You are taking care of a 73-year-old white man with a locally advanced rectal cancer. He has finished total neoadjuvant therapy with a limited response. The tumor invades the left sciatic notch and external iliac vein and artery as well as the left ureter. One physician on his team has recommended he undergo an external hemipelvectomy with curative intent. The patient also suffers from chronic obstructive pulmonary diseaseand congestive heart failure after a myocardial infarction last year. The patient has deferred decision-making to his physicians. Which ethical priniciple is most associated with your decision to refuse to perform the hemipelvectomy in this patient?