Reduced Acute Bowel Toxicity in Patients Treated With Intensity-Modulated Radiotherapy for Rectal Cancer

Intensity-modulated radiation therapy can reduce acute toxicities in long-course neoadjuvant radiation therapy combined with S-1 for locally advanced rectal cancer

BACKGROUND

The purpose of this study was to compare outcomes and adverse events between three-dimensional conformal radiation therapy (3D-CRT) and intensity-modulated radiation therapy (IMRT) in patients undergoing long-course neoadjuvant radiation therapy (NA-RT) for locally advanced rectal adenocarcinoma (LARC).

METHODS

We retrospectively analyzed a total of 47 consecutive patients who received NA-RT for LARC between January 2011 and September 2022. Seven and 40 patients were diagnosed with clinical stages II and III, respectively. The prescribed dose per fraction was 1.8 Gy for total doses of 45 or 50.4 Gy. Seventeen and 30 patients received 3D-CRT and IMRT, respectively. NA-RT was delivered with concurrent chemotherapy of oral administration of S-1.

RESULTS

Planned NA-RT was completed without any treatment interruption in 43 of the 47 patients. Two patients experienced treatment interruption, and two patients discontinued due to grade ≥ 3 toxicities. No significant differences were observed between patients receiving 3D-CRT and IMRT in local control, progression-free survival, and overall survival (P = 0.488, 0.259, and 0.636, respectively). Patients receiving IMRT showed significantly fewer non-hematological grade ≥ 2 acute toxicities than those receiving 3D-CRT (33.3% vs. 70.6%, P = 0.018). In addition, patients who received IMRT tended to have less intestinal toxicity of grade ≥ 2 than those who received 3D-CRT (P = 0.057).

CONCLUSION

IMRT significantly reduced grade ≥ 2 acute toxicities without compromising oncologic outcomes compared to 3D-CRT. Therefore, IMRT may be considered as a current standard treatment in the total neoadjuvant therapy era.

Evaluating the Effectiveness of Proton Beam Therapy Compared to Conventional Radiotherapy in Non-Metastatic Rectal Cancer: A Systematic Review of Clinical Outcomes

Background and Objectives: Conventional radiotherapies used in the current management of rectal cancer commonly cause iatrogenic radiotoxicity. Proton beam therapy has emerged as an alternative to conventional radiotherapy with the aim of improving tumour control and reducing off-set radiation exposure to surrounding tissue. However, the real-world treatment and oncological outcomes associated with the use of proton beam therapy in rectal cancer remain poorly characterised. This systematic review seeks to evaluate the radiation dosages and safety of proton beam therapy compared to conventional radiotherapy in patients with non-metastatic rectal cancer. Materials and Methods: A computer-assisted search was performed on the Medline, Embase and Cochrane Central databases. Studies that evaluated the adverse effects and oncological outcomes of proton beam therapy and conventional radiotherapy in adult patients with non-metastatic rectal cancer were included. Results: Eight studies were included in this review. There was insufficient evidence to determine the adverse treatment outcomes of proton beam therapy versus conventional radiotherapy. No current studies assessed radiotoxicities nor oncological outcomes. Pooled dosimetric comparisons between proton beam therapy and various conventional radiotherapies were associated with reduced radiation exposure to the pelvis, bowel and bladder. Conclusions: This systematic review demonstrates a significant paucity of evidence in the current literature surrounding adverse effects and oncological outcomes related to proton beam therapy compared to conventional radiotherapy for non-metastatic rectal cancer. Pooled analyses of dosimetric studies highlight greater predicted radiation-sparing effects with proton beam therapy in this setting. This evidence, however, is based on evidence at a moderate risk of bias and clinical heterogeneity. Overall, more robust, prospective clinical trials are required.

Markov models for clinical decision-making in radiation oncology: A systematic review

The intrinsic stochasticity of patients' response to treatment is a major consideration for clinical decision-making in radiation therapy. Markov models are powerful tools to capture this stochasticity and render effective treatment decisions. This paper provides an overview of the Markov models for clinical decision analysis in radiation oncology. A comprehensive literature search was conducted within MEDLINE using PubMed, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Only studies published from 2000 to 2023 were considered. Selected publications were summarized in two categories: (i) studies that compare two (or more) fixed treatment policies using Monte Carlo simulation and (ii) studies that seek an optimal treatment policy through Markov Decision Processes (MDPs). Relevant to the scope of this study, 61 publications were selected for detailed review. The majority of these publications (n = 56) focused on comparative analysis of two or more fixed treatment policies using Monte Carlo simulation. Classifications based on cancer site, utility measures and the type of sensitivity analysis are presented. Five publications considered MDPs with the aim of computing an optimal treatment policy; a detailed statement of the analysis and results is provided for each work. As an extension of Markov model-based simulation analysis, MDP offers a flexible framework to identify an optimal treatment policy among a possibly large set of treatment policies. However, the applications of MDPs to oncological decision-making have been understudied, and the full capacity of this framework to render complex optimal treatment decisions warrants further consideration.

The Impact on Survival of Neoadjuvant Treatment Interruptions in Locally Advanced Rectal Cancer Patients

The standard oncologic treatment of locally advanced rectal cancer is long-course radio-chemotherapy followed by surgery and adjuvant chemotherapy. This can result in a lengthy total treatment duration, sometimes up to one year from the diagnosis. Interruptions to neoadjuvant treatment can occur for a variety of reasons, forced or unforced. The main purpose of this study is to analyze the survival data of locally advanced rectal cancer patients who received neoadjuvant treatment and to find a cut-off point showing exactly how many days of interruption of neoadjuvant treatment the risk of death or disease relapse increases. We conducted a retrospective study on 299 patients with locally advanced rectal cancer using survival analysis (Kaplan-Meier curve and Cox regression) to determine survival probabilities for overall survival, local control, and disease-free survival. Patients with 0 to 3 days of neoadjuvant therapy interruption had a higher overall survival probability compared to patients with 4 or more days (90.2% compared to 57.9%, p-value < 0.001), hazard ratio 5.89 (p < 0.001). Local control and disease-free survival had a higher probability in patients with 0-2 days of interruption compared to people with 3 or more days (94% vs. 75.4%, and 82.2% vs. 50.5%, respectively, both p-values < 0.001). Patients with tumoral or nodal downstaging experienced fewer days of interruption than patients with no downstage. These findings reinforce the need for radiation oncologists to be well-organized when starting neoadjuvant treatment for rectal cancer, in order to anticipate and prevent potential treatment interruptions and achieve the best therapeutic results.

A Retrospective Comparison of Toxicity, Response and Survival of Intensity-Modulated Radiotherapy Versus Three-Dimensional Conformal Radiation Therapy in the Treatment of Rectal Carcinoma

INTRODUCTION

The main target of neoadjuvant treatment in rectal cancer is to downstage and downsize large tumours to increase the chance of complete surgical resection, and therefore decrease the chances of local recurrence. With or without the addition of chemotherapy, until recently, three-dimensional conformal radiotherapy (3D-CRT) used to be the radiotherapy treatment modality of choice. However, intensity-modulated radiotherapy (IMRT) is being increasingly adopted by many radiotherapy centres as a more modern, conformal technique due to its ability to minimize radiation dose to nearby organs. The aim of our analysis was to assess the difference in toxicity, response to treatment, and survival between the patients treated with these two different treatment modalities in our institution.

METHODS

We performed a retrospective analysis of data and compared two groups of patients with locally advanced rectal cancer who were treated with either 3D-CRT or IMRT. The main outcomes were radiation toxicity and response to treatment. Overall survival was a secondary outcome.

RESULTS

One hundred and thirty-six patients were included in the study: 71 patients treated with 3D-CRT and 65 patients treated with IMRT. With regard to toxicity, there was no significant difference between the groups for bladder and skin toxicity, but there was a significant reduction in acute grade 2 bowel toxicity in patients treated with a long course of IMRT [3D-CRT 77% (48/62) vs IMRT 64% (30/47) p=0.042]. There was no statistically significant difference in the treatment response rates of these two radiotherapy treatment modalities, as well as in overall survival between the groups (p=0.604).  Conclusion: Our study showed that IMRT can significantly reduce acute bowel side effects for patients undergoing neoadjuvant radiotherapy for locally advanced rectal cancers. Further studies are needed to confirm the clinical advantage of IMRT in rectal carcinoma.

The Association of Rural Residence With Surgery and Adjuvant Radiation in Medicare Beneficiaries With Rectal Cancer

Purpose

Radiation therapy and surgery are fundamental site-directed therapies for nonmetastatic rectal cancer. To understand the relationship between rurality and access to specialized care, we characterized the association of rural patient residence with receipt of surgery and radiation therapy among Medicare beneficiaries with rectal cancer.

Methods and Materials

We identified fee-for-service Medicare beneficiaries aged 65 years or older diagnosed with nonmetastatic rectal cancer from 2016 to 2018. Beneficiary place of residence was assigned to one of 3 geographic categories (metropolitan, micropolitan, or small town/rural) based on census tract and corresponding rural urban commuting area codes. Multivariable regression models were used to determine associations between levels of rurality and receipt of both radiation and proctectomy within 180 days of diagnosis. In addition, we explored associations between patient rurality and characteristics of surgery and radiation such as minimally invasive surgery (MIS) or intensity modulated radiation therapy (IMRT).

Results

Among 13,454 Medicare beneficiaries with nonmetastatic rectal cancer, 3926 (29.2%) underwent proctectomy within 180 days of being diagnosed with rectal cancer, and 1792 (13.3%) received both radiation and proctectomy. Small town/rural residence was associated with an increased likelihood of receiving both radiation and proctectomy within 180 days of diagnosis (adjusted subhazard ratio, 1.15; 95% CI, 1.02-1.30). Furthermore, small town/rural radiation patients were significantly less likely to receive IMRT (adjusted odds ratio, 0.62; 95% CI, 0.48-0.80) or MIS (adjusted odds ratio, 0.80; 95% CI, 0.66-0.97) than metropolitan patients.

Conclusions

Although small town/rural Medicare beneficiaries were overall more likely to receive both radiation and proctectomy for their rectal cancer, they were less likely to receive preoperative IMRT or MIS as part of their treatment regimen. Together, these findings clarify that among Medicare beneficiaries, there appeared to be a similar utilization of radiation resources and time to radiation treatment regardless of rural/urban status.

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.

Advantages and robustness of partial VMAT with prone position for neoadjuvant rectal cancer evaluated by CBCT-based offline adaptive radiotherapy

BACKGROUND AND PURPOSE

This study aims to explore the advantages and robustness of the partial arc combined with prone position planning technique for radiotherapy in rectal cancer patients. Adaptive radiotherapy is recalculated and accumulated on the synthesis CT (sCT) obtained by deformable image registration between planning CT and cone beam CT (CBCT). Full and partial volume modulation arc therapy (VMAT) with the prone position on gastrointestinal and urogenital toxicity, based on the probability of normal tissue complications (NTCP) model in rectal cancer patients were evaluated.

MATERIALS AND METHODS

Thirty-one patients were studied retrospectively. The contours of different structures were outlined in 155 CBCT images. First, full VMAT (F-VMAT) and partial VMAT (P-VMAT) planning techniques were designed and calculated using the same optimization constraints for each individual patient. The Acuros XB (AXB) algorithm was used in order to generate more realistic dose distributions and DVH, considering the air cavities. Second, the Velocity 4.0 software was used to fuse the planning CT and CBCT to obtain the sCT. Then, the AXB algorithm was used in the Eclipse 15.6 software to conduct re-calculation based on the sCT to obtain the corresponding dose. Furthermore, the NTCP model was used to analyze its radiobiological side effects on the bladder and the bowel bag.

RESULTS

With a CTV coverage of 98%, when compared with F-VMAT, P-VMAT with the prone position technique can effectively reduce the mean dose of the bladder and the bowel bag. The NTCP model showed that the P-VMAT combined with the prone planning technique resulted in a significantly lower complication probability of the bladder (1.88 ± 2.08 vs 1.62 ± 1.41, P = 0.041) and the bowel bag (1.28 ± 1.70 vs 0.95 ± 1.52, P < 0.001) than the F-VMAT. In terms of robustness, P-VMAT was more robust than F-VMAT, considering that less dose and NTCP variation was observed in the CTV, bladder and bowel bag.

CONCLUSION

This study analyzed the advantages and robustness of the P-VMAT in the prone position from three aspects, based on the sCT fused by CBCT. Whether it is in regards to dosimetry, radiobiological effects or robustness, P-VMAT in the prone position has shown comparative advantages.

Current and emerging therapeutic approaches for colorectal cancer: A comprehensive review

Colorectal cancer (CRC) affects 1 in 23 males and 1 in 25 females, making it the third most common cancer. With roughly 608000 deaths worldwide, CRC accounts for 8% of all cancer-related deaths, making it the second most common cause of death due to cancer. Standard and conventional CRC treatments include surgical expurgation for resectable CRC and radiotherapy, chemotherapy, immunotherapy, and their combinational regimen for non-resectable CRC. Despite these tactics, nearly half of patients develop incurable recurring CRC. Cancer cells resist the effects of chemotherapeutic drugs in a variety of ways, including drug inactivation, drug influx and efflux modifications, and ATP-binding cassette transporter overexpression. These constraints necessitate the development of new target-specific therapeutic strategies. Emerging therapeutic approaches, such as targeted immune boosting therapies, non-coding RNA-based therapies, probiotics, natural products, oncolytic viral therapies, and biomarker-driven therapies, have shown promising results in preclinical and clinical studies. We tethered the entire evolutionary trends in the development of CRC treatments in this review and discussed the potential of new therapies and how they might be used in conjunction with conventional treatments as well as their advantages and drawbacks as future medicines.

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.

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.

[Impact of IMRT for neoadjuvant rectal cancer?]

The standard management of locally advanced rectal tumors as cT3-T4 and/or N0/N1 is based on preoperative treatment combining radiotherapy of 45 to 50Gy and chemotherapy based on 5-fluorouracil. Intensity-modulated radiotherapy has already shown its interest compared to conformal radiotherapy in other locations, like in pelvic cancer. The role of intensity-modulated radiotherapy in the pre/postoperative treatment of rectal cancers is not a standard of care. Published studies showed its feasibility with the objective of less toxicity with equivalent efficacy.

Simultaneous Integrated Boost Volumetric Modulated Arc Therapy for Rectal Cancer: Long-Term Results after Protocol-Based Treatment

Background

Volumetric modulated arc therapy (VMAT) with simultaneous integrated boost (SIB) is an advanced form of radiotherapy (RT) technology. The purpose of this study was to report long-term treatment outcomes in patients with locally advanced rectal cancer undergoing VMAT-SIB based concurrent chemoradiotherapy (CRT).

Methods

Between January 2016 and January 2018, a total of 22 patients with operable stage II-III rectal adenocarcinoma were recruited for the pre-designed VMAT-SIB RT protocol. All patients underwent standard diagnostic and staging work-up. The RT target volumes included the following areas: PTV1 = mesorectum that contained gross tumors and enlarged lymph node regions and PTV2 = mesorectum and regional lymphatics from L4-5/S1 to 3-4 cm below the tumor or levator ani muscle, excluding PTV1. The VMAT-SIB dose prescription was as follows: PTV1 = 52.5 Gy/daily 2.1 Gy/25 fractions, PTV2 = 45 Gy/daily 1.8 Gy/25 fractions.

Results

The mean age of the study population was 64 (range, 18-84) years, and 15 (68.2%) patients were male. Radical operation (total mesorectal excision) was performed by either low anterior resection, ultralow anterior resection, or abdominal perineal resection. All five (22.7%) of the patients with confirmed increasing serum carcinoembryonic antigen (CEA) level at diagnosis showed normalization of serum CEA level after the planned treatment. Among 20 patients who underwent preoperative CRT and surgery, tumor down staging in T- and N-stages was achieved in 10 patients (50%) and 13 patients (65%), respectively, with 20% of ypT0/Tis. With a median follow-up of 54.2 (range, 22.6-61.1) months, the 5-year disease-free survival, overall survival, and local control rates were 64.6%, 81.8%, and 84.4%, respectively. Five patients developed distant metastasis and one developed local recurrence as a first event. Two cases with anastomosis site leakage, three with adhesive ileus, and two with abscess formation were observed during postoperative periods.

Conclusions

The current VMAT-SIB-based CRT protocol provided acceptable treatment and toxicity outcomes.

Locally Advanced Rectal Cancer: What We Learned in the Last Two Decades and the Future Perspectives

The advancement in surgical techniques, optimization of systemic chemoradiotherapy, and development of refined diagnostic and imaging modalities have brought a phenomenal shift in the treatment of the locally advanced rectal cancer. Although each therapeutic option has shown substantial progress in their field, it is finding their ideal amalgamation which has baffled the clinician and researchers alike. In the effort to identifying the perfect salutary treatment plan, we have even shifted our attention from the trimodal approach to non-operative "watchful waiting" to more recent individualized care. In this article, we acknowledge the scientific progress in the management of locally advanced rectal cancer and compare the opportunities as well as the obstacles while implementing them clinically. We also explore the current challenges and controversies surrounding the multidisciplinary approach and highlight the new trends and recent advances with an ultimate goal to improve the patients' quality of life.

Prediction of Neoadjuvant Chemoradiotherapy Response in Rectal Cancer with Metric Learning Using Pretreatment 18F-Fluorodeoxyglucose Positron Emission Tomography

OBJECTIVES

Neoadjuvant chemoradiotherapy (NCRT) followed by surgery is the mainstay of treatment for patients with locally advanced rectal cancer. Based on baseline 18F-fluorodeoxyglucose ([18F]-FDG)-positron emission tomography (PET)/computed tomography (CT), a new artificial intelligence model using metric learning (ML) was introduced to predict responses to NCRT.

PATIENTS AND METHODS

This study used the data of 236 patients with newly diagnosed rectal cancer; the data of 202 and 34 patients were for training and validation, respectively. All patients received pretreatment [18F]FDG-PET/CT, NCRT, and surgery. The treatment response was scored by Dworak tumor regression grade (TRG); TRG3 and TRG4 indicated favorable responses. The model employed ML combined with the Uniform Manifold Approximation and Projection for dimensionality reduction. A receiver operating characteristic (ROC) curve analysis was performed to assess the model's predictive performance.

RESULTS

In the training cohort, 115 patients (57%) achieved TRG3 or TRG4 responses. The area under the ROC curve was 0.96 for the prediction of a favorable response. The sensitivity, specificity, and accuracy were 98.3%, 96.5%, and 97.5%, respectively. The sensitivity, specificity, and accuracy for the validation cohort were 95.0%, 100%, and 98.8%, respectively.

CONCLUSIONS

The new ML model presented herein was used to determined that baseline 18F[FDG]-PET/CT images could predict a favorable response to NCRT in patients with rectal cancer. External validation is required to verify the model's predictive value.

Proton beam therapy in rectal cancer: A systematic review and meta-analysis

INTRODUCTION

Locally advanced rectal cancer is often treated with neoadjuvant chemoradiotherapy and surgery. Radiotherapy carries significant risk of toxicity to organs at risk (OAR). Proton beam therapy (PBT) has demonstrated to be effective in other cancers, delivering equivalent dosimetric radiation but with the benefit of improved sparing of OAR. This review compares dosimetric irradiation of OAR and oncological outcomes for PBT versus conventional photon-based radiotherapy in locally advanced rectal cancer.

METHODS

An electronic literature search was performed for studies with comparative cohorts receiving proton beam therapy and photon-based radiotherapy for rectal cancer.

RESULTS

Eight articles with a total of 127 patients met the inclusion criteria. There was significantly less irradiated small bowel with PBT compared to three-dimensional conformal radiation therapy (3DCRT) and intensity-modulated radiation therapy (IMRT) (MD -17.01, CI [-24.06, -9.96], p < 0.00001 and MD -6.96, CI [-12.99, -0.94], p = 0.02, respectively). Similar dosimetric results were observed for bladder and pelvic bone marrow. Three studies reported clinical and oncological results for PBT in recurrent rectal cancer with overall survival reported as 43 %, 68 % and 77.2 %, and one study in primary rectal cancer with 100 % disease free survival.

CONCLUSION

PBT treatment plans revealed significantly less irradiation of OAR for rectal cancer compared to conventional photon-based radiotherapy. Trials for recurrent rectal cancer and PBT have shown promising results. There are currently no ongoing clinical trials for primary rectal cancer and PBT. More research is required to validate its potential role in dose escalation, higher complete response rate and organ preservation without increasing toxicity.

Feasibility of Conebeam CT-based online adaptive radiotherapy for neoadjuvant treatment of rectal cancer

Background

Online adaptive radiotherapy has the potential to reduce toxicity for patients treated for rectal cancer because smaller planning target volumes (PTV) margins around the entire clinical target volume (CTV) are required. The aim of this study is to describe the first clinical experience of a Conebeam CT (CBCT)-based online adaptive workflow for rectal cancer, evaluating timing of different steps in the workflow, plan quality, target coverage and patient compliance.

Methods

Twelve consecutive patients eligible for 5 × 5 Gy pre-operative radiotherapy were treated on a ring-based linear accelerator with a multidisciplinary team present at the treatment machine for each fraction. The accelerator is operated using an integrated software platform for both treatment planning and delivery. In all directions for all CTVs a PTV margin of 5 mm was used, except for the cranial/caudal borders of the total CTV where a margin of 8 mm was applied. A reference plan was generated based on a single planning CT. After aligning the patient the online adaptive procedure started with acquisition of a CBCT. The planning CT scan was registered to the CBCT using deformable registration and a synthetic CT scan was generated. With the support of artificial intelligence, structure guided deformation and the synthetic CT scan contours were adapted by the system to match the anatomy on the CBCT. If necessary, these contours were adjusted before a new plan was generated. A second and third CBCT were acquired to validate the new plan with respect to CTV coverage just before and after treatment delivery, respectively. Treatment was delivered using volumetric modulated arc treatment (VMAT). All steps in this process were defined and timed.

Results

On average the timeslot needed at the treatment machine was 34 min. The process of acquiring a CBCT, evaluating and adjusting the contours, creating the new plan and verifying the CTV on the CBCT scan took on average 20 min. Including delivery and post treatment verification this was 26 min. Manual adjustments of the target volumes were necessary in 50% of fractions. Plan quality, target coverage and patient compliance were excellent.

Conclusions

First clinical experience with CBCT-based online adaptive radiotherapy shows it is feasible for rectal cancer.

Trial registration Medical Research Involving Human Subjects Act (WMO) does not apply to this study and was retrospectively approved by the Medical Ethics review Committee of the Academic Medical Center (W21_087 # 21.097; Amsterdam University Medical Centers, Location Academic Medical Center, Amsterdam, The Netherlands).

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-021-01866-7.

MV CBCT-Based Synthetic CT Generation Using a Deep Learning Method for Rectal Cancer Adaptive Radiotherapy

Due to image quality limitations, online Megavoltage cone beam CT (MV CBCT), which represents real online patient anatomy, cannot be used to perform adaptive radiotherapy (ART). In this study, we used a deep learning method, the cycle-consistent adversarial network (CycleGAN), to improve the MV CBCT image quality and Hounsfield-unit (HU) accuracy for rectal cancer patients to make the generated synthetic CT (sCT) eligible for ART. Forty rectal cancer patients treated with the intensity modulated radiotherapy (IMRT) were involved in this study. The CT and MV CBCT images of 30 patients were used for model training, and the images of the remaining 10 patients were used for evaluation. Image quality, autosegmentation capability and dose calculation capability using the autoplanning technique of the generated sCT were evaluated. The mean absolute error (MAE) was reduced from 135.84 ± 41.59 HU for the CT and CBCT comparison to 52.99 ± 12.09 HU for the CT and sCT comparison. The structural similarity (SSIM) index for the CT and sCT comparison was 0.81 ± 0.03, which is a great improvement over the 0.44 ± 0.07 for the CT and CBCT comparison. The autosegmentation model performance on sCT for femoral heads was accurate and required almost no manual modification. For the CTV and bladder, although modification was needed for autocontouring, the Dice similarity coefficient (DSC) indices were high, at 0.93 and 0.94 for the CTV and bladder, respectively. For dose evaluation, the sCT-based plan has a much smaller dose deviation from the CT-based plan than that of the CBCT-based plan. The proposed method solved a key problem for rectal cancer ART realization based on MV CBCT. The generated sCT enables ART based on the actual patient anatomy at the treatment position.

Assessing the Effect of Radiotherapy in Addition to Surgery in Colon Adenocarcinomas: a Systematic Review and Meta-analysis of Contemporary Evidence

PURPOSE

This study aims to review the contemporary evidence investigating radiotherapy (RT) in addition to surgery for colon adenocarcinomas.

METHODS

We searched the following databases: PubMed, Science Direct, Scopus, ASCOpubs, the Cochrane Library, and Google Scholar. Studies (since January 2005) comparing outcomes of high-risk colon adenocarcinomas who underwent RT in addition to surgery versus no RT were eligible. Pooling of outcomes from published results or from analysis of survival curves was done. Subgroup analysis was conducted to determine if the efficacy of RT varies with RT timing.

RESULTS

Eight studies were included (five retrospective cohorts, three population-based studies). Pooled analysis from retrospective cohorts showed a reduction in 5-year LR (OR 0.41; 95% CI 0.21-0.79; p = 0.007) in the RT group. A benefit in 3-year (OR 1.81; 95% CI 1.15-2.87; p = 0.01) and 5-year (OR 2.10; 95% CI 1.21-3.63; p = 0.008) DFS and in 3-year (OR 2.55; 95% CI 1.43-4.54; p = 0.001) and 5-year (OR 2.00; 95% CI 1.17-3.41; p = 0.01) OS was seen in the RT group. The OS benefit was demonstrated in the subgroup analysis of neoadjuvant RT, but not with adjuvant RT. The improvement in OS with neoadjuvant RT was supported by a population-based study from NCDB, while results from two population-based studies investigating adjuvant RT were conflicting.

CONCLUSION

Taking into account the limitations of the studies, our review of evidence suggests a possible role of RT in improving oncologic outcomes of select colon adenocarcinomas. Prospective studies are needed to definitively assess the value of RT for colon cancer.

Rectal Dose Is the Other Dosimetric Factor in Addition to Small Bowel for Prediction of Acute Diarrhea during Postoperative Whole-Pelvic Intensity-Modulated Radiotherapy in Gynecologic Patients

Simple Summary

Although the small bowel volume effect for acute diarrhea during radiotherapy has been investigated, no study has reported the influence of rectal dose. We analyzed 108 patients undergoing intensity-modulated radiotherapy after hysterectomy. Acute diarrhea was defined as onset during radiotherapy based on Common Terminology Criteria for Adverse Events (CTCAE) version 3. Both small bowel and rectum dosimetric parameters affected Grade 2 to 3 diarrhea. The high-dose volume effects on the small bowel still play an important role in postoperative intensity-modulated radiotherapy. This is the first large cohort study to demonstrate the role of both IMRT dosimetric factors of the rectum and the small bowel in acute diarrhea in gynecological patients with a previous hysterectomy. A small bowel volume of 39.6 Gy < 60 mL and a mean rectal dose of <32.75 Gy are suggested as constraints to treatment planning.

Abstract

We studied the association of rectal dose with acute diarrhea in patients with gynecologic malignancies undergoing whole-pelvic (WP) intensity-modulated radiotherapy (IMRT). From June 2006 to April 2019, 108 patients with previous hysterectomy who underwent WP IMRT were enrolled in this cohort study. WP irradiation of 39.6–45 Gy/22–25 fractions was initially delivered to the patients. Common Terminology Criteria for Adverse Events (CTCAE) version 3 was used to evaluate acute diarrhea during radiotherapy. Small bowel volume at different levels of isodose curves (Vn%) and mean rectal dose (MRD) were measured for statistical analysis. The multivariate analysis showed that the MRD ≥ 32.75 Gy (p = 0.005) and small bowel volume of 100% prescribed (V100%) ≥ 60 mL (p = 0.008) were independent factors of Grade 2 or higher diarrhea. The cumulative incidence of Grade 2 or higher diarrhea at 39.6 Gy were 70.5%, 42.2%, and 15.0% (p < 0.001) in patients with both high (V100% ≥ 60 mL and MRD ≥ 32.75 Gy), either high, and both low volume-dose factors, respectively. Strict constraints for the rectum/small bowel or image-guided radiotherapy to reduce these doses are suggested.

Dosimetric comparison of organs at risk in 5 different radiotherapy plans in patients with preoperatively irradiated rectal cancer

BACKGROUND

Intensity-modulated radiotherapy (IMRT) is a widely used irradiation technique in rectal cancer patients. We aimed to compare 4 different IMRT plans with 3-dimensional conformal radiotherapy (3D-CRT) considering organs at risk (OARs) in patients with rectal carcinoma.

METHODS

This retrospective study included 27 rectal cancer patients who were irradiated preoperatively between January 2016 and December 2018. Five different plans (4-field 3D-CRT in 2 phases, 7-field IMRT in 2 phases, 9-field IMRT in 2 phases, 7-field simultaneous integrated boost [SIB] IMRT, and 9-field SIB IMRT) were generated for each patient. Comparison of 5 different plans according to bladder and bilateral femoral head mean doses, bladder V40, bilateral femoral head V40, and small bowel V35 values were evaluated.

RESULTS

Most of the OAR parameters significantly favored IMRT plans compared to the 3D-CRT plan. The largest difference was observed in bladder V40 values (reduction of V40 value up to 51.2% reduction) in favor of IMRT. In addition, SIB plans showed significantly better reduction in OARs than phase plans except for small bowel V35 values.

CONCLUSIONS

IMRT plans reduced almost all the OARs doses compared with the 3D-CRT plan in rectal cancer patients. Furthermore, SIB plans demonstrated lower OAR doses than the phase plans. IMRT techniques, especially SIB plans, reduce OAR doses and provide safer doses for the treatment of rectal carcinoma.

Factors affecting pathological response and survival following neoadjuvant chemoradiotherapy in rectal cancer patients

Background

Despite all advanced treatment methods for rectal cancer, not all patients can provide an adequate response, and hence, possible prognostic factors must be evaluated. The aim of this study was to evaluate the relationship between systemic inflammatory markers and pathological response, overall survival (OS) and disease-free survival (DFS) in patients treated with neoadjuvant chemoradiotherapy (nCRT).

Methods

We evaluated data of 117 patients for the period 2010 to 2017. Serum measurements of albumin, hemoglobin, C-reactive protein, modified Glasgow prognostic score (mGPS), and white cell counts were obtained. Rodel scoring system was used to determine pathologic tumor regression.

Results

Overall, 77% of the patients were in the good response group according to the radiological images. A total of 48% of patients were categorized as a good pathologic response. Pathologic response to treatment was associated with a mGPS of 0 (P = 0.001), normal platelet lymphocyte ratio (PLR) (P = 0.003), TNM stage (P = 0.03), pathologic T stage (P = 0.001), radiologic response to nCRT (P = 0.04), tumor differentiation (P = 0.001), lymphovascular invasion (LVI) (P = 0.001) and perineural invasion (P = 0.02). LVI (P = 0.04), albumin level (P = 0.05), C-reactive protein (P = 0.01), neutrophil platelet score (NPS) (P = <0.001) and mGPS (P = 0.01) had a statistically significant effect on OS. Operation type (P = 0.03), tumor differentiation (P = 0.01), depth of invasion (P = 0.03), NPS (P < 0.01), mGPS (P = 0.01), PLR (P = 0.004), neutrophil-lymphocyte ratio (P = 0.01) and LVI (P = 0.05) were statistically significant on DFS.

Conclusions

There was an association between systemic inflammatory markers and pathologic response and also, between OS and DFS. This study can be preliminary data for prospective controlled studies.

Online adaptive radiotherapy compared to plan selection for rectal cancer: quantifying the benefit

Background

To compare online adaptive radiation therapy (ART) to a clinically implemented plan selection strategy (PS) with respect to dose to the organs at risk (OAR) for rectal cancer.

Methods

The first 20 patients treated with PS between May–September 2016 were included. This resulted in 10 short (SCRT) and 10 long (LCRT) course radiotherapy treatment schedules with a total of 300 Conebeam CT scans (CBCT). New dual arc VMAT plans were generated using auto-planning for both the online ART and PS strategy.

For each fraction bowel bag, bladder and mesorectum were delineated on daily Conebeam CTs. The dose distribution planned was used to calculate daily DVHs. Coverage of the CTV was calculated, as defined by the dose received by 99% of the CTV volume (D99%). The volume of normal tissue irradiated with 95% of the prescribed fraction dose was calculated by calculating the volume receiving 95% of the prescribed fraction or more dose minus the volume of the CTV. For each fraction the difference between the plan selection and online adaptive strategy of each DVH parameter was calculated, as well as the average difference per patient.

Results

Target coverage remained the same for online ART. The median volume of the normal tissue irradiated with 95% of the prescribed dose dropped from 642 cm3 (PS) to 237 cm3 (online-ART)(p < 0.001). Online ART reduced dose to the OARs for all tested dose levels for SCRT and LCRT (p < 0.001). For V15Gy of the bowel bag the median difference over all fractions of all patients was − 126 cm³ in LCRT, while the average difference per patient ranged from − 206 cm³ to − 40 cm³. For SCRT the median difference was − 62 cm³, while the range of the average difference per patient was − 105 cm3 to − 51 cm³.

For V15Gy of the bladder the median difference over all fractions of all patients was 26% in LCRT, while the average difference per patient ranged from − 34 to 12%. For SCRT the median difference of V95% was − 8%, while the range of the average difference per patient was − 29 to 0%.

Conclusions

Online ART for rectal cancer reduces dose the OARs significantly compared to a clinically implemented plan selection strategy, without compromising target coverage.

Trial registration

Medical Research Involving Human Subjects Act (WMO) does not apply to this study and was retrospectively approved by the Medical Ethics review Committee of the Academic Medical Center (W19_357 # 19.420; Amsterdam University Medical Centers, Location Academic Medical Center, Amsterdam, The Netherlands).

Clinical Implementation of Preoperative Short-Course Pencil Beam Scanning Proton Therapy for Patients With Rectal Cancer

Purpose

For treatment of rectal cancer, pencil beam scanning proton therapy (PBS-PT) may reduce radiation exposure to normal tissues compared with 3-dimensional conformal photon radiation therapy (3DCRT) or volumetric modulated arc photon radiation therapy (VMAT). The purpose of this study was to report the clinical implementation and dosimetric analysis of preoperative short-course PBS-PT for rectal cancer.

Methods and Materials

Eleven patients with stage IIA-IVB rectal cancer received preoperative short-course (25 Gy in 5 fx) PBS-PT between 2018 and 2019 preceding curative-intent total mesorectal excision. PBS-PT plans were generated using single-field optimization with 2 posterior-oblique fields. Verification computed tomography scans were performed on the first 3 days of treatment. Each patient had a backup 3DCRT and VMAT plan.

Results

Clinical target volume coverage was similar between PBS-PT, 3DCRT, and VMAT. PBS-PT had statistically significant reductions in dose to the small bowel, large bowel, bladder, and femoral heads across multiple dosimetric parameters. All patients completed PBS-PT as planned without need for replanning. All computed tomography verification scans demonstrated good target coverage with clinical target volume V100 > 95%.

Conclusions

Preoperative short-course PBS-PT has been successfully implemented and offers a significant reduction of dose to normal tissues. Prospective studies are warranted to evaluate if dosimetric advantages translate into clinical benefit.

[Preoperative intensity-modulated radiotherapy of rectal cancers: Relevance and modalities]

Preoperative radiotherapy boosted by chemotherapy is a recommended treatment in locally advanced rectal cancers. This treatment is delivered by three dimensional conformal irradiation, which is usually well tolerated but can induce potential toxicity such as rectitis, cystitis and hematologic adverse effects. Intensity-modulated radiotherapy, widely available nowadays, allows optimization of volume covering and sparing of organs at risk such as bladder and bone marrow. This review presents relevant clinical situations and requirements for a beneficial and safe preoperative irradiation of rectal cancers by intensity-modulated technique. This technique is compared to three-dimensional conformal radiotherapy.

A comparative analysis between radiation dose intensification and conventional fractionation in neoadjuvant locally advanced rectal cancer: a monocentric prospective observational study

PURPOSE

The potential role of neoadjuvant radiation dose intensification in locally advanced rectal cancer (LARC) is still largely debated. In the present study, a comparative analysis between radiation dose intensification and conventional fractionation was performed.

MATERIALS AND METHODS

In the current prospective observational study (protocol ID RT-03/2011), 56 patients diagnosed with LARC were enrolled between January 2013 and December 2016. More specifically, 25 patients underwent preoperative conventional radiation dose [i.e., 50.4 Gy in 28 fractions here defined as standard dose radiotherapy (SDR)-group 1], whereas 31 patients were candidate for radiation dose intensification (RDI) (i.e., 60 Gy in 30 fractions-group 2). The primary endpoint was the complete pathological response (pCR) rate. Secondary endpoints were postoperative complications and ChT-RT-related toxicity.

RESULTS

No statistical significance was observed in pCR rate (20.8% and 22.6% in SDR and RDI group, respectively, p = 0.342). Of contrast, the RDI group showed a significantly higher primary tumor downstaging in case of T3 tumor compared to SDR group (p = 0.049). Sphincter-preserving surgery was 84% and 93.5% in SDR and RDI groups, respectively (p = 0.25). All patients had R0 margins. No surgical-related death was recorded. No statistically significant difference was observed regarding surgical complications and incomplete mesorectal excision. Acute genitourinary toxicity was significantly higher in RDI group (p = 0.015).

CONCLUSIONS

The intensification of the neoadjuvant radiotherapy for LARC seems to produce a major pathological response in T3 tumors. The radiation dose intensification appears probably associated with a higher rate of genitourinary toxicity.

Predicting pathological complete response in rectal cancer after chemoradiotherapy with a random forest using 18F-fluorodeoxyglucose positron emission tomography and computed tomography radiomics

Background

Neoadjuvant chemoradiotherapy (NCRT) followed by surgery is the standard treatment for patients with locally advanced rectal cancer. This study developed a random forest (RF) model to predict pathological complete response (pCR) based on radiomics derived from baseline ¹⁸F-fluorodeoxyglucose ([¹⁸F]FDG)-positron emission tomography (PET)/computed tomography (CT).

Methods

This study included 169 patients with newly diagnosed rectal cancer. All patients received ¹⁸F[FDG]-PET/CT, NCRT, and surgery. In total, 68 radiomic features were extracted from the metabolic tumor volume. The numbers of splits in a decision tree and trees in an RF were determined based on their effects on predictive performance. Receiver operating characteristic curve analysis was performed to evaluate predictive performance and ascertain the optimal threshold for maximizing prediction accuracy.

Results

After NCRT, 22 patients (13%) achieved pCR, and 42 features that could differentiate tumors with pCR were used to construct the RF model. Six decision trees and seven splits were suitable. Accordingly, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 81.8%, 97.3%, 81.8%, 97.3%, and 95.3%, respectively.

Conclusions

By using an RF, we determined that radiomics derived from baseline ¹⁸F[FDG]-PET/CT could accurately predict pCR in patients with rectal cancer. Highly accurate and predictive values can be achieved but should be externally validated.

Impact of diabetes on gastrointestinal and urinary toxicity after radiotherapy for gynecologic malignancy

Objective

Although diabetes is a common co-morbidity in patients with gynecologic cancer, information about its impact on radiation toxicity in patients with gynecologic cancer treated with external pelvic irradiation is scarce. We aimed to investigate the relation of diabetes with acute toxicity in patients with gynecologic tumors who underwent pelvic +/- paraaortic radiotherapy.

Materials and Methods

One hundred twenty-nine patients with endometrium or cervix carcinoma were enrolled in the study. Demographic features, presence of diabetes, incidence and severity of upper gastrointestinal (UGIS), lower gastrointestinal (LGIS), and urinary symptoms were recorded from files. Correlation and logistic regression analysis was used to determine the impact of diabetes, age, chemotherapy, paraaortic irradiation on toxicities, and a prediction model was developed.

Results

The median age of 77 patients with endometrium cancer and 52 cervix cancer was 61 (range, 25-92) years, and 28 (21.7%) of them had diabetes. The median pelvic and tumor/tumor bed dose was 5040+247.65 cGy and 5040+222.91 cGy, respectively. Age and Gr 0 UGIS toxicity were significantly related (p=0.047). LGIS Gr 0 toxicity was found to be significantly higher in patients with diabetes (p=0.045). Gr 0 and 2 UGIS toxicities were both found to be significantly correlated with paraaortic irradiation (both p<0.001). Diabetes is also an important determinant on UGIS toxicity in patients who underwent paraaortic irradiation.

Conclusion

The correlation we found between toxicity and diabetes, concurrent chemotherapy or paraaortic radiation necessitates special care and risk stratification for patients with diabetes. Further prospective studies with long follow-up and larger patient groups are warranted.

Surgical treatment following neoadjuvant chemoradiotherapy in locally advanced rectal cancer

Colorectal cancer is a major public health problem worldwide, and locally advanced rectal cancer (LARC) is known for its poor prognosis. A multimodal treatment approach is the only method to achieve satisfactory local recurrence and survival rates in LARC. Determining which therapeutic modality for LARC has the most satisfactory influence on quality of life and disease outcome is still controversial. LARC treatment is subject to continuous advancement due to the development of new and better diagnostic tools, radiotherapy techniques, and chemotherapeutic agents. Herein, we review various therapeutic modalities for LARC from several aspects. In addition to radiotherapy techniques such as neoadjuvant chemoradiotherapy (NCRT), we discuss the progress of chemotherapy, appropriate time interval between NCRT and surgery, relationship between tumor location and NCRT efficacy/safety, wait-and-watch policy, and predictors of treatment response following NCRT. Because of the controversies and unanswered questions regarding NCRT treatments for LARC, additional investigations are required to determine which therapeutic approach is the most feasible for LARC patients.

Oncologic Outcome and Morbidity in the Elderly Rectal Cancer Patients After Preoperative Chemoradiotherapy and Total Mesorectal Excision: A Multi-institutional and Case-matched Control Study

OBJECTIVE

To determine the toxicity and oncologic outcome of neoadjuvant chemoradiotherapy (CRT) followed by curative total mesorectal excision (TME) in the elderly (≥70 yrs) and younger (<70 yrs) rectal cancer patients.

BACKGROUND

Sufficient data for elderly rectal cancer patients who received definitive trimodality have not been accumulated yet.

PATIENTS AND METHODS

A total of 1232 rectal cancer patients who received neoadjuvant CRT and TME were enrolled in this study. After propensity-score matching, 310 younger patients and 310 elderly patients were matched with 1:1 manner. Treatment response, toxicity, surgical outcome, recurrence, and survival were assessed and compared between the 2 groups of patients.

RESULTS

The median age was 58 years for the younger patient group and 74 years for the elderly group. Pathologic complete response rates were not significantly different between the 2 groups (younger and elderly: 17.1% vs 14.8%, P = 0.443). The 5-year recurrence-free survival (younger and elderly: 67.7% vs 65.5%, P = 0.483) and overall survival (younger and elderly: 82.9% vs. 79.5%, P = 0.271) rates were not significantly different between the 2 groups either. Adjuvant chemotherapy after surgery was less frequently delivered to the elderly than that to younger patients (83.9% vs 69.0%). Grade 3 or higher acute hematologic toxicity was observed more frequently in the elderly than that in the younger group (9.0% vs 16.1%, P = 0.008). Late complication rate was higher in the elderly group compared with that in the younger group without statistical significance (2.6% vs 4.5%, P = 0.193).

CONCLUSIONS

Although acute hematologic toxicity was observed more frequently in the elderly patients than that in the younger patients, elderly rectal cancer patients with good performance status who received preoperative CRT and TME showed favorable tumor response and recurrence-free survival similar to younger patients.

Robust dose planning objectives for mesorectal radiotherapy of early stage rectal cancer - A multicentre dose planning study

BACKGROUND AND PURPOSE

Organ preservation strategies are increasingly being explored for early rectal cancer. This requires revision of target volumes according to disease stage, as well as new guidelines for treatment planning. We conducted an international, multicentre dose planning study to develop robust planning objectives for modern radiotherapy of a novel mesorectal-only target volume, as implemented in the STAR-TReC trial (NCT02945566).

MATERIALS AND METHODS

The published literature was used to establish relevant dose levels for organ at risk (OAR) plan optimisation. Ten representative patients with early rectal cancer were identified. Treatment scans had mesorectal target volumes as well as bowel cavity, bladder and femoral heads outlined, and were circulated amongst the three participating institutions. Each institution produced plans for short course (SCRT, 5 × 5 Gy) and long course (LCRT, 25 × 2 Gy) treatment, using volumetric modulated arc therapy on different dose planning systems. Optimisation objectives for OARs were established by determining dose metric objectives achievable for ≥90% of plans.

RESULTS

Sixty plans, all fulfilling target coverage criteria, were produced. The planning results and literature review suggested optimisation objectives for SCRT: V 10Gy < 180 cm3, V 18Gy < 110 cm3, V 23Gy < 85 cm3 for bowel cavity; V 21Gy < 15% and V 25Gy < 5% for bladder; and V 12.5Gy < 11% for femoral heads. Corresponding objectives for LCRT: V 20Gy < 180 cm3, V 30Gy < 130 cm3, V 45Gy < 90 cm3 for bowel cavity; V 35Gy < 22% and V 50Gy < 7% for bladder; and V 25Gy < 15% for femoral heads. Constraints were validated across all three institutions.

CONCLUSION

We utilized a multicentre planning study approach to develop robust planning objectives for mesorectal radiotherapy for early rectal cancer.

MR-guided radiotherapy in rectal cancer: First clinical experience of an innovative technology

•This study represents one of the first reports of online MRgRT.•Integrated Low-field MR provides better anatomical visualization than CBCT or MVCT.•Better visualization of the target can help to reduce the margins from CTV to PTV.•MRgRT appears a feasible option in rectal cancer treatment offering potential benefits.•MRgRT represents a promising technology for rectal cancer management.

mARC preoperative rectal cancer treatments vs. 3D conformal radiotherapy. A dose distribution comparative study

PURPOSE

mARC (modulated arc) is the arc therapy technique provided by Siemens. The present study analyses the dose distributions and treatment times corresponding to preoperative rectal cancer mARC treatments. The results are compared to those corresponding to 3D-CRT plans.

METHODS

The plans of 30 patients, each having one mARC and one 3D-CRT plan, were evaluated. Every plan was calculated on a sequential two-phase treatment scheme with prescription doses of 45 Gy in the initial phase and 5.4 Gy in the boost phase. Dosimetric parameters and mean DVHs corresponding to the PTVs and OARs were assessed for both techniques.

RESULTS

All mARC plans were considered valid for treatment and yielded a highly significant improvement in the CI over 3D-CRT plans (p <0.001). They also showed statistically significant advantage on the parameters D98%, D95% and D2% of the high dose PTV. Regarding the OARs, mARC plans showed reductions in the mean dose of 3.5 Gy in the bladder and greater than 4 Gy in the femoral heads. Considering the small bowel, the mARC plans resulted in a 2.7 Gy mean reduction in the mean dose and lower irradiated volumes over the entire dose range.

CONCLUSIONS

Arc therapy plans with the mARC technique for preoperative rectal cancer treatment in a sequential two-phase treatment scheme provide important advantages in the PTVs and OARs. mARC plans show superior protection of the femoral heads, bladder and small bowel, similar to the results found with other more widespread arc therapy techniques.

Systematic review and meta-analysis of small bowel dose-volume and acute toxicity in conventionally-fractionated rectal cancer radiotherapy

INTRODUCTION

The limited radiation tolerance of the small-bowel causes toxicity for patients receiving conventionally-fractionated radiotherapy for rectal cancer. Safe radiotherapy dose-escalation will require a better understanding of such toxicity. We conducted a systematic review and meta-analysis using published datasets of small bowel dose-volume and outcomes to analyse the relationship with acute toxicity.

MATERIALS AND METHODS

SCOPUS, EMBASE & MEDLINE were searched to identify twelve publications reporting small-bowel dose-volumes and toxicity data or analysis. Where suitable data were available (mean absolute volume with parametric error measures), fixed-effects inverse-variance meta-analysis was used to compare cohorts of patients according to Grade ≥3 toxicity. For other data, non-parametric examinations of irradiated small-bowel dose-volume and incidence of toxicity were conducted, and a univariate logistic regression model was fitted.

RESULTS

On fixed-effects meta-analysis of three studies (203 patients), each of the dose-volume measures V_5Gy-V_40Gy were significantly greater (p < 0.00001) for patients with Grade ≥3 toxicity than for those without. Absolute difference was largest for the lowest dose-volume parameter; however relative difference increases with increasing dose. On logistic regression multiple small-bowel DVH parameters were predictive of toxicity risk (V_5Gy, V_10Gy, V_30Gy - V_45Gy), with V_10Gy the strongest (p = 0.004).

CONCLUSIONS

Analysis of published clinical cohort dose-volume data provides evidence for a significant dose-volume-toxicity response effect for a wide range of clinically-relevant doses in the treatment of rectal cancer. Both low dose and high dose are shown to predict toxicity risk, which has important implications for radiotherapy planning and consideration of dose escalation for these patients.

A Review on the Special Radiotherapy Techniques of Colorectal Cancer

Colorectal cancer is one of the commonest cancers worldwide. Radiotherapy has been established as an indispensable component of treatment. Although conventional radiotherapy provides good local control, radiotherapy treatment side-effects, local recurrence and distant metastasis remain to be the concerns. With the recent technological advancements, various special radiotherapy treatment options have been offered. This review article discusses the recently-developed special radiotherapy treatment modalities for various conditions of colorectal cancer ranging from early stage, locally advanced stage, recurrent, and metastatic diseases. The discussion focuses on the areas of feasibility, local control, and survival benefits of the treatment modalities. This review also provides accounts of the future direction in radiotherapy of colorectal cancer with emphasis on the coming era of personalized radiotherapy.

To what extent is the low anterior resection syndrome (LARS) associated with quality of life as measured using the EORTC C30 and CR38 quality of life questionnaires?

PURPOSE

Treatment of rectal cancer often results in disturbed anorectal function, which can be quantified by the Low Anterior Resection Syndrome (LARS) score. This study investigates the association of impaired anorectal function as measured with the LARS score with quality of life (QoL) as measured with the EORTC-QLQ-C30 and CR38 questionnaires.

METHODS

All stoma-free patients who had undergone sphincter-preserving surgery for rectal cancer from 2000 to 2014 in our institution were retrieved from a prospective database. They were contacted by mail and asked to return the questionnaires. QoL was evaluated in relation to LARS and further patient- and treatment factors using univariate and multivariate analysis.

RESULTS

Of the eligible patients (n = 331), 261 (78.8%) responded with a complete LARS score. Mean score for global QoL according to the EORTC-QLQ-C30 questionnaire was 63 ± 21 for all patients. If major LARS was present, mean score decreased to 56 ± 19 in contrast to 67 ± 20 in patients with no/minor LARS (p < 0.001). In regression analysis, major LARS was furthermore associated with reduced physical, role, emotional, cognitive and social functioning as well as impaired body image, more micturition problems and poorer future perspective. It was not related to sexual function. The variance explained by major LARS in the differences of QoL was approximately 10%.

CONCLUSION

The presence of major LARS after rectal resection for cancer is negatively associated with global health as well as many other aspects of QoL. Preserving anorectal function and treatment of LARS are potential measures to improve QoL in this patient group.

Neoadjuvant chemoradiotherapy delivered with helical tomotherapy under daily image guidance for rectal cancer patients: efficacy and safety in a large, multi-institutional series

Purpose

Helical tomotherapy (HT) has been recently introduced in the neoadjuvant treatment of locally advanced rectal cancer. Aim of this study is to report the toxicity and local control rates of a large series of locally advanced rectal cancer patients treated with neoadjuvant chemotherapy and HT under daily image guidance followed by surgery.

Methods

Data from 117 locally advanced rectal cancer patients treated at two Swiss Radiotherapy departments were collected and analyzed. Radiotherapy consisted of 45 Gy (1.8 Gy/fraction, 5 fractions/week delivered in 5 weeks) to the regional pelvic lymph nodes. Seventy patients also received a simultaneous integrated boost (SIB) up to 50 Gy to the tumor and involved nodes (2 Gy/fraction, 5 fractions/week delivered in 5 weeks). Chemotherapy consisted of capecitabine 825 mg/m², twice daily, during the irradiation days. After a median interval of 59 days [95% confidence interval (CI) 53–65 days), all patients underwent surgery.

Results

Median follow-up was 45 months (range 4–90 months). The overall rate of acute grade 2–4 toxicity was 18.8% (n = 22). Four patients (3.4%) presented a grade 3 dermatitis (n = 1) or diarrhea (n = 3), and 1 (0.8%) demonstrated grade 4 rectal toxicity. No patients presented with grade ≥ 3 hematologic toxicity. Six patients (5.1%) had late grade 3 gastrointestinal toxicity. The 4-year local control rate was 88.4% (95% CI 87.5–88.5%).

Conclusions

Neoadjuvant chemoradiotherapy delivered with HT under daily image guidance is well tolerated and shows a high 4-year local control rates.

A novel dynamic arc treatment planning solution to reduce dose to small bowel in preoperative radiotherapy for rectal cancer

Preoperative radiotherapy or combined chemoradiotherapy for locally advanced rectal cancer (LARC) can cause acute and late gastrointestinal (GI) side-effects. There is thought to be a dose-volume relationship between small bowel irradiation and the development of these effects. A planning study was undertaken to compare small bowel sparing for a range of 3D conformal and dynamic arc planning solutions. A planning study was carried out for 20 LARC patients. Organs at risk (OAR) contoured included bowel loops and peritoneal space (PS). For each of the 20 patients, 5 plans were created: (1) standard 3D conformal plan; (2) standard dual dynamic arc plan; (3) dual dynamic arc plan with 90° avoidance sector through the anterior portion of the patient; (4) dual dynamic arc plan with an anterior avoidance structure in the optimizer; (5) dual dynamic arc plan with both an anterior avoidance structure and an avoidance sector. The prescription was 50.4 Gy in 28 fractions to the planning target volume (PTV). Five Dose Volume Levels (DVLs; V_{15 Gy}, V_{20 Gy}, V_{25 Gy}, V_{35 Gy}, V_{40 Gy}, and V_{50.4 Gy}) for bowel and PS were selected. The DVLs were compared between the plans using Friedman Tests and Wilcoxon Signed Rank Tests. Comparison of the 5 plans revealed that a dual dynamic arc plan containing both an anterior avoidance sector and structure significantly improved the dose to the bowel compared to a standard 3D conformal plan and to a standard dual dynamic arc plan. This improvement was achieved while maintaining PTV coverage. This novel dual dynamic arc planning technique that uses both an avoidance sector and structure reduces the dose to the bowel and PS, which may lead to a reduction in GI toxicity.

Is long interval from neoadjuvant chemoradiotherapy to surgery optimal for rectal cancer in the era of intensity-modulated radiotherapy?: a prospective observational study

OBJECTIVES

To evaluate the impact of interval between neoadjuvant chemoradiotherapy (NACRT) and surgery on therapeutic and adverse effects of surgery, and long-term outcome of patients with locally advanced rectal cancer (RC), in the era of intensity-modulated radiotherapy (IMRT).

PATIENTS AND METHODS

Patients diagnosed with stage II-III RC and treated with IMRT-based NACRT followed by radical surgery were enrolled consecutively from April 2011 to March 2014. The data of all the patients were collected prospectively and grouped according to their NACRT-to-surgery interval. The therapeutic and adverse effects of surgery, and survivals were compared between the patients with interval ≤7 weeks and those with interval ≥8 weeks.

RESULTS

A total of 231 patients were eligible for analysis, including 106 cases with interval ≤7 weeks and 125 cases with interval ≥8 weeks. The therapeutic and adverse effects of surgery were similar between these two groups of patients. However, interval ≥8 weeks appeared to lead to poorer overall, distant-metastasis-free and disease-free survivals, compared with interval ≤7 weeks. The HRs were 1.805, 1.714, and 1.796 (P-values were 0.045, 0.049, and 0.028), respectively.

CONCLUSION

For patients with locally advanced RC, a long NACRT-to-surgery interval might bring a potential risk of increased distant metastasis rather than a better tumor regression in the era of IMRT.

[Image-guided radiotherapy contribution and patient setup for anorectal cancer treatment]

Intensity-modulated radiation therapy is recommended in anal squamous cell carcinoma treatment and is increasingly used in rectal cancer. It adapts the dose to target volumes, with a high doses gradient. Intensity-modulated radiation therapy allows to reduce toxicity to critical normal structures and to consider dose-escalation studies or systemic treatment intensification. Image-guided radiation therapy is a warrant of quality for intensity-modulated radiation therapy, especially for successful delivery of the dose as planned. There is no recommended international or national anorectal cancer image-guided radiation therapy protocol currently available. Dose-escalation trials or expert opinions about intensity-modulated/image-guided radiation therapy good practice guidelines recommend daily volumetric imaging throughout the treatment or during the five first fractions and weekly thereafter as a minimum. Image-guided radiation therapy allows to reduce margins related to patient setup errors. Internal margin, related to the internal organ motion, needs to be adapted according to short- or long-course radiotherapy, gender, rectal location; it can be higher than current recommended planning target volume margins, particularly in the upper and anterior part of mesorectum, which has the most significant movement. Image-guided radiation therapy based on volumetric imaging allows to take target volume shrinkage into account and to develop adaptive strategies, in particular for mesorectum shrinkage during rectal cancer treatment. Lastly, the emergence of new image-guided radiation therapy technologies including MRI (which plays a major role in pelvic tumours assessment and diagnosis) opens up interesting perspectives for adaptive radiotherapy, taking into account both organs' movements and tumour shrinkage.

Neoadjuvant PET and MRI-based intensity modulated radiotherapy leads to less toxicity and improved pathologic response rates in locally advanced rectal cancer

Background

Neoadjuvant chemoradiation (NeoCRT) is standard of care for the treatment of locally advanced rectal cancer (LARC). Contemporary radiation techniques and pre-treatment imaging may impact toxicities and pathologic response (PR). Herein we compare intensity modulated radiotherapy (IMRT) and advanced pre-treatment imaging in the neoadjuvant treatment of LARC and resulting impact on toxicities and pathologic outcomes relative to 3 dimensional conformal radiotherapy (3DCRT).

Methods

LARC patients treated at 4 large academic centers in the US from 2007-2016 were reviewed. Patients received 5-FU-based NeoCRT concurrently with IMRT or 3DCRT. PR was recorded as none, partial, or complete. Common terminology for adverse events version 4 was used to grade toxicities. Toxicity rates were compared using Chi-square analysis. Multivariable models were fit adjusting for age, gender, pre-tx CT to identify independent predictors of PR and toxicity.

Results

A total of 128 patients were analyzed: 60.1% male and 39.8% female, median age 57.7 years (range, 31-85 years). Clinical characteristics were similar across RT groups. The outcome of partial and complete PR was similar for IMRT and 3DCRT (48.1%, 23.1% vs. 31.7%, 23.3%), respectively. After adjusting for gender, age, and pre-RT chemotherapy type, IMRT and pretreatment PET and/or MRI imaging was significantly associated with increased odds for complete and partial response (OR =2.95, 95% CI: 1.21-7.25, P=0.018; OR =14.70, 95% CI: 3.69-58.78, P<0.0001). Additionally, IMRT was associated with reduced rates of dehydration, dermatitis, rectal pain, rectal bleeding, and diverting ostomy (P<0.05). Overall rates of grade 2 and higher toxicities were significantly reduced in IMRT vs. 3DCRT after adjusting for confounders (OR =0.27, 95% CI: 0.08-0.87).

Conclusions

NeoCRT IMRT with pretreatment PET and/or MRI for LARC leads to reduced acute toxicities and improved PR compared to 3DCRT. Given the challenges associated with prospective validation of these data, IMRT with pretreatment PET and/or MRI should be considered standard treatment for LARC.

Outcome of bowel function following anterior resection for rectal cancer-an analysis using the low anterior resection syndrome (LARS) score

PURPOSE

Severity of anorectal dysfunction after low anterior resection is associated with various patient- and treatment-related factors. We aimed to quantify anorectal dysfunction after treatment for rectal cancer using the low anterior resection syndrome (LARS) score.

METHODS

We retrieved from a prospective database 331 eligible patients on whom anterior resection for rectal cancer had been performed from 2000 to 2014. All patients were sent a LARS score accompanied by a supplementary questionnaire. Response rate was 78.8% (261 patients). The main outcome measure was the relation of the LARS score to potentially associated patient and treatment factors. Secondary endpoints were further measures that reflect anorectal dysfunction, e.g., Vaizey score.

RESULTS

Overall, 144 (55.2%) patients exhibited scores > 20 reflecting minor (n = 51 (19.5%)) or major (n = 93 (35.6%)) LARS. A significant difference for scores > 20 was found for intersphincteric resection (IR, 73.2% affected patients) compared to total mesorectal excision (TME, 58.4%) and partial mesorectal excision (PME, 38.0%, p = 0.001). Radio(chemo)therapy resulted in LARS scores > 20 in 64.6% of patients compared to 43.1% in patients without irradiation (p = 0.001). Type of procedure (TME and IR as compared to PME), radio(chemo)therapy, and younger age were independently associated with LARS in logistic regression analysis. However, younger age remained the only independent factor for higher scores after exclusion of PME.

CONCLUSIONS

The LARS score identified a substantial proportion of patients after surgery for rectal cancer with anorectal dysfunction. The extent of surgical procedure is independently associated with the severity of symptoms whereas the role of radiotherapy needs further assessment.