Variation in the Thoroughness of Pathologic Assessment and Response Rates of Locally Advanced Rectal Cancers After Chemoradiation.

BACKGROUND: Pathologic complete response (pCR) is associated with better prognosis and guides management for patients with advanced rectal cancer. Response rates vary between series for unclear reasons. We examine whether the thoroughness of pathologic assessment explains differences in pCR rates. METHODS: We retrospectively reviewed pathology reports from patients with stage II/III rectal cancer who underwent chemoradiation and resection in a prospective, multicenter trial. We utilized a novel measure for the thoroughness of pathologic assessment by dividing residual tumor size by the number of cassettes evaluated (tumor size to cassette ratio, TSCR), and evaluated whether TSCR is associated with pCR. We validated our findings using a separate cohort. RESULTS: From the trial cohort, 71 of 247 (29%) patients achieved pCR. The pCR rate ranged from 0 to 45% and mean TSCR ranged 0.29 to 0.87 across 12 institutions. Within each institution, a lower TSCR was associated with pCR, demonstrating a higher degree of thoroughness used for tumors that achieved pCR. Moreover, across all samples, low TSCR was independently associated with pCR on multivariable analysis. This finding was corroborated in a separate cohort of 201 tumors evaluated by five pathologists; each pathologist had a lower mean TSCR for pCR calls compared with non-pCR calls. However, the mean TSCR for an institution was not associated with its overall pCR rate. CONCLUSIONS: Pathologists assess rectal cancers that have responded significantly to neoadjuvant therapy more thoroughly. Thoroughness does not appear to explain differences in pCR rates between institutions. Our results suggest pCR is not a sampling artifact.

KRAS and Combined KRAS/TP53 Mutations in Locally Advanced Rectal Cancer are Independently Associated with Decreased Response to Neoadjuvant Therapy.

BACKGROUND: The response of rectal cancers to neoadjuvant chemoradiation (CRT) is variable, but tools to predict response remain lacking. We evaluated whether KRAS and TP53 mutations are associated with pathologic complete response (pCR) and lymph node metastasis after adjusting for neoadjuvant regimen. METHODS: Retrospective analysis of 229 pretreatment biopsies from patients with stage II/III rectal cancer was performed. All patients received CRT. Patients received 0-8 cycles of FOLFOX either before or after CRT, but prior to surgical excision. A subset was analyzed to assess concordance between mutation calls by Sanger Sequencing and a next-generation assay. RESULTS: A total of 96 tumors (42 %) had KRAS mutation, 150 had TP53 mutation (66 %), and 59 (26 %) had both. Following neoadjuvant therapy, 59 patients (26 %) achieved pCR. Of 133 KRAS wild-type tumors, 45 (34 %) had pCR, compared with 14 of 96 (15 %) KRAS mutant tumors (p = .001). KRAS mutation remained independently associated with a lower pCR rate on multivariable analysis after adjusting for clinical stage, CRT-to-surgery interval and cycles of FOLFOX (OR 0.34; 95 % CI 0.17-0.66, p < .01). Of 29 patients with KRAS G12V or G13D, only 2 (7 %) achieved pCR. Tumors with both KRAS and TP53 mutation were associated with lymph node metastasis. The concordance between platforms was high for KRAS (40 of 43, 93 %). CONCLUSIONS: KRAS mutation is independently associated with a lower pCR rate in locally advanced rectal cancer after adjusting for variations in neoadjuvant regimen. Genomic data can potentially be used to select patients for "watch and wait" strategies.

Integrated genomic profiling identifies microRNA-92a regulation of IQGAP2 in locally advanced rectal cancer.

Locally advanced rectal cancer (LARC) is treated with chemoradiation prior to surgical excision, leaving residual tumors altered or completely absent. Integrating layers of genomic profiling might identify regulatory pathways relevant to rectal tumorigenesis and inform therapeutic decisions and further research. We utilized formalin-fixed, paraffin-embedded pre-treatment LARC biopsies (n=138) and compared copy number, mRNA, and miRNA expression with matched normal rectal mucosa. An integrative model was used to predict regulatory interactions to explain gene expression changes. These predictions were evaluated in vitro using multiple colorectal cancer cell lines. The Cancer Genome Atlas (TCGA) was also used as an external cohort to validate our genomic profiling and predictions. We found differentially expressed mRNAs and miRNAs that characterize LARC. Our integrative model predicted the upregulation of miR-92a, miR-182, and miR-221 expression to be associated with downregulation of their target genes after adjusting for the effect of copy number alterations. Cell line studies using miR-92a mimics and inhibitors demonstrate that miR-92a expression regulates IQGAP2 expression. We show that endogenous miR-92a expression is inversely associated with endogenous KLF4 expression in multiple cell lines, and that this relationship is also present in rectal cancers of TCGA. Our integrative model predicted regulators of gene expression change in LARC using pre-treatment FFPE tissues. Our methodology implicated multiple regulatory interactions, some of which are corroborated by independent lines of study, while others indicate new opportunities for investigation.

Organ Preservation in Rectal Adenocarcinoma: a phase II randomized controlled trial evaluating 3-year disease-free survival in patients with locally advanced rectal cancer treated with chemoradiation plus induction or consolidation chemotherapy, and total mesorectal excision or nonoperative management.

BACKGROUND: Treatment of patients with non-metastatic, locally advanced rectal cancer (LARC) includes pre-operative chemoradiation, total mesorectal excision (TME) and post-operative adjuvant chemotherapy. This trimodality treatment provides local tumor control in most patients; but almost one-third ultimately die from distant metastasis. Most survivors experience significant impairment in quality of life (QoL), due primarily to removal of the rectum. A current challenge lies in identifying patients who could safely undergo rectal preservation without sacrificing survival benefit and QoL. METHODS/DESIGN: This multi-institutional, phase II study investigates the efficacy of total neoadjuvant therapy (TNT) and selective non-operative management (NOM) in LARC. Patients with MRI-staged Stage II or III rectal cancer amenable to TME will be randomized to receive FOLFOX/CAPEOX: a) before induction neoadjuvant chemotherapy (INCT); or b) after consolidation neoadjuvant chemotherapy (CNCT), with 5-FU or capecitabine-based chemoradiation. Patients in both arms will be re-staged after completing all neoadjuvant therapy. Those with residual tumor at the primary site will undergo TME. Patients with clinical complete response (cCR) will receive non-operative management (NOM). NOM patients will be followed every 3 months for 2 years, and every 6 months thereafter. TME patients will be followed according to NCCN guidelines. All will be followed for at least 5 years from the date of surgery or--in patients treated with NOM--the last day of treatment. DISCUSSION: The studies published thus far on the safety of NOM in LARC have compared survival between select groups of patients with a cCR after NOM, to patients with a pathologic complete response (pCR) after TME. The current study compares 3-year disease-free survival (DFS) in an entire population of patients with LARC, including those with cCR and those with pCR. We will compare the two arms of the study with respect to organ preservation at 3 years, treatment compliance, adverse events and surgical complications. We will measure QoL in both groups. We will analyze molecular indications that may lead to more individually tailored treatments in the future. This will be the first NOM trial utilizing a regression schema for response assessment in a prospective fashion. TRIAL REGISTRATION: NCT02008656.

Effect of adding mFOLFOX6 after neoadjuvant chemoradiation in locally advanced rectal cancer: a multicentre, phase 2 trial.

BACKGROUND: Patients with locally advanced rectal cancer who achieve a pathological complete response to neoadjuvant chemoradiation have an improved prognosis. The need for surgery in these patients has been questioned, but the proportion of patients achieving a pathological complete response is small. We aimed to assess whether adding cycles of mFOLFOX6 between chemoradiation and surgery increased the proportion of patients achieving a pathological complete response. METHODS: We did a phase 2, non-randomised trial consisting of four sequential study groups of patients with stage II-III locally advanced rectal cancer at 17 institutions in the USA and Canada. All patients received chemoradiation (fluorouracil 225 mg/m(2) per day by continuous infusion throughout radiotherapy, and 45·0 Gy in 25 fractions, 5 days per week for 5 weeks, followed by a minimum boost of 5·4 Gy). Patients in group 1 had total mesorectal excision 6-8 weeks after chemoradiation. Patients in groups 2-4 received two, four, or six cycles of mFOLFOX6, respectively, between chemoradiation and total mesorectal excision. Each cycle of mFOLFOX6 consisted of racemic leucovorin 200 mg/m(2) or 400 mg/m(2), according to the discretion of the treating investigator, oxaliplatin 85 mg/m(2) in a 2-h infusion, bolus fluorouracil 400 mg/m(2) on day 1, and a 46-h infusion of fluorouracil 2400 mg/m(2). The primary endpoint was the proportion of patients who achieved a pathological complete response, analysed by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT00335816. FINDINGS: Between March 24, 2004, and Nov 16, 2012, 292 patients were registered, 259 of whom (60 in group 1, 67 in group 2, 67 in group 3, and 65 in group 4) met criteria for analysis. 11 (18%, 95% CI 10-30) of 60 patients in group 1, 17 (25%, 16-37) of 67 in group 2, 20 (30%, 19-42) of 67 in group 3, and 25 (38%, 27-51) of 65 in group 4 achieved a pathological complete response (p=0·0036). Study group was independently associated with pathological complete response (group 4 compared with group 1 odds ratio 3·49, 95% CI 1·39-8·75; p=0·011). In group 2, two (3%) of 67 patients had grade 3 adverse events associated with the neoadjuvant administration of mFOLFOX6 and one (1%) had a grade 4 adverse event; in group 3, 12 (18%) of 67 patients had grade 3 adverse events; in group 4, 18 (28%) of 65 patients had grade 3 adverse events and five (8%) had grade 4 adverse events. The most common grade 3 or higher adverse events associated with the neoadjuvant administration of mFOLFOX6 across groups 2-4 were neutropenia (five in group 3 and six in group 4) and lymphopenia (three in group 3 and four in group 4). Across all study groups, 25 grade 3 or worse surgery-related complications occurred (ten in group 1, five in group 2, three in group 3, and seven in group 4); the most common were pelvic abscesses (seven patients) and anastomotic leaks (seven patients). INTERPRETATION: Delivery of mFOLFOX6 after chemoradiation and before total mesorectal excision has the potential to increase the proportion of patients eligible for less invasive treatment strategies; this strategy is being tested in phase 3 clinical trials. FUNDING: National Institutes of Health National Cancer Institute.

Optimal timing of surgery after chemoradiation for advanced rectal cancer: preliminary results of a multicenter, nonrandomized phase II prospective trial.

OBJECTIVE: To determine whether extending the interval between chemoradiation (CRT) and surgery, and administering additional chemotherapy during the waiting period has an impact on tumor response, CRT-related toxicity and surgical complications in patients with advanced rectal cancer. BACKGROUND: Locally advanced rectal cancer is usually treated with preoperative CRT followed by surgery approximately 6 weeks later. The Timing of Rectal Cancer Response to Chemoradiation Consortium designed a prospective, multicenter, Phase II clinical trial to investigate extending the interval between CRT and surgery, and administering additional chemotherapy during the waiting period. Here, we present preliminary results of this trial, reporting the tumor response, CRT-related toxicity and surgical complications. METHODS: Stage II and III rectal cancer patients were treated concurrently with 5-Fluorouracil (FU) and radiation for 5 to 6 weeks. Patients in study group (SG) 1 underwent total mesorectal excision (TME) 6 weeks later. Patients in SG2 with evidence of a clinical response 4 weeks after CRT received 2 cycles of modified FOLFOX-6 (mFOLFOX-6) followed by TME 3 to 5 weeks later. Tumor response, CRT-related toxicity and surgical complications were recorded. RESULTS: One hundred and forty-four patients were accrued. One hundred and thirty-six (66, SG1; 70, SG2) were evaluated for CRT-related toxicity. One hundred and twenty-seven (60, SG1; 67, SG2) were assessed for tumor response and surgical complications. A similar proportion of patients completed CRT per protocol in both SGs, but the cumulative dose of sensitizing 5-FU and radiation was higher in SG2. CRT-related toxicity was comparable between SGs. Average time from CRT-to-surgery was 6 (SG1) and 11 weeks (SG2). Pathologic complete response (pCR) was 18% (SG1) and 25% (SG2). Postoperative complications were similar between SGs. CONCLUSIONS: Intense neoadjuvant therapy consisting of CRT followed by additional chemotherapy (mFOLFOX-6), and delaying surgery may result in a modest increase in pCR rate without increasing complications in patients undergoing TME for locally advanced rectal cancer.