G9090 HCPCS - ONCOLOGY; DISEASE STATUS; RECTAL CANCER, LIMITED TO INVASIVE CANCER, ADENOCARCINOMA AS PREDOMINANT CELL TYPE; EXTENT OF DISEASE INITIALLY ESTABLISHED AS T1-2, N0, M0 (PRIOR TO NEO-ADJUVANT THERAPY, IF ANY) WITH NO EVIDENCE OF DISEASE PROGRESSION, RECURRENCE, OR METASTASES (FOR USE IN A MEDICARE-APPROVED DEMONSTRATION PROJECT)