The influence of radiotherapy techniques on the plan quality and on the risk of secondary tumors in patients with pituitary adenoma

Radiation therapy in functioning and no functioning pituitary neuroendocrine tumor: systematic review of the recent literature after 2011

Neuroendocrine pituitary tumor, a benign cells proliferation, can cause significant morbidity due to its local invasiveness and secretory properties. Historically, radiotherapy has been employed as a second or third-line treatment option, with studies dating back to the mid-20th century. However, advancements in radiotherapy techniques, such as intensity-modulated radiation therapy (IMRT), stereotactic radiosurgery, and proton therapy, have revolutionized treatment approaches. This review aims to critically evaluate the recent literature (2011-2022) on the use of radiotherapy in both functioning and nonfunctioning neuroendocrine pituitary tumor. We employed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology to systematically analyze 52 articles, focusing on local and hormonal control, radiotherapy protocols, and treatment-related side effects.

Recommendations for reducing exposure to medical X-ray irradiation (Review)

With the increasing frequency of X-ray examinations in clinical medicine, public concern regarding the harm caused by exposure to X-ray radiation is also increasing. However, some physicians are not completely aware of the dangers of exposure to X-ray irradiation. Individuals specialized in this field, including physicians, have a better understanding of these dangers, which limits the use of X-rays in medicine. The present study aimed to address strategies for reducing the harm caused by exposure to medical X-rays and increase public awareness regarding X-ray radiation. Through a literature search and review, combined with the current status of clinical X-ray examination and the authors' professional experience, the present study highlights the importance of reducing X-ray exposure, and proposes several specific recommendations and measures for reducing the frequency or dose of X-ray irradiation. On the whole, the finding discussed in the present review suggest the minimal use of medical X-ray examinations and that alternative tests should be selected whenever possible. When medical X-ray screening and treatments are necessary, the risk-benefit ratio should be assessed, possibly aiming to achieve avoidable exposure. Further attention should be paid to protect sensitive glands and reduce the risks in children.

Treatment plan comparison of proton vs photon radiotherapy for lower-grade gliomas

Background and purpose

Patients with lower-grade gliomas are long-term survivors after radiotherapy and may benefit from the reduced dose to normal tissue achievable with proton therapy. Here, we aimed to quantify differences in dose to the uninvolved brain and contralateral hippocampus and compare the risk of radiation-induced secondary cancer for photon and proton plans for lower-grade glioma patients.

Materials and methods

Twenty-three patients were included in this in-silico planning comparative study and had photon and proton plans calculated (50.4 Gy(RBE = 1.1), 28 Fx) applying similar dose constraints to the target and organs at risk. Automatically calculated photon plans were generated with a 3 mm margin from clinical target volume (CTV) to planning target volume. Manual proton plans were generated using robust optimisation on the CTV. Dose metrics of organs at risk were compared using population mean dose-volume histograms and Wilcoxon signed-rank test. Secondary cancer risk per 10,000 persons per year (PPY) was estimated using dose-volume data and a risk model for secondary cancer induction.

Results

CTV coverage (V95%>98%) was similar for the two treatment modalities. Mean dose (D_mean) to the uninvolved brain was significantly reduced from 21.5 Gy (median, IQR 17.1–24.4 Gy) with photons compared to 10.3 Gy(RBE) (8.1–13.9 Gy(RBE)) with protons. D_mean to the contralateral hippocampus was significantly reduced from 6.5 Gy (5.4–11.7 Gy) with photons to 1.5 Gy(RBE) (0.4–6.8 Gy(RBE)) with protons. The estimated secondary cancer risk was reduced from 6.7 PPY (median, range 3.3–10.4 PPY) with photons to 3.0 PPY (1.3–7.5 PPY) with protons.

Conclusion

A significant reduction in mean dose to uninvolved brain and contralateral hippocampus was found with proton planning. The estimated secondary cancer risk was reduced with proton therapy.

Out-of-field organ doses and associated risk of cancer development following radiation therapy with photons

Innovations in cancer treatment have contributed to the improved survival rate of these patients. Radiotherapy is one of the main options for cancer management nowadays. High doses of ionizing radiation are usually delivered to the tumor site with high energy photon beams. However, the therapeutic radiation exposure may lead to second cancer induction. Moreover, the introduction of intensity-modulated radiation therapy over the last decades has increased the radiation dose to out-of-field organs compared to that from conventional irradiation. The increased organ doses might result in elevated probabilities for developing secondary malignancies to critical organs outside the treatment volume. The organ-specific dosimetry is considered necessary for the theoretical second cancer risk assessment and the proper analysis of data derived from epidemiological reports. This study reviews the methods employed for the measurement and calculation of out-of-field organ doses from exposure to photons and/or neutrons. The strengths and weaknesses of these dosimetric approaches are described in detail. This is followed by a review of the epidemiological data associated with out-of-field cancer risks. Previously published theoretical cancer risk estimates for adult and pediatric patients undergoing radiotherapy with conventional and advanced techniques are presented. The methodology for the theoretical prediction of the probability of carcinogenesis to out-of-field sites and the limitations of this approach are discussed. The article also focuses on the factors affecting the magnitude of the probability for developing radiotherapy-induced malignancies. The restriction of out-of-field doses and risks through the use of different types of shielding equipment is presented.

Risk and survival of second primary malignancies following diagnosis of gastric mucosa-associated lymphoid tissue lymphomas: A population-based study

Whether gastric mucosa-associated lymphoid tissue lymphoma (GML) is associated with a higher risk of second primary malignancy (SPM) remains controversial. This study aimed to evaluate the detailed risk of SPM and its prognosis in patients with GML based on a large population-based cohort. The Surveillance, Epidemiology, and End Results database was searched to identify patients who were diagnosed with GML during 2000-2014. The standardized incidence ratio was used to estimate the relative risk of developing SPM. Overall survival was evaluated using the Kaplan-Meier method with the log-rank test, as well as Cox regression analysis. Among 3,379 patients with GML, 416 patients (12.31%) developed SPMs. Compared to the general US population, GML patients had a significantly increased risk of developing SPM (standardized incidence ratio: 1.46, 95% CI: 1.33-1.61). The SPM sites were stomach, lung and bronchus, small intestine, thyroid, mouth, and non-Hodgkin's lymphoma. The risk of developing SPM in GML patients varied according to clinical and demographic characteristics. Patients with younger age (<50 year), chemotherapy use and radiotherapy use had the higher risk of developing SPMs. Relative to patients with only GML, GML patients who developed the SPMs had significantly poorer overall survival (P < 0.001). Among GML patients with SPMs, poor overall survival was independently associated with non-localized SPM disease, shorter latency period (<60 months), chemotherapy use and older age (≥70 year). Patients with GML had an elevated risk of developing SPM, which was associated with a poor prognosis. These findings may be useful for improving follow-up surveillance for patients with GML.

Role of epigenetic mechanisms in propagating off-targeted effects following radiation based therapies - A review

Despite being an important diagnostic and treatment modality, ionizing radiation (IR) is also known to cause genotoxicity and multiple side effects leading to secondary carcinogenesis. While modern cancer radiation therapy has improved patient recovery and enhanced survival rates, the risk of radiation-related adverse effects has become a growing challenge. It is now well-accepted that IR-induced side effects are not exclusively restricted to exposed cells but also spread to distant 'bystander' cells and even to the unexposed progeny of the irradiated cells. These 'off-targeted' effects involve a plethora of molecular events depending on the type of radiation and tumor tissue background. While the mechanisms by which off-targeted effects arise remain obscure, emerging evidence based on the non-mendelian inheritance of various manifestations of them as well as their persistence for longer periods supports a contribution of epigenetic factors. This review focuses on the major epigenetic phenomena including DNA methylation, histone modifications, and small RNA mediated silencing and their versatile role in the manifestation of IR induced off-targeted effects. As short- and long-range communication vehicles respectively, the role of gap junctions and exosomes in spreading these epigenetic-alteration driven off-targeted effects is also discussed. Furthermore, this review emphasizes the possible therapeutic potentials of these epigenetic mechanisms and how beneficial outcomes could potentially be achieved by targeting various signaling molecules involved in these mechanisms.

Secondary malignancy risk for patients with localized prostate cancer after intensity-modulated radiotherapy with and without flattening filter

Men treated for localized prostate cancer by radiotherapy have often a remaining life span of 10 yr or more. Therefore, the risk for secondary malignancies should be taken into account. Plans for ten patients were evaluated which had been performed on an Oncentra® treatment planning system for a treatment with an Elekta Synergy™ linac with Agility™ head. The investigated techniques involved IMRT and VMTA with and without flattening filter. Different dose response models were applied for secondary carcinoma and sarcoma risk in the treated region and also in the periphery. As organs at risk we regarded for carcinoma risk urinary bladder, rectum, colon, esophagus, thyroid, and for sarcoma risk bone and soft tissue. The excess absolute risk (EAR) was found very similar in the treated region for both techniques (IMRT and VMAT) and also for both with and without flattening filter. The secondary sarcoma risk resulted about one magnitude smaller than the secondary carcinoma risk. The EAR to the peripheral organs was statistically significant reduced by application of the flattening filter free mode concerning the flattening filter as main source of scattered dose. Application of flattening filter free mode can thus support to reduce second malignancy risk for patients with localized prostate cancer.

The diagnosis and management of primary and iatrogenic soft tissue sarcomas of the sella

PURPOSE

Soft tissue sarcoma (STS) of the sella is exceptionally rare. We conducted a case series, literature review, and nationwide analysis of primary and iatrogenic (radiation-associated) STS of the sella to define the clinical course of this entity.

METHODS

This study employed a multi-institutional retrospective case review, literature review, and nationwide analysis using the National Cancer Database (NCDB).

RESULTS

We report five patients who were diagnosed at three institutions with malignant STS of the sella. All patients presented with symptoms related to mass effect in the sellar region. All tumors extended to the suprasellar space, with the majority displaying extension into the cavernous sinus. All patients underwent an operation via a transsphenoidal approach with a goal of maximal safe tumor resection in four patients and biopsy for 1 patient. Histopathologic evaluation demonstrated STS in all patients. Post-operative adjuvant radiotherapy and chemotherapy were given to 2 and 1 out of 4 patients with known post-operative clinical course, respectively. The 1-year and 5-year overall survival rates were 100% (5/5) and 25% (1/4). Twenty-two additional reports of primary, non-iatrogenic STS of the sella were identified in the literature. Including the three cases from our series, treatment included resection in all cases, and adjuvant radiotherapy and chemotherapy were utilized in 50% (12/24) and 17% (4/24) of cases, respectively. The national prevalence of malignant STS is estimated to be 0.01% among all pituitary and sellar tumors within the NCDB.

CONCLUSIONS

We report the prevalence and survival rates of STS of the sella. Multimodal therapy, including maximal safe resection, chemotherapy, and radiotherapy are necessary to optimize outcomes for this uncommon pathology.