Prospective screening and proposed treatment algorithm for immune checkpoint inhibitor induced myositis in neoadjuvant-treated rectal cancer patients: data from the phase II CHINOREC trial

Abstract Background Myositis is an infrequent (<1%) but potentially life-threatening (case fatality rate 40-50%) immune-related adverse event (irAEs) of immune checkpoint inhibitors (ICI), such as ipilimumab (IPI) and nivolumab (NIVO). The true incidence is likely to be underestimated and may not be representative for curative neoadjuvant treatment approaches in gastrointestinal (GI) cancers, especially in combination with chemoradiotherapy (CRT). Currently, the summary of product characteristics (SmPC) does not suggest any pre-emptive screening or surveillance. Methods The CHINOREC study is an ongoing prospective, randomized, open-label, multicenter, phase II investigator-initiated trial (IIT). Patients with intermediate to locally advanced rectal cancer (LARC) receive either neoadjuvant CRT alone or in combination with a single dose of IPI and 3 cycles of NIVO, following surgical resection. Patients are monitored at baseline and throughout the whole study period for myotoxicity biomarkers, including cardiac troponin T (cTnT) and cardiac troponin I (cTnI). Findings From 06/2020 to 11/2023, 80 patients have been enrolled of whom 50 patients were randomized to the CRT+IPI/NIVO arm. Six patients (12%) developed biopsy-verified myositis. Myositis treatment was promptly implemented using a pragmatic step-up approach. Patients received glucocorticoids (GC) with concomitant intravenous immunoglobulin (IVIG). If myotoxicity biomarkers did not improve, patients received infliximab (INFLIXI) and/or plasma exchange (PLEX). Although all patients had strikingly elevated cTnT (median peak 284 ng/L, 95% CI 39-3097), cTnI levels remained largely normal, correlating with a negative cardiac magnetic resonance (CMR). All patients underwent successful tumor surgery without any major surgical complication. As of today, all patients' creatine kinase (CK) and myoglobin (MB) levels have normalized and they are tumor free without any major sequela. Interpretation Longitudinal biomarker screening (cTnT/cTnI) for ICI-induced myotoxicities is pivotal in curative neoadjuvant-treated cancer patients to initiate an early counter treatment in a holistic step-up approach, without compromising oncological principles.