Purpose To inform the evolving implementation of CancerLinQ and other rapid-learning systems for oncology care, we sought to evaluate perspectives of patients with cancer regarding ethical issues. Methods Using the GfK Group online research panel, representative of the US population, we surveyed 875 patients with cancer; 621 (71%) responded. We evaluated perceptions of appropriateness (scored from 1 to 10; 10, very appropriate) using scenarios and compared responses by age, race, and education. We constructed a scaled measure of comfort with secondary use of deidentified medical information and evaluated its correlates in a multivariable model. Results Of the sample, 9% were black and 9% Hispanic; 38% had completed high school or less, and 59% were age ≥ 65 years. Perceptions of appropriateness were highest when consent was obtained and university researchers used data to publish a research study (weighted mean appropriateness, 8.47) and lowest when consent was not obtained and a pharmaceutical company used data for marketing (weighted mean appropriateness, 2.7). Most respondents (72%) thought secondary use of data for research was very important, although those with lower education were less likely to endorse this (62% v 78%; P < .001). Overall, 35% believed it was necessary to obtain consent each time such research was to be performed; this proportion was higher among blacks/Hispanics than others (48% v 33%; P = .02). Comfort with the use of deidentified information from medical records varied by scenario and overall was associated with distrust in the health care system. Conclusion Perceptions of patients with cancer regarding secondary data use depend on the user and the specific use of the data, while also frequently differing by patient sociodemographic factors. Such information is critical to inform ongoing efforts to implement oncology learning systems.