Clinical use of prognostic markers in head and neck cancer

Abstract

Head and neck cancer (HNC) is a heterogeneous group of tumors where squamous cell carcinoma is the most dominant. In 2020, 1640 new cases of HNC were reported in Sweden which accounted for 2.3% of the total cancer incidence. In Sweden, as in other Nordic countries, HNC is a relatively uncommon form of cancer, but in global terms it is a significant group of disease. The dominant etiological factor for HNC is traditionally smoking but in 2007 human papillomavirus (HPV) was recognized as carcinogenic to oropharyngeal cancer (OPSCC), which include tonsillar- (TSCC) and base of tongue cancer (BOTSCC). Human papillomavirus (HPV) are small DNA viruses, best known for its role in cervical cancer and its prevention with HPV-vaccines. But they are also linked to the tonsillar cancer and cancer of the base of tongue. Today there are more than 170 known types of HPV, but only a fraction infects the mucosal surfaces and only a few of these types oncogenic. The most common oncogenic types in HNC are HPV 16, 31 and 33. In the last decades there has been a sharp rise in tonsillar cancer and cancer of the base of tongue (TSCC, BOTSCC). HPV is the dominating cause of this. HPV-induced oropharyngeal cancers (OPSCC) correlates strongly to better prognosis. A disease with worse prognosis is hypopharyngeal cancer (HPSCC), here the role of HPV is more unclear.

In study 1 we wanted to see if HPV can be used as a marker for OPSCC in fine needle aspiration cytology (FNAC) of cervical neck masses. This in a prospective setting where 66 patients with cervical masses were tested for HPV in their FNAC-sample. All 17 patients who had HPV-positive OPSCC as final diagnosis also had HPV in FNAC. No patients with benign neck masses had HPV in FNAC. The challenge of distinguishing a cystic metastasis of an HPV-positive OPSCC from a branchial cleft cyst, which is a benign condition, is well known. It is also known that the neck metastases of HPV-positive OPSCC are HPV-positive and that HPV-DNA in the FNAC correlates to an HPV positive OPSCC. It has not been investigated if HPV-DNA also can be present in benign neck cysts. In study 2 we wanted to see if branchial cleft cysts could be HPV-positive. From 112 patients diagnosed with branchial cleft cyst under the years 2007-2015 DNA was extracted from formalin fixed paraffin embedded surgically resected material. None of the branchial cleft cysts contained HPV-DNA. In the third study we evaluated the expression of immune related proteins and tumor infiltrating lymphocytes in tumor samples compared to normal tissue and in relation to HPV-status and clinical outcome in patients with HPSCC. Fresh frozen tissue from 33 patients were analyzed for protein expression by the Proseek immuno-oncology immunoassay. Tumors, especially HPV-positive, had more immunological activity than normal tissue. In addition to this, 144 formalin-fixed biopsies, from patients with HPSCC, were analyzed for CD8+ TILs in relation to clinical outcome. Patients with high numbers of CD8+TILS hade improved clinical outcome. OPSCC are often diagnosed with presence of metastases in the neck and different strategies has been used for treatment of the neck after radio/chemoradiotherapy, (RT/CRT). The impact of RT/CRT in the tissue of the neck makes surgery of the neck surgically complicated and the risk of long-term side effect increases why more reduced surgery would benefit the patient. I the fourth study all patients diagnosed with TSCC and BOTSCC between 2017 and 2021 in the County of Stockholm were identified through the Swedish Cancer Registry. 217 patients who had post-treatment PET-CT or salvage ND were assessed included for further analysis including HPV and p16 status. Neck dissection was performed in 36 patients due to PET-CT criteria, the result of PET-CT was compared to pathological report from the neck specimen regarding location of metastases with viable cancer. In total, 26/36 patients examined by PET-CT and treated with ND had no sign of viable cancer. In 8/36 patients, the localization of metastasis in histopathological examination and the PET-CT was consistent. Thus, in two of the 10 patients with viable tumor the viable tumor cells was found in cervical lymph nodes other than those seen in PET-CT; both tumors were HPV-DNA and p16-positive.

Conclusions for the thesis are: HPV DNA in FNAC of neck masses is a strong indicator of TSCC or BOTSCC and was not present in any benign conditions or other malignant masses. HPV-DNA is absent in FFPEs of branchial cleft cysts. HPSCC have higher expression of immune related protein than normal tissue, and the expression was even higher in HPV-positive tumors. High numbers of CD8+ TILs in HPSCC are related to better clinical outcome. Reduced neck dissection after post treatment PET-CT may be feasible for patients with TSCC or BOTSCC.