Introduction

Three abstracts from this year's ASCO meeting speak to very different parts of the colorectal cancer journey: what happens after surgery and chemotherapy are done, whether a familiar over-the-counter drug still has a role, and whether patients with a complete response to immunotherapy really need to stay on it indefinitely.

Structured Exercise After Colon Cancer Surgery Is Not Just Effective, It's Cost-Saving

Last year's CHALLENGE trial, published in the New England Journal of Medicine, showed that a three-year structured exercise program after adjuvant chemotherapy for colon cancer improved both disease-free and overall survival compared with health education alone, a genuinely remarkable finding for what amounts to a behavioral intervention. Patients were randomized to a structured program (working with a trainer, regular sessions) versus general health education, and the exercise group lived longer.

This year's follow-up asked the practical question every health system eventually asks: is it worth paying for? A cost analysis of the trial (conducted in Canada) found the exercise program cost about $3,000 per patient, but avoided costs elsewhere, recurrence, additional therapy, hospitalization, that were high enough to produce a net cost savings of roughly $1,600 per patient overall. This is genuinely the first economic evidence supporting routine structured exercise programs as part of colon cancer survivorship care, on top of the already-established survival benefit.

The practical challenge is infrastructure: most centers cannot give every patient a personal trainer. A reasonable middle path is limited coaching sessions that patients can build on independently, alongside insurance coverage that, at least in the U.S. system, does not yet reliably support this kind of program the way Canada's system apparently does. Preoperative counseling matters too: framing surgery and postop recovery like a marathon, and discussing activity expectations before the operation, helps set patients up to participate once they are able.

Aspirin After Colon Cancer Surgery: Still an Open Question

Aspirin has shown some potential as an adjunct after colorectal cancer surgery in prior observational and pathway-specific data, but its role in an unselected patient population has remained uncertain. A randomized trial tested chemotherapy plus daily low-dose aspirin against chemotherapy plus placebo after resection for stage III colon cancer.

In the overall, unselected population, aspirin did not significantly improve disease-free survival; there was a numerical trend toward benefit, but it did not reach statistical significance. The subgroup most likely to benefit, based on prior data, appears to be patients with alterations in the PI3K/PIK3CA pathway specifically, not the general colon cancer population. Practically, this means the overall role of aspirin in colorectal cancer remains genuinely unclear, and broader use should probably wait for either confirmatory data in molecularly selected patients or a clearer signal in the unselected population; routinely starting aspirin in every resected stage III patient is not currently well supported.

Can Patients With a Complete Response to PD-1 Therapy in dMMR Colorectal Cancer Stop Treatment?

PD-1 blockade has become a genuinely transformative option in mismatch-repair-deficient (dMMR) colorectal cancer, both in locally advanced rectal cancer and in colon cancer, sparing some patients the morbidity of major pelvic surgery entirely. But once a patient has a complete clinical response, does continuing immunotherapy indefinitely actually help, or can it be safely stopped?

A multi-cohort study (2018-2025) followed patients with dMMR colorectal cancer who achieved a non-operative complete response to PD-1 blockade, comparing those who continued on maintenance immunotherapy against those who were simply observed. Both groups had excellent survival, with no clear difference in disease-free or overall survival between maintenance and observation, while the maintenance group experienced more cumulative toxicity from continued treatment. The study has real limitations, it was non-randomized, follow-up was longer in the maintenance group, and patients received a variety of different PD-1 inhibitors rather than one consistent agent, but the practical signal is clear: close observation after a complete clinical response appears to be a reasonable, adequate strategy, without the added toxicity burden of prolonged immunotherapy.

For rectal cancer patients with MMR deficient tumors specifically, this matters enormously. Even a technically excellent low anterior resection or abdominoperineal resection carries real, lasting morbidity, including low anterior resection syndrome, so patients who achieve a complete response to PD-1 blockade and can avoid both surgery without prolonged immunotherapy representing a genuine, meaningful win for patients with MMR deficient tumors.

For Patients

If you or a family member is recovering from colon cancer surgery and chemotherapy, structured exercise is not just a nice-to-have, it's now shown to improve both quality of life and survival, and it's worth asking your care team about local resources (like the LIVESTRONG program at the YMCA, offered free for a limited period to cancer survivors) even if a fully personalized program isn't available. For patients with mismatch-repair-deficient colorectal or rectal cancer who achieve a complete response to immunotherapy, current evidence suggests that closely monitored observation, rather than staying on the drug indefinitely, is a reasonable path that avoids unnecessary side effects without compromising outcomes.

Key Takeaways

  • A cost analysis of the CHALLENGE trial found a structured post-chemotherapy exercise program, already shown to improve disease-free and overall survival in colon cancer, is also cost-saving overall, at roughly $1,600 per patient net savings despite a $3,000 per-patient program cost.

  • A randomized trial found aspirin did not significantly improve disease-free survival in an unselected population of resected stage III colon cancer patients; potential benefit may be concentrated in patients with PI3K/PIK3CA pathway alterations specifically.

  • In dMMR colorectal cancer patients with a complete clinical response to PD-1 blockade, a multi-cohort study found no clear survival advantage to continuing maintenance immunotherapy over close observation, while toxicity was higher with continued treatment.

  • For rectal cancer patients able to avoid surgery through a complete response to immunotherapy, being able to also stop treatment once in complete response, rather than continuing indefinitely, meaningfully reduces treatment burden without an apparent survival tradeoff.

References

  1. Booth CM, Friedenreich CM, Vergidis D, et al. Structured exercise after adjuvant chemotherapy for colon cancer (CHALLENGE trial). N Engl J Med. 2025; cost-effectiveness analysis presented ASCO 2026.

  2. Randomized phase 3 trial of adjuvant aspirin versus placebo after resection for stage III colon cancer. Presented ASCO 2026.

  3. Multi-cohort study of PD-1 blockade maintenance versus observation after complete clinical response in mismatch-repair-deficient colorectal cancer. Presented ASCO 2026.