Personalized total neoadjuvant therapy (pTNT) for advanced rectal cancer with tailored treatment sequencing based on clinical stage at presentation

Oncological Outcomes and Response Rate After Total Neoadjuvant Therapy for Locally Advanced Rectal Cancer: A Network Meta-Analysis Comparing Induction vs. Consolidation Chemotherapy vs. Standard Chemoradiation

TNT is now considered the preferred option for stage II-III locally advanced rectal cancer (LARC). However, the prognostic benefit and optimal sequence of TNT remains unclear. This network meta-analysis (NMA) compared short- and long-term outcomes amongst patients with LARC receiving total neoadjuvant therapy (TNT) as induction (iTNT) or consolidation chemotherapy (cTNT) with those receiving neoadjuvant chemoradiation (nCRT) alone. A systematic literature search was performed between 2012 and 2023. A Bayesian NMA was conducted using a Markov Chain Monte Carlo method with a random-effects model and vague prior distribution to calculate odds ratios (OR) with 95% credible intervals (CrI). The surface under the cumulative ranking (SUCRA) curves were used to rank treatment(s) for each outcome. In total, 11 cohorts involving 8360 patients with LARC were included. There was no significant difference in disease-free survival (DFS) and overall survival (OS) amongst the 3 treatments. Compared with nCRT, both cTNT (OR 2.36; 95% CrI, 1.57-3.66) and iTNT (OR 1.99; 95% CrI, 1.44-2.95) significantly improved complete response (CR) rate. Notably, cTNT ranked as the best treatment for CR (SUCRA 0.90) and iTNT as the best treatment for 3-year DFS and OS (SUCRA 0.72 and 0.87, respectively). Both iTNT and cTNT strategies significantly improved CR rates compared with nCRT. cTNT was ranked highest for CR rates, while iTNT was ranked highest for 3-year survival outcomes. However, no other significant differences in DFS, OS, sphincter-saving surgery, R0 resection and postoperative complications were found amongst the treatment groups.

Association Between RAS/BRAF Mutations and Complete Response Following Total Neoadjuvant Therapy in Patients with Rectal Cancer: A Prospective Multicentered Study

BACKGROUND

The impact of RAS/BRAF mutation on primary response rates after total neoadjuvant therapy (TNT) in patients with advanced rectal cancer is unclear. The aim of this study was to assess complete response rates after TNT according to RAS/BRAF mutation status.

METHODS

A prospective observational study was performed in patients with rectal cancer who underwent TNT with curative intent at three South Australian hospitals between 2019 and 2023. Patients were classified according to their mutation status: mutant RAS/BRAF (mutRAS) or wild-type RAS/BRAF (wtRAS). The primary endpoint was overall complete response (oCR) rate, defined as the proportion of patients who achieved clinical complete response (cCR) and/or pathological complete response (pCR).

RESULTS

Of the 150 patients eligible for inclusion, 80 patients with RAS/BRAF status available were identified. Of these, 43 (53.8%) patients were classified as mutRAS and 37 (46.3%) patients as wtRAS. Patients with mutRAS had significantly lower cCR and oCR rates after TNT than patients with wtRAS (14% vs. 37.8%, p = 0.014; 11.6% vs. 43.2%, p = 0.001, respectively). There was no significant difference in pCR rate between the groups. Of the 80 rectal cancer patients tested, 35 (43.8%) had metastatic disease (M1). There was no significant difference in complete M1 response rates between the groups (17.6% vs. 38.9%, p = 0.254).

CONCLUSION

RAS/BRAF mutations negatively impact primary tumor response rates after TNT in patients with advanced rectal cancer. Large-scale national studies are needed to determine whether RAS/BRAF status could be used to select optimal oncologic therapy in rectal cancer patients.

The Predictors of Complete Pathologic Response in Rectal Cancer during the Total Neoadjuvant Therapy Era: A Systematic Review

The modern rectal cancer treatment paradigm offers additional opportunities for organ preservation, most notably via total neoadjuvant therapy (TNT) and consideration for a watch-and-wait (WW) surveillance-only approach. A major barrier to widespread implementation of a WW approach to rectal cancer is the potential discordance between a clinical complete response (cCR) and a pathologic complete response (pCR). In the pre-TNT era, the identification of predictors of pCR after neoadjuvant therapy had been previously studied. However, the last meta-analysis to assess the summative evidence on this important treatment decision point predates the acceptance and dissemination of TNT strategies. The purpose of this systematic review was to assess preoperative predictors of pCR after TNT to guide the ideal selection criteria for WW in the current era. An exhaustive literature review was performed and the electronic databases Embase, Ovid, MEDLINE, PubMed, and Cochrane were comprehensively searched up to 27 June 2023. Search terms and their combinations included "rectal neoplasms", "total neoadjuvant therapy", and "pathologic complete response". Only studies in English were included. Randomized clinical trials or prospective/retrospective cohort studies of patients with clinical stage 2 or 3 rectal adenocarcinoma who underwent at least 8 weeks of neoadjuvant chemotherapy in addition to chemoradiotherapy with pCR as a measured study outcome were included. In this systematic review, nine studies were reviewed for characteristics positively or negatively associated with pCR or tumor response after TNT. The results were qualitatively grouped into four categories: (1) biochemical factors; (2) clinical factors; (3) patient demographics; and (4) treatment sequence for TNT. The heterogeneity of studies precluded meta-analysis. The level of evidence was low to very low. There is minimal data to support any clinicopathologic factors that either have a negative or positive relationship to pCR and tumor response after TNT. Additional data from long-term trials using TNT is critical to better inform those considering WW approaches following a cCR.

Post-Surgical Imaging Assessment in Rectal Cancer: Normal Findings and Complications

Rectal cancer (RC) is one of the deadliest malignancies worldwide. Surgery is the most common treatment for RC, performed in 63.2% of patients. The type of surgical approach chosen aims to achieve maximum residual function with the lowest risk of recurrence. The selection is made by a multidisciplinary team that assesses the characteristics of the patient and the tumor. Total mesorectal excision (TME), including both low anterior resection (LAR) and abdominoperineal resection (APR), is still the standard of care for RC. Radical surgery is burdened by a 31% rate of major complications (Clavien-Dindo grade 3-4), such as anastomotic leaks and a risk of a permanent stoma. In recent years, less-invasive techniques, such as local excision, have been tested. These additional procedures could mitigate the morbidity of rectal resection, while providing acceptable oncologic results. The "watch and wait" approach is not a globally accepted model of care but encouraging results on selected groups of patients make it a promising strategy. In this plethora of treatments, the radiologist is called upon to distinguish a physiological from a pathological postoperative finding. The aim of this narrative review is to identify the main post-surgical complications and the most effective imaging techniques.