Local tumor regrowth after clinical complete response following neoadjuvant therapy for rectal cancer: what happens when organ preservation falls short.

Organ preservation strategies, especially watch and wait, after neoadjuvant treatment in locally advanced rectal cancer, have become topics that generate significant interest, for both patients and clinicians. The obvious advantage of these strategies is the avoidance of surgery with its associated risks and functional consequences. Over time, it has become evident that these strategies offer acceptable safety in oncological terms and, in most patients, allows preservation of the rectum without harming patients in terms of distant metastasis or survival. However, there is a small group of patients in whom the tumor returns after an initially diagnosed clinical complete response; patients with local tumor regrowth. The main threat in these patients is not simply local disease, which can be successfully managed in most cases, but the possible effects it may have on distant metastases. The pathophysiology of the phenomenon of local tumor regrowth is not well known and, therefore, strategies to minimize possible impact on survival are not well defined. Our aim is to review key issues in this subgroup that pose a substantial threat to the safety and viability of organ-preserving and watch-and-wait strategies. We also explore possible pathophysiologic explanations and future directions and perspectives that may improve both local and systemic disease control.

Effect of Akt activation and experimental pharmacological inhibition on responses to neoadjuvant chemoradiotherapy in rectal cancer.

BACKGROUND: Neoadjuvant chemoradiotherapy (CRT) is one of the preferred initial treatment strategies for locally advanced rectal cancer. Responses are variable, and most patients still require surgery. The aim of this study was to identify molecular mechanisms determining poor response to CRT. METHODS: Global gene expression and pathway enrichment were assessed in pretreatment biopsies from patients with non-metastatic cT2-4 N0-2 rectal cancer within 7 cm of the anal verge. Downstream Akt activation was assessed in an independent set of pretreatment biopsies and in colorectal cancer cell lines using immunohistochemistry and western blot respectively. The radiosensitizing effects of the Akt inhibitor MK2206 were assessed using clonogenic assays and xenografts in immunodeficient mice. RESULTS: A total of 350 differentially expressed genes were identified, of which 123 were upregulated and 199 downregulated in tumours from poor responders. Mitochondrial oxidative phosphorylation (P < 0·001) and phosphatidylinositol signalling pathways (P < 0·050) were identified as significantly enriched pathways among the set of differentially expressed genes. Deregulation of both pathways is known to result in Akt activation, and high immunoexpression of phosphorylated Akt S473 was observed among patients with a poor histological response (tumour regression grade 0-2) to CRT (75 per cent versus 48 per cent in those with a good or complete response; P = 0·016). Akt activation was also confirmed in the radioresistant cell line SW480, and a 50 per cent improvement in sensitivity to CRT was observed in vitro and in vivo when SW480 cells were exposed to the Akt inhibitor MK2206 in combination with radiation and 5-fluorouracil. CONCLUSION: Akt activation is a key event in the response to CRT. Pharmacological inhibition of Akt activation may enhance the effects of CRT. Surgical relevance Organ preservation is an attractive alternative in rectal cancer management following neoadjuvant chemoradiotherapy (CRT) to avoid the morbidity of radical surgery. Molecular steps associated with tumour response to CRT may provide a useful tool for the identification of patients who are candidates for no immediate surgery. In this study, tumours resistant to CRT were more likely to have activation of specific genetic pathways that result in phosphorylated Akt (pAkt) activation. Pretreatment biopsy tissues with high immunoexpression of pAkt were more likely to exhibit a poor histological response to CRT. In addition, the introduction of a pAkt inhibitor to cancer cell lines in vitro and in vivo led to a significant improvement in sensitivity to CRT. Identification of pAkt-activated tumours may thus allow the identification of poor responders to CRT. In addition, the concomitant use of pAkt inhibitors to increase sensitivity to CRT in patients with rectal cancer may constitute an interesting strategy for increasing the chance of a complete response to treatment and organ preservation.

Magnetic resonance imaging following neoadjuvant chemoradiation and transanal endoscopic microsurgery for rectal cancer.

AIM: Full-thickness local excision after neoadjuvant chemoradiotherapy (CRT) for patients with rectal cancer and incomplete clinical response has been a treatment strategy for organ preservation. Follow-up of these patients is challenging since anatomic distortion and postoperative changes may be clinically indistinguishable from tumour recurrence. MRI may have a role in detecting recurrence. The aim of this study was to describe the MRI findings during follow-up in patients having local excision following CRT with and without local recurrence. METHOD: The data were collected retrospectively from a single centre. Fifty-three patients with rectal cancer who had full-thickness local excision after neoadjuvant CRT and near-complete response were eligible for the study. Patients with local recurrence were treated by radical salvage surgery. The main outcome was local MRI assessment findings during follow-up. RESULTS: Fifteen patients (five who developed local recurrence and 10 with no evidence of local recurrence) had MR images available for review and were included in the study. High signal intensity and thickening of the rectal wall were present in all patients with recurrent disease within the rectal wall. Overall, 80% of the patients with recurrence showed diffusion restriction. MRI mesorectal fascia status and circumferential resection margin showed agreement in all cases. A low signal intensity scar was seen in all patients without recurrent disease. CONCLUSION: MRI shows high signal intensity and thickening of the rectal wall in recurrent disease in comparison to a low signal intensity fibrotic scar in non-recurrent disease. These findings may be useful in surveillance of these patients.

Predicting complete response to neoadjuvant CRT for distal rectal cancer using sequential PET/CT imaging.

BACKGROUND: Molecular imaging using positron emission tomography/computerized tomography (PET/CT) may add relevant incremental diagnostic information to standard structural cross-sectional imaging. Such information may allow identification of patients with rectal cancer that are more likely to develop complete tumor regression after neoadjuvant chemoradiation therapy (CRT). The objective of this report was to identify PET/CT features that are associated with a complete response after CRT. METHODS: 99 cT2-4N0-2M0 distal rectal cancer patients (≤7 cm from anal verge) were included in this prospective single center trial (NCT 00254683). Patients underwent baseline PET/CT followed by 54 Gy and 5-fluorouracil-based neoadjuvant CRT. After completion of therapy, patients underwent 6- and 12-week PET/CT. Clinical assessment of tumor response was performed at 12 weeks and was blinded to radiological information. Patients were treated according to clinical assessment. RESULTS: There were seven patients with a complete pathological response (pCR) and 16 with a complete clinical response (cCR) (23 complete responders). Comparison of pCR exclusively and non-pCR revealed that only baseline primary tumor standard uptake value (SUV) was a significant predictor of response. Comparison of complete responders (pCR or cCR) and non-complete responders showed that depth of rectal wall uptake at baseline PET/CT (p = 0.002) and variation between baseline and 12-week maximum standard uptake value (SUVmax) of primary tumor (p = 0.001) were independent predictors for complete response at multivariate analysis. A decrease >67 % between baseline and 6-week or 76 % between baseline and 12-week SUVmax were associated with complete response (pCR or cCR; p = 0.02 and p < 0.001, respectively). CONCLUSIONS: Positron emission tomography/computerized tomography at baseline, 6 and 12 weeks, may provide information regarding patients with a higher likelihood of developing complete tumor regression following neoadjuvant CRT.

Clinical relevance of positron emission tomography/computed tomography-positive inguinal nodes in rectal cancer after neoadjuvant chemoradiation.

AIM: Inguinal nodes may be a possible route for lymphatic spread in patients with distal rectal cancer. The outcome was examined for patients with distal rectal cancer undergoing neoadjuvant chemoradiation (CRT) and having 2-fluorine-18-fluoro-2-deoxy-d-glucose (FDG)-avid inguinal nodes using positron emission tomography/computed tomography (PET/CT) imaging. METHOD: Ninety-nine consecutive patients with cT2-4N0-2M0 distal rectal adenocarcinoma were enrolled in a clinical trial (NCT00254683) and underwent baseline PET/CT followed by 54 Gy and 5-fluorouracil-based CRT. After CRT, patients underwent 6- and 12-week PET/CT. Patients with positive inguinal node uptake were compared with patients with negative uptake. The inguinal region was not included in the field of radiation therapy. RESULTS: Seventeen (17%) patients had baseline positive inguinal node FDG uptake. They were more likely to have the tumour closer to the anal verge (2.0 vs 4.2 cm; P = 0.001). Of these, eight (47%) demonstrated a positive inguinal uptake at PET/CT after 12 weeks from CRT. Patients with inguinal node FDG uptake after CRT (positive PET at baseline and 12 weeks) had a significantly worse 3-year overall and disease-free survival (P = 0.02 and P = 0.03). After a median follow-up period of 22 months, none of these patients had developed inguinal recurrence. CONCLUSION: Uptake of inguinal nodes at PET/CT may be present in up to 17% of patients with distal rectal cancer, particularly with ultra-low tumours. Nearly half of these nodes no longer show uptake after CRT despite the groin area not being included in the radiation field. Persistence of inguinal node uptake 12 weeks after CRT completion may be a marker for worse oncological outcome.

Factors affecting management decisions in rectal cancer in clinical practice: results from a national survey.

BACKGROUND: Management of rectal cancer has become increasingly complex and a multidisciplinary approach is considered of key importance for improving outcomes. A national survey among specialists involved in this multidisciplinary setting was performed. METHODS: A web-based survey containing 11 questions regarding rectal cancer management was sent to surgeons and medical oncologists registered by their corresponding societies as members. Statistical analysis was performed using the chi-square and Fisher's exact tests for all categorical variables according to response to individual questions. Multivariate analysis was performed using Cox's logistic regression. RESULTS: Overall, 418 email recipients responded the survey. Local staging was performed without either magnetic resonance imaging or endorectal ultrasound by 64% of responders. Seventy-two percent considered that final management decision should be made after neoadjuvant chemoradiation therapy. Additionally, 46% considered that an alternative procedure (local excision or observation) was appropriate in a patient with a complete clinical response. Colorectal surgeons were more frequently in favor of longer intervals after completion of chemoradiation therapy (P = 0.001) and of alternative management procedures after a complete clinical response (P = 0.02). After multivariate analysis, the choice of a watch and wait approach after a complete clinical response following neoadjuvant chemoradiation therapy was significantly more frequent among surgeons (OR 3.5, 95% CI 1.8-7.1). CONCLUSIONS: Surgeons seem to be more in favor of tailoring management of rectal cancer according to tumor response after neoadjuvant chemoradiation therapy, with longer intervals after chemoradiation therapy, decisions about treatment strategy being made after chemoradiation therapy instead of before, and the use of alternative surgical procedures after a complete clinical response following neoadjuvant therapy.