‘Unprecedented’ Responses to Neoadjuvant Tx in dMMR Colon Cancer

PARIS — “Unprecedented” pathologic responses were seen after a neoadjuvant 4-week course of ipilimumab (Yervoy) plus nivolumab (Opdivo) was given before surgery to patients with DNA mismatch repair deficient (dMMR) colon cancer, say researchers reporting new results from the NICHE-2 trial.

The trial involved 112 patients with dMMR colon cancer who were given one cycle of low-dose ipilimumab and two cycles of nivolumab followed by surgery.

The results show that 95% of patients had a major pathologic response (MPR) and 67% had a pathologic complete response (pCR) to immunotherapy.

To date, none of these patients have had disease recurrence after a median follow-up of 13.1 months.

Study presenter Myriam Chalabi, MD, an oncologist at the Netherlands Cancer Institute, Amsterdam, described the findings as “unprecedented,” especially as many of the patients had stage 3 and high-risk disease, and the expected disease recurrence rate with standard-of-care adjuvant chemotherapy in these patients would usually have been around 15%.

“Importantly, this treatment was very well-tolerated,” she added.

Chabai presented the new results here during a presidential session at the European Society for Medical Oncology (ESMO) Annuak Meeting 2022, held in Paris, France.

Neoadjuvant immunotherapy “has the potential to become standard of care” in these patients, she said, adding that the “future has never been brighter” for dMMR colon cancer.

Around 10%-15% of colon cancers are dMMR, and around 33% of these are associated with Lynch syndrome, she noted.

She also urged pharmaceutical companies to seek approval for immunotherapy in this patient population, to warm applause from the audience.

Commenting on the results, Andrés Cervantes, MD, PhD, professor of medicine at the University of Valencia, Spain, said in an ESMO press release that the “innovative” study “questions the need for surgery and postoperative chemotherapy in all patients in whom the primary tumor has disappeared.”

He observed that adjuvant chemotherapy has remained standard of care, “despite the fact that chemotherapy is not so active and a complete disappearance of the tumor in the surgical specimen is not observed.”

Overall, Cervantes said that dMMR status is a “strong predictor of the positive effect observed with this short-course immunotherapy,” adding that “determining dMMR can be easily done by immunohistochemistry in the conventional pathology lab, without the need for complex molecular testing.”

The “minimal toxicity” seen in the study “may also facilitate the implementation of this strategy, potentially sparing patients from surgery.”

Details of the New Results

For the NICHE-2 study, patients with stage cT3 dMMR colon cancer and/or nodal involvement but without metastases and no signs of obstruction received one dose of ipilimumab 1 mg/kg and two doses of nivolumab 3 mg/kg before undergoing surgery within 6 weeks of enrollment.

The 112 participants were a median age of 60 years and just over half were women. High-risk stage 3 disease was present in 74% of patients, which included 64% of patients with clinical T4a or T4b tumors and 62% with radiologic N2 stage cancer.

Median time from the first immunotherapy dose to surgery was 5.4 weeks.

Immune-related adverse event were seen in 61% patients, but just 4% of patients experienced grade 3-4 immune-related adverse events, and 2% consequently had a delay in surgery, meaning the study met its primary safety endpoint.

In the end, all patients underwent surgery, with 100% having R0 resections.

A pathologic response was seen in 99% of patients, with 95% having an MPR, defined as ≤ 10% residual viable tumor, and 4% a partial response, defined as 10%–≤50% residual viable tumor. A pCR, which included both the tumor bed and lymph nodes, was seen in 67% of participants.

There was a borderline significant difference in pCR patients between the 66 patients with sporadic tumors and the 32 with Lynch syndrome, at 58% versus 78% (P = .056).

At the meeting, discussant James Larkin, MD, PhD, consultant medical oncologist, The Royal Marsden, London, UK, who was not involved with the study, agreed that the results were “striking,” with “brief treatment…[showing] a major effect.”

However, he emphasized that it will “important” to see the prespecified 3-year disease-free survival data, and he questioned whether the single low dose of ipilimumab was, in fact, necessary.

Larkin also emphasized that organ-sparing strategies in colon cancer are less “clear cut” than they are in rectal cancer and would require ongoing follow-up with colonoscopies and, potentially, biopsies. He also said it is “critical” to get patients’ views on the desirability of organ sparing.

The study was funded by Bristol Myers Squibb. Chalabi has reported no financial interests. Disclosures for the other authors are listed with the abstract. Larkin has declared relationships with Eisai, Novartis, Merck, Pfizer, BMS, iOnctura, Debiopharm, Incyte, MSD, Pierre Fabre, Ibsen, Roche, EUSA Pharma, AstraZeneca, GSK, Calithera, Ultimovacs, Seagen, and Nektar Therapeutics.

ESMO 2022. Abstract LBA7. Presented September 11, 2022.

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