In silico comparison of the dosimetric impacts of a greater omentum spacer for abdominal and pelvic tumors in carbon-ion, proton and photon radiotherapy

Post-Chemoradiation Metastatic, Persistent and Resistant Nodes in Locally Advanced Rectal Cancer: Metrics and Their Impact on Long-Term Outcome

BACKGROUND

The purpose of this study was to evaluate the long-term oncological progression pattern of locally advanced rectal cancer patients with post-neoadjuvant nodal metastatic disease (ypN+) and correlate potential prognostic features associated with proven radiochemoresistant nodal biology.

METHODS

Individual patient data (100 variables) from a 20-year consecutive single-institution multidisciplinary experience (1995-2015), delivering multimodal therapy to rectal cancer patient candidates for radical treatment, including a neoadjuvant component and surgical resection with or without intraoperative radiotherapy followed by optional adjuvant chemotherapy. The ypN+ disease data was registered in the context of initial staging categories post-neoadjuvant T status (ypT).

RESULTS

Data on 487 patients showed histologically confirmed diagnoses of metastatic nodal disease in 108 specimens (ypN+, 22.1). There was a significant age difference (p = 0.009) between the ypN groups: age ≥ 65 was 57.6% in pN0 and 43.5% in ypN+ and patients aged < 65 constituted 42.4% of pN0 and 56.5% of ypN+. According to the clinical stage there were statistically significant differences (p = 0.001) in the categories' distribution: ypN+ patients 10.8% were stage II and 89.2% were stage III. Univariant analysis on outcome variables showed statistically significant differences in overall survival at 7 years (63.8% vs. 55.7%, p = 0.016) disease-free survival (DFS) (78% vs. 53.8%, p = 0.000) and local recurrence-free survival (LRFS) (93.6% vs. 84%, p = 0.002).

CONCLUSIONS

The presence of nodal metastases (ypN+) after neoadjuvant therapy containing long-course pelvic irradiation severely impacts the long-term outcome for patients with locally advanced rectal cancer and correlates with multiple clinical and therapeutic variable metrics. Implementation of local and systemic therapies should be adapted and intensified in relation to the finding of ypN+ category in surgical specimens.

Rotating Gantries Provide Individualized Beam Arrangements for Charged Particle Therapy

PURPOSE

This study evaluates beam angles used to generate highly individualized proton therapy treatment plans for patients eligible for carbon ion radiotherapy (CIRT).

METHODS AND MATERIALS

We retrospectively evaluated patients treated with pencil beam scanning intensity modulated proton therapy from 2015 to 2020 who had indications for CIRT. Patients were treated with a 190° rotating gantry with a robotic patient positioning system. Treatment plans were individualized to provide maximal prescription dose delivery to the tumor target volume while sparing organs at risk. The utilized beam angles were grouped, and anatomic sites with at least 10 different beam angles were sorted into histograms.

RESULTS

A total of 467 patients with 484 plans and 1196 unique beam angles were evaluated and characterized by anatomic treatment site and the number of beam angles utilized. The most common beam angles used were 0° and 180°. A wide range of beam angles were used in treating almost all anatomic sites. Only esophageal cancers had a predominantly unimodal grouping of beam angles. Pancreas cancers showed a modest grouping of beam angles.

CONCLUSIONS

The wide distribution of beam angles used to treat CIRT-eligible patients suggests that a rotating gantry is optimal to provide highly individualized beam arrangements.

Is omentectomy necessary in the treatment of benign or malignant abdominal pathologies? A systematic review

BACKGROUND

The omentum is an organ that is easily sacrificed during abdominal surgery. The scope of omentectomy and whether a routine omentectomy should be performed are still unknown.

AIM

To review the literature in order to determine the physiological functions of the omentum and the roles it plays in pathological events in order to reveal the necessity for removal and preservation of the omentum.

METHODS

A clinical review of the English language literature based on the MEDLINE (PubMed) database was conducted using the keywords: “abdomen”, “gastrointestinal”, “tumor”, “inflammation”, “omental flap”, “metastasis”, “omentum”, and “omentectomy”. In addition, reports were also identified by systematically reviewing all references in retrieved papers.

RESULTS

The omentum functions as a natural barrier in areas where pathological processes occur in the abdominal cavity. The omentum limits and controls inflammatory and infectious pathologies that occur in the abdomen. It also aids in treatment due to its cellular functions including lymphatic drainage and phagocytosis. It shows similar behavior in tumors, but it cannot cope with increasing tumor burden. The stage of the disease changes due to the tumor mass it tries to control. Therefore, it is considered an indicator of poor prognosis. Due to this feature, the omentum is one of the first organs to be sacrificed during surgical procedures. However, there are many unknowns regarding the role and efficacy of the omentum in cancer.

CONCLUSION

The omentum is a unique organ that limits and controls inflammatory processes, foreign masses, and lesions that develop in the abdominal cavity. Omental flaps can be used in all anatomical areas, including the thorax, abdomen, pelvis, and extremities. The omentum is an organ that deserves the title of the abdominal policeman. It is generally accepted that the omentum should be removed in cases where there is tumor invasion. However, the positive or negative contribution of omental resection in the treatment of abdominal pathologies should be questioned.

Prediction of the minimum spacer thickness required for definitive radiotherapy with carbon ions and photons for pelvic tumors: an in silico planning study using virtual spacers

We aimed to predict the minimum distance between a tumor and the gastrointestinal (GI) tract that can satisfy the dose constraint by creating simulation plans with carbon-ion (C-ion) radiotherapy (RT) and photon RT for each case assuming insertion of virtual spacers of various thicknesses. We enrolled 55 patients with a pelvic tumor adjacent to the GI tract. Virtual spacers were defined as the overlap volume between the GI tract and the volume expanded 7-17 mm from the gross tumor volume (GTV). Simulation plans (70 Gy in 35 fractions for at least 95% of the planning target volume [PTV]) were created with the lowest possible dose to the GI tract under conditions that meet the dose constraints of the PTV. We defined the minimum thickness of virtual spacers meeting D2 cc of the GI tract <50 Gy as 'MTS'. Multiple regression was used with explanatory variables to develop a model to predict MTS. We discovered that MTSs were at most 9 mm and 13 mm for C-ion RT and photon RT plans, respectively. The volume of overlap between the GI tract and a virtual spacer of 14 mm in thickness (OV14)-PTV was found to be the most important explanatory variable in the MTS prediction equation for both C-ion and photon RT plans. Multiple R2 values for the regression model were 0.571 and 0.347 for C-ion RT and photon RT plans, respectively. In conclusion, regression equations were developed to predict MTS in C-ion RT and photon RT.