September 1910... The Philippine General Hospital starts operations with a Department of X-ray and Electrotherapeutic Department. There was a small radium emanation room under the direct charge of Dr. A. Clemente, PhD in Chemistry.

1926... Several Filipino doctors are already practicing radium therapy including Drs. Angelo Singian, Nicanor Jacinto, Jesus Ascano, Daniel Ledesma and Jose Borromeo.

1937... The X-ray Department of PGH expanded to include the cancer treatment center. Dr. Paterno Chikiamco served as hospital physicist and was the first radiation physicist in the country.

1938... Pres. Manuel Quezon signed Commonwealth Act No. 398 creating the Cancer Institute at PGH. This was inaugurated and opened to the public in 1941, two months beforethe start of World War II.

Early 1940's... Dr. Daniel Ledesma established the first private practice clinic with a Stabilivolt Superficial X-ray Unit.

Late 1940's... Dr. Paulino J. Garcia became head radiologist at the University of Santo Tomas Hospital where a Picker Deep x-ray therapy unit was installed.

1955... Radiotherapy facilities were set up in Veterans Memorial Hospital.

1956... Dr. Carlos Marquez acquired a Picker Cobalt-60 machine for Manila Doctors Hospital, the first of its kind in Manila.

1958... The Jose Reyes Memorial Hospital acquired a Cobalt-60 machine that was used by Drs. Silverio, Lopez, Elicano and Anatalio.

Early 1960's... Cobalt machine was set up in the GSIS Hospital, now known as the East Avenue Medical Center.

1962... The Philippine General Hospital acquires a cobalt machine and cesium sources for brachytherapy.

1967... Another cobalt machine was installed in Iloilo under Dr. Daniel Ledesma.

1974... A Japanese philanthropist donates a Cobalt-60 machine to Ospital ng Maynila where Drs. Leon Lopez and Eduardo Tan practiced.

1976... The Radiotherapy Group was formed as a special interest group of the Philippine College of Radiology (PCR). Its president was Dr. Reynaldo Gregorio.

1983... The Lung Center was inaugurated. It had a linear accelerator and a cobalt-60 machine.

September 12, 1984... The Radiotherapy Group of the PCR reorganized into the Section of Radiation Oncology. Organizational meeting was at the Manila Polo Club. The founding president was Dr. Reynaldo Gregorio.

1988... The Philippine Radiation Oncology Society (PROS was formed as a distinct subspecialty society of the PCR. The president was Dr. Bienvenido Lapuz. Dr. Tranquilino Elicano acquired three linear accelerators for the National Cancer Control Center.

1990... Dr. Eduardo Nievera is elected president of PROS.

1990's... St. Luke's Medical Center obtains cobalt therapy machines which were later upgraded to linear accelerators. High dose rate brachytherapy unites were likewise obtained.

1993... Dr. Gaudencio Vega Jr. is elected president of PROS.

1998... PROS holds its first "mini-convention" during the PCR Annual Convention.

2002... Dr. Teresa Sy Ortin is elected president of PROS.

2004... PROS holds its first "stand-alone" convention at the Manila Polo Club.

2005...  The Benavides Cancer Center opens at the UST Hospital.

2006...  PROS and the American Society for Therapeutic Radiology and Oncology (ASTRO) co-sponsor an international educational course held in Manila Hotel.

2007...  Dr. Edilberto Joaquin Fragante is president of PROS. The South East Asian Radiation Oncology Group (SEAROG) is established. The PROS is a charter member.

2009... Dr. Miriam Joy Calaguas is elected president of PROS. PROS and the European Society for Therapeutic Radiology and Oncology (ESTRO) co-sponsor a brachytherapy workshop held in the Hyatt Hotel, Manila.