Radiation dose-response model for locally advanced rectal cancer after preoperative chemoradiation therapy

Trends and Variation in the Use of Radiotherapy in Non-metastatic Rectal Cancer: a 14-year Nationwide Overview from the Netherlands

AIMS

This study describes nationwide primary radiotherapy utilisation trends for non-metastasised rectal cancer in the Netherlands between 2008 and 2021. In 2014, both colorectal cancer screening and a new guideline specifying prognostic risk groups for neoadjuvant treatment were implemented.

MATERIALS AND METHODS

Patients with non-metastasised rectal cancer in 2008-2021 (n = 37 510) were selected from the Netherlands Cancer Registry and classified into prognostic risk groups. Treatment was studied over time and age. Multilevel logistic regression analyses were carried out to identify factors associated with (i) radiotherapy versus chemoradiotherapy use for intermediate rectal cancer and (ii) chemoradiotherapy without versus with surgery for locally advanced rectal cancer.

RESULTS

For early rectal cancer, the use of neoadjuvant radiotherapy decreased (15% to 5% between 2008 and 2021), whereas the use of endoscopic resections increased (8% in 2015, 17% in 2021). In intermediate-risk rectal cancer, neoadjuvant chemoradiotherapy (43% until 2011, 25% in 2015) shifted to radiotherapy (42% in 2008, 50% in 2015), the latter being most often applied in older patients. In locally advanced rectal cancer, the use of chemoradiotherapy without surgery increased (2-4% in 2008-2013, 17% in 2019-2021). Both neoadjuvant treatment in intermediate disease and omission of surgery following chemoradiotherapy in locally advanced disease varied with increasing age (odds ratio>75vs<50: 2.17, 95% confidence interval 1.54-3.06) and treatment region (Southwest and Northwest odds ratio 0.63, 95% confidence interval 0.42-0.93 and odds ratio 0.65, 95% confidence interval 0.44-0.95, respectively, compared with the North).

CONCLUSION

Treatment patterns in non-metastasised rectal cancer significantly changed over time. Effects of both the national screening programme and the new treatment guideline were apparent, as well as a paradigm shift towards organ preservation (watch-and-wait). Observed regional variations may indicate adoption differences regarding new treatment strategies.

Treatment Options for Distal Rectal Cancer in the Era of Organ Preservation

OPINION STATEMENT

The introduction of total mesorectal excision into the radical surgery of rectal cancer has significantly improved the oncological outcome with longer survival and lower local recurrence. Traditional treatment modalities of distal rectal cancer, relying on radical surgery, while effective, take their own set of risks, including surgical complications, potential damage to the anus, and surrounding structure owing to the pursuit of thorough resection. The progress of operating methods as well as the integration of systemic therapies and radiotherapy into the peri-operative period, particularly the exciting clinical complete response of patients after neoadjuvant treatment, have paved the way for organ preservation strategy. The non-inferiority oncological outcome of "watch and wait" compared with radical surgery underscores the potential of organ preservation not only to control local recurrence but also to reduce the need for treatments followed by structure destruction, hopefully improving the long-term quality of life. Radical radiotherapy provides another treatment option for patients unwilling or unable to undergo surgery. Organ preservation points out the direction of treatment for distal rectal cancer, while additional researches are needed to answer remaining questions about its optimal use.

Brachytherapy for rectal and anal cancer: Where are we and current perspectives?

Anal and rectal cancers were some of the first disease sites treated with brachytherapy due to the anatomic ease of implantation. As external beam radiotherapy grew in popularity the use of ano-rectal brachytherapy declined. However, the past few years have seen a steady resurgence in the use of brachytherapy in the ano-rectum supported by the use of large clinical series and randomized trials. The increasing acceptance by the surgical community of organ preservation as a valid treatment strategy for rectal cancer has encouraged the use of nonsurgical approaches and brachytherapy has shown itself to be a valuable tool for this. The current role of anal and rectal brachytherapy is presented with perspectives on its future use.

Rectal Cancer MRI Guided Radiotherapy: A Practical Review for the Physician

MR-guided radiotherapy is a treatment approach that combines the advantages of magnetic resonance imaging (MRI) with the precision of radiation therapy. This practical review provides an overview of the current state-of-the-art of MR-guided radiotherapy for rectal cancer, including its technical aspects, clinical outcomes, and existing limitations. Even though some studies have demonstrated the feasibility and safety of this treatment modality, challenges remain in terms of patient selection, treatment planning optimization, and long-term follow-up. Despite these issues, MR-guided radiotherapy shows promise as a potentially valuable rectal cancer treatment approach.

Radiotherapy dose escalation using pre-treatment diffusion-weighted imaging in locally advanced rectal cancer: a planning study

Objectives

Diffusion-weighted MRI (DWI) may provide biologically relevant target volumes for dose-escalated radiotherapy in locally advanced rectal cancer (LARC). This planning study assessed the dosimetric feasibility of delivering hypofractionated boost treatment to intra-tumoural regions of restricted diffusion prior to conventional long-course radiotherapy.

Methods

Ten patients previously treated with curative-intent standard long-course radiotherapy (50 Gy/25#) were re-planned. Boost target volumes (BTVs) were delineated semi-automatically using 40th centile intra-tumoural apparent diffusion coefficient value with expansions (anteroposterior 11 mm, transverse 7 mm, craniocaudal 13 mm). Biased-dosed combined plans consisted of a single-fraction volumetric modulated arc therapy flattening-filter-free (VMAT-FFF) boost (phase 1) of 5, 7, or 10 Gy before long-course VMAT (phase 2). Phase 1 plans were assessed with reference to stereotactic conformality and deliverability measures. Combined plans were evaluated with reference to standard long-course therapy dose constraints.

Results

Phase 1 BTV dose targets at 5/7/10 Gy were met in all instances. Conformality constraints were met with only 1 minor violation at 5 and 7 Gy. All phase 1 and combined phase 1 + 2 plans passed patient-specific quality assurance. Combined phase 1 + 2 plans generally met organ-at-risk dose constraints. Exceptions included high-dose spillage to bladder and large bowel, predominantly in cases where previously administered, clinically acceptable non-boosted plans also could not meet constraints.

Conclusions

Targeted upfront LARC radiotherapy dose escalation to DWI-defined is feasible with appropriate patient selection and preparation.

Advances in knowledge

This is the first study to evaluate the feasibility of DWI-targeted upfront radiotherapy boost in LARC. This work will inform an upcoming clinical feasibility study.

Tata Memorial Centre Evidence Based Management of Colorectal cancer

ABSTRACT

This review article examines the evidence-based management of colorectal cancers, focusing on topics characterized by ongoing debates and evolving evidence. To contribute to the scientific discourse, we intentionally exclude subjects with established guidelines, concentrating instead on areas where the current understanding is dynamic. Our analysis encompasses a thorough exploration of critical themes, including the evidence surrounding complete mesocolic excision and D3 lymphadenectomy in colon cancers. Additionally, we delve into the evolving landscape of perioperative chemotherapy in both colon and rectal cancers, considering its nuanced role in the context of contemporary treatment strategies. Advancements in surgical techniques are a pivotal aspect of our discussion, with an emphasis on the utilization of minimally invasive approaches such as laparoscopy and robotic surgery in both colon and rectal cancers, including advanced rectal cases. Moving beyond conventional radical procedures, we scrutinize the feasibility and implications of endoscopic resections for small tumors, explore the paradigm of organ preservation in locally advanced rectal cancers, and assess the utility of total neoadjuvant therapy in the current treatment landscape. Our final segment reviews pivotal trials that have significantly influenced the management of colorectal liver and peritoneal metastasis.

Radiotherapy in the preoperative neoadjuvant treatment of locally advanced rectal cancer

Radiotherapy and chemotherapy are effective treatments for patients with locally advanced rectal cancer (LARC) and can significantly improve the likelihood of R0 resection. Radiotherapy can be used as a local treatment to reduce the size of the tumor, improve the success rate of surgery and reduce the residual cancer cells after surgery. Early chemotherapy can also downgrade the tumor and eliminate micrometastases throughout the body, reducing the risk of recurrence and metastasis. The advent of neoadjuvant concurrent radiotherapy (nCRT) and total neoadjuvant treatment (TNT) has brought substantial clinical benefits to patients with LARC. Even so, given increasing demand for organ preservation and quality of life and the disease becoming increasingly younger in its incidence profile, there is a need to further explore new neoadjuvant treatment options to further improve tumor remission rates and provide other opportunities for patients to choose watch-and-wait (W&W) strategies that avoid surgery. Targeted drugs and immunologic agents (ICIs) have shown good efficacy in patients with advanced rectal cancer but have not been commonly used in neoadjuvant therapy for patients with LARC. In this paper, we review several aspects of neoadjuvant therapy, including radiation therapy and chemotherapy drugs, immune drugs and targeted drugs used in combination with neoadjuvant therapy, with the aim of providing direction and thoughtful perspectives for LARC clinical treatment and research trials.

Non-operative management involving chemoradiation therapy combined with high-dose-rate brachytherapy for T3 rectal cancer using a vaginal shielded cylindrical applicator: a technical report

It has been shown that a group of rectal cancer patients will achieve a pathological complete response following preoperative chemoradiotherapy, and non-operative management has recently gained attention. To escalate the tumour dose and increase the likelihood of pathological complete response, brachytherapy can play an important role in safely increasing the total dose. However, at the time this report was published, an applicator dedicated to rectal brachytherapy was unaffordable in Japan. Here, we report two T3 rectal cancer patients who were inoperable or refused surgery and treated by chemoradiotherapy following intracavitary brachytherapy involving a vaginal cylinder applicator with lead shielding.

Organ Preservation in MSS Rectal Cancer

Rectal cancer is a heterogeneous disease with complex genetic and molecular subtypes. Emerging progress of neoadjuvant therapy has led to increased pathological and clinical complete response (cCR) rates for microsatellite stable (MSS) rectal cancer, which responds poorly to immune checkpoint inhibitor alone. As a result, organ preservation of MSS rectal cancer as an alternative to radical surgery has gradually become a feasible option. For patients with cCR or near-cCR after neoadjuvant treatment, organ preservation can be implemented safely with less morbidity. Patient selection can be done either before the neoadjuvant treatment for higher probability or after with careful assessment for a favorable outcome. Those patients who achieved a good clinical response are managed with nonoperative management, organ preservation surgery, or radiation therapy alone followed by strict surveillance. The oncological outcomes of patients with careful selection and organ preservation seem to be noninferior compared with those of radical surgery, with lower postoperative morbidity. However, more studies should be done to seek better regression of tumor and maximize the possibility of organ preservation in MSS rectal cancer.

High-dose rate endorectal brachytherapy for rectal cancer: A state-of-the-art review

Rectal cancer is a common malignancy that requires multidisciplinary treatment. By utilizing the dose-response relationship in rectal cancer radiotherapy, increasing the radiotherapy dose can improve clinical complete remission rates. High-dose rate endorectal brachytherapy (HDREBT) is a novel technique that delivers high doses of radiotherapy directly to the tumor via an endorectal applicator, sparing the adjacent normal tissues from excessive radiation exposure. HDREBT includes contact X-ray brachytherapy and high-dose-rate intracavitary brachytherapy. We introduce the latest developments in applicators and imaging techniques for HDREBT in rectal cancer and summarize the current evidence on the efficacy, safety, and feasibility of HDREBT as a neoadjuvant, definitive, or palliative treatment option for all stages of rectal cancer patients. We also discuss the potential advantages and challenges of HDREBT in achieving organ preservation and improving the quality of life of rectal cancer patients. HDREBT has shown promising results in achieving high complete response rates, enabling nonoperative management, improving organ preservation rates, and providing effective palliation in rectal cancer patients. More studies are needed to optimize its dose and fractionation schemes in different clinical scenarios.

Radiological Biomarkers in MRI directed Rectal Cancer Radiotherapy Volume Delineation

Our study evaluated whether an MRI reporting system highlighting areas of contiguous and discontinuous extramural venous invasion (EMVI) can improve the accuracy of gross tumour volume (GTV) delineation. Initially, 27 consecutive patients with locally advanced rectal cancer treated between 2012 and 2014 were evaluated. We used an MRI reporting proforma that documented the position of the primary tumour, lymph nodes and EMVI. The new GTVs delineated were compared with historical radiotherapy treatment volumes to identify the frequency of GTV geographical miss. We observed that the delineation of involved nodes and areas of EMVI was more likely to represent sources of uncertainty wherein nodal GTV geographical miss was evident in 5 out of 27 patients (19%). Complete EMVI GTV geographical miss occurred in two patients (7%). We re-evaluated our radiotherapy practice in a further 27 patients after the implementation of a modified MRI reporting system. An improvement was seen; nodal miss was observed in two patients (7%) and partial EMVI miss in one patient (4%), although these areas were encompassed in the planning target volume (PTV). Our study shows that extramural venous invasion and involved nodes need to be highlighted on MRI to improve the accuracy of rectal cancer GTV delineation.

THeragnostic utilities for neoplastic DisEases of the rectum by MRI guided radiotherapy (THUNDER 2) phase II trial: interim safety analysis

BACKGROUND

The THUNDER-2 phase II single institutional trial investigates the benefits of MRI-guided radiotherapy (MRIgRT) in treating locally advanced rectal cancer (LARC). This study focuses on evaluating the impact of escalating radiation therapy dose in non-responder patients using the Early Tumour Regression Index (ERI) for predicting complete response (CR). The trial's primary endpoint is to increase the CR rate in non-responders by 10% and assess the feasibility of the delta radiomics-based MRIgRT predictive model. This interim analysis assesses the feasibility and safety of the proposed MRIgRT dose escalation strategy in terms of acute toxicity (gastrointestinal, genitourinary and haematological) and treatment adherence.

METHODS

Stage cT2-3, N0-2, or cT4 patients with anal sphincter involvement, N0-2a, M0, but without high-risk features were enrolled. MRIgRT treatment consisted of a standard dose of 55 Gy to the Gross Tumor Volume (GTV) and mesorectum, and 45 Gy to the mesorectum and drainage nodes in 25 fractions with concomitant chemotherapy. 0.35 T MRI was used for simulation imaging and daily alignment. ERI was calculated at the 10th fraction. Non-responders with an ERI above 13.1 received intensified dose escalation from the 11th fraction, resulting in a total dose of 60.1 Gy. Acute toxicity was assessed using the CTCAE v.5 scale.

RESULTS

From March 2021 to November 2022, 33 out of the total number of 63 patients to be enrolled (52.4%) were included, with one withdrawal unrelated to treatment. Sixteen patients (50%) underwent dose escalation. Treatment was well tolerated, with only one patient (3.1%) in the standard treatment group experiencing acute Grade 3 diarrhea, proctitis, and cystitis. No significant differences in toxicity were observed between the two groups (p = 0.5463).

CONCLUSIONS

MRIgRT treatment with dose escalation up to 60.1 Gy is well tolerated in LARC patients predicted as non-responders by ERI, confirming the feasibility and safety of this approach. The THUNDER-2 trial's primary and secondary endpoints will be fully analyzed when all planned patients will be enrolled.

Coverage of Lateral Lymph Nodes in Rectal Cancer Patients with Routine Radiation Therapy Practice and Associated Locoregional Recurrence Rates

PURPOSE

Involved internal iliac and obturator lateral lymph nodes (LLNs) are a known risk factor for the occurrence of ipsilateral local recurrences (LLR) in rectal cancer. This study examined coverage of LLNs with routine radiation therapy practice in the Netherlands and associated LLR rates.

METHODS AND MATERIALS

Patients with a primary tumor ≤8 cm of the anorectal junction, cT3-4 stage, and at least 1 internal iliac or obturator LLN with short axis ≥5 mm who received neoadjuvant (chemo)radiation therapy, were selected from a national, cross-sectional study of patients with rectal cancer treated in the Netherlands in 2016. Magnetic resonance images and radiation therapy treatment plans were reviewed regarding segmented LLNs as gross tumor volume (GTV), location of LLNs within clinical target volume (CTV), and received proportion of the planned radiation therapy dose.

RESULTS

A total of 223 out of 3057 patients with at least 1 LLN ≥5 mm were selected. Of those, 180 (80.7%) LLNs were inside the CTV, of which 60 (33.3%) were segmented as GTV. Overall, 202 LLNs (90.6%) received ≥95% of the planned dose. Four-year LLR rates were not significantly higher for LLNs situated outside the CTV compared with those inside (4.0% vs 12.5%, P = .092) or when receiving <95% versus ≥95% of the planned radiation therapy dose (7.1% vs 11.3%, P = .843), respectively. Two of 7 patients who received a dose escalation of 60 Gy developed an LLR (4-year LLR rate of 28.6%).

CONCLUSIONS

This evaluation of routine radiation therapy practice showed that adequate coverage of LLNs was still associated with considerable 4-year LLR rates. Techniques resulting in better local control for patients with involved LLNs need to be explored further.

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.

Preoperative Radiotherapy with a Simultaneous Integrated Boost Compared to Chemoradiotherapy for cT3-4 Rectal Cancer: Long-Term Results of a Multicenter Randomized Study

BACKGROUND

Preoperative chemoradiotherapy (CRT) is the standard treatment for T3-4 rectal cancer. Here, we compared image-guided and intensity-modulated RT (IG-IMRT) with a simultaneous integrated boost (SIB) (instead of concomitant chemotherapy) versus CRT in a multi-centric randomized trial.

METHODS

cT3-4 rectal cancer patients were randomly assigned to receive preoperative IG-IMRT 46 Gy/23 fractions plus capecitabine 825 mg/m² twice daily (CRT arm) or IG-IMRT 46 Gy/23 fractions with an SIB to the rectal tumor up to a total dose of 55.2 Gy (RTSIB arm).

RESULTS

A total of 174 patients were randomly assigned between April 2010 and May 2014. Grade 3 acute toxicities were 6% and 4% in the CRT and RTSIB arms, respectively. The mean fractional change in SUVmax at 5 weeks after completion of preoperative RT were -55.8% (±24.0%) and -52.9% (±21.6%) for patients in the CRT arm and RTSIB arm, respectively (p = 0.43). The pathologic complete response rate was 24% with CRT compared to 14% with RTSIB. There were no differences in 5-year overall survival (OS), progression-free survival (PFS) or local control (LC).

CONCLUSIONS

The preoperative RTSIB approach was not inferior to CRT in terms of metabolic response, toxicity, OS, PFS and LC, and could be considered an available option for patients unfit for fluorouracil-based CRT.

Organ and Function Preservation in Gastrointestinal Malignancies

Radiation plays an important role in organ preservation for gastrointestinal malignancies, with a watch and wait strategy enabling surgery to be avoided in patients who are not suitable or who are refusing surgery. Brachytherapy boost allows the radiation dose to be escalated, which plays a pivotal role in the successful outcome of achieving organ preservation. Here we describe the role of brachytherapy in two common gastrointestinal malignancies (oesophagus and rectum). Their indications and how the brachytherapy procedures are carried out, together with the dose and fractionation commonly used are discussed. The use of brachytherapy needs to be included in the training curriculum at all academic centres so that its use is developed by the newer generation of radiation oncologists. Its current non-use due to bias, lack of training and availability is no longer justified, given the overwhelming published evidence for the role of brachytherapy to improve organ preservation for both radical treatment and palliation in gastrointestinal malignancies.

pCR and 2-Year Disease-Free Survival: A Combination of the Two Endpoints as a New Classification for Locally Advanced Rectal Cancer Patients-An Updated Pooled Analysis of Eleven International Randomized Trials

LARC is managed by multimodal treatments whose intensity can be highly modulated. In this context, we need surrogate endpoints to help predict long-term outcomes and better personalize treatments. A previous study identified 2yDFS as a stronger predictor of OS than pCR in LARC patients undergoing neoadjuvant RT. The aim of this pooled analysis was to assess the role of pCR and 2yDFS as surrogate endpoints for OS in a larger cohort. The pooled and subgroup analyses were performed on large rectal cancer randomized trial cohorts who received long-course RT. Our analysis focused on the evaluation of OS in relation to the pCR and 2-year disease status. A total of 4600 patients were analyzed. Four groups were identified according to intermediate outcomes: 12% had both pCR and 2yDFS (the better); 67% achieved 2yDFS but not pCR (the good); 1% had pCR but not 2yDFS; and 20% had neither pCR nor 2yDFS (the bad). The pCR and 2yDFS were favorably associated with OS in the univariate analysis, and 2yDFS maintained a statistically significant association in the multivariate analysis independently of the pCR status. The combination of the pCR and 2yDFS results in a strong predictor of OS, whereas failure to achieve 2yDFS carries a poor prognosis regardless of the pCR status. This new stratification of LARC patients could help design predictive models where the combination of 2yDFS and pCR should be employed as the primary outcome.

A multi-centre randomized controlled trial investigating Consolidation Chemotherapy with and without oxaliplatin in distal rectal cancer and Watch & Wait

BACKGROUND

Neoadjuvant chemoradiation(nCRT) has been considered the preferred initial treatment strategy for distal rectal cancer. Advantages of this approach include improved local control after radical surgery but also the opportunity for organ preserving strategies (Watch and Wait-WW). Consolidation chemotherapy(cCT) regimens using fluoropyrimidine-based with or without oxalipatin following nCRT have demonstrated to increase complete response and organ preservation rates among these patients. However, the benefit of adding oxaliplatin to cCT compared to fluoropirimidine alone regimens in terms of primary tumor response remains unclear. Since oxalipatin-treatment may be associated with considerable toxicity, it becomes imperative to understand the benefit of its incorporation into standard cCT regimens in terms of primary tumor response. The aim of the present trial is to compare the outcomes of 2 different cCT regimens following nCRT (fluoropyrimidine-alone versus fluoropyrimidine + oxaliplatin) for patients with distal rectal cancer.

METHODS

In this multi-centre study, patients with magnetic resonance-defined distal rectal tumors will be randomized on a 1:1 ratio to receive long-course chemoradiation (54 Gy) followed by cCT with fluoropyrimidine alone versus fluoropyrimidine + oxaliplatin. Magnetic resonance(MR) will be analyzed centrally prior to patient inclusion and randomization. mrT2-3N0-1 tumor located no more than 1 cm above the anorectal ring determined by sagittal views on MR will be eligible for the study. Tumor response will be assessed after 12 weeks from radiotherapy(RT) completion. Patients with clinical complete response (clinical, endoscopic and radiological) may be enrolled in an organ-preservation program(WW). The primary endpoint of this trial is decision to organ-preservation surveillance (WW) at 18 weeks from RT completion. Secondary endpoints are 3-year surgery-free survival, TME-free survival, distant metastases-free survival, local regrowth-free survival and colostomy-free survival.

DISCUSSION

Long-course nCRT with cCT is associated with improved complete response rates and may be a very attractive alternative to increase the chances for organ-preservation strategies. Fluoropyrimidine-based cCT with or without oxaliplatin has never been investigated in the setting of a randomized trial to compare clinical response rates and the possibility of organ-preservation. The outcomes of this study may significantly impact clinical practice of patients with distal rectal cancer interested in organ-preservation.

TRIAL REGISTRATION

www.

CLINICALTRIALS

gov NCT05000697; registered on August 11^th, 2021.

New Opportunities for Minimizing Toxicity in Rectal Cancer Management

Advances in multimodal management of locally advanced rectal cancer (LARC), consisting of preoperative chemotherapy and/or radiotherapy followed by surgery with or without adjuvant chemotherapy, have improved local disease control and patient survival but are associated with significant risk for acute and long-term morbidity. Recently published trials, evaluating treatment dose intensification via the addition of preoperative induction or consolidation chemotherapy (total neoadjuvant therapy [TNT]), have demonstrated improved tumor response rates while maintaining acceptable toxicity. In addition, TNT has led to an increased number of patients achieving a clinical complete response and thus eligible to pursue a nonoperative, organ-preserving, watch and wait approach, thereby avoiding toxicities associated with surgery, such as bowel dysfunction and stoma-related complications. Ongoing trials using immune checkpoint inhibitors in patients with mismatch repair-deficient tumors suggest that this subgroup of patients with LARC could potentially be treated with immunotherapy alone, sparing them the toxicity associated with preoperative treatment and surgery. However, the majority of rectal cancers are mismatch repair-proficient and less responsive to immune checkpoint inhibitors and require multimodal management. The synergy noted in preclinical studies between immunotherapy and radiotherapy on immunogenic tumor cell death has led to the design of ongoing clinical trials that explore the benefit of combining radiotherapy, chemotherapy, and immunotherapy (mainly of immune checkpoint inhibitors) and aim to increase the number of patients eligible for organ preservation.

Neoadjuvant chemoradiotherapy with radiation dose escalation with contact x-ray brachytherapy boost or external beam radiotherapy boost for organ preservation in early cT2-cT3 rectal adenocarcinoma (OPERA): a phase 3, randomised controlled trial

BACKGROUND

Organ preservation after reaching clinical complete response on neoadjuvant therapy is gaining interest for rectal cancers, although the role of radiation dose escalation is still not known. We aimed to determine whether a contact x-ray brachytherapy boost, following or preceding neoadjuvant chemoradiotherapy, increases the probability of 3-year organ preservation for patients with early rectal cancers.

METHODS

OPERA was a multicentre, open-label, phase 3 randomised controlled trial done at 17 cancer centres that included operable patients, aged 18 years or older, with cT2, cT3a, or cT3b adenocarcinoma of low-mid rectum, tumours of less than 5 cm in diameter, and cN0 or cN1 smaller than 8 mm. All patients received neoadjuvant chemoradiotherapy and 45 Gy external beam radiotherapy in 25 fractions over 5 weeks with concurrent oral capecitabine (825 mg/m² twice a day). Patients were randomly assigned (1:1) to receive a boost of external beam radiotherapy at 9 Gy in five fractions (group A) or a boost with contact x-ray brachytherapy (90 Gy in three fractions; group B). Randomisation was done centrally using an independent web-based system and stratified by trial centre, tumour classification (cT2 vs cT3a or cT3b), tumour distance from rectum (<6 cm from anal verge vs ≥6 cm), and tumour diameter (<3 cm vs ≥3 cm). Treatment in group B was stratified by tumour diameter, with the contact x-ray brachytherapy boost given before neoadjuvant chemoradiotherapy in patients with tumours smaller than 3 cm. The primary outcome was organ preservation at 3 years, analysed in the modified intention-to-treat population. This study was registered with ClinicalTrials.gov, NCT02505750, and is ongoing.

FINDINGS

Between June 14, 2015, and June 26, 2020, 148 patients were assessed for eligibility and were randomly assigned to group A (n=74) or group B (n=74). Seven patients withdrew their consent (five in group A and two in group B). 141 patients were included in the primary efficacy analysis, including 69 assigned to group A (29 with tumours <3 cm in diameter and 40 with tumours ≥3 cm) and 72 assigned to group B (32 with tumours <3 cm and 40 with tumours ≥3 cm). After a median follow-up of 38·2 months (IQR 34·2-42·5), the 3-year organ preservation rate was 59% (95% CI 48-72) in group A versus 81% (72-91) in group B (hazard ratio [HR] 0·36, 95% CI 0·19-0·70; p=0·0026). For patients with tumours less than 3 cm in diameter, 3-year organ preservation rates were 63% (95% CI 47-84) in group A versus 97% (91-100) in group B (HR 0·07, 95% CI 0·01-0·57; p=0·012). For patients with tumours of 3 cm or larger, 3-year organ preservation rates were 55% (95% CI 41-74) in group A versus 68% (54-85) in group B (HR 0·54, 95% CI 0·26-1·10; p=0·11). 21 (30%) patients in group A and 30 (42%) in group B had an early grade 2-3 adverse event (p=1·0). The most common early grade 2-3 adverse events were proctitis (four [6%] in group A, nine [13%] in group B) and radiation dermatitis (seven [10%] in group A, two [3%] in group B). The main late side-effect was grade 1-2 rectal bleeding due to telangiectasia, which was more frequent in group B (37 [63%] of 59) than in group A (five [12%] of 43; p<0·0001) and subsided after 3 years.

INTERPRETATION

Neoadjuvant chemoradiotherapy with a contact x-ray brachytherapy boost significantly improved the 3-year organ preservation rate, particularly for patients with tumours smaller than 3 cm who were treated with contact x-ray brachytherapy first, compared with neoadjuvant chemoradiotherapy with a boost via external beam radiotherapy. This approach could be discussed and offered to operable patients with early cT2-cT3 disease who are keen to avoid surgery and seek organ preservation.

FUNDING

The French Programme Hospitalier de Recherche Cinique.

Implications of recent neoadjuvant clinical trials on the future practice of radiotherapy in locally advanced rectal cancer

Over the last two decades, the standard treatment for locally advanced rectal cancer (LARC) has been neoadjuvant chemoradiotherapy plus total mesorectal excision followed by adjuvant chemotherapy. Total neoadjuvant treatment (TNT) and immunotherapy are two major issues in the treatment of LARC. In the two latest phase III randomized controlled trials (RAPIDO and PRODIGE23), the TNT approach achieved higher rates of pathologic complete response and distant metastasis-free survival than conventional chemoradiotherapy. Phase I/II clinical trials have reported promising response rates to neoadjuvant (chemo)-radiotherapy combined with immunotherapy. Accordingly, the treatment paradigm for LARC is shifting toward methods that increase the oncologic outcomes and organ preservation rate. However, despite the progress of these combined modality treatment strategies for LARC, the radiotherapy details in clinical trials have not changed significantly. To guide future radiotherapy for LARC with clinical and radiobiological evidence, this study reviewed recent neoadjuvant clinical trials evaluating TNT and immunotherapy from a radiation oncologist’s perspective.

Online Adaptive MRI-Guided Radiotherapy for Primary Tumor and Lymph Node Boosting in Rectal Cancer

The purpose of this study was to characterize the motion and define the required treatment margins of the pathological mesorectal lymph nodes (GTV_ln) for two online adaptive MRI-guided strategies for sequential boosting. Secondly, we determine the margins required for the primary gross tumor volume (GTV_prim). Twenty-eight patients treated on a 1.5T MR-Linac were included in the study. On T2-weighted images for adaptation (MRI_adapt) before and verification after irradiation (MRI_post) of five treatment fractions per patient, the GTV_ln and GTV_prim were delineated. With online adaptive MRI-guided radiotherapy, daily plan adaptation can be performed through the use of two different strategies. In an adapt-to-shape (ATS) workflow the interfraction motion is effectively corrected by redelineation and the only relevant motion is intrafraction motion, while in an adapt-to-position (ATP) workflow the margin (for GTV_ln) is dominated by interfraction motion. The margin required for GTV_prim will be identical to the ATS workflow, assuming each fraction would be perfectly matched on GTV_prim. The intrafraction motion was calculated between MRI_adapt and MRI_post for the GTV_ln and GTV_prim separately. The interfraction motion of the GTV_ln was calculated with respect to the position of GTV_prim, assuming each fraction would be perfectly matched on GTV_prim. PTV margins were calculated for each strategy using the Van Herk recipe. For GTV_ln we randomly sampled the original dataset 20 times, with each subset containing a single randomly selected lymph node for each patient. The resulting margins for ATS ranged between 3 and 4 mm (LR), 3 and 5 mm (CC) and 5 and 6 mm (AP) based on the 20 randomly sampled datasets for GTV_ln. For ATP, the margins for GTV_ln were 10-12 mm in LR and AP and 16-19 mm in CC. The margins for ATS for GTV_prim were 1.7 mm (LR), 4.7 mm (CC) and 3.2 mm anterior and 5.6 mm posterior. Daily delineation using ATS of both target volumes results in the smallest margins and is therefore recommended for safe dose escalation to the primary tumor and lymph nodes.

Understanding the Benefit of Magnetic Resonance-guided Adaptive Radiotherapy in Rectal Cancer Patients: a Single-centre Study

AIMS

Neoadjuvant chemoradiotherapy followed by surgery is the mainstay of treatment for patients with rectal cancer. Standard clinical target volume (CTV) to planning target volume (PTV) margins of 10 mm are used to accommodate inter- and intrafraction motion of target. Treating on magnetic resonance-integrated linear accelerators (MR-linacs) allows for online manual recontouring and adaptation (MRgART) enabling the reduction of PTV margins. The aim of this study was to investigate motion of the primary CTV (CTVA; gross tumour volume and macroscopic nodes with 10 mm expansion to cover microscopic disease) in order to develop a simultaneous integrated boost protocol for use on MR-linacs.

MATERIALS AND METHODS

Patients suitable for neoadjuvant chemoradiotherapy were recruited for treatment on MR-linac using a two-phase technique; only the five phase 1 fractions on MR-linac were used for analysis. Intrafraction motion of CTVA was measured between pre-treatment and post-treatment MRI scans. In MRgART, isotropically expanded pre-treatment PTV margins from 1 to 10 mm were rigidly propagated to post-treatment MRI to determine overlap with 95% of CTVA. The PTV margin was considered acceptable if overlap was >95% in 90% of fractions. To understand the benefit of MRgART, the same methodology was repeated using a reference computed tomography planning scan for pre-treatment imaging.

RESULTS

In total, nine patients were recruited between January 2018 and December 2020 with T3a-T4, N0-N2, M0 disease. Forty-five fractions were analysed in total. The median motion across all planes was 0 mm, demonstrating minimal intrafraction motion. A PTV margin of 3 and 5mm was found to be acceptable in 96 and 98% of fractions, respectively. When comparing to the computed tomography reference scan, the analysis found that PTV margins to 5 and 10 mm only acceptably covered 51 and 76% of fractions, respectively.

CONCLUSION

PTV margins can be reduced to 3-5 mm in MRgART for rectal cancer treatment on MR-linac within an simultaneous integrated boost protocol.

DWI-MR and PET-CT Functional Imaging for Boost Tumor Volume Delineation in Neoadjuvant Rectal Cancer Treatment

BACKGROUND/AIM

T2 weighted magnetic resonance (MR) imaging is the gold standard for locally advanced rectal cancer (LARC) staging. The potential benefit of functional imaging, as diffusion-weighted MR (DWI) and positron emission tomography-computed tomography (PET-CT), could be considered for treatment intensification strategies. Dose intensification resulted in better pathological complete response (pCR) rates. This study evaluated the inter-observer agreement between two radiation oncologists, and the difference in gross tumor volume (GTV) delineation in simulation-CT, T2-MR, DWI-MR, and PET-CT in patients with LARC.

PATIENTS AND METHODS

Two radiation oncologists prospectively delineated GTVs of 24 patients on simul-CT (CT_GTV), T2-weighted MR (T2_GTV), echo planar b1000 DWI (DWI_GTV) and PET-CT (PET_GTV). Observers' agreement was assessed using Dice index. Kruskal-Wallis test assessed differences between methods.

RESULTS

Mean CT_GTV, T2_GTV, DWI_GTV, and PET_GTV were 41.3±26.9 cc, 25.9±15.2 cc, 21±14.8 cc, and 37.7±27.7 cc for the first observer, and 42.2±27.9 cc, 27.6±16.9 cc, 19.9±14.9cc, and 34.8±24.3 cc for the second observer, respectively. Mean Dice index was 0.85 for CT_GTV, 0.84 for T2_GTV, 0.82 for DWI_GTV, and 0.89 for PET_GTV, representative of almost perfect agreement. Kruskal-Wallis test showed a statistically significant difference between methods (p=0.009). Dunn test showed there were differences between DWI_GTV vs. PET_GTV (p=0.040) and DWI_GTV vs. CT_GTV (p=0.008).

CONCLUSION

DWI resulted in smaller volume delineation compared to CT, T2-MR, and PET-CT functional images. Almost perfect agreements were reported for each imaging modality between two observers. DWI-MR seems to remain the optimal strategy for boost volume delineation for dose escalation in patients with LARC.

Radiotherapy dose escalation using endorectal brachytherapy in elderly and frail patients with rectal cancer unsuitable for surgery: Lessons from studies in fit patients and future perspectives

Epidemiological data indicate that more than 50 % of patients with newly-diagnosed rectal cancer are older than 70 years, with rising numbers expected over the next decades. Treatment decision-making is challenging in elderly and frail patients with rectal cancer, whereas standardized treatment guidelines for this patient cohort are lacking. Elderly and frail rectal cancer patients are often considered by surgeons as unfit to undergo radical surgery as the risk of surgical complications and postoperative mortality rises with increasing age and comorbidity. Furthermore, these patients often receive no treatment at all, resulting in local and/or systemic disease progression with associated symptoms and impaired quality of life (QoL). Recent data from randomized trials in young fit patients with early stage rectal cancer indicate that RT dose escalation can be safely delivered using external beam (chemo)radiotherapy (EBRT) followed by endoluminal radiotherapeutic modalities, such as contact X-ray brachytherapy (CXB) or high-dose rate endorectal brachytherapy (HDR-BT). However, prospective studies testing this therapeutic concept in elderly and frail patients remain limited. Here, we review the current evidence in the epidemiology and the management of elderly and frail patients with rectal cancer. We summarize the potential of RT dose escalation to achieve long-term local control of the primary tumour, prevent disease-related morbidity, improve QoL and even organ preservation. Future perspectives and open questions will be discussed as well.

Cytokeratin 7 Expression and Mismatch Repair Status for Survival Prediction in Patients With Low Rectal Cancer After Neoadjuvant Therapy

BACKGROUND

More than half of the patients with locally advanced low rectal cancer exhibit no or minor response to nCRT. It is important to investigate the predictive and prognostic values of potential biomarkers in patients with locally advanced low rectal cancer receiving nCRT.

MATERIALS AND METHODS

This retrospective study included 162 patients with locally advanced low rectal cancer who underwent nCRT, followed by total mesorectal excision (TME) between 2016 and 2019. Cytokeratin 7 (CK7) expression and mismatch repair (MMR) status were determined by immunohistochemistry (IHC). Categorical variables were compared using the chi-square test. Overall survival (OS) and disease-free survival (DFS) curves were estimated using the Kaplan-Meier and Cox methods.

RESULTS

There were predominance significant differences in distance from anus margin (P < .0001) and circumferential extent of the tumor (P < .0001).CK7 positive expression was detected in 21 of the 162 patients (13%). The univariate and multivariate analysis revealed that patients whose tumors had CK7 positive expression had significantly shorter OS (HR = 3.878, P = .038; HR = 1.677, P = .035) and DFS (HR = 3.055, P = .027;HR = 3.569, P = .038) than those with CK7 negative expression. While patients with CK7 positive expression had a higher proportion of worse TRG compared with CK7 negative patients (P = .001). Patients with deficient mismatch repair (dMMR) just occupied a small proportion (8.6%), but there was still a close connection between the MMR status and recurrence after TME (P = .045). MMR status was an independent risk factor affecting the OS (HR = .307, P < .0001; HR = .123, P < .0001) and DFS (HR = .288, P < .0001; HR = .286, P < .0001) by univariate and multivariate analysis. But no significant difference in the proportion of TRG was observed between patients with dMMR and pMMR (P = .920).

CONCLUSIONS

The result confirms negative prognostic role of CK7-positive and dMMR statuses, which have potential predictive value for neoadjuvant chemoradiotherapy response. This provides opportunity to modify individualized treatment strategies for patients with different CK7 expression levels and dMMR statuses.

Impact of endorectal filling on interobserver variability of MRI based rectal primary tumor delineation

Background

Online adaptive MR-guided radiotherapy allows for the reduction of safety margins in dose escalated treatment of rectal tumors. With the use of smaller margins, precise tumor delineation becomes more critical. In the present study we investigated the impact of rectal ultrasound gel filling on interobserver variability in delineation of primary rectal tumor volumes.

Methods

Six patients with locally advanced rectal cancer were scanned on a 1.5 T MRI-Linac without (MRI_e) and with application of 100 cc of ultrasound gel transanally (MRI_f). Eight international radiation oncologists expert in the treatment of gastrointestinal cancers delineated the gross tumor volume (GTV) on both MRI scans. MRI_f scans were provided to the participating centers after MRI_e scans had been returned. Interobserver variability was analyzed by either comparing the observers' delineations with a reference delineation (approach 1) and by building all possible pairs between observers (approach 2). Dice Similarity Index (DICE) and 95 % Hausdorff-Distance (95 %HD) were calculated.

Results

Rectal ultrasound gel filling was well tolerated by all patients. Overall, interobserver agreement was superior in MRI_f scans based on median DICE (0.81 vs 0.74, p < 0.005 for approach 1 and 0.76 vs 0.64, p < 0.0001 for approach 2) and 95 %HD (6.9 mm vs 4.2 mm for approach 1, p = 0.04 and 8.9 mm vs 6.1 mm, p = 0.04 for approach 2). Delineated median tumor volumes and inter-quartile ranges were 26.99 cc [18.01-50.34 cc] in MRI_e and 44.20 [19.72-61.59 cc] in MRI_f scans respectively, p = 0.012.

Conclusions

Although limited by the small number of patients, in this study the application of rectal ultrasound gel resulted in higher interobserver agreement in rectal GTV delineation. The endorectal gel filling might be a useful tool for future dose escalation strategies.

The safety of an MRI simulation-guided boost after short-course preoperative radiotherapy for unresectable rectal cancer (SUNRISE): interim analysis of a randomized phase II trial

PURPOSE

The safety of an MRI simulation-guided boost after short-course preoperative radiotherapy (SCPRT) for unresectable rectal cancer is assessed with a planned interim analysis.

METHODS AND MATERIALS

Patients diagnosed with clinical stage T3-4 or regional lymph node-positive disease with positive mesorectal fascia or T4b disease evaluated by pelvic MRI were randomly assigned to the SCPRT-boost group (25 Gy in 5 fractions plus 4 Gy delivered to the gross tumor volume, followed by four cycles of chemotherapy) or preoperative chemoradiotherapy group (50 Gy in 25 fractions with concurrent chemotherapy). Then, patients received total mesorectal excision surgery after preoperative treatment. The primary endpoint was the R0 resection rate. The interim analysis was performed when 42 patients completed their assigned treatments.

RESULTS

From October 2018 to November 2019, a total of 43 patients were enrolled, and 42 patients were included in the interim analysis. During preoperative therapy, grade 3 or above toxicities were observed in 10/21 (47.6%) patients in the experimental group, and 4/21 (19.0%) patients in the control group. A total of 17 (81.0%) and 13 (61.9%) patients in the experimental group and control group underwent surgery, respectively. Overall, 65.1% of the patients achieved R0 resection in the intention-to-treat analysis. Surgery-related adverse complications were observed in 2 patients (11.8%) in the experimental group and 1 patient (7.7%) in the control group.

CONCLUSION

Our results show that the toxicity of an MRI simulation-guided boost after SCPRT for unresectable rectal cancer is acceptable. Thus, this clinical trial will be continued as planned.

Preoperative short-course radiation therapy with PROtons compared to photons in high-risk RECTal cancer (PRORECT): Initial dosimetric experience

Background and purpose

Neoadjuvant short-course radiotherapy (SCRT) followed by full-dose systemic chemotherapy is an established treatment modality in locally advanced rectal cancer (LARC). Until recently, SCRT has been exclusively delivered with photons. Proton beam therapy (PBT) may minimize acute toxicity, which in turn likely impacts favorably on the tolerability to subsequent chemotherapy. The aim of this study is a dosimetric comparison between SCRT with photons and protons in the randomized phase II trial PRORECT (NCT04525989).

Materials and methods

From June 2021 to June 2022, twenty consecutive patients with LARC have been treated according to study protocol. For each patient, both a VMAT and a PBT treatment plans have been generated and compared pairwise.

Results

Dose-volume histogram (DVH) analysis revealed that SCRT with protons significantly reduced radiation dose to pelvic organs at risk including bladder, bones, and bowel in comparison to SCRT with photons. Photon and proton treatment plans had equivalent conformity and homogeneity indexes.

Conclusion

Preoperative SCRT with protons offers a significant reduction of radiation dose to normal tissues compared with current photon-based radiotherapy technique. Demonstrated dosimetric advantages may translate into measurable clinical benefits in patients with LARC. Clinical implications of the dosimetric superiority of SCRT with protons will be presented in the coming reports from the PRORECT trial.

Features on Endoscopy and MRI after Treatment with Contact X-ray Brachytherapy for Rectal Cancer: Explorative Results

After neoadjuvant (chemo)radiotherapy for rectal cancer, contact X-ray brachytherapy (CXB) can be applied aiming at organ preservation. This explorative study describes the early features on endoscopy and MRI after CXB. Patients treated with CXB following (chemo)radiotherapy and a follow-up of ≥12 months were selected. Endoscopy and MRI were performed every 3 months. Expert readers scored all the images according to structured reporting templates. Thirty-six patients were included, 15 of whom obtained a cCR. On endoscopy, the most frequently observed feature early in follow-up was an ulcer, regardless of whether patients developed a cCR. A flat, white scar and tumor mass were common at 6 months. Focal tumor signal on T2W-MRI and mass-like high signal on DWI were generally absent in patients with a cCR. An ulceration on T2W-MRI and "reactive" mucosal signal on DWI were observed early in follow-up regardless of the final tumor response. The distinction between a cCR and a residual tumor generally can be made at 6 months. Features associated with a residual tumor are tumor mass on endoscopy, focal tumor signal on T2W-MRI, and mass-like high signal on DWI. Early recognition of these features is necessary to identify patients who will not develop a cCR as early as possible.

BioXmark® liquid fiducials to enable radiotherapy tumor boosting in rectal cancer, a feasibility trial

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BioXmark® is a novel liquid fiducial marker for image-guided radiotherapy.

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The marker remained stable during chemoradiotherapy in 96% of rectal cancer cases.

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The fiducial allows for image tracking on CT-based imaging modalities.

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Marker visibility was good using CT-based imaging without any relevant artifacts.

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The marker is easy to inject without marker related adverse events.

Background and purpose

Dose-escalation in rectal cancer (RCa) may result in an increased complete response rate and thereby enable omission of surgery and organ preservation. In order to implement dose-escalation, it is crucial to develop a technique that allows for accurate image-guided radiotherapy. The aim of the current study was to determine the performance of a novel liquid fiducial marker (BioXmark®) in RCa patients during the radiotherapy course by assessing its positional stability on daily cone-beam CT (CBCT), technical feasibility, visibility on different imaging modalities and safety.

Materials and methods

Prospective, non-randomized, single-arm feasibility trial with inclusion of twenty patients referred for neoadjuvant chemoradiotherapy for locally advanced RCa. Primary study endpoint was positional stability on CBCT. Furthermore, technical aspects, safety and clinical performance of the marker, such as visibility on different imaging modalities, were evaluated.

Results

Seventy-four markers from twenty patients were available for analysis. The marker was stable in 96% of the cases. One marker showed clinically relevant migration, one marker was lost before start of treatment and one marker was lost during treatment. Marker visibility was good on computed tomography (CT) and CBCT, and moderate on electronic portal imaging (EPI). Marker visibility on magnetic resonance imaging (MRI) was poor during response evaluation.

Conclusion

The novel liquid fiducial marker demonstrated positional stability. We provide evidence of the feasibility of the novel fiducial marker for image-guided radiotherapy on daily cone beam CT for RCa patients.

Impact of preoperative chemoradiation with higher dose intensity modulated radiotherapy on pathological complete response for locally advanced rectal cancer: a systematic review

INTRODUCTION

Neoadjuvant chemoradiation (CRT) followed by total mesorectal excision is the current standard-of-care for locally advanced UICC II-III stage rectal cancer (LARC). A pathological complete response (pCR) correlates with survival. Improvements of pCR, including dose escalation, should be explored. The aim of this explorative analysis is to assess the impact on pCR of intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB).

AREAS COVERED

A literature search via PICO (Population, Intervention, Comparison, Outcome) in MEDLINE/PubMed and EMBASE and a systematic review according to PRISMA (Preferred Reporting Items for Systematic Reviews and Metanalysis) methodology were performed. Studies that reported pCR rate in patients with LARC in clinical stage T2N+M0 or cT3/4 N0/+M0 treated with preoperative CRT with SIB-IMRT/VMAT (Volumetric Modulated Arc Therapy) were included. Sixty-two studies were identified, but only eight clinical trials with a total of 311 patients were included . Median follow-up was 16-61 months. pCR reached the value of 38%. Good survival outcomes were observed with a mild toxicity profile.

EXPERT OPINION

Radiotherapy dose intensification in LARC showed a slight increase of pCR compared to historical studies. Prospective evaluations are necessary to define which patients would benefit most.

Image-Guided Brachytherapy for Rectal Cancer: Reviewing the Past Two Decades of Clinical Investigation

(1) Background: The introduction of total mesorectal excision (TME) for rectal cancer has led to improvement in local recurrence (LR) outcomes. Furthermore, the addition of preoperative external beam radiotherapy to TME reduces LR to less than 6%. As a trade-off to these gradual improvements in local therapies, the oncology community’s work is now focusing on mitigating treatment-related toxicities. In other words, if a small proportion of 4–6% of rectal cancer patients benefit from additional local therapy beyond TME, the burden of acute and long-term side effects must be considered with care. (2) Methods: With the introduction of better-quality imaging for tumor visualization and treatment planning, a new conformed radiation treatment was introduced with high-dose-rate endorectal brachytherapy. The treatment concept was tested in phase I and II studies: first in the pre-operative setting, and then as a boost after external beam radiation therapy, as a dose-escalation study, to achieve higher local tumor control. (3) Results: HDREBT is safe and effective in achieving a high tumor regression rate and was well tolerated in a phase II multicenter and two matched-pair studies. (4) Conclusions: HDREBT is a conformed radiation therapy that is safe and effective, and is presently explored in a phase III dose-escalation study in the NOM of patients with operable rectal cancer.

Zebrafish Avatars of rectal cancer patients validate the radiosensitive effect of metformin

Neoadjuvant chemoradiation (nCRT) followed by surgery represents the standard of care in patients with locally advanced rectal cancer. Increasing radiotherapy (RT) doses and chemotherapy cycles with 5FU have been associated with increased rates of complete response, however these strategies imply significant toxicity. In the last years, epidemiologic findings have demonstrated that metformin is associated with significantly higher rates of pathological complete response to nCRT. Also, pre-clinical studies using cell lines provide evidence for the radiosensitive effect of metformin. However, no studies have been performed using rectal cancer patient samples to test this radiosensitive effect of metformin and compared it to the standard 5FU. Here, we designed an experimental study to compare both radiosensitizers in the zebrafish xenograft model (zAvatar), using rectal cancer surgical specimens and diagnostic biopsies. Patient zAvatars confirmed that metformin has indeed a powerful in vivo radiosensitizer effect, similar to 5FU. Our work confirms that metformin constitutes a promising less toxic alternative to the standard 5FU, which could be game changing in elderly/frail patients to optimize tumor regression.

The in-silico feasibility of dose escalated, hypofractionated radiotherapy for rectal cancer

Background and purpose

Short course radiotherapy (SCRT) has a low biological prescription dose. Rectal cancer has a dose response relationship and moderate α/β ratio (∼5). We hypothesise hypofractionated dose escalation has radiobiological advantages. We assessed in-silico dose escalation to the primary tumour using a simultaneous integrated boost (SIB) technique.

Materials and methods

Patients who had received 25 Gy/5# were enrolled. GTV was macroscopic tumour including lumen. CTVA was GTV + 10 mm. CTVB included elective nodes. PTV_Low was created from CTVF (CTVA + CTVB) + 7 mm. PTV_High (SIB) was GTV + 5 mm margin. OAR were as per RTOG guidelines. Each patient had 4 plans created at increasing dose levels (27.5 Gy, 30 Gy, 32.5 Gy and 35 Gy) to PTV_High. PTV_Low was 25 Gy/5#.5 test plans were created for each patient in Eclipse™ v15.5 and consisted of 2 VMAT full arcs (6 MV), Varian Truebeam (2.7). Planning objectives were set in the Photon optimiser (PO) and recalculated using Acuros v15.5. A priori feasibility was defined as 90% of plans achieving the planning objectives at 32.5 Gy dose level (EqD2 53.4 Gy).

Results

20 SCRT patients median age 70, F (n = 5), M (n = 15). Rectum level; low (n = 12), mid (n = 3) and upper (n = 5). 100 plans were analysed. Mean volume of PTV_High was 130 cm³ (SD 81.5) and PTV_Low 769.6 cm³ (SD 241.1). 100% plans complied with mandatory planning dose metrics for each structure at the 25 Gy/5# plan and each dose level.

Conclusion

Hypofractionated dose escalation to the primary tumour up to 35 Gy/5# is technically feasible in rectal cancer radiotherapy.

Clinical applications of high dose rate endorectal brachytherapy for patients with rectal cancer

With the establishment of total mesorectal excision for the treatment of rectal cancer, local recurrence rates have significantly decreased. The addition of preoperative external beam irradiation further reduces this risk to less than 6%. As the local treatment becomes successful and more widely used, the associated treatment-related toxicity is becoming clinically important. If 4 to 6% of the patients are to benefit from neo-adjuvant therapy before total mesorectal excision, the acute and the long-term toxicity burden must be reasonable. With the introduction of better-quality imaging for tumour visualization and treatment planning, a new-targeted radiation treatment was introduced with high dose rate endorectal brachytherapy. The treatment concept was tested in phase I and II studies first in the preoperative setting, then as a boost after external beam radiation therapy as a dose escalation study to achieve higher tumour local control in a radical treatment setting with no surgery. High dose rate endorectal brachytherapy is safe and effective in achieving high tumour regression rate and was well tolerated. It is presently explored in a phase III dose escalation study in the non-operative management of patients with operable rectal cancer.

[Organ preservation for rectal cancer: What are the arguments in favor of radiotherapy?]

Standard care for rectal cancers relies on both tumor (location relative to the sphincter, T and N stage, sphincter involvement) and patients characteristics. Radical surgery (total mesorectal excision) following short-course radiotherapy (RT) or standard chemo-radiotherapy, associated with induction or consolidation chemotherapy (total neoadjuvant treatment), remains the cornerstone of locally advanced rectal cancer (T3cd, T4 and/or N+) treatment. Nevertheless, for early stages, this radical resection could be avoided in favor of conservative approaches combining RT (external, contact, brachytherapy) with or without chemotherapy (concurrent, induction or consolidative), or even be limited, for good responders, to a local excision with view of organ-preservation strategies. This conservative approach could also be offered selectively to patients with complete clinical response after the induction sequence, irrespective of initial tumor characteristics. The Watch and Wait strategy relies on clinical, endoscopic and radiological evaluations, as well as sustained surveillance. Ongoing studies aim to improve response rates, either with chemotherapy intensification, or RT boost dose escalation with brachytherapy or contact-therapy.

MORPHEUS Phase II–III Study: A Pre-Planned Interim Safety Analysis and Preliminary Results

Background: We explored image-guided adaptive endorectal brachytherapy patients electing non-operative management for rectal cancer. We present the first pre-planned interim analysis. Methods: In this open-label phase II–III randomized study, patients with operable cT2-3ab N0 M0 rectal cancer received 45 Gy in 25 fractions of pelvic external beam radiotherapy (EBRT) with 5-FU/Capecitabine. They were randomized 1:1 to receive either an EBRT boost of 9 Gy in 5 fractions (Arm A) or three weekly adaptive brachytherapy (IGAEBT) boosts totaling 30 Gy (Arm B). Patient characteristics and toxicity are presented using descriptive analyses; TME-free survival between arms with the intention to treat the population is explored using the Kaplan–Meier method. Results: A total of 40 patients were in this analysis. Baseline characteristics were balanced; acute toxicities were similar. Complete clinical response (cCR) was 50% (n = 10/20) in Arm A and 90% in Arm B (n = 18/20). Median follow-up was 1.3 years; 2-year TME-free survival was 38.6% (95% CI: 16.5–60.6%) in the EBRT arm and 76.6% (95% CI: 56.1–97.1%) in the IGAEBT arm. Conclusions: Radiation intensification with IGAEBT is feasible. This interim analysis suggests an improvement in TME-free survival when comparing IGAEBT with EBRT, pending confirmation upon completion of this trial.

Quantitative analysis of diffusion weighted imaging in rectal cancer during radiotherapy using a magnetic resonance imaging integrated linear accelerator

Background and purpose

Magnetic resonance imaging integrated linear accelerator (MR-Linac) platforms enable acquisition of diffusion weighted imaging (DWI) during treatment providing potential information about treatment response. Obtaining DWI on these platforms is technically different from diagnostic magnetic resonance imaging (MRI) scanners. The aim of this project was to determine feasibility of obtaining DWI and calculating apparent diffusion coefficient (ADC) parameters longitudinally in rectal cancer patients on the MR-Linac.

Materials and methods

Nine patients undergoing treatment on MR-Linac had DWI acquired using b-values 0, 30, 150, 500 s/mm2. Gross tumour volume (GTV) and normal tissue was delineated on DWI throughout treatment and median ADC was calculated using an in-house tool (pyOsirix ®).

Results

Seven out of nine patients were included in the analysis; all demonstrated downstaging at follow-up. A total of 63 out of 70 DWI were analysed (7 excluded due to poor image quality). An increasing trend of ADC median for GTV (1.15 × 10-3 mm2/s interquartile range (IQ): 1.05-1.17 vs 1.59 × 10-3 mm2/s IQ: 1.37 - 1.64; p = 0.0156), correlating to treatment response. In comparison ADC median for normal tissue remained the same between first and last fraction (1.61 × 10-3 mm2/s IQ: 1.56-1.71 vs 1.67 × 10-3 mm2/s IQ: 1.37-2.00; p = 0.9375).

Conclusions

DWI assessment in rectal cancer patients on MR-Linac is feasible. Initial results provide foundations for further studies to determine DWI use for treatment adaptation in rectal cancer.

High dose chemoradiotherapy increases chance of organ preservation with satisfactory functional outcome for rectal cancer

BACKGROUND

High dose chemoradiotherapy offers a curative chance for patients with rectal cancer that are unfit or unwilling to undergo surgical resection, yet its long-term survival and functional outcomes have been rarely investigated.

METHODS

Patients with non-metastatic rectal adenocarcinoma who received pelvic radiation for curative intent from April 2006 to July 2017 were retrospectively investigated. Survival rates were analyzed using the Kaplan-Meier method. Quality of life and functional outcomes were evaluated using the EORTC quality of life questionnaire.

RESULTS

A total of 57 patients were included, with a median age of 59.0 (range, 29-84) years. The numbers of patients who were diagnosed as stage I, II and III were 5 (8.8%), 16 (28.1%) and 36 (63.2%), respectively. 53 (93.0%) patients had tumor located within 5 cm from the anal verge. All patients received fluorouracil-based concurrent chemoradiotherapy with a median radiation dose of 80 (range, 60-86) Gy. All kinds of grade 3-4 adverse events occurred in 18 (31.6%) patients. 42 (73.7%) patients achieved a clinical complete response after chemoradiotherapy. After a median follow-up of 43.5 (range 14.9-163.2) months, 12 (21.1%) patients had local progression and 11 (19.3%) developed distant metastasis. The 3-year local recurrence-free survival and distant metastasis-free survival were 77.3% (95% CI, 65.7-88.8%) and 79.2% (95% CI, 68.2-90.2%), while the 3-year progression-free survival, cancer-specific survival, overall survival were 61.9% (95% CI, 48.8-75.0%), 93.1% (95% CI, 85.8-100.0%) and 91.4% (95% CI, 83.6-99.2%), respectively. For patients who had tumor located within 3 cm from the anal verge, the sphincter preservation rate was 85.3% at last follow-up. Long-term adverse events mainly were anal blood loss. 21 patients completed the quality-of-life questionnaire and had a score of the global health status of 78.57 ± 17.59. Of them, 95.2% reported no urinary incontinence and 85.7% reported no fecal incontinence.

CONCLUSIONS

High dose chemoradiation demonstrated promising survival outcomes with acceptable short-term and long-term side effects, and satisfying long-term functional outcomes and quality of life. It could be considered as a non-invasive alternative for rectal cancer patients who refuse surgery.

The Multimodal Management of Locally Advanced Rectal Cancer: Making Sense of the New Data

In the past 40 years, the treatment of locally advanced rectal cancer has evolved with the addition of radiotherapy or chemoradiotherapy and providing (neo)adjuvant systemic chemotherapy to major surgery. However, recent trends have focused on improving our ability to risk-stratify patients and tailoring treatment to achieve the best oncologic outcome while limiting the impact on long-term quality of life. Therefore, there has been increasing interest in pursuing a watch-and-wait approach to achieve organ preservation. Several retro- and prospective studies suggest safety of the watch-and-wait approach, though it is still considered controversial due to limited clinical evidence, concerns about tumor regrowth, and subsequent distant progression. To further reduce treatment, MRI risk stratification, together with patient characteristics and patient preferences, can guide personalized treatment and reserve radiation and chemotherapy for a select patient population. Ultimately, improved options for reassessment during neoadjuvant treatment may allow for more adaptive therapy options based on treatment response. This article provides an overview of some major developments in the multimodal treatment of locally advanced rectal cancer. It reviews some relevant, controversial issues of the watch-and-wait approach and opportunities to personally tailor and reduce treatment. It also reviews the overall neoadjuvant treatment, including total neoadjuvant therapy trials, and how to best optimize for a potential complete response. Finally, it provides an algorithm as an example of how such a personalized, tailored, adaptive, and reduced treatment could look like in the future.

A Multidisciplinary Approach for the Personalised Non-Operative Management of Elderly and Frail Rectal Cancer Patients Unable to Undergo TME Surgery

Despite it being the optimal curative approach, elderly and frail rectal cancer patients may not be able to undergo a total mesorectal excision. Frequently, no treatment is offered at all and the natural course of the disease is allowed to unfold. These patients are at risk for developing debilitating symptoms that impair quality of life and require palliative treatment. Recent advancements in non-operative treatment modalities have enhanced the toolbox of alternative treatment strategies in patients unable to undergo surgery. Therefore, a proposed strategy is to aim for the maximal non-operative treatment, in an effort to avoid the onset of debilitating symptoms, improve quality of life, and prolong survival. The complexity of treating elderly and frail patients requires a patient-centred approach to personalise treatment. The main challenge is to optimise the balance between local control of disease, patient preferences, and the burden of treatment. A comprehensive geriatric assessment is a crucial element within the multidisciplinary dialogue. Since limited knowledge is available on the optimal non-operative treatment strategy, these patients should be treated by dedicated multidisciplinary rectal cancer experts with special interest in the elderly and frail. The aim of this narrative review was to discuss a multidisciplinary patient-centred treatment approach and provide a practical suggestion of a successfully implemented clinical care pathway.

The Long and the Short of it: the Role of Short-course Radiotherapy in the Neoadjuvant Management of Rectal Cancer

Total mesorectal excision is the cornerstone of treatment for rectal cancer. Multiple randomised trials have shown a reduction in local recurrence rates with the addition of preoperative radiotherapy, either as a 1-week hypofractionated short-course (SCRT) or a conventionally fractionated long-course (LCRT) schedule with concurrent chemotherapy. There is also increasing interest in the addition of neoadjuvant chemotherapy to radiotherapy with the aim of improving disease-free survival. The relative use of SCRT and LCRT varies considerably across the world. This is reflected in, and is probably driven in part by, disparity between international guideline recommendations. In addition, different approaches to treatment may exist both between and within countries, with variation related to patient, disease and treatment centre and financial factors. In this review, we will specifically focus on the use of SCRT for the treatment of rectal cancer. We will discuss the literature base and current guidelines, highlighting the challenges and controversies in clinical application of this evidence. We will also discuss potential future applications of SCRT, including its role in optimisation and intensification of treatment for rectal cancer.

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).

A Phase II trial of Higher RadiOtherapy Dose In The Eradication of early rectal cancer (APHRODITE): protocol for a multicentre, open-label randomised controlled trial

INTRODUCTION

The standard of care for patients with localised rectal cancer is radical surgery, often combined with preoperative neoadjuvant (chemo)radiotherapy. While oncologically effective, this treatment strategy is associated with operative mortality risks, significant morbidity and stoma formation. An alternative approach is chemoradiotherapy to try to achieve a sustained clinical complete response (cCR). This non-surgical management can be attractive, particularly for patients at high risk of surgical complications. Modern radiotherapy techniques allow increased treatment conformality, enabling increased radiation dose to the tumour while reducing dose to normal tissue. The objective of this trial is to assess if radiotherapy dose escalation increases the cCR rate, with acceptable toxicity, for treatment of patients with early rectal cancer unsuitable for radical surgery.

METHODS AND ANALYSIS

APHRODITE (A Phase II trial of Higher RadiOtherapy Dose In The Eradication of early rectal cancer) is a multicentre, open-label randomised controlled phase II trial aiming to recruit 104 participants from 10 to 12 UK sites. Participants will be allocated with a 2:1 ratio of intervention:control. The intervention is escalated dose radiotherapy (62 Gy to primary tumour, 50.4 Gy to surrounding mesorectum in 28 fractions) using simultaneous integrated boost. The control arm will receive 50.4 Gy to the primary tumour and surrounding mesorectum. Both arms will use intensity-modulated radiotherapy and daily image guidance, combined with concurrent chemotherapy (capecitabine, 5-fluorouracil/leucovorin or omitted). The primary endpoint is the proportion of participants with cCR at 6 months after start of treatment. Secondary outcomes include early and late toxicities, time to stoma formation, overall survival and patient-reported outcomes (European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaires QLQ-C30 and QLQ-CR29, low anterior resection syndrome (LARS) questionnaire).

ETHICS AND DISSEMINATION

The trial obtained ethical approval from North West Greater Manchester East Research Ethics Committee (reference number 19/NW/0565) and is funded by Yorkshire Cancer Research. The final trial results will be published in peer-reviewed journals and adhere to International Committee of Medical Journal Editors guidelines.

TRIAL REGISTRATION NUMBER

ISRCTN16158514.

Image-guided high-dose-rate brachytherapy for rectal cancer: technical note and first clinical experience on an organ-preserving approach

PURPOSE

As the population ages, the incidence of rectal cancer among elderly patients is rising. Due to the risk of perioperative morbidity and mortality, alternative nonoperative treatment options have been explored in elderly and frail patients who are clinically inoperable or refuse surgery.

METHODS

Here we present technical considerations and first clinical experience after treating a cohort of six rectal cancer patients (T1‑3, N0‑1, M0; UICC stage I-IIIB) with definitive external-beam radiation therapy (EBRT) followed by image-guided, endorectal high-dose-rate brachytherapy (HDR-BT). Patients were treated with 10-13 × 3 Gy EBRT followed by HDR-BT delivering 12-18 Gy in two or three fractions. Tumor response was evaluated using endoscopy and magnetic resonance imaging of the pelvis.

RESULTS

Median age was 84 years. All patients completed EBRT and HDR-BT without any high-grade toxicity (> grade 2). One patient experienced rectal bleeding (grade 2) after 10 weeks. Four patients (67%) demonstrated clinical complete response (cCR) or near cCR, there was one partial response, and one residual tumor and hepatic metastasis 8 weeks after HDR-BT. The median follow-up time for all six patients is 42 weeks (range 8-60 weeks). Sustained cCR without evidence of local regrowth has been achieved in all four patients with initial (n)cCR to date.

CONCLUSION

Primary EBRT combined with HDR-BT is feasible and well tolerated with promising response rates in elderly and frail rectal cancer patients. The concept could be an integral part of a highly individualized and selective nonoperative treatment offered to patients who are not suitable for or refuse surgery.