Colorectal cohort analysis from the Intraperitoneal Chemotherapy After Cytoreductive Surgery for Peritoneal Metastasis (ICARuS) clinical trial

160

Background: ICARuS is a randomized phase II, multicenter trial to evaluate the relative efficacy of Hyperthermic Intraperitoneal Chemotherapy (HIPEC) with mitomycin C vs. Early Postoperative Intraperitoneal Chemotherapy (EPIC) with floxuridine (FUDR), after cytoreductive surgery (CRS), for the treatment of peritoneal metastases (PM) from colorectal (CRC) or appendiceal cancer (AC). PRODIGE7 results failed to demonstrate benefit of HIPEC therapy after complete gross resection of CRC PM, prompting termination of CRC accrual and early cohort analysis. Methods: Patients with isolated, confirmed PM were eligible for 1:1 randomization to CRS plus HIPEC with mitomycin C or CRS plus EPIC with FUDR. Patients were stratified by recent systemic chemotherapy and disease (AC vs. CRC). The trial was originally powered to evaluate 212 patients for a 20% gain in a primary endpoint of 3-year progression free survival (PFS: HR = 1.75). Results: Seventy-five CRC patients were included between 4/2013 and 12/2018 for HIPEC (N = 40) or EPIC (N = 35) treatment. Baseline characteristics were well balanced. After a median follow up of 36 months, the median PFS was 7.7 months (95% CI: 6.3-11.1) in the HIPEC arm and 8.8 months (95% CI: 7.1-21.9) in the EPIC arm, HR = 0.69 (95% CI: 0.42-1.14) p = 0.14. In the 42 left-sided primary cancers, the median PFS was 8.4 months (95% CI: 6.4-17.7) in the HIPEC arm and 12.5 months (95% CI: 8.1-NR) in the EPIC arm, HR = 0.60 (95% CI: 0.29-1.22) p = 0.14. In the 33 right-sided primary cancers, the median PFS was 6.5 months (95% CI: 5.5-14.1) in the HIPEC arm and 8 months (95% CI: 5.8-24.1) in the EPIC arm, HR = 0.80 (95% CI: 0.39-1.64) p = 0.53. PFS was significantly better in the EPIC arm among patients with BRAF wildtype (WT) tumors and patients with higher PM burden (PCI > 7). There was no difference between HIPEC and EPIC in the primary toxicity endpoint of complications grade 3 or above (23 vs. 34%, p = 0.3). Conclusions: Three-year PFS did not significantly differ between treatment arms. The lack of survival benefit of HIPEC in the entire cohort and in subset analysis is consistent with the findings of PRODIGE7. ICARuS remains open to accrual for AC. These data support further investigation of the potential benefit of EPIC with CRS in carefully selected patients with CRC PM. Clinical trial information: NCT01815359 .

Development of memorial Sloan Kettering (MSK) surgery stress score for older adults with cancer

e24014

Background: The stress from oncologic surgeries for older adults may lead to poor surgical outcomes. In this study, we aim to develop a MSK Surgery Stress Score to measure the complexity of surgery for these patients. The score could then be used for future analyses using datasets where patients undergoing a variety of procedures. Methods: This is a retrospective analysis of adults aged 75 and older who underwent elective cancer surgery in our institution with hospital length of stay of at least one day in 2015 to 2020. Based on surgery stress score developed by Haga et al., we explored various models including at least one or some of these variables as linear or non-linear terms: operation time, weight (kg), blood loss (cc), type of surgery, body mass index, and incision score. The primary outcome of interest evaluated was defined as the composite outcome of death within 90-day of surgery, readmission or emergency room visit or major complications (grade 3-5) within 30 days of surgery. We additionally explored models for a secondary outcome, where minor complications (grade 1-2) were included in the definition, and lastly, we looked at major complications alone as a tertiary outcome. For each of the model and outcomes, we used a logistic regression. We then used the logit transformation of the predicted probability to represent the proposed surgery stress score. Using this score, we evaluated the area under the curve (AUC) for each outcome. Results: In total, 1573 patients were included in the study. The median age was 80 (quartiles 77, 83) and just under half (49%) were male. The median (quartile) operation time was 181 minutes (115, 259), weight was 71 kg (62, 84), blood loss was 100 mL (50, 300), and just over (51%) of patient underwent an abdominopelvic procedure. The rate of 90-day mortality was 3.8%, while the rate of 30-day major complication, readmission and emergency room visit was 7.4%, 10% and 13%, respectively Furthermore, 21%, and 35% experienced primary, and secondary outcomes, respectively. Overall, 18 predictive models for each of the outcomes were developed and assessed. AUC for our different models ranged from 0.59 to 0.73 for the different definitions of our outcomes. Among the various models, the one defined using whether patients underwent an abdominopelvic procedure, incision score, operation time, weight, and blood loss (the latter two both included as non-linear terms) appeared to the front runner. Conclusions: We explored potential models to be used as the MSK Surgery Stress Score. Currently the model is being optimized by additional work. Following optimization of the model, future studies should validate this score in other cohorts of older surgical patients with cancer.

Clinical activity of pembrolizumab monotherapy in diffuse malignant peritoneal mesothelioma

8557

Background: Among patients with malignant mesothelioma, pembrolizumab has demonstrated activity in diffuse pleural mesothelioma (DPM), with limited data available for those with diffuse malignant peritoneal mesothelioma (DMPM). DMPM represents a clinically distinct entity from DPM and disease specific outcomes data is needed. We present real world data on the efficacy of pembrolizumab in DMPM. Methods: In this retrospective study, we identified patients with DMPM treated with pembrolizumab at two tertiary care cancer centers between 1/1/2009 and 1/1/2021. Clinicopathologic features were annotated. Median progression free survival (mPFS) and median overall survival (mOS) were calculated using Kaplan-Meier curves. Best overall response rate (BOR) was determined using RECIST 1.1 criteria. Association of partial response with disease characteristics was evaluated using Fisher’s exact test. Results: We identified 24 patients with DMPM who received pembrolizumab (median age 62 years, 63% never smokers, 58% female, 75% had epithelioid histology). All patients received systemic chemotherapy prior to pembrolizumab (median prior lines of therapy: 3). BOR was 17% (3 partial responses, 10 stable disease, 5 progressive disease, 6 lost to follow-up). With a median follow up time of 29.2 months, mPFS was 4.9 months and mOS 20.9 months from pembrolizumab initiation. Three patients experienced PFS of > 2 years. Among the 14 patients who underwent next generation sequencing of tumor tissue, there were 8 somatic BAP1 alterations. Among the 17 patients tested for PDL1, 6 had positive PDL1 expression (1-80%). There was no association between partial response and presence of a BAP1 somatic alteration (p = 0.453), PDL1 positivity (p = 0.7) or non-epithelioid histology (p = 0.55). Conclusions: Pembrolizumab is active in a PDL1 unselected cohort of patients with DMPM. The overall response rate of 17% and mPFS of 4.9 months in this 75% epithelioid histology cohort warrants further investigation to identify those most likely to respond to immunotherapy, especially among epithelioid histology.

Peritoneal mesotheliomas characterized by less cell-cycle alterations and more TRAF7 alterations than malignant pleural mesotheliomas

9059

Background: While peritoneal mesotheliomas (PM) are clinically distinct from malignant pleural mesotheliomas (MPM) it is unknown if genetic alterations reflect these differences. Here we report the molecular alterations and clinicopathologic characteristics of a prospectively collected PM cohort as compared to MPM. Methods: Patients with PM (n = 59) and targeted next generation sequencing (NGS; MSK-IMPACT) from January 2014 to January 2019 were assessed and followed through February 2020. Germline variants were analyzed in consented patients. NGS was compared to patients with MPM (n = 194) assessed in the same time interval. Results: Median age at diagnosis was 61 (range: 20-77), 56% were women (n = 33), and 92% had epithelioid histology (n = 54). 66% had ascites (n = 39) and 24% developed extra-abdominal metastases (n = 14; including lung, pleura, and mediastinum). 68% (n = 40) underwent surgical debulking and 80% (n = 47) had infusional therapy (median lines: 3) including platinum/pemetrexed (n = 38), EPIC (n = 22), HIPEC (n = 15), and immunotherapy (n = 16). The median overall survival (OS) from diagnosis was 5.4 years (median follow up 3.5 years). The median tumor mutation burden (TMB) was 1.8 mut/Mb (range: 0-14.9) in PM vs 2.0 mut/Mb (range: 0-31.5) in MPM (p = 0.049). More patients with PM had TRAF7 alterations than in MPM (5/59 vs 3/194; p = 0.02) while fewer had CDKN2A/ CDKN2B (4 vs 55; p = 0.0004). All patients with TRAF7 altered PM had well-differentiated papillary epithelioid histology. There was no difference in the prevalence of other common alterations such as BAP1 (32 vs 98; p = 0.66), NF2 (12 vs 55, p = 0.24), SETD2 (11 vs 24; p = 0.28), and TP53 (9 vs 28; p = 0.84) in PM vs MPM respectively. Patients with BAP1-altered PM had shorter OS (4.6 vs 9.8 years; HR 2.6, 95% CI 1.1-6.4; p = 0.04) while TRAF7-altered PM had improved OS (not reached vs 4.8 years; HR 0.3, 95% CI 0.1-0.9; p = 0.04) compared to wild type. 13% (4/30) of patients with PM had pathogenic variants on germline NGS ( POT1 I78T, MUTYH R109Y, BAP1 E402*, APC I1037K). Conclusions: NGS confirms the distinct biology of PM compared to MPM. Specifically, the former shows fewer cell cycle ( CDKN2) alterations compared to MPM. In contrast to MPM, BAP1 alteration was associated with shorter survival. As previously described, we found enrichment of TRAF7 in well differentiated papillary epithelioid PM associated with improved survival but notably some TRAF7 alterations were identified in poorly differentiated MPM. Consistent with other reports, the prevalence of germline alterations was 13%.

A phase II study of induction PD-1 blockade in subjects with locally advanced mismatch repair-deficient rectal adenocarcinoma

TPS4123

Background: The treatment of patients with locally advanced rectal cancer includes total neoadjuvant therapy with chemotherapy, chemoradiation followed by surgery. While most rectal cancers respond to combination induction chemotherapy, patients with mismatch repair deficient (dMMR) or MSI-H tumors have a significantly higher chance of progression with this treatment regimen. dMMR or MSI-H tumors have shown remarkable responses to PD-1 blockade, but the effect of neoadjuvant checkpoint inhibition has not been well studied. In this trial we will determine the pathologic complete response rate (pCR) of neoadjuvant anti-PD-1 blockade followed by standard chemoradiation in dMMR or MSI-H locally advanced rectal cancer. We hypothesize that treatment naïve dMMR or MSI-H rectal cancers will achieve a robust clinical response to PD-1 blockade and that the total neodjuvant therapy with PD-1 blockade followed by chemoradiation will improve pCR rates. Methods: Eligible patients ≥18 years of age with Stage II (T3-4, N-) or Stage III (any T, N+) histologically confirmed dMMR or MSI-H (by NGS) rectal adenocarcinoma will be enrolled. Patients will receive TSR-042 (500mg IV) every 3 weeks for a maximum of 8 cycles (6 months of treatment). Imaging, internal endoscopic exam and ctDNA blood draw will be performed at 6 weeks and every 3 months during induction anti-PD-1 treatment. Adverse events and surgical complications will be graded according to the NCI CTCAE v5 and the Clavien-Dindo classification, respectively. Following neoadjuvant checkpoint blockade, patients will undergo conventional chemoradiotherapy followed by surgical resection. The primary endpoint is pathologic complete response compared with historical control in pMMR patients. Patients will be followed up every 6 months for assessment of disease-free survival for up to five years. Clinical trial information: NCT04165772 .

Changes in the multidisciplinary management of rectal cancer from 2009 to 2015 and associated improvements in short-term outcomes

AIM

Significant recent changes in management of locally advanced rectal cancer (LARC) include preoperative staging, use of extended neoadjuvant therapies and minimally invasive surgery (MIS). This study was aimed at characterizing these changes and associated short-term outcomes.

METHOD

We retrospectively analysed treatment and outcome data from patients with T3/4 or N+ LARC ≤ 15 cm from the anal verge who were evaluated at a comprehensive cancer centre in 2009-2015.

RESULTS

In total, 798 patients were identified and grouped into five cohorts based on treatment year: 2009-2010, 2011, 2012, 2013 and 2014-2015. Temporal changes included increased reliance on MRI staging, from 57% in 2009-2010 to 98% in 2014-2015 (P < 0.001); increased use of total neoadjuvant therapy, from 17% to 76% (P < 0.001); and increased use of MIS, from 33% to 70% (P < 0.001). Concurrently, median hospital stay decreased (from 7 to 5 days; P < 0.001), as did the rates of Grade III-V complications (from 13% to 7%; P < 0.05), surgical site infections (from 24% to 8%; P < 0.001), anastomotic leak (from 11% to 3%; P < 0.05) and positive circumferential resection margin (from 9% to 4%; P < 0.05). TNM downstaging increased from 62% to 74% (P = 0.002).

CONCLUSION

Shifts toward MRI-based staging, total neoadjuvant therapy and MIS occurred between 2009 and 2015. Over the same period, treatment responses improved, and lengths of stay and the incidence of complications decreased.

Effectiveness of a multidisciplinary patient care bundle for reducing surgical-site infections

BACKGROUND

Surgical-site infection (SSI) is associated with significant healthcare costs. To reduce the high rate of SSI among patients undergoing colorectal surgery at a cancer centre, a comprehensive care bundle was implemented and its efficacy tested.

METHODS

A pragmatic study involving three phases (baseline, implementation and sustainability) was conducted on patients treated consecutively between 2013 and 2016. The intervention included 13 components related to: bowel preparation; oral and intravenous antibiotic selection and administration; skin preparation, disinfection and hygiene; maintenance of normothermia during surgery; and use of clean instruments for closure. SSI risk was evaluated by means of a preoperative calculator, and effectiveness was assessed using interrupted time-series regression.

RESULTS

In a population with a mean BMI of 30 kg/m² , diabetes mellitus in 17·5 per cent, and smoking history in 49·3 per cent, SSI rates declined from 11·0 to 4·1 per cent following implementation of the intervention bundle (P = 0·001). The greatest reductions in SSI rates occurred in patients at intermediate or high risk of SSI: from 10·3 to 4·7 per cent (P = 0·006) and from 19 to 2 per cent (P < 0·001) respectively. Wound care modifications were very different in the implementation phase (43·2 versus 24·9 per cent baseline), including use of an overlying surface vacuum dressing (17·2 from 1·4 per cent baseline) or leaving wounds partially open (13·2 from 6·7 per cent baseline). As a result, the biggest difference was in wound-related rather than organ-space SSI. The median length of hospital stay decreased from 7 (i.q.r. 5-10) to 6 (5-9) days (P = 0·002). The greatest reduction in hospital stay was seen in patients at high risk of SSI: from 8 to 6 days (P < 0·001). SSI rates remained low (4·5 per cent) in the sustainability phase.

CONCLUSION

Meaningful reductions in SSI can be achieved by implementing a multidisciplinary care bundle at a hospital-wide level.

Influence of timing of surgery on perioperative morbidity after neoadjuvant therapy for locally advanced rectal cancer

754

Background: Timing of surgery following completion of neoadjuvant therapy (NT) for locally advanced rectal cancer (LARC) has important implications for treatment response. However, it was recently reported in the GRECCAR 6 trial that delayed surgery beyond 8 weeks from completion of NT is associated with increased complications. Within a cohort of LARC patients treated with NT (CRT alone, Total NT (TNT) and chemotherapy alone) we examine perioperative complications based on time from NT to surgery. Methods: Patients with Stage II/III LARC ≤15cm from the anal verge who received NT from 06/01/09 – 03/01/15 were identified and preoperative morbidity collected on those undergoing rectal resection. Patients were grouped according to time of surgery from completion of NT (5-8 weeks – early surgery / 8-12 weeks – late surgery). Results: 798 patients were identified and 547 underwent rectal resection within 12 weeks of completing NT (440 LAR and 107 APR). Surgery was performed 5-8 following NT in 252 pts and 8-12 weeks following NT in 246 pts. 204 patients (41%) had a post-op complication: 53 (10%) Grade 3-5 complication and 83 (17%) SSI. There were no statistically significant differences in rates of all complications (44% vs 38%), grade 3-5 complications (9% vs 11%), SSI (17% vs 17%), and LOS (median 6 days vs 6 days) between the early and late surgery groups. Similar results were obtained when evaluating the subgroups by type of NT (CRT alone, chemo alone or TNT), surgical approach (open vs minimally invasive and sphincter preservation vs colostomy), post-treatment TNM stage and year of treatment (all NS). In addition, we did not observe differences in rates of downstaging responses: T downstaging (63% vs 64%), N downstaging (61% vs 54%), > 95% regression (34% vs 34%) or pCR rates (18% vs 18%) between the early and later surgery groups. Conclusions: In patients undergoing radical surgery for LARC post NT, we do not observe an effect of timing of surgery on surgical complications. Although timing of surgery is reported to influence response rates, we did not reproduce these findings, likely as a consequence of the high rate of deferral of surgery/ non-operative management in this cohort.

Total neoadjuvant chemotherapy to facilitate delivery and tolerance of systemic chemotherapy and response in locally advanced rectal cancer

3519

Background: The most common therapy for locally advanced (T3/4 or N+) rectal cancer (LARC) consists of preoperative chemoradiotherapy (chemoRT) followed by surgery and adjuvant chemotherapy. Recently, use of total neoadjuvant therapy (TNT) with preoperative chemotherapy in addition to chemoRT prior to resection has been accepted as an alternative. Methods: Of 811 consecutive patients (pts) who presented with LARC at our cancer center in 2009-2015, 320 received chemoRT with planned adjuvant chemotherapy, and 308 received TNT (induction FOLFOX/CAPOX chemotherapy followed by chemoRT). Treatment and outcome data for those two cohorts were compared. Results: Pts in the TNT cohort received greater percentages of the planned oxaliplatin and fluorouracil prescribed dose than those in the chemoRT with planned adjuvant chemotherapy cohort (p < 0·005 and p < 0·001, respectively). The complete response (CR) rate, which includes pathological CR (pCR) and clinical CR (cCR) at 6 months post-treatment, was 21% in the chemoRT with planned adjuvant chemotherapy cohort and 36% in the TNT cohort. The median follow-up was 40 months in the chemoRT with planned adjuvant chemotherapy cohort and 23 months in the TNT cohort. Fewer distant recurrences were seen in patients who had T downstaging (p < 0·001), N downstaging (p < 0·005), a cCR (p = 0·005), or a pCR (p < 0·005). There was no statistically significant difference in distant-recurrence-free survival between the two cohorts. Conclusions: Our findings provide additional support for the National Comprehensive Cancer Network (NCCN) guidelines for rectal cancer treatment, which categorizes TNT as a viable treatment strategy that facilitates superior compliance and delivery of systemic therapy. Given its high CR rate, TNT may be beneficial as part of a nonoperative treatment strategy aimed at organ preservation.

Total neoadjuvant therapy for locally advanced rectal cancer

662

Background: Current therapy for locally advanced rectal cancer (LARC) consists of 6 months of perioperative therapy, either with pre-operative chemo-radiotherapy (CRT) and post operative adjuvant chemotherapy (PAC) or total neoadjuvant therapy (TNT) with induction chemotherapy (ICT) followed by CRT then surgery. The aim of our study was to report on the safety, efficacy and complete response rates comparing TNT to PAC in a larger series of LARC patients (pts) at Memorial Sloan Kettering Cancer Center (MSKCC). Methods: Pts treated at MSKCC (2009-15) were analyzed based on the intended treatment schedule (TNT or PAC). 730 LARC pts were treated with CRT, of these 320 received neoadjuvant CRT and 308 received TNT. Results: In the TNT group 205 pts (73%) underwent surgery within 26 weeks of completion of treatment, of which 38 (19%) had a pCR. Of the 78 pts who did not undergo surgery within 26 weeks, 68 (87%) had a complete clinical response (cCR). In the PAC group 293 pts (92%) underwent surgery within 26 weeks and 45 (15%) had a pCR. Of the 27 pts who did not undergo surgery within 26 weeks 22 (81%) had a cCR. The median follow up was 25 mo in the TNT group and 29 mo in the PAC group. There was no statistically significant difference in the distant metastasis free survival between the treatment regimens, despite a higher number of cT4 and cN + tumors in the TNT group. Fewer distant recurrences were seen in pts who had evidence of T downstaging (P < 0.001), N downstaging (P < 0.005), the presence of a cCR (P = 0.005) or a pCR (P < 0.005). Of the pts who received all treatment at MSKCC, comparison of dose of 5-FU and oxaliplatin between the preoperative (N = 249) and postoperative regimens (N = 101) was notable for a higher average dose received of both 5FU and oxaliplatin (p < 0.005 and p < 0.001) in the ICT group. Conclusions: These data add weight to the evidence already included in the NCCN guidelines that pre-operative chemotherapy as part of TNT is a viable treatment strategy with superior compliance and delivery of systemic therapy. Given the high complete response rate, TNT may be used as part of an organ preservation treatment strategy.

Poorly differentiated clusters as a prognostic marker at the invasive front of colon cancer

621

Background: Histology at the invasive front of colon cancer can predict malignant potential. However, the optimal histological marker is yet to be established. This study compares the various invasive front histologic markers. Methods: A single-institution prospective database was queried for consecutive patients who underwent curative resection for Stage I-III colon adenocarcinoma from 2007-14. Histologic features were reviewed by a pathologist, including poorly differentiated clusters (PDC), tumor budding (BD), perineural invasion (PN), desmoplastic reaction (DR) and Crohn’s like reaction (CLR) at the invasive front, and WHO grade of the whole tumor. PDC was defined as cancer clusters of ≥ 5 cancer cells that lack a gland-like structure, and was graded into G1 ( < 5), G2 (5-9) and G3 ( ≥ 10) by the highest number of the clusters /HPF. Clinical outcome included recurrence free survival (RFS) and peak hazard function of recurrence and death identified using the kernel-smoothing method. Predictive accuracy was measured with concordance probability estimate (CPE) for proportional hazards regression. Inter-observer agreement was assessed by weighted kappa values on diagnoses rendered by 3 pathologists on 50 randomly selected cases. Results: The study cohort consisted of 851 patients with a median follow up of 36 months. PDC, BD, PN, DR and CLR at the invasive front were significantly associated with RFS. When analyzed by stage, PDC, BD and PN were associated with RFS both in Stage II and Stage III, while the others were prognostic only in Stage III. CPE was the highest in PDC (0.642), indicating the best predictive accuracy, while it was the lowest in WHO grade (0.526). Weighted kappa was also the highest for PDC, indicating the best inter-observer agreement (PDC: 0.824, WHO grade: 0.568). The smoothed graph of the hazard function showed that the risk of recurrence was not only the highest but peaked earlier for PDC G3 (between0 and 12 months) than PDC G2 (between12 and 24 months) and G1 (no evident peak). Conclusions: Of the commonly evaluated histologic markers at the invasive front, PDC grade is the most predictive and reproducible. Further confirmatory investigations are warranted to determine if PDC can replace WHO grade.

Evolution in multimodality management of locally advanced rectal cancer

684

Background: This study reports the evolving multimodality management of locally advanced rectal cancer (LARC) and associated outcomes at a high volume center. Methods: Patients with Stage II/III LARC <15cm from the anal verge evaluated by the colorectal surgery service were identified from a prospective database. Clinical management including neoadjuvant therapy (NT) and surgical treatment along with pathologic and perioperative outcomes were collected. Results: Between June 2009 and March 2015, 798 patients were evaluated and received NT for LARC. Majority were staged cT3/T4 (84%) or cN+ (78%), and 635 had surgery within 26wks following NT. Reliance on MRI staging increased from 57% to 98% during the study period (P < 0.001). There was increased usage of total NT (NEO) with pre-op chemotherapy (CT) and chemoradiotherapy (CRT) (17% to 76%, p < 0.001) with a concomitant decrease in use of CRT alone (77% to 16%, p < 0.001) and post-op CT (70% to 15%, p < 0.001). The proportion undergoing surgery beyond 8wks after NT rose from 41% to 62% (P < 0.001) and beyond 8 wks after CRT rose from 45% to 72% (p < 0.001). The percentage of patients not undergoing resection by 26wks (nonoperative management) rose from 12% to 27%, P < 0.001). Minimally invasive surgery (MIS) increased from 33% to 71% (P < 0.001); in 2014-15 98% of MIS was robot-assisted. Over the study period there was a decrease in LOS (mean 8.1 to 6.5 days, p < 0.001), grade III-V complications (13% to 7%, p < 0.05), surgical site infections (25% to 8%, p < 0.001), and anastomotic leak (11% to 3%, p < 0.05). The proportion undergoing ileostomy closure within 15 wks rose from 7% to 73% (P < 0.001). Involved CRM rates decreased from 9% to 3% (P < 0.01). TNM downstaging increased from 62% to 74% (p = 0.002). Complete response rates (clinical and pathologic) at 26wks was 26% in 2009-10 and 32% in 2014/5 (p = 0.067). Conclusions: Over the past decade, there has been a shift to MRI staging, total NT (NEO), and MIS rectal resection at 8-12 weeks. This has been associated with higher response rates, shorter LOS, and fewer complications.

SMAD4 loss in colorectal cancer: Correlation with recurrence, chemoresistance, and immune infiltrate

587

Background: Few markers reliably identify colorectal cancer (CRC) patients at risk of recurrence and death. SMAD4 loss occurs in 10-20% of cases and has shown promise in identifying high-risk stage II/III patients. We examined SMAD4 status and association with clinical/pathologic features in 446 stage I-IV CRC patients at Memorial Sloan Kettering (MSK). Methods: Patients undergoing curative resection were included (1981-2010). Familial polyposis syndrome patients and those with inadequate tissue were excluded. Tissue microarrays were constructed (n=364). Immunohistochemistry for SMAD4 and mismatch repair (MMR) proteins was completed. SMAD4 nuclear stain intensity was scored (scale=0-3; 0=loss). On whole sections, MMR proteins (present or absent), tumor-infiltrating lymphocytes (TILs) and peritumoral lymphocyte aggregates (PLAs) were scored (scale=0-3). Associations between clinical/pathologic features and SMAD4 loss vs. retention were analyzed. Kaplan-Meier estimates and log-rank test were used for recurrence-free and overall survival analyses (RFS and OS). Results: SMAD4 loss was noted in 13%. Median age at diagnosis was 53 years, and 51% were male. The cohort consisted of 61% hindgut tumors and 62% stage II/III patients. With up to 33 years of follow-up, the mean was 6 years. SMAD4 loss correlated with higher tumor and nodal stage, adjuvant therapy use, and lower TIL and PLA scores (p<0.04 for all). Unlike prior studies, no significant differences in OS based on SMAD4 status across the entire cohort were noted; however, older patients (>median) were noted to have worse OS with SMAD4 loss (p<0.01). SMAD4 loss did correlate with worse RFS (p=0.02), persisting even when excluding MMR-deficient patients. Additionally, SMAD4 loss was associated with worse RFS in both the adjuvant chemotherapy group (median RFS=3.8 vs. 13 years; p=0.06) and the resection-only group (median RFS=4.2 years vs. not yet reached; p< 0.01). Conclusions: SMAD4 loss correlates with worse RFS and resistance to adjuvant therapy. SMAD4 loss also correlates with lower TIL and PLA scores. Future work will address chemoresistance mechanisms, relevance to adjuvant therapy use, and loss of immune infiltrate in SMAD4-null tumors.

Incisional hernias after laparoscopic and robotic right colectomy

PURPOSE

Incisional hernia (IH) is a common complication after colectomy, with impacts on both health care utilization and quality of life. The true incidence of IH after minimally invasive colectomy is not well described. The purpose of this study was to examine IH incidence after minimally invasive right colectomies (RC) and to compare the IH rates after laparoscopic (L-RC) and robotic (R-RC) colectomies.

METHODS

This is a retrospective review of patients undergoing minimally invasive RC at a single institution from 2009 to 2014. Only patients undergoing RC for colonic neoplasia were included. Patients with previous colectomy or intraperitoneal chemotherapy were excluded. Three L-RC patients were included for each R-RC patient. The primary outcome was IH rate based on clinical examination or computed tomography (CT). Univariate and multivariate time-to-event analyses were used to assess predictors of IH.

RESULTS

276 patients where included, of which 69 had undergone R-RC and 207 L-RC. Patient and tumor characteristics were similar between the groups, except for higher tumor stage in L-RC patients. Both the median time to diagnosis (9.2 months) and the overall IH rate were similar between the groups (17.4 % for R-RC and 22.2 % for L-RC), as were all other postoperative complications. In multivariable analyses, the only significant predictor of IH was former or current tobacco use (hazard raio 3.0, p = 0.03).

CONCLUSIONS

This study suggests that the incidence of IH is high after minimally invasive colectomy and that this rate is equivalent after R-RC and L-RC. Reducing the IH rate represents an important opportunity for improving quality of life and reducing health care utilization after minimally invasive colectomy.

Genomic profiling and efficacy of anti-EGFR therapy in appendiceal adenocarcinoma

574

Background: Metastatic appendiceal adenocarcinoma (AAC) is a heterogenous disease and the majority of patients present with diffuse metastases in the peritoneal cavity. Cytotoxic and targeted therapies are typically extrapolated from colorectal adenocarcinoma (CRC), however, it is not known whether this is effective or not. Herein we investigated the genetic profiles of these tumors in an effort to identify molecular characteristics and potentially actionable mutations, as well as the response to anti-EGFR therapy in RAS/BRAF wild type (wt) AAC. Methods: We identified patients (pts) with ACC treated at MSKCC who had tumor who had undergone molecular profiling, either by next generation sequencing using our MSK-IMPACT platform, or by MALDI-TOF mass spectroscopy genotyping (Sequenom). MSK-IMPACT tumors and matched normal samples were analyzed either on 410 gene panel. Sequenom (provided an 8 gene panel including KRAS, NRAS, BRAF, and PIK3CA). Via an IRB approved waiver, we collected tumor histology and evaluated pts who were RAS/RAF wt and had been treated with anti-EGFR therapy. Results: We identified a total 97 AAC pts, of whom 60 had Sequenom testing and 37 had IMPACT. Among pts analyzed with IMPACT, 24 had mucinous adenocarcinoma, 3 adenocarcinoma with signet ring, 7 adenocarcinoma ex goblet cell carcinoid, 3 invasive adenocarcinoma. In total 159 alterations were identified with a median 4.2 alterations/patient (range 0-10). Alterations were seen most commonly in KRAS (21/37), GNAS (12/37), TP53 (10/37), SOX9 (5/37), and SMAD4 (4/37). Potentially treatable alterations were present in 15% of patients and included BRAF V600E (1), MTOR (2), ERBB2 (1) and NTRK(2). Of the total 97 pts, 50 (52%) were RAS/BRAF wt. Of those,13 evaluable patients received anti-EGFR therapy with either panitumumab or cetuximab. There were no responders. Conclusions: Mutational sequencing in AAC indicates that 16% have mutations in genes such as BRAFV600E, MTOR, ERBB2 and NTRK with the potential to expand investigational options through increased access to trials of selectively targeted agents. Additionally, in RAS/BRAF wt pts, panitumumab/cetuximab does not appear to have therapeutic efficacy comparable to historic controls in RAS/RAF wt CRC.

Organ preservation in patients with rectal cancer with clinical complete response after neoadjuvant therapy

509

Background: Nonoperative management (NOM) of rectal cancer following a clinical complete response (cCR) to neoadjuvant therapy is a non-standard approach. We review our experience with NOM to evaluate safety and efficacy. Methods: A retrospective review of prospectively collected data between 2006 and 2014 was conducted. We compared patients completing neoadjuvant therapy for stage I to III rectal cancers who: a) achieved cCR and were treated with NOM, or b) underwent standard total mesorectal excision (TME) and achieved a pathologic complete response (pCR). Kaplan-Meier estimates and the log-rank test were used. Results: Seventy-three patients underwent NOM after cCR. From 369 rectal resections performed, 72 (20%) achieved pCR and form the comparison group. Median follow-up across both groups was 3.3 years. Rectal preservation was achieved in 56 (77%) of the patients treated with NOM. Of the 19 NOM patients with local regrowth, 18 were salvaged successfully with standard TME (n=16) or local excision (n=2), with one patient pending a salvage operation (n=1). No significant differences were noted in the number of distant recurrences between the NOM and pCR groups. Four-year disease-specific survival and overall survival between the two groups were not significantly different. Conclusions: In this highly selected group of patients with cCR to neoadjuvant treatment, NOM with surgical salvage of local tumor regrowth achieved local control in all patients. The oncologic outcome for NOM patients at 4 years was comparable to patients with pCR after rectal resection. These data continue to suggest that NOM does not compromise oncologic outcome, and that preservation of the rectum is achieved in a majority of patients. [Table: see text]

Chemotherapy first, followed by chemoradiation (CRT) and then surgery, in the management of locally advanced rectal cancer (LARC)

3605

Background: Standard pre-op CRT and post-op chemo for LARC delays the start of optimal systemic therapy by 18-22 weeks. To more promptly address micrometastases that could lead to distant failure, and supported by evidence of excellent primary tumor response to FOLFOX, we began offering FOLFOX as initial treatment for patients (pts) with high-risk LARC. More recently, we have begun offering all planned FOLFOX prior to CRT and surgery. Methods: We obtained an IRB waiver to review records of all clinical stage II/III RC pts treated with initial FOLFOX followed by CRT and total mesorectal excision (TME) at our institution between 2007 and 2012. Of approximately 300 rectal pts treated with CMT, 61 received some or all of their planned FOLFOX as initial therapy. Results: The median age of these 61 pts was 52 years, 54% male. At diagnosis, 84% had T3N1-2 or T4N0-1 tumors and 16% had T3N0 tumors. Of these, 57 received induction FOLFOX (median 7 cycles) then received pre-op CRT, while 4 pts achieved an excellent response to chemotherapy alone, declined CRT, and went directly to TME. Twelve pts did not undergo surgery; 9 had a complete clinical response and elected to be managed non-operatively; 1 refused recommended surgery despite incomplete tumor regression, 1 had surgery deferred due to comorbidities, and 1 developed distant metastatic disease prior to planned surgery. Of the 61 patients, 19 (31%) had either a pathCR (14) or a complete clinical response (5) leading to non-operative management. Of the 49 pts who underwent TME, all had R0 resections and 23 (47%) had tumor response >90%, including 13 (27%) with pathCR. Of the 28 patients who received all 8 cycles of initial FOLFOX, 8 achieved a pathCR (29%) and 3 achieved a complete clinical responses (11%), managed non-operatively. All patients completed therapy as planned. There were no SAEs requiring delay in treatment during either FOLFOX or CMT. Conclusions: FOLFOX before CRT results in substantial tumor regression, a high rate of delivery of all planned therapy, and a substantial rate of pathCRs. Chemo and CMT before planned TME provides a favorable opportunity for consideration of non-operative management.

Characterization of rectal cancer in patients with Lynch syndrome

350

Background: Lynch syndrome (LS), resulting from a germline mutation in a DNA mismatch repair (MMR) gene, is associated with ~70% lifetime colorectal cancer (CRC) risk. Although LS-associated colon cancer is associated with both favorable prognosis and lack of efficacy to 5-fluorouracil, clinical features of LS-associated rectal cancer (RC) have not been characterized. Methods: Clinical genetics database review (1998–2012) identified all probands with CRC and a deleterious germline mutation in a MMR gene (MLH1, MSH2, MSH6, PMS2) diagnostic of LS. Probands without identifiable mutations or variants of unknown significance were excluded. Clinical history and pedigree was extracted from medical records and Progeny. Results: Of 119 LS patients with CRC, 16 (13.4%) had RC. Mean age at RC diagnosis was 40.6 (range, 23-56) with 31% having synchronous (n=3) or metachronous (n=2) colon cancer. All RC patients met Revised Bethesda and 63% met Amsterdam II criteria. As opposed to LS-associated colon cancer, the majority of RC patients harbored MSH2 mutations (36% colon vs 69% RC, p value 0.01). 11 tumors were analyzed for MSI or defective MMR protein expression by IHC; results were abnormal and thereby concordant with germline test results in all cases. Of 14 RC patients with clinical data, 5 proceeded directly to surgery (4 stage 0/I; 1 stage II). Nine patients received pre-op treatment for clinical stage II/III (n=7) or IV (n=2) disease, with all receiving chemoradiation and five also receiving pre-op FOLFOX. Downstaging of primary tumor occurred in 66.6% (6/9) and of lymph nodes in 77.7% (7/9) of cases. All nine patients underwent R0 resections; however, pCR was not observed in any of the cases. Notably, one patient with clinical T3N+ disease (by MRI and EUS) had upfront surgery identifying pT2N0 disease with prominent tumor infiltrating lymphocytes. Of 14 patients, mean follow-up of 4.3 years (range, 0.3-13.5), none had disease recurrence; however, one was diagnosed with a new primary colon cancer. Conclusions: Although less common than colon cancer,RC is an important component of LS and may be overrepresented in MSH2 mutation carriers. Given high risk of synchronous or metachronous cancers, appropriate surveillance for second malignancies is necessary.

Induction chemotherapy followed by chemoradiotherapy and total mesenteric excision for locally advanced rectal cancer with resectable metastases

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Background: Optimal management of patients with locally advanced rectal cancer (LARC) and synchronous, resectable metastases remains controversial and treatment decisions benefit from a multidisciplinary approach. To better characterize the role of induction chemotherapy followed by chemoradiation and surgery, we evaluated patterns of distal progression and overall survival in this subset of patients. Methods: We reviewed records of 25 LARC patients with synchronous resectable metastases treated with induction chemotherapy (ICT) followed by 5-fluorouracil-based concurrent chemoradiation (CRT) at our institution between December 2006 and December 2010. Radiation was delivered using a standardized three-field technique or IMRT. The incidence and sites of failure were analyzed. Overall survival (OS) and progression-free survival (PFS) were calculated from the completion of CRT using the Kaplan-Meier method. Results: Of the 25 patients who received ICT followed by CRT, 21 (84%) underwent total mesorectal excision and metastectomy. Eleven patients (44%) had liver metastases. The median ICT duration was 2.4 months. Twenty patients (80%) received a FOLFOX-based ICT regimen and 5 patients (20%) received irinotecan-based chemotherapy. Two patients had unresectable disease, one was medically inoperable, and surgery was aborted due to intra-operative complications in one patient. Eighteen of the 21 were NED after surgery and metastatectomy (86%) with 24% pathologic complete response rate in the primary tumor; 10 (56%) received adjuvant chemotherapy. None of the patients recurred locally. Six of the 18 (33%) progressed distally, four of whom had received adjuvant chemotherapy. Four distal recurrences were in the lungs. With a median follow-up of 29.6 months, the 3-year OS was 50.4%. Median OS and PFS were 25.1 months and 13.5 months, respectively. Conclusions: ICT prior to CRT is associated with acceptable toxicity, substantial primary tumor regression, and promising clinical outcomes in patients with high-risk LARC with synchronous, resectable metastatic disease.

Goblet cell carcinoid neoplasm of the appendix: clinical and CT features

PURPOSE

To describe the clinical and CT imaging features of goblet cell carcinoid (GCC) neoplasm of the appendix.

METHODS AND MATERIALS

A computer search of pathology and radiology records over a 19-year period at our two institutions was performed using the search string "goblet". In the patients with appendiceal GCC neoplasms who had abdominopelvic CT, imaging findings were categorized, blinded to gross and surgical description, as: "Appendicitis", "Prominent appendix without peri-appendiceal infiltration", "Mass" or "Normal appendix". The CT appearance was correlated with an accepted pathological classification of: low grade GCC, signet ring cell adenocarcinoma ex, and poorly differentiated adenocarcinoma ex GCC group.

RESULTS

Twenty-seven patients (age range, 28-80 years; mean age, 52 years; 15 female, 12 male) with pathology-proven appendiceal GCC neoplasm had CT scans that were reviewed. Patients presented with acute appendicitis (n=12), abdominal pain not typical for appendicitis (n=14) and incidental finding (n=1). CT imaging showed 9 Appendicitis, 9 Prominent appendices without peri-appendiceal infiltration, 7 Masses and 2 Normal appendices. Appendicitis (8/9) usually correlated with typical low grade GCC on pathology. In contrast, the majority of Masses and Prominent Appendices without peri-appendiceal infiltration were pathologically confirmed to be signet ring cell adenocarcinoma ex GCC. Poorly differentiated adenocarcinoma ex GCC was seen in only a small minority of patients. Hyperattenuation of the appendiceal neoplasm was seen in a majority of cases.

CONCLUSIONS

GCC neoplasm of the appendix should be considered in the differential diagnosis in patients with primary appendiceal malignancy. Our cases demonstrated close correlation between our predefined CT pattern and the pathological classification.

Multivisceral resections for rectal cancer

BACKGROUND

En bloc resection of adjacent pelvic organ(s) may be needed to achieve clear surgical margins in rectal cancer surgery. An institutional experience is reported with perioperative morbidity and oncological outcomes.

METHODS

Patients were identified retrospectively from a prospectively collected institutional database (1992-2010). Outcomes, and clinical and pathological factors were determined from medical records. Estimated overall survival, overall recurrence and local recurrence were compared using the log rank method and Cox regression analysis.

RESULTS

Among 1831 patients with rectal cancer, 124 (6·8 per cent) underwent en bloc resection of part or all of an adjacent organ (vagina/uterus/ovary 90, prostate/seminal vesicle 23, bladder/ureter 15, small bowel/appendix 7). Five-year overall survival and local recurrence rates were 53·3 and 18·8 per cent respectively. There was one postoperative death, from multiple organ failure in a patient with liver cirrhosis. Fifty-two patients underwent sphincter-preserving surgery and three (6 per cent) developed an anastomotic leak. On univariable analysis, the only factor associated with local recurrence was completeness of resection (local recurrence rate 15 per cent versus 69 per cent for R0 versus R1 resection; P < 0·001). On multivariable analysis, factors associated with overall survival were sphincter-preserving surgery, absence of metastatic disease and R0 resection.

CONCLUSION

Multiple organ resection for locally advanced primary rectal cancer had good oncological outcomes when clear resection margins were achieved.

Is there any significant difference between tumor regression grade systems of rectal cancer?

3583

Background: Tumor regression grade (TRG) is a measure of histopathologic response of rectal cancer to preoperative chemoradiation (CRT) and correlates with outcomes. Several TRG systems have been reported including Mandard (5, 3 tier), Dowrak/Rodel (5, 3 tier), Memorial Sloan Kettering Cancer Center (MSKCC), and American Joint Committee of Cancer (AJCC). The purpose of this study is to compare the different TRG systems and determine which one(s) best predict recurrence and survival. Methods: Review of prospective maintained database from 1998 to 2007 identified 563 patients with locally advanced rectal cancer (T3/4 and/or N1) and treated with long-course CRT followed by total mesorectal excision. TRG was determined by measuring proportion of tumor mass replaced by fibrosis. Patients were then classified into the various TRG schemes which were compared by analyzing association with recurrence and survival using concordance index (CI) and reclassification index. CI is a measure that summarizes the predictive strength of a marker. Computing and contrasting CI across several markers is a way of selecting the best prognostic marker. Results: 75% of patients were noted to have clinical stage III disease by endorectal ultrasound or rectal MRI. Following resection with median follow-up of 39.3 months, 2% developed local recurrence and 17% developed distant metastasis. The median interval time between completion of CRT and surgery is 48 days. 20% demonstarted complete pathological response. CI of the 3 tier Mandard, 3 tier Dowrak/Rodel, MSKCC and AJCC are 0.665, 0.653, 0.683, and 0.694, respectively (higher number indicates better prediction). The AJCC was significantly more accurate in predicting recurrence than the 3- tier Mandard (p=0.002), and Dowrak/Rodel (p=0.006). AJCC had a higher CI than MSKCC although it did not reach significance (p=0.068). Comparing the 3 tier systems, MSKCC was most accurate and correctly reclassified 17 % and 23 % of the patients Mandard and Dowrak/Rodel systems, respectively. Conclusions: TRG predicts recurrence and survival following combined modality therapy for rectal cancer. The TRG system that recently was proposed in the 7thAJCC staging is currently the most accurate predictor.

Minimally invasive surgery is safe and effective for urgent and emergent colectomy

OBJECTIVE

There are a limited number of studies describing the role of minimally invasive colectomy for urgent or emergent conditions of the large bowel. We hypothesize that laparoscopic colectomy in urgent and emergent setting can be performed safely in select settings.

METHOD

A cohort of patients treated at a single institution from 2001 to 2006 was identified from a prospective database. Patients who underwent open or minimally invasive surgery (MIS), including laparoscopic (LAP) or hand-assisted laparoscopic surgery (HALS) colectomy for urgent and emergent conditions were included.

RESULTS

A total of 68 [open 32, MIS 36 [HALS 22, LAP 14)] patients underwent urgent or emergent colectomy on our colorectal service during the 5-year time period. Patients with toxic colitis were more often selected for MIS. Patients with colon perforation or large bowel obstruction were more often selected for open surgery. The MIS group had a lower body mass index (BMI), lower American Society of Anesthesiologists fitness grade and was more likely to have been immunosuppressed. There was no difference in patient morbidity between the open and MIS groups. The MIS group had a longer median operative time and fewer cases of prolonged hospitalization.

CONCLUSION

We conclude that minimally invasive colectomy by experienced surgeons appears to be safe and effective for appropriately selected patients with emergent and urgent conditions of the large bowel.

Automated, multiplex assay for high-frequency microsatellite instability in colorectal cancer

PURPOSE

In a series of hereditary nonpolyposis colorectal cancer (HNPCC) patients, we evaluated the sensitivities of the individual microsatellites recommended by the National Cancer Institute (NCI) consensus workshop for detection of high-frequency microsatellite instability (MSI-H). On the basis of this evaluation, we developed a three-marker assay that assigns microsatellite instability (MSI) in a multiplex polymerase chain reaction.

METHODS

Individual marker sensitivity was assessed in 18 HNPCC tumors. Multiplex and NCI assays were then assessed in a series of 120 patients with early-onset colon cancer.

RESULTS

The sensitivity of microsatellite markers BAT25, BAT26, D2S123, D5S346, and D17S250 for ASI in HNPCC cancers was 100%, 94%, 72%, 50%, and 50%, respectively. The three most accurate markers were combined and optimized in a multiplex assay that assigned MSI-H whenever at least two of three markers revealed ASI. In early-onset colon cancers, the prevalence of MSI-H determined by the multiplex assay and by the NCI assay was 16% and 23%, respectively. The additional MSI-H tumors and patients with MSI-H identified by the NCI assay lacked the traits characteristic of MSI-H seen in tumors and patients identified by the multiplex assay: retention of heterozygosity (NCI additional 22% v multiplex 84%; P =.003), characteristic tumor morphology (0% v 64%; P =.006), and 5-year cancer survival rate (44% v 100%; P =.0003).

CONCLUSION

The multiplex assay identifies colon cancers with MSI-H by assessing three highly accurate microsatellite markers. This assay identifies a smaller MSI-H cohort with more homogeneous clinical features and is superior as a marker of favorable prognosis. It merits prospective evaluation as a marker of prognosis and as a screening test for HNPCC.