A Study of Atezolizumab With or Without Tiragolumab in Participants With Unresectable Esophageal Squamous Cell Carcinoma Whose Cancers Have Not Progressed Following Definitive Concurrent Chemoradiotherapy

National Taiwan University Hospital, Taipei

China Medical University Hospital, Taichung

Chi-Mei Medical Centre, Tainan City

AKH - Medizinische Universität Wien, Vienna

UZ Antwerpen, Edegem

UZ Leuven Gasthuisberg, Leuven

Inselspital Bern, Insel-Gruppe AG, Bern

Austin Health, Heidelberg

Tauranga Hospital, Clinical Trials Unit, Tauranga

CHU de Liège (Sart Tilman), Liège

Ordensklinikum Linz Barmherzige Schwestern, Linz

Princess Alexandra Hospital, Woolloongabba

St John of God Hospital, Subiaco

Tiroler Landeskrankenanstalten Ges.M.B.H., Innsbruck

Cancercare, Port Elizabeth

Szegedi Tudományegyetem, Szeged

Pécsi Tudományegyetem, Pécs

UniversitätsSpital Zürich, Zurich

Klinikum Klagenfurt am Wörthersee, Klagenfurt

Institut National D'oncologie Sidi Med Benabdellah, Rabat

Vajira Hospital, Bangkok

Chulalongkorn Hospital, Bangkok

Ramathibodi Hospital, Bangkok

Siriraj Hospital, Bangkok

Hopital Timone Adultes, Marseille

Hospital Universitario Reina Sofia, Córdoba

Great Lakes Cancer Center, Williamsville

Complejo Hospitalario Universitario A Coruña (CHUAC), A Coruña

Ajou University Medical Center, Gyeonggi-do

CHU Dijon Bourgogne Hôpital François Mitterand, Dijon

Vinnytsya Regional Clinical Oncology Dispensary, Vinnytsia

Ataturk University Medical Faculty Yakutiye Research Hospital Medical Oncology Department, Erzurum

Fundacion Jimenez Diaz, Madrid

Hospital Regional Universitario Carlos Haya, Málaga

CHRU De Brest - Hopital Morvan - Institut De Cancerologie Et D'Hematologie, Brest

Centre Hospitalier Universitaire Hassan II, Fes

International Cancer Institute (ICI), Eldoret

Hopital Rangueil, Toulouse

Hospital Univ. Central de Asturias, Oviedo

Asu Fc S. M. Della Misericordia, Udine

Hopital Du Haut-Leveque, Pessac

Florida Cancer Specialists - Fort Myers (Broadway), Fort Myers

Klinikum der Philipps-Universität Marburg, Marburg

Istituto Oncologico Veneto IRCCS, Padua

Klinik für Gastroenterologie und Gastrointestinale Onkologie der UMG, Göttingen

Med. Fak. d. Otto-von-Guericke-Universität, Magdeburg

Centre Hospitalier Universitaire Mohamed VI, Marrakesh

RCI Sumy Regional Clinical Oncological Dispensary, Sumy

Kyungpook National University Chilgok Hospital, Daegu

Inonu University Faculty of Medicine Turgut Ozal Medical Center, Malatya

Universitätsklinikum Essen Klinik f.Strahlentherapie, Essen

Kliniken Essen-Mitte, Evang. Huyssens-Stiftung, Klinik für Internistische Onkologie / Haematologie, Essen

Hospital Clinico Universitario de Valencia, Valencia

Ospedale Degli Infermi - Faenza, Faenza

Chonnam National University Hwasun Hospital, Jeollanam-do

Hopital Claude Huriez, Lille

Municipal Noncommercial Institution Regional Center of Oncology, Kharkiv

Centre Leon Berard, Lyon

European Hospital Georges Pompidou (HEGP), Paris

Università degli Studi della Campania Luigi Vanvitelli, Napoli

Chu La Miletrie, Poitiers

Songklanagarind Hospital, Songkhla

Universitätsklinikum Klinik u.Poliklinik f.Strahlentherapie, Regensburg

Cancer Hospital Chinese Academy of Medical Sciences., Beijing

Liaoning cancer Hospital & Institute, Shenyang

Taipei Veterans General Hospital, Taipei

Russian Oncology Research Center n.a. N.N. Blokhin Dpt of Clinical Pharmacology and Chemotherapy, Moscow

Shanghai Chest Hospital, Shanghai

Fudan University Shanghai Cancer Center, Shanghai

Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing

Changzhou Cancer hospital, Changzhou

The Affiliated Hospital of Xuzhou Medical College, Xuzhou

The First People's Hospital of Lian Yun Gang, Lianyungang

Subei People's Hospital of Jiangsu province, Yangzhou

Affiliated Hospital of Bengbu Medical College, Bengbu

Shandong Cancer Hospital, Jinan

Affiliated Hospital of Jining Medical University, Jining

Tianjin Cancer Hospital, Tianjin

Zhejiang Cancer Hospital, Hangzhou

Fujian Cancer Hospital, Fuzhou

The First Affiliated Hospital of Xiamen University, Xiamen

Zhongshan Hospital Xiamen University, Xiamen

Chongqing Cancer Hospital, Chongqing

Chongqing Sanxia Central Hospital, Chongqing

Hunan Cancer Hospital, Changsha

Republican Clinical Oncology Dispensary of Ministry of Healthcare of Tatarstan Republic, Kazan'

City Oncological Hospital, Izhevsk

Wuhan Union Hospital Tongji Medical College, Huazhong University of Science and Technology, Wuhan

Hubei Cancer Hospital, Wuhan

Anyang Tumor Hosptial, Anyang

The First Affiliated Hospital to Henan University of Science and Technology, Luoyang

Sun Yet-sen University Cancer Center, Guangzhou

Nanfang Hospital, Southern Medical University, Guangzhou

Cancer Hospital of Shantou University Medical College, Shantou

Sichuan Provincial Cancer Hospital, Chengdu

West China Hospital, Sichuan University, Chengdu

"Limited Liability Company RC Medical", Novosibirsk

Regional Oncology Dispensary, Tomsk

Krasnoyarsk Regional Oncology Dispensary n.a. Krizhanovsky, Krasnoyarsk

Rambam Health Corporation, Rambam

Tel Aviv Sourasky Medical Ctr, Tel Aviv

Hadassah Ein Karem Hospital, Jerusalem

Cancer Center of Kansas, Wichita

Instituto de Investigaciones Metabolicas (Idim), Buenos Aires

Fundacion Favaloro, Buenos Aires

Centro Oncologico Riojano Integral (CORI), La Rioja

Heping Hospital Affiliated to Changzhi Medical College, Changzhi

Jieyang People's Hospital, Jieyang

Lishui Central Hospital, Lishui

Cancer Hospital Chinese Academy of Medical Sciences Shenzhen Center, Shenzhen

The First Affiliated Hospital of Xinxiang Medical University, Xinxiang

Limpopo Cancer Research Institute, Polokwane

Eugene Marais Hospital, Pretoria

Hospital La Fe, Valencia

Chang Gung Medical Foundation - Kaohsiung;Oncology, Kaohisung

Van Yuzuncu Yil University Hospital, Van

Zhytomyr Regional Oncology Center, Zhytomyr

Hebei Medical University Fourth Hospital, Shijiazhuang

Centre Antoine Lacassagne, Nice

Universitaetsklinikum Leipzig, Leipzig

"Evgenidio Hospital Agia Trias", Athens

Univ General Hosp Heraklion, Heraklion

Euromedical General Clinic of Thessaloniki, Thessaloniki

Aichi Cancer Center Hospital, Aichi

National Cancer Center Hospital East, Chiba

Hiroshima University Hospital, Hiroshima

Kobe University Hospital, Hyōgo

Yokohama City University Medical Center, Kanagawa

Kanagawa Cancer Center, Kanagawa

Tohoku University Hospital, Miyagi

Niigata Cancer Center Hospital, Niigata

Osaka International Cancer Institute, Osaka

The University of Osaka Hospital, Osaka

Saitama Medical University International Medical Center, Saitama

Saitama Cancer Center, Saitama

Shizuoka Cancer Center, Shizuoka

The Cancer Institute Hospital of JFCR, Tokyo

Keio University Hospital, Tokyo

Aga Khan University Hospital, Nairobi

Centrum Onkologii, Bydgoszcz

Centrum Onkologii Ziemi Lubelskiej Im. ?W. Jana Z Dukli, Lublin

Szpital Kliniczny MSWiA z Warmi?sko-Mazurskim Centrum Onkologii, Olsztyn

Wielkopolskie Centrum Onkologii im. Marii Sk?odowskiej-Curie, Późna

NIO im Marii Sklodowskiej-Curie, Warsaw

Dolno?l?skie Centrum Onkologii, Wroc?aw

HUC, Coimbra

Centro Hospitalar do Porto ? Hospital de Santo António, Porto

IPO do Porto, Porto

Severance Hospital, Yonsei University Health System, Seoul

Asan Medical Center, Seoul

Samsung Medical Center, Seoul

Korea University Guro Hospital, Seoul

Hospital Universitari Vall d'Hebron, Barcelona

Hospital Clinic I Provincial, Barcelona

National Cheng Kung University Hospital, Tainan City

Baskent University Adana Dr. Turgut Noyan Practice and Research Hospital, Adana

Ankara University Faculty of Medicine Cebeci Hospital, Ankara

Ankara City Hospital, Ankara

Royal Bournemouth Hospital, Bournemouth

Addenbrookes Hospital, Cambridge

Ninewells Hospital, London

Royal Marsden Hospital - Fulham, London

Clatterbridge Cancer Centre, Metropolitan Borough of Wirral

Royal Marsden Hospital (Sutton), Sutton

New Cross Hospital, Wolverhampton