Validation of an MRI-only planning workflow for definitive pelvic radiotherapy.

PURPOSE: Previous work on Magnetic Resonance Imaging (MRI) only planning has been applied to limited treatment regions with a focus on male anatomy. This research aimed to validate the use of a hybrid multi-atlas synthetic computed tomography (sCT) generation technique from a MRI, using a female and male atlas, for MRI only radiation therapy treatment planning of rectum, anal canal, cervix and endometrial malignancies. PATIENTS AND METHODS: Forty patients receiving radiation treatment for a range of pelvic malignancies, were separated into male (n = 20) and female (n = 20) cohorts for the creation of gender specific atlases. A multi-atlas local weighted voting method was used to generate a sCT from a T1-weighted VIBE DIXON MRI sequence. The original treatment plans were copied from the CT scan to the corresponding sCT for dosimetric validation. RESULTS: The median percentage dose difference between the treatment plan on the CT and sCT at the ICRU reference point for the male cohort was - 0.4% (IQR of 0 to - 0.6), and - 0.3% (IQR of 0 to - 0.6) for the female cohort. The mean gamma agreement for both cohorts was > 99% for criteria of 3%/2 mm and 2%/2 mm. With dose criteria of 1%/1 mm, the pass rate was higher for the male cohort at 96.3% than the female cohort at 93.4%. MRI to sCT anatomical agreement for bone and body delineated contours was assessed, with a resulting Dice score of 0.91 ± 0.2 (mean ± 1 SD) and 0.97 ± 0.0 for the male cohort respectively; and 0.96 ± 0.0 and 0.98 ± 0.0 for the female cohort respectively. The mean absolute error in Hounsfield units (HUs) within the entire body for the male and female cohorts was 59.1 HU ± 7.2 HU and 53.3 HU ± 8.9 HU respectively. CONCLUSIONS: A multi-atlas based method for sCT generation can be applied to a standard T1-weighted MRI sequence for male and female pelvic patients. The implications of this study support MRI only planning being applied more broadly for both male and female pelvic sites. Trial registration This trial was registered in the Australian New Zealand Clinical Trials Registry (ANZCTR) ( www.anzctr.org.au ) on 04/10/2017. Trial identifier ACTRN12617001406392.

Post-transplant lymphoproliferative disorder in the pelvis successfully treated with consolidative radiotherapy.

BACKGROUND: Post-transplant lymphoproliferative disorders (PTLDs) are aggressive malignancies which represent one of the major post-transplant complications. However, treatment options vary significantly and localized disease may be curatively treated with radiotherapy (RT) or surgery. We report a case of recurrent rectal PTLD, which was successfully treated by chemoimmunotherapy followed by RT. CASE PRESENTATION: We describe a patient who developed a rectal lymphoproliferative lesion 11 years after kidney transplant, which was successfully treated with consolidative RT using 25.4 Gy sequential to chemoimmunotherapy (R-CHOP). RT was well tolerated and the patient showed no signs of grade 3 or 4 toxicity. This patient is free of recurrence 52 months after RT, with an overall survival of 62 months since diagnosis. CONCLUSION: Conventionally fractionated moderate-dose RT appears to be a tolerable and effective treatment option for localized PTLD if a sufficient systemic treatment cannot be applied.

A novel arc geometry setting for pelvic radiotherapy with extensive nodal involvement.

The aim of this study was to find optimal planning approach for large planning targets with complicated geometry requiring wide field openings. The study presents a novel approach for arc geometry design for pelvic targets with extensive nodal involvement. A total of 15 patients with anorectal carcinoma or vulvar cancer were selected retrospectively. For each patient, one seven-field IMRT plan and three VMAT plans were calculated: one with two 360° arcs with no limitations for the field size (VMATw); one with two asymmetrically field-size-restricted 360° arcs (VMATr); and the proposed novel approach which consisted of one 360° arc with the field size restricted to the central PTV, and another arc divided into two 180° arcs, restricting the field sizes with the focus on the lymph nodes. The techniques were compared in terms of PTV coverage (VPTV(95%)), dose maximum (D(max)), dose conformity index (CI), homogeneity index (HI), and organs at risk doses. The proposed novel approach with one full and two half arcs tended to have better PTV coverage (VPTV(95%) = 97% ± 2%, compared to 95% ± 3%, 95% ± 3%, and 97% ± 2% in VMATw, VMATr, and 7f-IMRT, respectively) and lower maxima (D(max) = 107% ± 1%, compared to 110% ± 3%, 110% ± 4%, and 110% ± 4% in VMATw, VMATr, and 7f-IMRT, respectively); and lower or equal organs at risk doses. The superiority of the proposed technique (CI = 1.16 ± 0.05, HI = 9 ± 2) was more pronounced compared with the VMATw plans (CI = 1.41 ± 0.10, paired t-test p < 0.001; HI = 12 ± 2, p < 0.001), but the proposed technique was slightly better also in comparison with the VMATr plans (CI = 1.21 ± 0.07, p < 0.001; HI= 11 ± 4, p = 0.015) and 7f-IMRT plans (CI = 1.18 ± 0.03, p = 0.016; HI = 10 ± 2, p = 0.215). Radiotherapy treatment planning for large and complicated treatment volumes benefits not only from restricting the field size but also from careful field design that considers PTV geometry. This optimizes multileaf collimator movements, leading to better dose conformity and homogeneity.

Anal wall thickness under normal and inflammatory conditions of the anorectum as determined by endoluminal ultrasonography.

OBJECTIVES: To determine the normal dimensions of the anal wall and if there were detectable differences in inflammatory disorders. METHODS: A cross-sectional survey was performed on all patients referred to a university anorectal ultrasound clinic who had either perianal Crohn's disease (17 patients), ileoanal pouches (15 patients), perianal fistula (15 patients), or previous radiation to the rectum (5 patients). Results were compared to 40 normal controls. Anal wall thickness (AWT), mucosa, submucosa, internal sphincter thickness (MSIT), and external sphincter thickness (EST) were measured or calculated. Intra- and interobserver reliability was assessed. RESULTS: The mean AWT was 14.8 mm (95% CI: 14.0-15.6), mean EST was 8.3 mm (95% CI: 7.6-9.0), and the mean MSIT was 6.5 mm (95% CI: 5.8-7.2) in the control subjects. Measurements did not differ significantly with sex or with an increase in age. Patients with perianal Crohn's disease, ileoanal pouches with septic complications, and previous local radiotherapy had significant increases in anal wall thickness. In Crohn's disease, the significant increase was in MSIT, whereas, in the pouch patients, the increase was in the EST. Reliability studies demonstrated a learning curve with experience and a better correlation with determination of AWT than MSIT. CONCLUSIONS: Patients with anorectal inflammatory conditions have increased thickness in anal wall dimensions.

Endoscopic Nd:YAG laser in the palliative treatment of advanced low rectal carcinoma in Singapore.

We used the Nd:YAG laser to palliate symptoms of bleeding and obstruction in 27 cases of rectal carcinoma. Twenty of these patients had advanced inoperable rectal carcinoma, three were at high surgical risk, and four refused surgery. Obstructive symptoms were the main complaint in 10 cases, while 17 patients presented with bleeding. Good palliation of obstructive symptoms was achieved in all obstructive cases with one laser treatment session. However, bleeding tumors required an average of two sessions for complete hemostasis. There were no major complications; minor complications of bleeding after treatment occurred in two patients. Good symptomatic relief was achieved in all cases. The mean survival for all patients was five months. Nd:YAG laser therapy is a safe and efficacious means for palliation of obstructive symptoms and bleeding in advanced rectal carcinoma.