Long-term outcome of a phase III trial on neoadjuvant chemoradiation with capecitabine and irinotecan in patients with locally advanced rectal cancer: Updated results of the CinClare trial.

3603 Background: Adding UGT1A1-guided irinotecan to capecitabine-based neoadjuvant chemoradiotherapy (CRT) significantly increased the pathological complete response (pCR) rate nearly doubling [J Clin Oncol. 2020 Dec 20;38(36):4231-4239]. Here, results of long-term outcome are reported. Methods: Eligible patients with clinical stage II/III rectal adenocarcinoma, UGT1A1 genotype *1*1 or *1*28 were randomized to the control group: pelvic radiation of 50 Gy/25 fractions with concurrent capecitabine, followed by a cycle of oxaliplatin and capecitabine; or the experimental group: radiation with capecitabine combined with weekly irinotecan 80 mg/m2 for patients with *1*1 or 65 mg/m2 for patients with *1*28, followed by a cycle of irinotecan and capecitabine. Surgery was scheduled for 8 weeks after completion of CRT. Five cycles of adjuvant XELOX chemotherapy were administered regardless of the pathologic result. Patients were stratified by UGT1A1 genotype (*1*1 vs. *1*28) clinical T stage (cT3 vs. cT4) and tumor distance from the anal verge (≤5 cm vs. > 5 cm). The primary end point of pCR was reached. Survival time was calculated from the date of randomization to the date of event or the last follow-up. Secondary endpoints were defined as local failure for local control (LC), tumor recurrence or death from any cause for disease-free survival (DFS), and death from any cause for overall survival (OS). Results: Of the 360 patients initially enrolled, 356 were evaluated as the modified intention-to-treat population (n = 178 in both groups). A total of 311 patients underwent surgery and pCR was achieved in 80 patients, another 10 patients undergo a watch-and-wait approach after achieving cCR. With a median follow-up time of 48 months (Q25-Q75, 41-55 months), 57 deaths (33 and 24), 17 local failures (11 and 6) and 69 distant metastases (37 and 32) were observed, respectively. Overall, the 4y LC rate were 93% and 96% in control and experimental groups, with estimated LC HR of 0.53 (95% confidence interval [CI], 0.20-1.43), the 4y DFS rates were 69% and 74% (HR = 0.74, 95% CI 0.49-1.10), and the 4y OS were 80% and 85%, (HR = 0.70, 95% CI 0.42-1.19), respectively. In the subgroup analysis, irinotecan showed a significant improvement in DFS (HR = 0.77, 95% CI 0.61-0.98) and OS (HR = 0.71, 95% CI 0.51-0.98) in UGT1A1 *1*1 patients. Conclusions: The addition of irinotecan to standard capecitabine-based CRT had a tendency towards improving LC, DFS, and OS, but without reaching statistical significance. UGT1A1 *1*1 patients seem to benefit the most from irinotecan. Molecular studies and subsequent therapies should be considered. Clinical trial information: NCT02605265.

Safety and pharmacokinetic analysis of UGT1A1 genotype-guided dosing of irinotecan.

3574 Background: Irinotecan is commonly used in the treatment of advanced colorectal and pancreatic cancer. The polymorphisms UGT1A1*28 (7 TA repeats) and UGT1A1*93 (SNP -3156G > A) are significantly associated with increased systemic exposure of irinotecan’s active metabolite SN-38 and subsequently severe irinotecan-associated adverse-events (AEs) including (febrile) neutropenia and diarrhea. Severe AEs may lead to hospitalization, loss of quality of life, treatment delay and/or treatment discontinuation. Nonetheless, prospective genetic screening is not yet routinely performed. The aim of this study was to determine the safety and pharmacokinetics of UGT1A1 genotype-guided dosing of irinotecan in UGT1A1 poor metabolizers (PMs), i.e. UGT1A1 *28/*28 and/or UGT1A1*93/*93 individuals, in order to reduce the incidence of severe irinotecan-associated AEs. Methods: A prospective, multi-center, non-randomized study was conducted in patients intended to be treated with irinotecan at a dose of ≥ 180 mg/m2 or 450-600 mg flat dose. All patients were pre-therapeutically genotyped for UGT1A1*28 and UGT1A1*93. In UGT1A1 PMs, an initial 30% dose reduction in the first cycle was applied followed by further individual dose titration based on neutrophil count and clinical tolerability. The primary endpoint was the incidence of febrile neutropenia in the first 2 cycles of irinotecan treatment. UGT1A1 PMs were compared to 1] historical control patients, i.e. homozygous polymorphic patients treated with full dose therapy identified from systematic literature review and to 2] UGT1A1 non-PMs treated with standard dose therapy. In addition, systemic SN-38 exposure (AUC0-500h) of reduced dosing in the UGT1A1 PM cohort was compared to a standard dosed irinotecan patient cohort [doi: 10.1200/JCO.2000.18.1.195] by an independent T-test. Results: A total of 349 patients were pre-therapeutically genotyped and included for analysis. Thirty-one (8.9%) patients were UGT1A1 PM, in whom an initial median 30% dose reduction was applied. The incidence of febrile neutropenia in this group was 6.5% compared to 24% in historical controls (n = 50) (p = 0.042) and comparable with the incidence (4.1%; p = 0.632) in UGT1A1 non-PMs treated with full dose therapy. The systemic exposure of SN-38 of reduced dosing in UGT1A1 PMs (n = 17) was comparable to the systemic exposure of the standard dosed irinotecan patient cohort (n = 46) with a relative difference of +24% (p = 0.054) with a geometric mean (CV) of SN-38 AUC0-500h of 391 (43.7%) versus 298 (75.3%) ng*h/mL, respectively. Conclusions: UGT1A1 genotype-guided dosing significantly reduces the incidence of febrile neutropenia in UGT1A1 PM patients treated with irinotecan. In addition, systemic drug exposure remained adequate, despite the 30% dose reduction. Therefore, UGT1A1 genotype-guided dosing of irinotecan should be considered standard of care in order to improve the individual patient safety. Clinical trial information: Trial NL6270 (NTR6612).

Multicenter, Randomized, Phase III Trial of Neoadjuvant Chemoradiation With Capecitabine and Irinotecan Guided by UGT1A1 Status in Patients With Locally Advanced Rectal Cancer

PURPOSE Differentiating the irinotecan dose on the basis of the uridine diphosphate glucuronosyltransferase 1A1 ( UGT1A1) genotype improves the pathologic complete response (pCR) rate. In this study, we further investigated preoperative irinotecan combined with capecitabine-based chemoradiotherapy for locally advanced rectal cancer. PATIENTS AND METHODS We conducted this randomized, open-label, multicenter, phase III trial in China. Eligible patients with clinical T3-4 and/or N+ rectal adenocarcinoma, UGT1A1 genotype *1*1 or *1*28 were randomly allocated to the control group: pelvic radiation of 50 Gy/25 fractions with concurrent capecitabine, followed by oxaliplatin and capecitabine; or the experimental group: radiation with capecitabine combined with weekly irinotecan 80 mg/m2 for patients with UGT1A1*1*1 or 65 mg/m2 for patients with UGT1A1*1*28, followed by irinotecan and capecitabine. The primary end point was pCR. This trial was registered with ClinicalTrials.gov (ClinicalTrials.gov identifier: NCT02605265). RESULTS Of the 360 patients initially enrolled, 356 were evaluated as the modified intention-to-treat population (n = 178 in both groups). Surgery was performed in 87% and 88% of patients in the control and experimental groups, respectively. The pCR rates were 15% (n = 27 of 178) and 30% (n = 53 of 178) in the control and experimental groups (risk ratio, 1.96; 95% CI, 1.30 to 2.97; P = .001). Four and 6 patients achieved complete clinical response in the control and experimental groups, respectively. Grade 3-4 toxicities were recorded in 11 (6%) and 68 (38%) patients in the control and experimental groups, respectively ( P < .001). The commonest grade 3-4 toxicities were leukopenia, neutropenia, and diarrhea. The overall surgical complication rate was not significantly different between the two groups (11% v 15%; P < .001). CONCLUSION Adding irinotecan guided by UGT1A1 genotype to capecitabine-based neoadjuvant chemoradiotherapy significantly increased complete tumor response in Chinese patients.

Perioperative (P) UGT1A1 genotype guided irinotecan (iri) dosing ‘gFOLFIRINOX’ for gastroesophageal adenocarcinoma (GEA).

4050 Background: Complete resection (R0) and pathologic response grade (PRG) correlate with long-term GEA outcome. FOLFIRINOX demonstrated efficacy in advanced GEA; gFOLFIRINOX improved tolerability. We evaluated R0, PRG and tolerability in this pilot P study. Methods: Gastric body (GB) + esophagogastric (EGJ) GEA patients (pts) with ≥T3Nx or TxN+ were enrolled & treated with 4 pre + 4 postoperative biweekly cycles of gFOLFIRINOX (5-FU 2400mg/m2 over 46 hrs; oxaliplatin 85mg/m2; iri: 180mg/m2 for UGT1A1 genotype 6/6, 135mg/m2 for 6/7, 90mg/m2 for 7/7) (+ trastuzumab (T) 6mg/kg then 4mg/kg for HER2+) with prophylactic peg-filgastrim. 1°endpoint R0 resection required 36 pts to assess for a 90% R0 rate (intention to treat (ITT)) with 90% power + 0.05 alpha; ≥30/36 R0 considered positive. Co-1°endpoint was PRG (Becker); 36 pts provided 85% power with 0.05 alpha for a complete (pCR G1a) rate of 16%. 2°endpoints were safety/toxicity, PET response, & R0/PRG by tumor site, histologic subtype, HER2 status, & UGT1A1 genotype. We report efficacy and toxicity data from the neoadjuvant (Neo) portion of the study; postop data & survival outcomes will be presented at the meeting. Results: 4 sites enrolled 36 ITT pts between 2/2014-8/2018; 75% male, median age 66 (range 27-85). All pts completed all 4 cycles of Neo therapy: 10% had any dose reduction of iri (16%/0%/25% by genotype 6/6, 6/7, 7/7); any G3+ toxicity occurred in 35% of pts (32% 6/6, 29% 6/7, 75% 7/7). G3+ toxicity in ≥5% of pts: diarrhea (17.5%; 6/6 21%, 6/7 11%, 7/7 25%), anemia (5%), vomiting (5%). Efficacy is shown in the Table. Of pts going to surgery, both R1 resections were GB linitus. PRG1(a+b) was achieved in 36% of ITT pts, 46% of intestinal type histology. Conclusions: Neo gFOLFIRINOX was tolerable with surrogate efficacy comparable to FLOT. Clinical trial information: NCT02366819. [Table: see text]