Objective: The loss of chance in healthcare has been forcibly introduced in the adjudications pronounced in recent years. Our objective was to analyse the verdicts of guilt resulting from the loss of chance ordered by the Contentious-Administrative Court (i.e., in the public healthcare system), in which both the origin of the disease to be treated and the sequelae were oncological processes. Method: We analysed 137 cancer-related court judgments from the Contentious-Administrative Court, which referred to the concept of loss of chance, issued in Spain up to May 2014. Results: Of the 137 sentences, 119 (86.9%), were pronounced due to diagnostic error and 14 (10.2%) due to inadequate treatment. Since 2010, 100 sentences have been passed (73.0%), representing an increase of more than 170% with respect to the 37 (27.0%) ordered in the first six years of the study (from 2004 to 2009). Most of the patients (68.6%) died, predominantly from breast cancer and gynaecological cancer (24.1%), and gastrointestinal cancers (21.1%). These malignancies were the ones most often involved in the sentences. Conclusions: The litigant activity due to loss of chance in oncological processes in the public health care has significantly increased in the last years. The judgments were mainly given because of diagnostic error or inadequate treatment.