Prediction of Poor Response to Neoadjuvant Chemoradiation in Patients With Rectal Cancer Using a DNA Repair Deregulation Score: Picking the Losers Instead of the Winners

Clinical predictors of rectal cancer response after neo-adjuvant (Chemo)Radiotherapy in Australia and New Zealand: Analysis of the Bi-National Colorectal Cancer Audit (BCCA)

Pathological complete response (pCR) is observed in 11-26% of locally advanced rectal cancers undergoing neoadjuvant chemoradiotherapy (nCRT). This study aims to determine pCR rates and clinicopathological predictors in the Australian and New Zealand (ANZ) cohort. The Bi-National Colorectal Cancer Audit (BCCA) was interrogated for all rectal cancer patients who underwent nCRT prior to surgical resection between 2007 and 2020. Patients were divided in two groups: pCR (AJCC tumour regression grade 0) and partial/no response (pPR, regression grade 1,2 or 3). In total, 3230 patients were included. Rates of pCR and pPR were 704 (21.8%) and 2526 (78.2%), respectively. Long-course nCRT (p < 0.0001), lower clinical tumour stage (cT; p < 0.0001), and nodal stage (cN; p = 0.003) were associated with pCR on univariate analysis. On multivariable analysis, cN0 stage and long-course nCRT remained independent factors for a pCR. Awareness of these predictors provides valuable information when counseling patients regarding prognosis and treatment options.

Sialyltransferase ST6GAL-1 mediates resistance to chemoradiation in rectal cancer

Locally advanced rectal cancer is typically treated with chemoradiotherapy followed by surgery. Most patients do not display a complete response to chemoradiotherapy, but resistance mechanisms are poorly understood. ST6GAL-1 is a sialyltransferase that adds the negatively charged sugar, sialic acid (Sia), to cell surface proteins in the Golgi, altering their function. We therefore hypothesized that ST6GAL-1 could mediate resistance to chemoradiation in rectal cancer by inhibiting apoptosis. Patient-derived xenograft and organoid models of rectal cancer and rectal cancer cell lines were assessed for ST6GAL-1 protein with and without chemoradiation treatment. ST6GAL-1 mRNA was assessed in untreated human rectal adenocarcinoma by PCR assays. Samples were further assessed by Western blotting, Caspase-Glo apoptosis assays, and colony formation assays. The presence of functional ST6GAL-1 was assessed via flow cytometry using the Sambucus nigra lectin, which specifically binds cell surface α2,6-linked Sia, and via lectin precipitation. In patient-derived xenograft models of rectal cancer, we found that ST6GAL-1 protein was increased after chemoradiation in a subset of samples. Rectal cancer cell lines demonstrated increased ST6GAL-1 protein and cell surface Sia after chemoradiation. ST6GAL-1 was also increased in rectal cancer organoids after treatment. ST6GAL-1 knockdown in rectal cancer cell lines resulted in increased apoptosis and decreased survival after treatment. We concluded that ST6GAL-1 promotes resistance to chemoradiotherapy by inhibiting apoptosis in rectal cancer cell lines. More research will be needed to further elucidate the importance and mechanism of ST6GAL-1-mediated resistance.

Nonoperative Management for T2 Low Rectal Cancer: A Western Approach

The possibility of organ preservation in early rectal cancer has gained popularity during recent years. Patients with early tumor stage and low risk for local recurrence do not usually require neoadjuvant chemoradiation for oncological reasons. However, these patients may be considered for chemoradiation exclusively for the purpose of achieving a complete clinical response and avoid total mesorectal excision. In addition, cT2 tumors may be more likely to develop complete response to neoadjuvant therapy and may constitute ideal candidates for organ-preserving strategies. In the setting where the use of chemoradiation is exclusively used to avoid major surgery, one should consider maximizing tumor response. In this article, we will focus on the rationale, indications, and outcomes of patients with early rectal cancer being treated by neoadjuvant chemoradiation to achieve organ preservation by avoiding total mesorectal excision.

Organ Preservation in the Treatment of Stage II and III Rectal Cancer

A 65-year-old man underwent colonoscopy to evaluate rectal bleeding and was found to have a low rectal mass. Biopsy revealed moderately differentiated microsatellite stable adenocarcinoma. The tumor was palpable at the fingertip in the anterior rectum with the inferior border 5 cm from the anal verge by rigid proctoscopy. CEA was 0.8 ng/mL. CT imaging of the chest, abdomen, and pelvis showed no evidence of distant metastases. MRI confirmed a 5-cm mass with one 8-mm mesorectal lymph node metastasis and no extramural venous invasion. The tumor penetrated the mesorectal fat to a depth of 4 mm, and the circumferential margin was estimated to be 1 mm from the tumor (). He was presented at the multidisciplinary tumor board conference and interviewed and examined at the multidisciplinary clinic. He was dismayed at the prospect of his surgical options, a low anterior resection versus abdominoperineal resection, and wished to keep the options for organ preservation available. Standard long-course chemoradiation was initiated, with resolution of his bleeding after 2 weeks. He then completed 6 cycles of folinic acid, fluorouracil, and oxaliplatin (FOLFOX) chemotherapy (consolidation total neoadjuvant therapy (TNT)). The tumor was no longer palpable on office examination. A complete clinical response (cCR) was confirmed by flexible sigmoidoscopy () and MRI (). He was entered into the nonoperative management program with intense surveillance scheduling and has no evidence of recurrent disease almost 2 years after completion of TNT.