Preoperative radiation dose escalation for rectal cancer using a concomitant boost strategy improves tumor downstaging without increasing toxicity: A matched-pair analysis

Radioresistance in rectal cancer: can nanoparticles turn the tide?

Rectal cancer accounts for over 35% of the worldwide colorectal cancer burden representing a distinctive subset of cancers from those arising in the colon. Colorectal cancers exhibit a continuum of traits that differ with their location in the large intestine. Due to anatomical and molecular differences, rectal cancer is treated differently from colon cancer, with neoadjuvant chemoradiotherapy playing a pivotal role in the control of the locally advanced disease. However, radioresistance remains a major obstacle often correlated with poor prognosis. Multifunctional nanomedicines offer a promising approach to improve radiotherapy response rates, as well as to increase the intratumoral concentration of chemotherapeutic agents, such as 5-Fluorouracil. Here, we revise the main molecular differences between rectal and colon tumors, exploring the complex orchestration beyond rectal cancer radioresistance and the most promising nanomedicines reported in the literature to improve neoadjuvant therapy response rates.

Understanding the molecular mechanism responsible for developing therapeutic radiation-induced radioresistance of rectal cancer and improving the clinical outcomes of radiotherapy - A review

Rectal cancer accounts for the second highest cancer-related mortality, which is predominant in Western civilizations. The treatment for rectal cancers includes surgery, radiotherapy, chemotherapy, and immunotherapy. Radiotherapy, specifically external beam radiation therapy, is the most common way to treat rectal cancer because radiation not only limits cancer progression but also significantly reduces the risk of local recurrence. However, therapeutic radiation-induced radioresistance to rectal cancer cells and toxicity to normal tissues are major drawbacks. Therefore, understanding the mechanistic basis of developing radioresistance during and after radiation therapy would provide crucial insight to improve clinical outcomes of radiation therapy for rectal cancer patients. Studies by various groups have shown that radiotherapy-mediated changes in the tumor microenvironment play a crucial role in developing radioresistance. Therapeutic radiation-induced hypoxia and functional alterations in the stromal cells, specifically tumor-associated macrophage (TAM) and cancer-associated fibroblasts (CAF), play a crucial role in developing radioresistance. In addition, signaling pathways, such as - the PI3K/AKT pathway, Wnt/β-catenin signaling, and the hippo pathway, modulate the radiation responsiveness of cancer cells. Different radiosensitizers, such as small molecules, microRNA, nanomaterials, and natural and chemical sensitizers, are being used to increase the effectiveness of radiotherapy. This review highlights the mechanism responsible for developing radioresistance of rectal cancer following radiotherapy and potential strategies to enhance the effectiveness of radiotherapy for better management of rectal cancer.

Factors influencing pathological complete response and tumor regression in neoadjuvant radiotherapy and chemotherapy for high-risk breast cancer

BACKGROUND

Pathological complete response (pCR) is a well-established prognostic factor in breast cancer treated with neoadjuvant systemic therapy (naST). The determining factors of pCR are known to be intrinsic subtype, proliferation index, grading, clinical tumor and nodal stage as well as type of systemic therapy. The addition of neoadjuvant radiotherapy (naRT) to this paradigm might improve response, freedom from disease, toxicity and cosmetic outcome compared to adjuvant radiotherapy. The factors for pCR and primary tumor regression when neoadjuvant radiation therapy is added to chemotherapy have not been thoroughly described.

METHODS

We performed a retrospective analysis of 341 patients (cT1-cT4/cN0-N+) treated with naRT and naST between 1990 and 2003. Patients underwent naRT to the breast and mostly to the supra-/infraclavicular lymph nodes combined with an electron or brachytherapy boost. NaST was given either sequentially or simultaneously to naRT using different regimens. We used the univariate and multivariate regression analysis to estimate the effect of different subgroups and treatment modalities on pCR (ypT0/Tis and ypN0) as well as complete primary tumor response (ypT0/Tis; bpCR) in our cohort. Receiver operating characteristic (ROC) analysis was performed to evaluate the interval between radiotherapy (RT) and resection (Rx) as well as radiotherapy dose.

RESULTS

Out of 341 patients, pCR and pbCR were achieved in 31% and 39%, respectively. pCR rate was influenced by resection type, breast cancer subtype, primary tumor stage and interval from radiation to surgery in the multivariate analysis. Univariate analysis of bpCR showed age, resection type, breast cancer subtype, clinical tumor stage and grading as significant factors. Resection type, subtype and clinical tumor stage remained significant in multivariate analysis. Radiation dose to the tumor and interval from radiation to surgery were not significant factors for pCR. However, when treatment factors were added to the model, a longer interval from radiotherapy to resection was a significant predictor for pCR.

CONCLUSIONS

The factors associated with pCR following naST and naRT are similar to known factors after naST alone. Longer interval to surgery might to be associated with higher pCR rates. Dose escalation beyond 60 Gy did not result in higher response rates.

Roseburia intestinalis sensitizes colorectal cancer to radiotherapy through the butyrate/OR51E1/RALB axis

The radioresistant signature of colorectal cancer (CRC) hampers the clinical utility of radiotherapy. Here, we find that fecal microbiota transplantation (FMT) potentiates the tumoricidal effects of radiation and degrades the intertwined adverse events in azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced CRC mice. FMT cumulates Roseburia intestinalis (R. intestinalis) in the gastrointestinal tract. Oral gavage of R. intestinalis assembles at the CRC site and synthetizes butyrate, sensitizing CRC to radiation and alleviating intestinal toxicity in primary and CRC hepatic metastasis mouse models. R. intestinalis-derived butyrate activates OR51E1, a G-protein-coupled receptor overexpressing in patients with rectal cancer, facilitating radiogenic autophagy in CRC cells. OR51E1 shows a positive correlation with RALB in clinical rectal cancer tissues and CRC mouse model. Blockage of OR51E1/RALB signaling restrains butyrate-elicited autophagy in irradiated CRC cells. Our findings highlight that the gut commensal bacteria R. intestinalis motivates radiation-induced autophagy to accelerate CRC cell death through the butyrate/OR51E1/RALB axis and provide a promising radiosensitizer for CRC in a pre-clinical setting.

Stereotactic MR-guided adaptive radiotherapy (SMART) for primary rectal cancer: evaluation of early toxicity and pathological response

Background

The purpose of this study is to measure the effects of stereotactic MR-guided adaptive radiotherapy (SMART) for rectal cancer patients in terms of early toxicity and pathological response.

Materials and methods

For this prospective pilot study, patients diagnosed with locally advanced rectal cancer (LARC) with positive lymph node clinical staging underwent SMART on rectal lesion and mesorectum using hybrid MR-Linac (MRIdian ViewRay). Dose prescription at 80% isodose for the rectal lesion and mesorectum was 40 Gy (8 Gy/fr) and 25 Gy (5 Gy/fr), respectively, delivered on 5 days (3 fr/week). Response assessment by MRI was performed 3 weeks after SMART, then patients fit for surgery underwent total mesorectal excision. Primary endpoint was evaluation of adverse effect of radiotherapy. Secondary endpoint was pathological complete response rate. Early toxicity was graded according to the Common Terminology Criteria for Adverse Events (CTCAE v5.0).

Results

From October 2020 to January 2022, twenty patients underwent rectal SMART. No grade 3-5 toxicity was recorded. Twelve patients were eligible for total mesorectal excision (TME). Mean interval between the completion of SMART and surgery was 4 weeks. Pathological downstaging occurred in all patients; rate of pathological complete response (pCR) was 17%. pCR occurred with a prolonged time to surgery (> 7 weeks).

Conclusion

To our knowledge, this is the first study to use stereotactic radiotherapy for primary rectal cancer. SMART for rectal cancer is well tolerated and effective in terms of tumor regression, especially if followed by delayed surgery.

Prospective evaluation of dose-escalated preoperative concurrent chemo-radiation with image guided-IMRT in locally advanced rectal cancers

Purpose

To analyse the safety and efficacy of neoadjuvant chemoradiation (NACRT) with dose-escalated image-guided intensity modulated radiation therapy (IG-IMRT) in locally advanced (T3/4; T1-4N1-2) rectal cancers (LARCs).

Materials and methods

Twenty patients with the diagnosis of LARC were recruited in this prospective interventional single-arm study treated by IG-IMRT with 45 Gray (Gy) in 25 fractions to elective nodal volumes and 55 Gy in 25 fractions to the gross primary and nodal disease with concurrent capecitabine 825 mg/m2 twice daily on radiotherapy days. Patients underwent total mesorectal excision 6-8 weeks post completion of NACRT followed by adjuvant chemotherapy (Capecitabine and oxaliplatin every 3 weekly for 6-8 cycles). Primary end point was acute toxicity assessment and secondary end points were pathological complete response (pCR) and loco-regional control (LRC).

Results

Clinical T stage was T3:T4 in 19:1 and clinical N0:N1: N2 in 2:7:11 patients, respectively. With a median follow up of 21.2 months (13.8-25.6 months), 18 of 20 (90%) patients received the full course of treatment. Tumour and nodal downstaging was achieved in 78% and 84% of patients, respectively. pCR and overall complete response (defined as pCR and near CR) was achieved in 22.2% and 44.4% of patients, respectively. 2 (10%) patients completed NACRT, and achieved complete clinical response but refused surgery. Adjuvant chemotherapy course was completed by 17/18 (94.5%) patients. Grade 3 toxicities were observed in 2 (10%) patients during NACRT. All patients were disease-free at the time of the last follow up.

Conclusion

Dose-escalation of NACRT therapy with IG-IMRT in LARC patients offers decent rates of pCR and overall response with excellent LRC and acceptable toxicities.

More Is Not Better When It Comes to Treating Rectal Cancer With Multimodal Chemoradiation Beyond the Standard Radiation Dose of 5040 cGy

BACKGROUND

Radiation dose schedules for neoadjuvant chemoradiation for rectal cancers differ, with the most common dose schedule using 5040 cGy in 28 fractions.

OBJECTIVES

The aim of this retrospective study was to assess the benefit of higher radiation doses beyond 5040 cGy in the context of pathological response and follow-up events.

SETTING

The database from a provincial tertiary cancer center in Canada was the source of information for this study.

PATIENTS

Included in this study were 508 consecutive patients with rectal cancer with locally advanced disease (clinical T3/T4 or N1/N2) who received neoadjuvant chemoradiation followed by surgery. Of the 508 patients, 281 received the standard radiation dose of 4500 to 5040 cGy and 227 received a dose >5040 cGy.

MAIN OUTCOME MEASURE

The postsurgical pathology, late toxicities, and follow-up outcomes were analyzed. The outcomes were evaluated in relation to the dose of radiation received.

RESULTS

Data regarding the clinical outcomes were comparable between the 4500 to 5040 cGy and >5040 cGy radiation groups with pathological complete response rates of 20.9% and 15.4% (p = 0.104); distant recurrence rates of 17.4% and 19.4% (p = 0.36); local recurrence rates of 3.2% and 3.5% (p = 0.36); and the median overall survival rates of 61 and 60.5 months (p = 0.8). No statistically significant correlation of improvement in outcomes was noted with radiation doses beyond 5040 cGy.

LIMITATIONS

This is a retrospective study.

CONCLUSION

Our study showed that dose escalation beyond the standard dose of 4500 to 5040cGy failed to achieve meaningful clinical outcomes. See Video Abstract at http://links.lww.com/DCR/B633.

MS NO ES MEJOR CUANDO SE TRATA DE TRATAR EL CNCER DE RECTO CON QUIMIORRADIACIN MULTIMODAL MS ALL DE LA DOSIS DE RADIACIN ESTNDAR DE CGY

ANTECEDENTES:En neoadyuvancia de cáncer rectal es posible encontrar muchas variaciones, en radioterapia la dosis más común que usa 5040 cGy en 28 fracciones.OBJETIVOS:El objetivo de este estudio retrospectivo fue evaluar el beneficio de dosis de radiación más altas más allá de 5040cGy en el contexto de la respuesta patológica y en su seguimiento.AJUSTE:Base de datos de un centro de cáncer terciario provincial en Canadá.PACIENTES:Se incluyeron en este estudio quinientos ocho pacientes consecutivos con cáncer de recto y enfermedad localmente avanzada (clínica T3 / T4 o N1 / N2) que recibieron quimiorradiación neoadyuvante seguida de cirugía. De los 508 pacientes, 281 recibieron la dosis de radiación estándar de 4500-5040 cGy y 227 recibieron una dosis > 5040 cGy.PRINCIPAL MEDIDA DE RESULTADO:Se analizo evolucion posquirúrgica, toxicidad tardía y seguimiento. Los resultados se evaluaron en relación con la dosis de radiación recibida.RESULTADOS:Los datos con respecto a los resultados clínicos fueron comparables entre los grupos de radiación de 4500-5040 cGy y> 5040 cGy con tasas de respuesta patológica completa de 20,9% y 15,4% respectivamente (p = 0,104); tasas de recurrencia a distancia de 17,4% y 19,4%, respectivamente (p = 0,36); tasas de recurrencia local de 3,2% y 3,5%, respectivamente (p = 0,36); y la mediana de las tasas de supervivencia global de 61 y 60,5 meses, respectivamente (p = 0,8). No se observó una correlación estadísticamente significativa de mejoría en los resultados con dosis de radiación superiores a 5040 cGy.LIMITACIONES:Este es un estudio retrospectivo.CONCLUSIONES:Nuestro estudio mostró que el aumento de la dosis más allá de la dosis estándar de 4500-5040cGy no logró resultados clínicos significativos. Consulte Video Resumen en http://links.lww.com/DCR/B633. (Traducción-Dr. Gunther Bocic).

[Complete response after neoadjuvant therapy of rectal cancer: implications for surgery]

For (locally advanced) rectal cancer, a multimodal therapy concept comprising neoadjuvant radiotherapy/chemoradiotherapy, radical surgical resection with partial/complete mesorectal excision and subsequent adjuvant chemotherapy represents the current international standard of care. Further developments in neoadjuvant therapy concepts, such as the principle of total neoadjuvant therapy, lead to an increasing number of patients who show a complete clinical response in restaging after neoadjuvant therapy without clinically detectable residual tumor. In view of the risk associated with radical surgical resection in terms of perioperative morbidity and a potentially non-continence-preserving procedure, the question of the oncological justifiability of an organ-preserving procedure in the case of a complete clinical response under neoadjuvant therapy is increasingly being raised. The therapeutic principle of watch and wait, defined by refraining from immediate radical surgical resection and inclusion in a close-meshed, structured follow-up program, currently appears to be oncologically justifiable based on the current study situation; however, for the initial evaluation of the extent of the clinical response and for the structuring of the close-meshed follow-up program, further optimization and standardization based on broadly designed studies appear necessary in order to be able to provide this concept to a clearly defined patient collective as an oncologically equivalent therapy principle also outside specialized centers.

Neoadjuvant radiotherapy dose escalation for locally advanced rectal cancers in the new era of radiotherapy: A review of literature

BACKGROUND

The standard treatment of locally advanced rectal cancers (LARC) consists on neoadjuvant chemoradiotherapy followed by total mesorectal excision. Different data in literature showed a benefit on tumor downstaging and pathological complete response (pCR) rate using radiotherapy dose escalation, however there is shortage of studies regarding dose escalation using the innovative techniques for LARC (T3-4 or N1-2).

AIM

To analyze the role of neoadjuvant radiotherapy dose escalation for LARC using innovative radiotherapy techniques.

METHODS

In December 2020, we conducted a comprehensive literature search of the following electronic databases: PubMed, Web of Science, Scopus and Cochrane library. The limit period of research included articles published from January 2009 to December 2020. Screening by title and abstract was carried out to identify only studies using radiation doses equivalent dose 2 Gy fraction (EQD2) ≥ 54 Gy and Volumetric Modulated Arc Therapy (VMAT), intensity-modulated radiotherapy or image-guided radiotherapy (IGRT) techniques. The authors’ searches generated a total of 2287 results and, according to PRISMA Group (2009) screening process, 21 publications fulfil selection criteria and were included for the review.

RESULTS

The main radiotherapy technique used consisted in VMAT and IGRT modality. The mainly dose prescription was 55 Gy to high risk volume and 45 Gy as prophylactic volume in 25 fractions given with simultaneous integrated boosts technique (42.85%). The mean pCR was 28.2% with no correlation between dose prescribed and response rates (P value ≥ 0.5). The R0 margins and sphincter preservation rates were 98.88% and 76.03%, respectively. After a mean follow-up of 35 months local control was 92.29%. G3 or higher toxicity was 11.06% with no correlation between dose prescription and toxicities. Patients receiving EQD2 dose > 58.9 Gy and BED > 70.7 Gy had higher surgical complications rates compared to other group (P value = 0.047).

CONCLUSION

Dose escalation neoadjuvant radiotherapy using innovative techniques is safe for LARC achieving higher rates of pCR. EQD2 doses > 58.9 Gy is associated with higher rate of surgical complications.

Use of Poly (Ethylene Glycol) Coated Superparamagnetic Iron Oxide Nanoparticles as Radio Sensitizer in Enhancing Colorectal Cancer Radiation Efficacy

BACKGORUND

The aim of the radiotherapy is to deliver a lethal dose to tumor while reducing the impact on the normal tissue. This reduction in impact can be achieved to have a greater therapeutic ratio by using nanoparticles as radiosensitizer.

MATERIALS AND METHODS

In this article, the potential role of superparamagnetic iron oxide nanoparticles (SPIONs) as radiosensitization enhancer on HT 29 cell lines for different concentrations (0.007to 0.25 mg/ml) and different radiation doses (0.5to 2 Gy) of 6MV photon beam is presented.

RESULTS

The highest sensitization enhancement ratio (SER) value was observed with 2 Gy for 0.25 mg/ml concentration. Radio sensitization increases with increase in the concentration of nanoparticles. Combination of 6MV energy radiation and polyethylene glycol (PEG) coated SPIONs results in increasing cell killing of HT 29 as compared to cell killing with radiation therapy alone.

CONCLUSION

The results reveal that PEG coated nanoparticle might be a potential candidate to work as radiotherapy sensitizer in colorectal cancer.

Recent advances in (chemo-)radiation therapy for rectal cancer: a comprehensive review

The role of radiation therapy in the treatment of (colo)-rectal cancer has changed dramatically over the past decades. Introduced with the aim of reducing the high rates of local recurrences after conventional surgery, major developments in imaging, surgical technique, systemic therapy and radiation delivery have now created a much more complex environment leading to a more personalized approach. Functional aspects including reduction of acute or late treatment-related side effects, sphincter or even organ-preservation and the unsolved problem of still high distant failure rates have become more important while local recurrence rates can be kept low in the vast majority of patients. This review summarizes the actual role of radiation therapy in different subgroups of patients with rectal cancer, including the current standard approach in different subgroups as well as recent developments focusing on neoadjuvant treatment intensification and/or non-operative treatment approaches aiming at organ-preservation.

A systematic review of the role of carbon ion radiation therapy in recurrent rectal cancer

BACKGROUND

Colorectal cancer is the fourth leading cause of cancer-associated death in the world. The 5-year local recurrence rates in patients undergoing multimodality therapy are approximately 5-10%. The standard approach to treat locally recurrent rectal is re-irradiation followed by surgical resection. Recent reports have suggested that the treatment outcomes with carbon ion radiation therapy (CIRT) in recurrent rectal cancer are promising and have superior results compared to photon therapy. Hence, we performed a systematic review to evaluate the patterns of care and treatment outcomes of recurrent rectal cancer patients treated with CIRT.

METHODOLOGY

We performed a systematic search to identify the articles that reported on CIRT use in recurrent rectal cancer.

RESULTS

Systematic search of PubMed and Cochrane Central resulted in 98 abstracts. Eight studies fulfilled the predefined inclusion criteria. Among eight studies, one study is a prospective phase I/II study done in Japan; three prospective studies are ongoing (PANDORA-01 trial, HIMAT1351trial, and a phase II study of reirradiation for prior CIRT), and five studies are institutional reports on role of CIRT. These studies were predominantly reported from Japan and Germany. All reports except one were performed in patients who have not received prior radiation. The most commonly utilized treatment prescription was 73.4 Gy (RBE) in 16 fractions over 4 weeks in patients without any prior history of radiation and 36 Gy in 12 fractions over 3 weeks at 3 Gy per fraction in patients with prior photon radiation to the pelvis. There is one ongoing trial assessing the role of carbon ion re-irradiation in patients who had prior CIRT for rectal cancer.

CONCLUSION

CIRT holds immense promise in improving outcomes in locally recurrent rectal cancer. There is a need for more multi-institutional prospective clinical trials to assess the role of CIRT.

Neoadjuvant Radiotherapy Dose Escalation in Locally Advanced Rectal Cancer: a Systematic Review and Meta-analysis of Modern Treatment Approaches and Outcomes

AIMS

Improving pathological complete response (pCR) rates after neoadjuvant chemoradiotherapy for locally advanced rectal cancer may facilitate surgery-sparing treatment paradigms. Radiotherapy boost has been linked to higher rates of pCR; however, outcomes in moderately escalated inverse-planning studies have not been systematically evaluated. We therefore carried out a systematic review and meta-analysis of radiation dose-escalation studies in the context of neoadjuvant therapy for locally advanced rectal cancer.

MATERIALS AND METHODS

A systematic search of Pubmed, EMBASE and Cochrane databases for synonyms of 'rectal cancer', 'radiotherapy' and 'boost' was carried out. Studies were screened for radiotherapy prescription >54 Gy. Prespecified quality assessment was carried out for meta-analysis inclusion suitability. Pooled estimates of pCR, acute toxicity (grade ≥3) and R0 resection rates were determined with random-effects restricted maximum-likelihood estimation. Heterogeneity was assessed with Higgins I² and Cochran Q statistic. Subset analysis examined outcomes in modern inverse-planning studies. Meta-regression with permutation correction was carried out for each outcome against radiation dose, radiotherapy technique, boost technique, chemotherapy intensification and other patient- and treatment-related cofactors.

RESULTS

Forty-nine primary and three follow-up publications were included in the systematic review. Pooled estimates of pCR, toxicity and R0 resection across 37 eligible publications (n = 1817 patients) were 24.1% (95% confidence interval 21.2-27.4%), 11.2% (95% confidence interval 7.2-17.0%) and 90.7% (95% confidence interval 87.9-93.8%). Within inverse-planning studies (17 publications, n = 959 patients), these rates were 25.7% (95% confidence interval 21.0-31.1%), 9.8% (95% confidence interval 4.6-19.7%) and 95.3% (95% confidence interval 91.6-97.4%). Regression analysis did not identify any significant predictor of pCR (P > 0.05).

CONCLUSIONS

Radiotherapy dose escalation above 54 Gy is associated with high rates of pCR and does not seem to increase the risk of acute grade ≥3 toxicity events. pCR rates approaching 25% may be achievable utilising moderate escalation (54-60 Gy) with modern inverse-planning techniques; however, a clear dose-response relationship was not identified in regression analysis and additional evidence is awaited given the prevalence of heterogenous single-arm studies to date.

Dose-time fractionation schedules of preoperative radiotherapy and timing to surgery for rectal cancer

Chemoradiotherapy (CRT) is extensively used prior to surgery for rectal cancer to provide significantly better local control, but the radiotherapy (RT), as the other component of CRT, has been subject to less interest than the drug component in recent years. With considerable developments in RT, the use of advanced techniques, such as intensity-modulated radiotherapy (IMRT) in rectal cancer, is garnering more attention nowadays. The radiation dose can be better conformed to the target volumes with possibilities for synchronous integrated boost without increased complications in normal tissue. Hopefully, both local recurrence and toxicities can be further reduced. Although those seem to be of interest, many issues remain unresolved. There is no international consensus regarding the radiation schedule for preoperative RT for rectal cancer. Moreover, an enormous disparity exists regarding the RT delivery. With the advent of IMRT, variations will likely increase. Moreover, time to surgery is also quite variable, as it depends upon the indication for RT/CRT in the clinical practices. In this review, we discuss the options and problems related to both the dose-time fractionation schedule and time to surgery; furthermore, it addresses the research questions that need answering in the future.

Magnetic Resonance Guided Radiotherapy for Rectal Cancer: Expanding Opportunities for Non-Operative Management

Colorectal cancer is the third most common cancer in men and the second most common in women worldwide, and the incidence is increasing among younger patients. 30% of these malignancies arise in the rectum. Patients with rectal cancer have historically been managed with preoperative radiation, followed by radical surgery, and adjuvant chemotherapy, with permanent colostomies in up to 20% of patients. Beginning in the early 2000s, non-operative management (NOM) of rectal cancer emerged as a viable alternative to radical surgery in select patients. Efforts have been ongoing to optimize neoadjuvant therapy for rectal cancer, thereby increasing the number of patients potentially eligible to forgo radical surgery. Magnetic resonance guided radiotherapy (MRgRT) has recently emerged as a treatment modality capable of intensifying preoperative radiation therapy for rectal cancer patients. This technology may also predict which patients will achieve a complete response to preoperative therapy, thereby allowing for more appropriate selection of patients for NOM. The present work seeks to illustrate the potential role MRgRT could play in personalizing rectal cancer treatment thus expanding the role of NOM in rectal cancer.

Predictive Significance of Mucinous Histology on Pathologic Complete Response Rate Following Capecitabine-Based Neoadjuvant Chemoradiation in Rectal Cancer: a Comparative Study

INTRODUCTION

Currently, neoadjuvant fluoropyrimidine-based chemoradiation followed by surgery is considered the standard of care for locally advanced rectal cancer. The current study aimed to investigate the predictive significance of mucinous histology on the pathologic complete response rate following neoadjuvant chemoradiation in locally advanced rectal cancer and to propose potential new treatment protocol for this specific histology.

MATERIAL AND METHOD

This retrospective study was conducted on 403 patients with locally advanced (clinically T3-4 and/or N1-2) rectal adenocarcinoma who had been treated at three tertiary academic hospitals between 2010 and 2015. Among those 403 patients, 46 (11%) had mucinous rectal cancer (MRC) and 358 (89%) had non-mucinous rectal cancer (NMRC). All patients underwent neoadjuvant chemoradiation with capecitabine followed by low anterior or abdominoperineal resection.

RESULTS

There were 268 men and 135 women with a median age of 55 years (range, 26-82 years). Patients with MRC were younger (p = 0.002) and presented with a larger tumor size (p < 0.001) and a more advanced tumor stage (p = 0.033) compared to the ones with MNRC. In the univariate analysis, female gender (p = 0.009), distal tumor location (p = 0.035), higher tumor stage (p = 0.049), node positivity (p = 0.001), MRC histology (p = 0.017), and high pretreatment CEA level (p = 0.013) were observed to be predictive of a poor pathologic complete response. However, in the multivariate analysis, tumor stage was the single most predictive factor of response to neoadjuvant chemoradiation.

CONCLUSION

Mucinous adenocarcinoma is a significant predictive factor for poor pathologic complete response to neoadjuvant capecitabine-based chemoradiation in patients with locally advanced rectal cancer. New treatment modality based on biomarkers may be considered in future prospective studies because of MRC poor prognosis. Immunotherapy combined with chemotherapy and/or radiotherapy may be an attractive option because of the tumor microsatellite instability-high status.

Enhancing Colorectal Cancer Radiation Therapy Efficacy using Silver Nanoprisms Decorated with Graphene as Radiosensitizers

Metal nanoparticles have significant interaction cross-sections with electromagnetic waves due to their large surface area-to-volume ratio, which can be exploited in cancer radiotherapy to locally enhance the radiation dose deposition in tumors. We developed a new type of silver nanoparticle composite, PEGylated graphene quantum dot (GQD)-decorated Silver Nanoprisms (pGAgNPs), that show excellent in vitro intracellular uptake and radiosensitization in radiation-sensitive HCT116 and relatively radiation-resistant HT29 colorectal cancer cells. Furthermore, following biodistribution analysis of intravenously injected nanoparticles in nude mice bearing HCT116 tumors radiosensitization was evaluated. Treatment with nanoparticles and a single radiation dose of 10 Gy significantly reduces the growth of colorectal tumors and increases the survival time as compared to treatment with radiation only. Our findings suggest that these novel nanoparticles offer a promising paradigm for enhancing colorectal cancer radiation therapy efficacy.

Impact of VMAT-IMRT compared to 3D conformal radiotherapy on anal sphincter dose distribution in neoadjuvant chemoradiation of rectal cancer

Background

Neoadjuvant radio- or chemoradiation (nIRT) therapy is the standard treatment for loco-regional advanced rectal cancer patients of the lower or middle third. Currently, intensity modulated radiation therapy (IMRT) is not the recommended radiation technique even though IMRT has advantages compared to 3D-radiation regarding dose sparing to organs at risk like small bowel and urinary bladder. So far, the benefit of IMRT concerning the anal sphincter complex is not examined. With this study we intended to evaluate the dose distribution on the anal sphincters of rectal cancer patients treated with IMRT in comparison with 3D-techniques.

Methods

We selected 16 patients for the IMRT-group and 16 patients for the 3D-group with rectal cancer of the middle third who were treated in our institute. All patients received 45 Gy in a chemoradiation protocol. Patients in both groups were matched regarding stage, primary tumor distance to the anal verge and size of the tumor. We delineated the internal and external anal sphincters, the addition of both sphincters and the levator ani muscle in all patients. Subsequently, we evaluated and compared dose parameters of the different sphincters in both groups and analysed the configuration of the isodoses in the area of the caudal radiation field, respectively.

Results

Most of the relevant dose parameters of the caudal sphincters (Dmean, Dmedian, V10–V40) were significantly reduced in the IMRT-group compared to the 3D-group. Accordingly, the isodoses at the caudal edge of the target volume in the IMRT group demonstrated a steep dose fall. The levator ani muscle always was included into the planned target volumes and received the full dose in both groups.

Conclusions

The modern VMAT-IMRT can significantly reduce the dose to the anal sphincters for rectal cancer patients of the middle third who were treated with conventional chemoradiation therapy.

Squamous cell carcinoma of the rectum: Practice trends and patient survival

Purpose

Leverage the National Cancer Database (NCDB) to evaluate trends in management of nonmetastatic squamous cell cancer (SCC) of the rectum and their effect on survival for this uncommon tumor.

Methods and Materials

Retrospective data was obtained from the NCDB for patients diagnosed with SCC of the rectum between 2004 and 2014, including cT1‐4, cN0‐2, cM0 tumors (cohort A, n = 2296). A subgroup analysis was performed on locally advanced tumors (cT1‐T2, N+ or cT3, N any, subcohort B, n = 883), treated with chemoradiation (n = 706) or trimodality therapy (n = 177) including chemotherapy, radiation, and surgery. Pathological complete response rate following neoadjuvant therapy was obtained. Univariate and multivariate logistic regression analyses were performed to generate hazard ratios (HR) investigating factors associated with overall survival. Kaplan‐Meier (K‐M) method was used to estimate overall surviving proportion at 5 and 10 years.

Results

The K‐M estimated 5 and 10 year overall survival for stage I disease was 71.3% and 57.8%, respectively; stage II disease was 57.0% and 38.9%, respectively; stage III disease was 57.8% and 41.5%, respectively. On multivariate analysis, higher cT category (P < 0.001) resulted in worse survival. For locally advanced tumors (subcohort B), there was no significant difference in survival between chemoradiation alone compared to trimodality therapy (P = 0.909 on multivariate analysis).

Conclusions

Most providers manage locally advanced SCC of the rectum similar to anal cancer, which results in equivalent overall survival and spares patients from the additional morbidity associated with surgical resection.