Risk factors related to interfractional variation in whole pelvic irradiation for locally advanced pelvic malignancies

Prospective evaluation of the setup errors and its impact on safety margin for cervical cancer pelvic conformal radiotherapy

Aim

The primary objective was to assess set-up errors (SE) and secondary objective was to determine optimal safety margin (SM).

Background

To evaluate the SE and its impact on the SM utilizing electronic portal imaging (EPI) for pelvic conformal radiotherapy.

Material and methods

20 cervical cancer patients were enrolled in this prospective study. Supine position with ankle and knee rest was used during CT simulation. The contouring was done using consensus guideline for intact uterus. 50 Gy in 25 fractions were delivered at the isocenter with ≥95% PTV coverage. Two orthogonal (Anterior and Lateral) digitally reconstructed radiograph (DRR) was constructed as a reference image. The pair of orthogonal [Anterior-Posterior and Right Lateral] single exposure EPIs during radiation was taken. The reference DRR and EPIs were compared for shifts, and SE was calculated in the X-axis, Y-axis, and Z-axis directions.

Results

320 images (40 DRRs and 280 EPIs) were assessed. The systematic error in the Z-axis (AP EPI), X-axis (AP EPI), and Y-axis (Lat EPI) ranged from -12.0 to 11.8 mm, -10.3 to 7.5 mm, and -8.50 to 9.70 mm, while the random error ranged from 1.60 to 6.15 mm, 0.59 to 4.93 mm, and 1.02 to -4.35 mm. The SM computed were 7.07, 6.36, and 7.79 mm in the Y-axis, X-axis, and Z-axis by Van Herk's equation, and 6.0, 5.51, and 6.74 mm by Stroom's equation.

Conclusion

The computed SE helps defining SM, and it may differ between institutions. In our study, the calculated SM was approximately 8 mm in the Z-axis, 7 mm in X and Y axis for pelvic conformal radiotherapy.

Challenges and impact of patient obesity in radiation therapy practice

INTRODUCTION

The prevalence of obesity is rapidly increasing globally and has tripled between 1975 and 2016. Obesity is reported within the literature as having a significant impact on medical practice, professionals, imaging departments and healthcare systems. It is not known how this epidemic will impact radiation therapists' working environment and practice. The aim of this study is to explore the perceived challenges and impacts of patient obesity on radiation therapy practice from the perception of radiation therapists.

METHODS

All radiation therapists working in the Republic of Ireland were invited to participate. Two focus groups were conducted with 6 and 7 participants respectively. A seven staged method of analysis, using a computerised long table approach was developed and used to analyse the data and create themes related to radiation therapists' perception of managing obese patients.

RESULTS

Perceived challenges from the radiation therapists were difficulties; (1) Setting up the patient (2) Imaging (3) communication and emotional impact.

CONCLUSION

An array of concerns were raised during this research about the increase and impact of obese patients on radiation therapists working environment. This study suggests that obese patients can present additional challenges to radiation therapists' current work practices. It is imperative that we recognise the additional challenges this patient cohort add to daily workflow. Further research is needed to identify the common key issues and how to manage this specific patient group.

IMPLICATIONS FOR PRACTICE

At the moment there are no specific management strategies/policies in place for managing obese patients; this study suggests that it is something we need to consider implementing as standard in radiation therapy departments.

Proton therapy- the modality of choice for future radiation therapy management of Prostate Cancer?

BACKGROUND

Proton Therapy (PR) is an emerging treatment for prostate cancer (Pca) patients. However, limited and conflicting data exists regarding its ability to result in fewer bladder and rectal toxicities compared to Photon Therapy (PT), as well as its cost efficiency and plan robustness.

MATERIALS AND METHODS

An electronic literature search was performed to acquire eligible studies published between 2007 and 2018. Studies comparing bladder and rectal dosimetry or Gastrointestinal (GI) and Genitourinary (GU) toxicities between PR and PT, the plan robustness of PR relative to motion and its cost efficiency for Pca patients were assessed.

RESULTS

28 studies were eligible for inclusion in this review. PR resulted in improved bladder and rectal dosimetry but did not manifest as improved GI/GU toxicities clinically compared to PT. PR plans were considered robust when specific corrections, techniques, positioning or immobilisation devices were applied. PR is not cost effective for intermediate risk Pca patients; however PR may be cost effective for younger or high risk Pca patients.

CONCLUSION

PR offers improved bladder and rectal dosimetry compared to PT but this does not specifically translate to improved GI/GU toxicities clinically. The robustness of PR plans is acceptable under specific conditions. PR is not cost effective for all Pca patients.

Impact of body mass index on treatment outcome of neoadjuvant chemoradiotherapy in locally advanced rectal cancer

AIM

To determine the effect of obesity, measured by body mass index (BMI), on tumor response and surgical outcome in patients with locally advanced rectal cancer (LARC) undergoing neoadjuvant chemoradiotherapy (nCRT) and radical surgery.

METHOD

LARC patients undergoing nCRT and radical surgery from 2008 to 2014 were included and divided into three groups: non-obese (BMI < 25.0 kg/m2), obese I (BMI 25.0-29.9 kg/m2), and obese II (BMI ≥ 30.0 kg/m2). Tumor response, surgical and oncological outcome were compared between groups. Multivariate analyses were performed to identify risk factors for local recurrence.

RESULTS

A total of 522 LARC patients were analyzed (407 non-obese, 93 obese I, 22 obese II). Post-operative complications did not differ between groups. Increased BMI was associated with poorer T downstaging and Rectal Cancer Regression Grade (P = 0.116, P = 0.036). With a mean follow-up of 57 months, the 5-year overall survival and distant metastasis rates did not differ between groups (P = 0.861, P = 0.116). The 5-year local recurrence rate in obese II patients was 14.6%, higher than that in non-obese and obese I groups (P = 0.015). Cox regression analysis demonstrated that BMI ≥30 kg/m2 (HR = 6.187, P = 0.010) was significantly associated with increased risk for local recurrence.

CONCLUSION

Obesity was associated with poorer T downstaging and Rectal Cancer Regression Grade, and thus poor local control in LARC following nCRT in Asian patients. More effective treatment strategies to improve treatment outcome for obese patients with LARC are warranted.

Influence of position and radiation technique on organs at risk in radiotherapy of rectal cancer

The influence of the position and radiation technique on the organs at risk (OARs) in radiotherapy of rectal cancer was evaluated. The relationship between the volume of irradiated small bowel (VSB) and acute bowel toxicity was determined. A total of 97 cases of rectal cancer were retrospectively randomized to receive radiotherapy with the designated treatment positions and radiation plans. Among 64 patients in the supine position, 32 patients were given three-dimensional conformal radiotherapy (3DCR) and 32 patients were subjected to intensity-modulated radiation therapy (IMRT) respectively. The rest 33 patients were treated with 3DCRT in the prone position with a belly board. The VSB was calculated for doses from 5 to 45 Gy at an interval of 5 Gy. With prescription dose in planned target volume (PTV) of 50 Gy, the dose distribution, conformal index for PTV (CI_PTV), dose-volume histogram (DVH) of OARs, the correlation of VSB and the acute toxicity were compared. The results were shown as follows: (1) Among the 3 methods, there were no differences in PTV's converge including V95 and D95; (2) For IMRT under a supine position, CI_PTV was closest to 1, the mean dose of small bowel decreased (P<0.05), and the mean VSB from V30 to V45 significantly decreased (P<0.05). (3) For 3DCRT with a belly board under a prone position, the mean dose and the mean VSB from 40 to 45 Gy were less than those for 3DCRT under a supine position (P<0.05); (4) Mean proportion of VSB was significantly greater in the patients experiencing diarrhea grade 2-4 than in those with diarrhea grade 0-1 at dose levels from V30 to V45 (P<0.05). It was concluded that for the radiotherapy of rectal cancer, IMRT technique might decrease the high-dose VSB to reduce the risk of acute injury. 3DCRT with a belly board under a prone position is superior to 3DCRT under a supine position, which could be a second choice for radiation of rectal cancer.

A randomized study of the effect of patient positioning on setup reproducibility and dose distribution to organs at risk in radiotherapy of rectal cancer patients

Background

The patient positioning in pelvic radiotherapy (RT) should be decided based on both reproducibility and on which position that yields the lowest radiation dose to the organs at risk (OAR), and thereby less side effects to patients. The present randomized study aimed to evaluate the influence of patient positioning on setup reproducibility and dose distribution to OAR in rectal cancer patients.

Methods

Ninety-one patients were randomized into receiving RT in either supine or prone position. The recruitment period was from 2005 to 2008. Position deviations were derived from electronic portal image registrations, and setup errors were defined as deviations between the expected and the actual position of bony landmarks. Setup deviations were expressed into three table shift values (∆x, ∆y, ∆z) from which the deviation vector \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left|\overrightarrow{v}\right| $$\end{document}v→ were calculated. The estimated lengths of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left|\overrightarrow{v}\right| $$\end{document}v→ defined the main outcome and were compared between prone and supine positions using linear mixed model statistics. The mean volume of each 5 Gy increments between 5 and 45 Gy was calculated for the small bowel and the total bowel, and the dose volumes were compared between prone and supine position.

Results and conclusion

Data from 83 patients was evaluable. The mean \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \left|\overrightarrow{v}\right| $$\end{document}v→ was 5.8 mm in supine position and 7.1 mm in prone position (p = 0.024), hence the reproducibility was significantly superior in supine position. However, the difference was marginal and may have borderline clinical importance. The irradiated volumes of the small bowel and the total bowel were largest in the supine position for all dose levels, but none of those were significantly different. The patient positioning in RT of rectal cancer patients may therefore be decided based on other factors such as the most comfortable position for the patients.

Obesity and cancer: at the crossroads of cellular metabolism and proliferation

Obesity is associated with an increased risk of cancer. The mechanisms underlying this association include but are not limited to increased systemic inflammation, an anabolic hormonal milieu, and adipocyte-cancer crosstalk, aberrant stimuli that conspire to promote neoplastic transformation. Cellular proliferation is uncoupled from nutrient availability in malignant cells, promoting tumor progression. Elucidation of the mechanisms underlying the obesity-cancer connection will lead to the development of novel metabolism-based agents for cancer prevention and treatment.

Radiotherapy is effective for desmoid tumors (aggressive fibromatosis) - long-term results of a German multicenter study

BACKGROUND

Desmoids (aggressive fibromatosis) are defined as benign neoplasms of the connective tissue that arise from the deep muscle fascia, aponeurosis, tendons, and scar tissue. Recurrence rates between 40 and 80% were reported after surgery alone. We addressed the impact of radiation therapy (RT) in the management of aggressive fibromatosis.

PATIENTS AND METHODS

A large literature review was performed, and the data was compared with the results of a multicenter study of the German Cooperative Group on Radiotherapy for Benign Diseases (GCG-BD).

RESULTS

This analysis included 52 patients treated with RT. 37 patients received postoperative RT (20 patients after R2 resection and 17 patients after R1 resection). 15 patients received RT alone (6 patients with inoperable primary tumor and 9 patients with inoperable recurrent tumor). In the case of postoperative RT, a median dose of 50 Gy (range 50-60 Gy) was used; for definitive RT, a median dose of 55 Gy (range 55-65 Gy) was used. The local control rate was 79% for the whole group. The median follow-up was 44 month (range 8-62 months).

CONCLUSION

Given the large number of patients, these data show that RT is highly effective in the treatment of desmoid tumors. RT is an attractive alternative to mutilating surgery.

Whole abdominopelvic radiotherapy in the palliative treatment of pseudomyxoma peritonei

BACKGROUND

Pseudomyxoma peritonei (PMP) is a rare clinical syndrome characterized by mucinous peritoneal disease arising from disseminated peritoneal adenomucinosis. Primary treatment involves a combination of cytoreductive surgery with hyperthermic intraperitoneal chemotherapy (HIPEC). There is no consensus on the proper treatment of recurrent PMP. In selected patients, repeated cytoreductive surgery with or without HIPEC might improve outcome. However, every repeated debulking procedure becomes less effective with increased morbidity.

CASE REPORT

We present a case of a patient with intestinal obstruction caused by recurrent pseudomyxoma peritonei. We treated the patient with whole abdominopelvic radiotherapy (WAPRT) using intensity-modulated arc therapy (IMAT) to a total dose of 33 Gy, delivered in 22 daily fractions. The treatment was well tolerated and resulted in resolution of the obstruction for a period of 24 months.

CONCLUSION

To the best of our knowledge, we present the first case report showing the possibility of resolving intestinal obstruction with WAPRT in a patient with recurrent PMP. It is our opinion that WAPRT delivered by IMAT, in analogy with ovarian cancer, should be considered as a palliative treatment option in managing patients with recurrent PMP especially in case of obstruction.

Set-up uncertainty during breast radiotherapy. Image-guided radiotherapy for patients with initial extensive variation

PURPOSE

The aim of this work was to establish a customized strategy for image-guided radiotherapy during whole breast irradiation. Risk factors associated with extensive errors were assessed.

METHODS AND MATERIALS

A series of 176 consecutive breasts in 174 patients were retrospectively assessed. Electronic portal images from 914 medial and 807 lateral directions were reviewed. On the basis of the chest wall, the deviations between the simulation and each treatment were measured. The systematic (Σ) and random error (σ) of population, and the planning target volume (PTV) margin (2 Σ + 0.7σ) were calculated for each direction. Extensive set-up errors were defined as the fraction over the PTV margins in any direction. For extensive set-up errors, χ(2) tests and logistic regression analyses were conducted.

RESULTS

The medial and lateral PTV margins for the right-left, superior-inferior, and anterior-posterior axes and the rotation of collimator were 2.6 and 2.4 mm, 4.6 and 4.6 mm, and 3.1 and 3.3 mm and 2.8 and 2.9 ° and cut-off values for extensive errors were 3, 5, and 4 mm and 3 °, respectively. In χ(2) tests, tumor in upper outer quadrant (p = 0.012) and chest wall thickness ≥ 2.0 cm (p = 0.003) for medial portals and age group (p = 0.036) for lateral portals were associated with extensive errors. In multivariate tests, the extensive error on the initial fraction had a high probability of extensive set-up errors in both medial (OR = 4.26, p < 0.001) and lateral portals (OR = 3.07, p < 0.001).

CONCLUSION

In terms of the set-up uncertainty during breast irradiation, patients with extensive error in the initial treatment should be closely observed with serial image-guided radiotherapy.