Over the past two decades of successive clinical trials in metastatic colorectal cancer (CRC), the median overall survival of both control and experimental arms has steadily improved. However, the incremental change in survival for metastatic CRC patients not treated on trial has not yet been quantified. We performed a retrospective review of 1420 patients with de novo metastatic CRC who received their primary treatment at the University of Texas M.D. Anderson Cancer Center (UTMDACC) from 2004 through 2019. Median OS was roughly stable for patients diagnosed between 2004 and 2012 (22.6 months) but since has steadily improved for those diagnosed in 2013 to 2015 (28.8 months), and 2016 to 2019 (32.4 months). Likewise, 5-year survival rate has increased from 15.7% for patients diagnosed from 2004 to 2006 to 26% for those diagnosed from 2013 to 2015. Notably, survival improved for patients with BRAFV600E mutant as well as microsatellite unstable (MSI-H) tumors. Multivariate regression analysis identified surgical resection of liver metastasis (HR = 0.26, 95% CI, 0.19–0.37), use of immunotherapy (HR = 0.44, 95% CI, 0.29–0.67) and use of third line chemotherapy (regorafenib or trifluridine/tipiracil, HR = 0.74, 95% CI, 0.58–0.95), but not year of diagnosis (HR = 0.99, 95% CI, 0.98–1), as associated with better survival, suggesting that increased use of these therapies are the drivers of the observed improvement in survival.

ImportanceAppendiceal adenocarcinoma is a rare tumor, and given the inherent difficulties in performing prospective trials in such a rare disease, there are currently minimal high-quality data to guide treatment decisions, highlighting the need for more preclinical and clinical investigation for this disease.ObjectiveTo prospectively evaluate the effectiveness of fluoropyrimidine-based systemic chemotherapy in patients with inoperable low-grade mucinous appendiceal adenocarcinoma.Design, Setting, and ParticipantsThis open-label randomized crossover trial recruited patients at a single tertiary care comprehensive cancer center from September 2013 to January 2021. The data collection cutoff was May 2022. Enrollment of up to 30 patients was planned. Eligible patients had histological evidence of a metastatic low-grade mucinous appendiceal adenocarcinoma, with radiographic imaging demonstrating the presence of mucinous peritoneal carcinomatosis and were not considered candidates for complete cytoreductive surgery. Key exclusion criteria were concurrent or recent investigational therapy, evidence of bowel obstruction, and use of total parenteral nutrition. Data were analyzed from November 2021 to May 2022.InterventionsPatients were randomized to either 6 months observation followed by 6 months of chemotherapy, or initial chemotherapy followed by observation.Main Outcomes and MeasuresThe primary end point was the percentage difference in tumor growth in treatment and observation groups. Key secondary end points included patient-reported outcomes in the chemotherapy and observation periods, objective response rate, rate of bowel complications, and differences in overall survival (OS).ResultsA total of 24 patients were enrolled, with median (range) age of 63 (38 to 82) years, and equal proportion of men and women (eg, 12 men [50%]); all patients had ECOG performance status of 0 or 1. A total of 11 patients were randomized to receive chemotherapy first, and 13 patients were randomized to receive observation first. Most patients (15 patients [63%]) were treated with either fluorouracil or capecitabine as single agent; 3 patients (13%) received doublet chemotherapy (leucovorin calcium [folinic acid], fluorouracil, and oxaliplatin or folinic acid, fluorouracil, and irinotecan hydrochloride), and bevacizumab was added to cytotoxic chemotherapy for 5 patients (21%). Fifteen patients were available to evaluate the primary end point of difference in tumor growth during treatment and observation periods. Tumor growth while receiving chemotherapy increased 8.4% (95% CI, 1.5% to 15.3%) from baseline but was not significantly different than tumor growth during observation (4.0%; 95% CI, −0.1% to 8.0%; P = .26). Of 18 patients who received any chemotherapy, none had an objective response (14 patients [77.8%] had stable disease; 4 patients [22.2%] had progressive disease). Median (range) OS was 53.2 (8.1 to 95.5) months, and there was no significant difference in OS between the observation-first group (76.0 [8.6 to 95.5] months) and the treatment-first group (53.2 [8.1 to 64.1] months; hazard ratio, 0.64; 95% CI, 0.16-2.55; P = .48). Patient-reported quality-of-life metrics identified that during treatment, patients experienced significantly worse fatigue (mean [SD] score, 18.5 [18.6] vs 28.9 [21.3]; P = .02), peripheral neuropathy (mean [SD] score, 6.67 [12.28] vs 38.89 [34.88]; P = .01), and financial difficulty (mean [SD] score, 8.9 [15.2] vs 28.9 [33.0]; P = .001) compared with during observation.Conclusions and RelevanceIn this prospective randomized crossover trial of systemic chemotherapy in patients with low-grade mucinous appendiceal adenocarcinoma, patients did not derive clinical benefit from fluorouracil-based chemotherapy, given there were no objective responses, no difference in OS when treatment was delayed 6 months, and no difference in the rate of tumor growth while receiving chemotherapy.Trial RegistrationClinicalTrials.gov Identifier: NCT01946854

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226 Background: Appendiceal adenocarcinoma (AA) is a rare and heterogenous cancer with marked differences in clinical course between high- and low-grade tumors. Unlike colorectal cancer (CRC) and other gastrointestinal malignancies, AA virtually never has hematogenous metastases, rather, metastasis is limited to the peritoneum. Here we present a retrospective, single institution study of AA to identify the prevalence of detectable ctDNA, evaluate the clinical predictive value of positive ctDNA, and assess what clinical, pathologic, or molecular features predict positive ctDNA. Methods: 160 blood samples from 147 patients with AA metastatic to the peritoneum were profiled with a CLIA approved 73 gene mutational panel as part of routine clinical practice. Paired tumor sequencing was available for 73 patients. Survival was measured starting from day ctDNA was drawn. Mutations that most likely represented clonal hematopoiesis were removed from analysis. Results: Out of 160 ctDNA samples, 120 were taken in the setting of radiographically apparent metastatic disease. Of these, 46 (38.3%) had any detectable mutation. 40 ctDNA tests were performed when patients had no radiographic evidence of disease (NED); 15 (37.5%) of which had any detectable mutation. High-grade tumors were more likely to have detectable ctDNA with detection rates of 10/46 (21.7%), 18/46 (39.1%), and 33/68 (48.5%) for well, moderately, and poorly-differentiated tumors, respectively. Restricting analysis to the 73 patients with paired tissue and blood samples and 73 genes sequenced in both, of 81 mutations detected in tumor only, 21 were detected in blood (sensitivity of 26%). Sensitivity was highest for mutation in TP53 (53.8%) suggesting these tumors may have a greater propensity to shed DNA into circulation. Overall, the sensitivity of ctDNA detection in metastatic AA was markedly less than what was observed in a cohort of 274 metastatic CRC patients from the same institution (288/581 = 49.6%). For AA patients with detectable ctDNA, variant allele frequency (VAF) in AA was significantly lower compared to CRC (median VAF 0.04% vs. 6%, p = <0.0001). Detectable ctDNA was associated with shorter overall survival (46.2 mo for positive ctDNA vs. not-yet-reached for negative ctDNA, HR = 2.5, p = 0.016) and shorter disease free survival (DFS) (60 mo vs. not-yet-reached, HR = 3.4, p = 0.05). As expected, patients with radiographic evidence of disease did worse than patients with NED (HR = 2.1. p = 0.08), but of note this hazard ratio was less than that for positive ctDNA. Conclusions: In patients with AA, the presence of detectable ctDNA is associated with shorter overall and disease-free survival. Sensitivity of ctDNA detection in metastatic AA is overall markedly lower than CRC, with detection more likely in high-grade tumors and higher sensitivity in tumors containing TP53 mutation.

163 Background: Appendiceal adenocarcinoma is both a rare and heterogenous tumor, with marked contrast in the natural history of low-grade and high-grade tumors (5-year OS 68% for low-grade vs. 7% for high-grade). While low-grade appendiceal adenocarcinoma is primarily treated with surgical resection sometimes followed by hyperthermic intraperitoneal chemotherapy (HIPEC), many inoperable candidates are treated with systemic chemotherapy although there is no prospective data supporting this practice. The purpose of our study was to objectively evaluate the effectiveness of systemic chemotherapy in low-grade mucinous appendiceal adenocarcinoma. Methods: A randomized crossover trial of surgically unresectable low-grade (well differentiated) mucinous appendiceal adenocarcinoma was performed with patients randomized to either 6 months observation followed by 6 months of chemotherapy (physician’s choice), or initial chemotherapy followed by observation. In this way each patient would serve as their own control. Enrollment of 30 patients was planned to have complete 6- and 12-month tumor measurements for 24 patients, providing 80% power at 0.05 significance level to detect a 5.0% difference in change in tumor size as measured by peritoneal RECIST in observation vs. treatment periods. Results: The trial closed early due to slow accrual. A total of 24 patients were enrolled. The majority of patients were treated with either 5FU or capecitabine (n = 15, 63%), bevacizumab was added for 3 (13%), and 3 were treated with doublet chemotherapy (FOLFOX/FOLFIRI). 15 patients who completed both treatment and observation periods were available for the primary analysis, the mean difference in tumor size was -4.5% (95% CI: -12.6, 3.7), indicating a slight trend towards faster growth on treatment than observation. This difference was not statistically or clinically significant (8.4% growth on treatment vs. 4.0% observation, p=0.26). Of the 18 patients who received any chemotherapy during the study period, zero achieved an objective response, 14 (77.8%) had stable disease during the entire year of follow up, and 4 (12.2%) had progression on study. Patient reported quality of life metrics identified that fatigue (p=0.02), peripheral neuropathy (p=0.014), and financial difficulty (p=0.0013) were all significantly worse while on treatment. There was not a significant difference in rate of bowel obstruction between the treatment first vs. observation first arms (12.5%, (n=3) vs 8.3%, (n=2)). Conclusions: These data from a prospective, randomized crossover trial indicate that patients with low-grade mucinous appendiceal adenocarcinoma do not derive benefit from 5FU based chemotherapy but do incur toxicity. These data further highlight the unique biology of low-grade appendiceal cancer and demonstrates the need to identify novel systemic therapies for this patient population. Clinical trial information: NCT01946854 .