Contraintes de doses aux organes à risque en radiothérapie conformationnelle et stéréotaxique : intestin grêle et duodénum

Dealing with rectum motion during radiotherapy: How can we anticipate it?

Introduction

Intra- and inter-fraction rectum motion is important for pelvic radiotherapy (RT). This study assesses how RT session duration, the presence or the absence of an intra-rectal tumour, and the distance from the anorectal junction (ARJd) impact rectal motion.

Materials and methods

Analyses used cone-beam computed tomographies (CBCTs) from RT patients treated for rectal and prostate cancer. Three structures were evaluated: (1) the entire rectum in patients without a rectal tumour (RectumProstate); (2) the non-invaded portion (RectumRectum) and (3) the tumour-invaded portion (RectumTumour) in rectal cancer patients.Intrafraction motion was assessed using the Hausdorff distance 95% and the Mean distance-to-agreement between structures delineated on the first CBCT and the 2 subsequent CBCTs within a same RT session. Interfraction motion was quantified by comparing structures delineated on the planning-CT and the first CBCT of each session.Linear mixed model evaluated rectum motion in relation to time, tumour presence, and ARJd, respectively.

Results

We included 10 patients with and 10 without rectal cancer, collecting 385 CBCTs. A significant correlation (p < 0.05) between rectum motion and RT session duration was found. Intrafraction motion was significantly higher in prostate cancer patients (RectumProstate motion > RectumRectum and RectumTumour, p < 0.01). For interfraction motion, only the mean distance to agreement was significantly higher for RectumProstate (p < 0.05). Motion increased significantly with ARJd for all three structures (p < 0.001).

Conclusions

Session duration, absence of a tumour, and ARJd are associated with larger intra- and interfraction rectal motion. This highlights the need for tailored RT treatment, including online-adaptive RT, to manage intra- and interfraction variations. Rectal motion should be handled differently for patients with prostate cancer and those with rectal cancer.

Deep learning application for abdominal organs segmentation on 0.35 T MR-Linac images

Introduction

Linear accelerator (linac) incorporating a magnetic resonance (MR) imaging device providing enhanced soft tissue contrast is particularly suited for abdominal radiation therapy. In particular, accurate segmentation for abdominal tumors and organs at risk (OARs) required for the treatment planning is becoming possible. Currently, this segmentation is performed manually by radiation oncologists. This process is very time consuming and subject to inter and intra operator variabilities. In this work, deep learning based automatic segmentation solutions were investigated for abdominal OARs on 0.35 T MR-images.

Methods

One hundred and twenty one sets of abdominal MR images and their corresponding ground truth segmentations were collected and used for this work. The OARs of interest included the liver, the kidneys, the spinal cord, the stomach and the duodenum. Several UNet based models have been trained in 2D (the Classical UNet, the ResAttention UNet, the EfficientNet UNet, and the nnUNet). The best model was then trained with a 3D strategy in order to investigate possible improvements. Geometrical metrics such as Dice Similarity Coefficient (DSC), Intersection over Union (IoU), Hausdorff Distance (HD) and analysis of the calculated volumes (thanks to Bland-Altman plot) were performed to evaluate the results.

Results

The nnUNet trained in 3D mode achieved the best performance, with DSC scores for the liver, the kidneys, the spinal cord, the stomach, and the duodenum of 0.96 ± 0.01, 0.91 ± 0.02, 0.91 ± 0.01, 0.83 ± 0.10, and 0.69 ± 0.15, respectively. The matching IoU scores were 0.92 ± 0.01, 0.84 ± 0.04, 0.84 ± 0.02, 0.54 ± 0.16 and 0.72 ± 0.13. The corresponding HD scores were 13.0 ± 6.0 mm, 16.0 ± 6.6 mm, 3.3 ± 0.7 mm, 35.0 ± 33.0 mm, and 42.0 ± 24.0 mm. The analysis of the calculated volumes followed the same behavior.

Discussion

Although the segmentation results for the duodenum were not optimal, these findings imply a potential clinical application of the 3D nnUNet model for the segmentation of abdominal OARs for images from 0.35 T MR-Linac.

[Duodenal bleeding due to metastasis from lung adenocarcinoma controlled by radiotherapy: A case report and literature review]

INTRODUCTION

Gastrointestinal (GI) metastases in lung cancer rarely occur.

CASE REPORT

We report here the case of a 43-year-old male active smoker who was admitted to our hospital for cough, abdominal pain and melena. Initial investigations revealed poorly differentiated adenocarcinoma of the superior-right lobe of the lung: positive for thyroid transcription factor-1 and negative for protein p40 and for antigen CD56, with peritoneal, adrenal and cerebral metastasis, as well as anemia requiring major transfusion support. Over 50% of cells were positive for PDL-1, and ALK gene rearrangement was detected. GI endoscopy showed a large ulcerated nodular lesion of the genu superius with active intermittent bleeding, as well as an undifferentiated carcinoma with positivity for CK AE1/AE3 and TTF-1, and negativity for CD117, corresponding to metastatic invasion originating from lung carcinoma. Palliative immunotherapy with pembrolizumab was proposed, followed by targeted therapy with brigatinib. Gastrointestinal bleeding was controlled with a single 8Gy dose of haemostatic radiotherapy.

CONCLUSION

GI metastases are rare in lung cancer and present nonspecific symptoms and signs but no characteristic endoscopic features. GI bleeding is a common revelatory complication. Pathological and immunohistological findings are critical to diagnosis. Local treatment is usually guided by the occurrence of complications. In addition to surgery and systemic therapies, palliative radiotherapy may contribute to bleeding control. However, it must be used cautiously, given a present-day lack of evidence and the pronounced radiosensitivity of certain gastrointestinal tract segments.

Organs at risk radiation dose constraints

Dose constraints are essential for performing dosimetry, especially for intensity modulation and for radiotherapy under stereotaxic conditions. We present the update of the recommendations of the French society of oncological radiotherapy for the use of these doses in classical current practice but also for reirradiation.

Hepatic tumours and radiotherapy

We present the update of the recommendations of the French society of oncological radiotherapy on hepatic tumours. Recent technological progress led to develop the concept of focused liver radiation therapy. We must distinguish primary and secondary tumours, as the indications are restricted and must be discussed as an alternative to surgical or medical treatments. The tumour volume, its liver location close to the organs at risk determine the irradiation technique (repositioning method, total dose delivered, dose fractionation regimens). Tumour (and liver) breathing related motions should be taken into account. Strict dosimetric criteria must be observed with particular attention to the dose-volume histograms of non-tumoral liver as well as of the hollow organs, particularly in case of hypofractionated high dose radiotherapy "under stereotaxic conditions". Stereotactic body radiotherapy is being evaluated and is often preferred to radiofrequency for primary or secondary tumours (usually less than 5cm). An adaptation can be proposed, with a conformal fractionated irradiation protocol with or without intensity modulation, for hepatocellular carcinomas larger than 5cm.

Unrecognized digestive toxicities of radiation therapy

The aim of this article is to review unrecognized toxicities resulting from radiation therapy of digestive neoplasms. Due to their precocious occurrence, acute toxicities are well-known by radiation oncologist, and their treatment well-established. Thus, acute toxicities will not be described in this review. We will focus on incidence, diagnosis, and management of late and uncommon toxicities occurring in the digestive tract and digestive organs. Prevention, by respecting healthy tissues constraints, is the main tool to reduce incidence of those rare complications. Nonetheless, once installed, late toxicities remain a major burden in terms of quality of life and can even be life threatening. Hence, information and education about their diagnosis and management is important.

Neobladder and ablative pelvic radiotherapy: still a taboo?

The presence of a neobladder constitutes a limitation for the radiation oncologist, as there is no clear evidence about its tolerance to radiotherapy (RT). The limited literature only concerns the conventional postoperative treatment in patients with bladder cancer after cystectomy. Here we report a case of a patient with neobladder who underwent a stereotactic RT for a pelvic recurrence of disease, with response to treatment and no toxicity to the neobladder. This case represents a promising example of the chance to perform RT with ablative intent, using advanced techniques, even on lesions close to the neobladder.

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.