Can Cancer Be Ruled Out If Having Abdominal Pain, Middle Lower Backpain While Undergoing Quantitative Phlebotomy And Having Done Prostatectomy Previously?

Male Age 59. 5 7 195lbs. Previous PC prostatectomy in 05 with good margins. PSA .05. Hyperlipidemia on crestor 10 mg/day for 5 years In July had some unusual achy abdominal pain after eating a large meal of mostly red meat (brazilian steakhouse). In Sept the pain had unusual bowel movement. Pain mostly on lower left. Stool is normal to soft but has slight yellowish residue left on toilet paper. Something like when I have diarreha. Diverticulitis suspect. Had a course of two antibiotics with no improvement. liver and Kidney bloodwork in Nov normal except ferritin 850, ggt 100 tsat 42%. RBC MCV, MCH, MCHC high normal. Platelets, Lymphocytes, monocytes, touch low normal. Abdominal CT negative and C282Y negative. Under going wkly phlebotomy (2wks now). Pain has worsened slightly now down to lower abdomen just below navel also bit more intense at times on left around rib cage. Also some transient mild pain in middle lower back. Curious on other investigations that should be considered while undergoing quantitative phlebotomy. Can cancer be ruled out?