Hanna, Nasser H.

e14683 Background: Immune checkpoint inhibitors (ICIs) have altered the landscape of cancer treatment. ICIs are associated with immune mediated diarrhea and colitis (IMDC) which can be challenging to diagnose and differentiate from other etiologies of diarrhea. Clostridium difficile infection (CDI) is a common cause of diarrhea in patients with cancer and can have similar symptoms. In a similar study, CDI was found to be relatively common in ICI-treated cancer patients and especially those with IMDC requiring immunosuppressants. Our study evaluates the incidence of CDI and IMDC in patients with ICI exposure and compares clinical characteristics between the two to determine risk factors that may predispose patients to CDI or IMDC. Methods: This is a retrospective, single-center study of cancer patients on an ICI from 1/1/2011 to 4/7/2022 who were tested for Clostridium difficile with stool nucleic acid amplification tests during or after treatment with an ICI. Patients were determined to have CDI if clinically suspected and had to have a positive stool GDH Ag along with positive C. difficile toxins A & B or a positive stool C. difficile toxin B gene. Patients with positive GDH Ag in the stool but with negative toxins A&B were determined to be colonized. The diagnosis of IMDC was based on the clinical presentation and had to be made by the treating oncologist. Results: 375 patients met our study criteria and got CDI testing at any point during or after ICI exposure. 27 patients tested positive for CDI, whereas 24 were colonized. 105 patients were determined to have IMDC and 97/105 received treatment with steroids or immunosuppressants. Among patients determined to have IMDC, 6 were colonized for clostridium difficile. There were no patients with IMDC who were also positive for clostridium difficile. 71 patients were on a dual ICI regimen whereas 304 patients were on a single ICI. In patients on the dual ICI regimen, 67.6% were diagnosed with IMDC when compared to patients on a single ICI regimen where 18.8% of patients were diagnosed with IMDC (p<0.0001). The absolute lymphocyte count on the day of CDI testing was 1.185 ± 0.066 in the IMDC group when compared to 0.948 ± 0.044 in the non-IMDC group (p=0.003). The mean duration of diarrhea was longer in the IMDC group at 16.905 ± 1.211 days when compared to the CDI group at 9.852 ± 2.387 days (p= 0.0094). Smoking status, sex, history of autoimmunity, and history of prior immune related adverse events did not impact incidence of IMDC or CDI. Conclusions: IMDC was a common cause of diarrhea in patients with ICI exposure who were tested for CDI. We did not find IMDC to be a risk factor for CDI. IMDC has a longer duration of diarrhea and colitis symptoms when compared to CDI. The absolute lymphocyte count on symptom onset is higher in patients with IMDC when compared to patients with CDI and may be useful in identifying patients with IMDC earlier.

e23078 Background: There are limited patient (pt) reported outcome data regarding CDDP neurotoxicity. Methods: CDDP-induced peripheral neuropathy was evaluated in pts with testicular cancer planning to receive CDDP (20 mg/m2/d for 5 days) for ≥ 3 cycles. Neurotoxicity was assessed with the EORTC QLQ-CIPN20 tool before each CDDP cycle and every 2-4 months after, out to 18 months. We compared these data to our studies evaluating pts receiving doxorubicin/cyclophosphamide (AC), paclitaxel and oxaliplatin. The total score of the EORTC QLQ-CIPN20, each of the three subscale scores and each individual item was computed following the standard scoring algorithm and converted to a 0-100 scale. Descriptive statistics and graphical plots were utilized. Results: 54 pts receiving CDDP (mean age 33 years) and 18 pts receiving AC were evaluated. Following completion of CDDP, neuropathy symptoms (sensory neuropathy score and numbness/tingling in toes/feet) worsened for about 6 months (consistent with the so-called “coasting phenomena”), similar to what had previously been seen with oxaliplatin (but different than what had been seen with paclitaxel). For CDDP pts, during therapy, numbness and tingling in fingers/hands were more prominent, than the same symptoms in the toes/feet. After therapy was completed, numbness, and tingling became more prominent in toes/feet, but improved in the fingers/hands. After stopping therapy, shooting/burning pain did not worsen in upper or lower extremities. During therapy, CDDP pts had less problems than had previously been seen with oxaliplatin or paclitaxel, maybe because of the younger ages of the CDDP pts. With AC, all of the CIPN-20 sensory neuropathy scores were better than was seen in the pts receiving CDDP and also in pts receiving paclitaxel and oxaliplatin in previous evaluations. Conclusions: CDDP-induced neuropathy is more similar to oxaliplatin-induced neuropathy than paclitaxel-induced neuropathy. AC chemotherapy pts do not have substantial changes in CIPN 20 scores, consistent with the CIPN 20 instrument being a measure of chemotherapy-induced neuropathy, as opposed to more general chemotherapy-induced toxicities. Clinical trial information: NCT02677727.