biomarker profiling of therapy-relevant factors in salivary gland carcinomas

OBJECTIVES

There is currently no established algorithm for the molecular profiling of therapy-relevant defects in salivary gland carcinomas (SGC). HER2 overexpression in a subfraction of SGC and low frequencies of EGFR mutations are known. Here, we established receptor and cell signalling profiles of 17 therapy-relevant factors and propose a molecular diagnostic algorithm for SGC.

MATERIALS AND METHODS

Formalin-fixed and paraffin-embedded tissue samples from SGC (n = 38) were analysed with immunohistochemistry and fluorescence in situ hybridisation (FISH).

RESULTS

Two or more expressed receptors and/or receptor gene amplification were detectable in eight of 38 (21%) tumours: HER2 3+/AR 1+, HER3 gene amplification/AR 1+/EGFR 1+, ER 3+/AR 1+, EGFR 2+/PR 1+ and EGFR 2+/PR 1+/AR 1+. No FGFR1-3, MET, ALK1, ROS1, RET, BRAF nor VEGFA defects were detectable, and ERCC1 was not overexpressed. No PD1+ tumour-infiltrating T cells were detectable.

CONCLUSION

Personalised therapy of patients with salivary gland carcinomas should include HER2 and EGFR signalling testing and, in negative cases, evaluation of rare potential target molecules. ERCC1 and PD1 do not appear to be reliable markers for the decision for or against chemotherapy or immunotherapy, respectively.

A rationale for chemoradiation (vs radiotherapy) in salivary gland cancers? On behalf of the REFCOR (French rare head and neck cancer network)

BACKGROUND

Salivary gland carcinomas constitute a heterogeneous group of tumors, with over 20 histological subtypes of various prognoses. The mainstay of treatment is surgery, with radiotherapy advocated for unresectable disease or postoperatively in case of poor prognostic factors such as high grade, locally advanced and/or incompletely resected tumors. Concurrent chemotherapy is sometimes advocated in routine practice based on criteria extrapolated from squamous cell carcinomas of the head and neck, on radioresistance of salivary gland tumors and on results obtained in the metastatic setting. The aim of this review was to identify situations where chemotherapy is advocated.

MATERIAL AND METHODS

A search of literature was performed with the following key words: parotid, salivary gland, neoplasm, cancer, malignant tumor, chemoradiation, chemotherapy, radiotherapy and treatment. Case report and studies published before 2000 were not included.

RESULTS

Platinum-based regimens were the most frequent. Other regimens were reported and seemed dependent on histology. The level of evidence for the concurrent delivery of chemotherapy with radiation therapy is supported by a low level of evidence. Prescribing chemotherapy mostly relies on poor prognostic factors similar to those used to indicate high dose radiotherapy. Protocols vary with histology.

CONCLUSION

The rationale for adding chemotherapy to radiotherapy remains to be demonstrated prospectively. Although the type of systemic treatments used may be adapted on histology, the strongest rationale remains in favor of cisplatin.