Presurgery radiation (usually chemoradiation since it's some form of 5FU+radiation) is usually effective. It almost certainly did help my husband since it seems to have killed some lymph-node mets as well as stopped the activity of the primary for a while. His CEA went all the way down to 1.6 after the radiation, the lowest it's been. I've just become skeptical about the benefit of presurgery folfox for more aggressive tumors (which are not particularly common for CRC). I'll also note that we were told that the biopsy specimen from when he was diagnosed was G2 (moderately differentiated), the most common grade for CRC, then the surgical specimen was graded G3 (poorly differentiated). So I'm not sure what the story there was. It was different pathologists and there is some subjectivity in the classification, or it could have been a heterogeneous tumor. So as far as his oncologist knew from his records at the time, it was the more usual G2, which probably would have responded better.
Unfortunately nearly all colorectal tumors are immunologically "cold" and do not respond to immunotherapy by itself. There are several clinical trials right now trying various other treatments along with checkpoint inhibitors (Keytruda etc.) but they don't know yet what may work. We are hoping to keep the boat afloat here with folfiri/bev until they figure out the best approach.
D/H Dx 10/2019 RC age 61
Clinical T4bN2M1a (common iliac and para-aortic lymph nodes)
MSS KRAS G12D
CRT 11/19-1/20 FOLFOX 3/20-7/20
Pelvic exenteration w/LAR 8/20
ypT4bN0Mx G3 0/14 nodes LVI not seen PNI-
CEA 10/19:20, 1/20-11/20:1.6, 4.3, 3.4, 2.7, 2/21:9.0 3/21:18,40 4/21:28,19, 5/21:13.3,8.6
PET 3/21 recurrence in distal nodes, L5 vertebra, pelvis