You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Outcome", "Participant", "Intervention"].

Please return the output as a JSON object of the format: {"Participant" : ["patients with COPD", ...], "Intervention" : ["Atenolol", ...], "Outcome" : ["blood pressure", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Enrollment of racial and ethnic minorities in the Prostate , Lung , Colorectal and Ovarian Cancer Screening Trial . BACKGROUND Minority populations in the United States , especially blacks and Hispanics , are generally underrepresented among participants in clinical trials . Here , we report the experience of enrolling ethnic minorities in a large cancer screening trial . METHODS The Prostate , Colorectal , Lung and Ovarian ( PLCO ) Cancer Screening Trial is a multicenter randomized trial designed to evaluate the effectiveness of screening for the PLCO cancers . Subjects were recruited at 10 U.S. centers between 1993 and 2001 . One screening center had a major special recruitment effort for blacks and another center had a major special recruitment effort for Hispanics . RESULTS Among almost 155,000 subjects enrolled in PLCO , minority enrollment was as follows : black ( 5.0 % ) , Hispanic ( 1.8 % ) and Asian ( 3.6 % ) . This compares to an age-eligible population in the combined catchment areas of the PLCO centers that was 14.0 % black , 2.9 % Hispanic and 5.4 % Asian , and an age-eligible population across the U.S. that was 9.5 % black , 6.5 % Hispanic and 3.0 % Asian . About half ( 45 % ) of Hispanics were recruited at the center with the special Hispanic recruitment effort . Seventy percent of blacks were recruited at two centers ; the one with the major special recruitment effort and a center in Detroit whose catchment area was 20 % black among age-eligibles . Blacks , Hispanics and ( non-Hispanic ) whites were all more highly educated , less likely to currently smoke and more likely to get regular exercise than their counterparts in the general population . CONCLUSION Significant efforts were made to recruit racial/ ethnic minorities into PLCO , and these efforts resulted in enrollment levels that were comparable to those seen in many recent cancer screening or prevention trials . Blacks and Hispanics were nonetheless underrepresented in PLCO compared to their levels among age-eligibles in the overall U.S. population or in the aggregate PLCO catchment areas .
{"Intervention": ["screening for the PLCO cancers", "Prostate , Colorectal , Lung and Ovarian ( PLCO ) Cancer Screening", "special recruitment effort for Hispanics", "special recruitment effort for blacks"], "Outcome": ["currently smoke", "recruited", "regular exercise"], "Participant": ["effectiveness of screening for the PLCO cancers", "Seventy percent of blacks were recruited at two centers", "racial and ethnic minorities in the Prostate , Lung , Colorectal and Ovarian Cancer Screening Trial .", "Hispanics", "155,000 subjects enrolled", "PLCO centers that was 14.0 % black , 2.9 % Hispanic and 5.4 % Asian", "that was 9.5 % black , 6.5 % Hispanic and 3.0 % Asian", "black ( 5.0 % ) , Hispanic ( 1.8 % ) and Asian ( 3.6 % )", "( 45 % ) of Hispanics were recruited at the center with the special Hispanic recruitment effort"]}