A multi-gene-based assay for analysis of the following: (a) oncogene expression; (b) DNA methylation of tumor suppressor genes; (c) non-coding RNA expression (microRNA profiling); and (d) long non-coding RNA expression in cancer samples is disclosed. The assay method and device for conducting the assay are applicable to diagnosis, prognosis, and treatment of various cancers such as lung, breast, colorectal, prostate, liver, bladder; kidney, cervix, pancreatic, gastric, brain, oral, endometrium, and ovary. The assay methods allow avoidance of surgery to remove cancerous tissue.