1. 1Second Department of Internal Medicine, Medical Oncology Section, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece.
2. 2Department of Pathology, Yale School of Medicine, New Haven, Connecticut.
3. 3Yale Cancer Center, Yale School of Medicine, New Haven, Connecticut.
4. 4Section of Biostatistics, Hellenic Cooperative Oncology Group, Data Office, Athens, Greece.
5. 5Second Department of Internal Medicine, Agios Savvas Cancer Hospital, Athens, Greece.
6. 6Second Department of Internal Medicine, Medical Oncology Section, Hippokration General Hospital, Athens, Greece.
7. 7Department of Otolaryngology-Head and Neck Surgery, Hippokration General Hospital, University of Athens, Athens, Greece.
8. 8Second Otolaryngology Department, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece.
9. 9Second Department of Pathology, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece.
10. 10Department of Oral and Maxillofacial Surgery, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
11. 11Department of Pathology, Aristotle University of Thessaloniki, School of Health Sciences, Faculty of Medicine, Thessaloniki, Greece.
12. 12Oral Medicine Clinics, A. Syggros Hospital of Dermatologic and Venereal Diseases, Department of Dermatology, School of Medicine, University of Athens, Athens, Greece.
13. 13Second Department of Radiology, Radiotherapy Unit, National and Kapodistrian University of Athens, Attikon University Hospital, Athens, Greece.
14. 14Department of Medical Oncology, Cyprus Oncology Centre, Nicosia, Cyprus.
15. 15Analysis of Circulating Tumor Cells Lab, Lab of Analytical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Athens, Greece.
16. 16German Oncology Center, Limassol, Cyprus.
17. 17Laboratory of Molecular Oncology, Hellenic Foundation for Cancer Research/Aristotle University of Thessaloniki, Thessaloniki, Greece.
18. 18Aristotle University of Thessaloniki, Thessaloniki, Greece.