Endoscopic and non-endoscopic approaches for the management of radiation-induced rectal bleeding

[Progressive radiation-induced rectal injury: is there an opportunity to get out of a vicious circle? A clinical case]

Radiation therapy is one of the main treatment option for prostate cancer used either independently or as a component of combined and complex treatment of the disease. Modern achievements make it possible to deliver doses of radiation that match the exact dimensions of the tumor for greater efficacy, with minimal exposure of the surrounding tissues, however, does not eliminate them. In most patients, clinical manifestations of chronic radiation proctitis occur during the first 2 years after radiation therapy. The article summarizes the current knowledge about pathophysiology, clinical manifestations, diagnostics and treatment options for this condition. In this paper, we present a case of complicated of chronic radiation proctitis.

The effectiveness of hyperbaric oxygen therapy for managing radiation-induced proctitis - results of a 10-year retrospective cohort study

Introduction

Despite modern radiotherapy (RT) techniques, radiation-induced proctitis (RIP) remains a significant complication of RT for pelvic organ malignancies. Over the last decades, an enormous therapeutic armamentarium has been considered in RIP, including hyperbaric oxygen therapy (HBOT). However, the evidence regarding the impact of HBOT on RIP is conflicting. This study aims to evaluate the effectiveness and safety of HBOT in the treatment of RIP.

Methods

Ten-year (2013-2023) retrospective analysis of all consecutive patients with RIP treated with HBOT at Centro de Medicina Subaquática e Hiperbárica (CMSH) (Armed Forces Hospital - Lisbon, Portugal). Patients were exposed to 100% oxygen at 2.5 ATA, in a multiplace first-class hyperbaric chamber, for 70-min periods, once daily, five times per week. Fisher's exact test was performed using SPSS (version 23.0); p<0.05 was accepted as statistically significant.

Results

Of a total of 151 patients with RIP, 88 were included in the final analysis, of whom 38.6% evidenced other concurrent radiation-induced soft tissue lesions. The most reported primary pelvic tumor treated with RT was prostate cancer (77.3%), followed by cervical cancer (10.2%). Hematochezia was the most observed clinical manifestation (86.4%). After a median of 60 HBOT sessions (interquartile range [IQR]: 40-87.5), 62.5% and 31.8% of patients achieved a clinical complete and partial response, respectively, with a hematochezia resolution rate of 93.7% (complete or partial). While partial and complete responses require fewer than 70 sessions of HBOT in terms of overall RIP symptoms (p=0.069), isolated hematochezia tends to require at least 70 sessions (p=0.075). Individuals with at least two concurrent late radiation tissue injuries were associated with a complete response to HBOT (p=0.029). Only about 5.7% of patients did not respond to the treatment. Eighteen patients (20.5%) developed reversible ear barotrauma. The number of HBOT sessions was a predictor of HBOT side effects (odds ratio: 1.010; 95% confidence interval, 1.000-1.020; p=0.047).

Conclusion

The HBOT proved to be an effective and safe treatment for RIP refractory to medical and/or endoscopic treatments. This real-world evidence study adds value to published data on the management of RIP with HBOT.

Clinical Features and Management of Acute and Chronic Radiation-Induced Colitis and Proctopathy

BACKGROUND

RICAP is a recognized adverse effect of radiation therapy (RT) that can adversely affect cancer patients' quality of life. Data on the clinical characteristics and outcomes of RICAP are scarce. We aimed to analyze the clinical and endoscopic characteristics of acute or chronic radiation-induced colitis and proctopathy (ARICAP and CRICAP) based on symptom onset after RT (≤ or >45 days, respectively).

METHODS

This is a retrospective observational study of a single tertiary cancer center, from January 2010 and December 2018, of cancer patients with endoscopically confirmed ARICAP and CRICAP. We conducted univariate and multivariate logistic regression analyses to associate clinical variables with endoscopic and medical outcomes.

RESULTS

One hundred and twelve patients were included (84% Caucasian; 55% female; median age of 59 years); 46% had ARICAP with non-bloody diarrhea as the predominant symptom, whereas 55% had CRICAP with mostly bloody diarrhea. Neovascularization was the most frequent finding on endoscopy, followed by bleeding. ARICAP patients more often received medical management (p < 0.001), whereas CRICAP patients with bleeding more often received argon plasma coagulation (APC) (p = 0.002). Female sex and undergoing less-intense RT treatments were more associated with medical treatment; bleeding clinically and during the endoscopy was more associated with APC treatment. However, APC treatment did not significantly reduce bleeding recurrence or RICAP symptoms.

CONCLUSION

Patients with ARICAP and CRICAP experience different symptoms. Medical management should be considered before endoscopic therapy. APC may be useful in patients with endoscopically apparent bleeding.

Administration of modified Gegen Qinlian decoction for hemorrhagic chronic radiation proctitis: A case report and review of literature

BACKGROUND

Hemorrhagic chronic radiation proctitis (CRP) is a common late complication of irradiation of the pelvis and seriously impairs life quality. There is no standard treatment for hemorrhagic CRP. Medical treatment, interventional treatment, and surgery are available, but they are limited in their applications due to nondefinite efficacy or side effects. Chinese herbal medicine (CHM), as a complementary or alternative therapy, may provide another option for hemorrhagic CRP treatment.

CASE SUMMARY

A 51-year-old woman with cervical cancer received intensity-modulated radiation therapy and brachytherapy with a total dose of 93 Gy fifteen days after hysterectomy and bilateral adnexectomy. She received six additional cycles of chemotherapy with carboplatin and paclitaxel. Nine months after radiotherapy treatment, she mainly complained of 5-6 times diarrhea daily and bloody purulent stools for over 10 d. After colonoscopy examinations, she was diagnosed with hemorrhagic CRP with a giant ulcer. After assessment, she received CHM treatment. The specific regimen was 150 mL of modified Gegen Qinlian decoction (GQD) used as a retention enema for 1 mo, followed by replacement with oral administration of 150 mL of modified GQD three times per day for 5 mo. After the whole treatment, her diarrhea reduced to 1-2 times a day. Her rectal tenesmus and mild pain in lower abdomen disappeared. Both colonoscopy and magnetic resonance imaging confirmed its significant improvement. During treatment, there were no side effects, such as liver and renal function damage.

CONCLUSION

Modified GQD may be another effective and safe option for hemorrhagic CRP patients with giant ulcers.

Pelvic Radiation Disease

Pelvic radiation is increasingly being used for the neoadjuvant and definitive treatment of pelvic organ malignancy. While this treatment can be highly effective, and may assist in organ sparing, it is also associated with significant toxicity and devastating adverse events that need to be considered. In broad terms, pelvic radiation disease affects both the primary target organ as well as adjacent organs and soft tissue structures, with complications that can be classified and graded according to consensus criteria. The complication grade is often modality, dose, and area dependent. The most common manifestations are proctitis, cystitis, recto-urethral fistula, ureteric stricture, and bone involvement. Toxicity can be misdiagnosed for many years, resulting in significant management delays. Complications can be difficult to prevent and challenging to treat, requiring specialized multi-disciplinary input to achieve the best possible strategy to minimize impact and improve patient quality of life.

The Effect of Hyperbaric Oxygen Therapy on Rectal Ulcers after Argon Plasma Coagulation

Chronic radiation proctitis usually develops 3 months after therapy. Despite the lack of standard guidelines regarding treatment, argon plasma coagulation is often a safe and effective endoscopic therapy. However, rectal ulcers are a common complication after argon plasma coagulation. Nevertheless, most patients are asymptomatic and do not require additional monitoring or treatment. We report a case of an argon plasma coagulation-induced ulcer with relevant symptoms and refractory to medical treatment. The patient was treated with hyperbaric oxygen therapy and had complete resolution of the rectal ulcer. Hyperbaric oxygen therapy has shown efficacy in severe chronic proctitis and radiation-induced rectal ulcers, but no clinical report has ever been published on using hyperbaric oxygen therapy for ulcers after argon plasma coagulation. In this case, hyperbaric oxygen therapy was an effective alternative option and can be considered in patients with refractory argon plasma coagulation-induced rectal ulcers.

Clinical Use of the Self-Assembling Peptide RADA16: A Review of Current and Future Trends in Biomedicine

RADA16 is a synthetic peptide that exists as a viscous solution in an acidic formulation. In an acidic aqueous environment, the peptides spontaneously self-assemble into β-sheet nanofibers. Upon exposure and buffering of RADA16 solution to the physiological pH of biological fluids such as blood, interstitial fluid and lymph, the nanofibers begin physically crosslinking within seconds into a stable interwoven transparent hydrogel 3-D matrix. The RADA16 nanofiber hydrogel structure closely resembles the 3-dimensional architecture of native extracellular matrices. These properties make RADA16 formulations ideal topical hemostatic agents for controlling bleeding during surgery and to prevent post-operative rebleeding. A commercial RADA16 formulation is currently used for hemostasis in cardiovascular, gastrointestinal, and otorhinolaryngological surgical procedures, and studies are underway to investigate its use in wound healing and adhesion reduction. Straightforward application of viscous RADA16 into areas that are not easily accessible circumvents technical challenges in difficult-to-reach bleeding sites. The transparent hydrogel allows clear visualization of the surgical field and facilitates suture line assessment and revision. The shear-thinning and thixotropic properties of RADA16 allow its easy application through a narrow nozzle such as an endoscopic catheter. RADA16 hydrogels can fill tissue voids and do not swell so can be safely used in close proximity to pressure-sensitive tissues and in enclosed non-expandable regions. By definition, the synthetic peptide avoids potential microbiological contamination and immune responses that may occur with animal-, plant-, or mineral-derived topical hemostats. In vitro experiments, animal studies, and recent clinical experiences suggest that RADA16 nanofibrous hydrogels can act as surrogate extracellular matrices that support cellular behavior and interactions essential for wound healing and for tissue regenerative applications. In the future, the unique nature of RADA16 may also allow us to use it as a depot for precisely regulated drug and biopharmaceutical delivery.

Endorectal formalin instillation or argon plasma coagulation for hemorrhagic radiation proctopathy therapy: a prospective and randomized clinical trial

BACKGROUND AND AIMS

Radiotherapy may cause hemorrhagic radiation proctopathy (HRP). For conservative treatment of refractory HRP, argon plasma coagulation (APC) is the first-choice therapy. Endorectal formalin instillation (EFI), in turn, is an attractive treatment option because of its satisfactory results, great availability, and low cost. Nevertheless, comparative studies between these procedures are rather scarce. This study aims to make a prospective and randomized comparison of the outcomes in 2 HRP patient groups treated with either APC or EFI.

METHODS

Twenty-seven patients (11 women), with a mean age of 67 years (range, 36-83), were randomized to receive either APC (n = 14) or EFI (n = 13). On completion of the treatment, comparisons were made in relation to the baseline for each patient and between groups for endoscopic findings according to the Vienna score and the telangiectasia distribution pattern score (TDP); the impact of radiation proctitis on patients' lives was made according to the modified radiation toxicity score (MRTS) and hemoglobin levels. Number of sessions, duration of therapy, and adverse events were also compared between groups. The endoscopic therapeutic success (ETS) was defined by the absence or only few residual telangiectasias (TDP ≤1) on conclusion.

RESULTS

An ETS of 92.8% was achieved in patients treated with APC and 92.3% for those treated with EFI (P > .05); there was an MRTS improvement of 85.7% in APC patients and 69.2% in EFI patients (P > .05). Mild adverse events occurred, respectively, in 23% and 28.5% in the EFI and APC groups (P > .05).

CONCLUSIONS

The study showed that APC and EFI have similar efficacy and a high safety profile for HRP treatment. (Clinical trial registration number: 3.120.353.).

Update on the management of the gastrointestinal effects of radiation

Radiation therapy is a long-established and essential modality in the treatment of many cancers. It is well known that tissue within a field of radiation can suffer indiscriminate effects, leading to acute and chronic problems. The gastrointestinal tract may be adversely affected by radiation. From the mouth to the rectum, patients can experience troublesome symptoms that require the concerted input of specialist teams. Interventions range from nursing care, dietetic optimization, pharmacological management, and mechanical procedures through endoscopy and surgery. Quality evidence exists mainly for radiation induced effects in four distinct areas of the gastrointestinal tract: oral mucosa, esophagus, small bowel, and rectum. This review explores the experiences of oncology and gastrointestinal teams in managing the most common conditions and some of the different practices for radiation associated morbidity.

A Ten-year-long Update on Radiation Proctitis Among Prostate Cancer Patients Treated With Curative External Beam Radiotherapy

This comprehensive synopsis summarizes the most relevant information obtained from a systematic analysis of studies of the last decade on radiation proctitis, one of the most feared radioinduced side effects among prostate cancer patients treated with curative external beam radiotherapy. The present review provides a useful support to radiation oncologists for limiting the onset or improving the treatment of radiation proctitis. This work shows that the past decade was a harbinger of significant new evidence in technological advances and technical tricks to avoid radiation proctitis, in addition to dosimetric perspectives and goals, understanding of pathogenesis, diagnostic work-up and treatment. We believe that a well-rounded knowledge of such an issue is fundamental for its appropriate management.

The use of hyperbaric oxygen to treat actinic rectal fistula after SpaceOAR use and radiotherapy for prostate cancer: a case report

Background

In definitive radiation therapy for prostate cancer, the SpaceOAR® System, a hydrogel spacer, is widely used to decrease the irradiated dose and toxicity of rectum. On the other hand, periprostatic abscesses formation and rectal perforation are known as rare adverse effects of SpaceOAR. Nevertheless, there is a lack of reports clarifying the association between aggravation of abscesses and radiation therapy, and hyperbaric oxygen therapy (HBOT) is effective for a peri-SpaceOAR abscess and rectal perforation.

Case presentation

We report a case of a 78-year-old high-risk prostate cancer patient. After SpaceOAR insertion into the correct space, he started to receive external beam radiation therapy (EBRT). He developed a fever, perineal pain and frequent urination after the completion of EBRT, and the magnetic resonance imaging (MRI) revealed a peri-SpaceOAR abscess. Scheduled brachytherapy was postponed, administration of antibiotics and opioid via intravenous drip was commenced, and transperineal drainage was performed. After the alleviation of the abscess, additional EBRT instead of brachytherapy was performed with MRI-guided radiation therapy (MRgRT). On the last day of the MRgRT, perineal pain reoccurred, and MRI and colonoscopy detected the rectal perforation. He received an intravenous antibiotics drip and HBOT, and fully recovered from the rectal perforation.

Conclusions

Our report indicates that EBRT can lead to a severe rectum complication by causing inflammation for patients with a peri-SpaceOAR abscess. Furthermore, HBOT was effective for the peri-SpaceOAR abscess and rectal perforation associated with EBRT.

LATE RADIATION TOXICITY AFTER RADICAL RADIOTHERAPY FOR GENITAL CANCER

Radiation therapy for malignant tumors of the female genital area, even with the use of modern radiotherapy equipment and dosimetric planning, causes the development of local radiation changes. An approach involving methodsof general and local exposure is used in their treatment. One of the most promising directions is the creation of optimal combinations of medicines (in the form of ointments, gels, aerosols, suppositories, etc.), which have a therapeutic effect on the inflammatory process. The article reflects the clinical course and stage of occurrence of late radiation reactions of the skin, vaginal/cervix mucosa, bladder, and intestines, as well as the features of their treatment.Literary data and own practical experience in the treatment of radiation complications are presented. Whenreviewing the topic under study, it could be concluded that the leading cause of the development of local radiationdamage is the errors in the planning and implementation of radiation therapy, when high absorbed doses thatexceed the tolerance of healthy tissues are used. Another reason for this is the poor accounting for dose distribution of ionizing radiation in tissues, the presence of concomitant diseases in patients, and the underestimation ofthe long-term effects of radiation.

Radiation-induced damage in the lower gastrointestinal tract: Clinical presentation, diagnostic tests and treatment options

Radiation therapy is an important ally when treating malignant lesions in the pelvic area, but it is not exempt of adverse events. There are some measures that can be taken to reduce the possibility of these effects, but some are non-modifiable factors related to previous treatments, location of the lesions or comorbidities. There is a wide variety of clinical presentations that can be of an acute or chronic onset that go from mild to severe forms or that can have a great impact in the quality of life. Medical available therapies as metronidazole, sucralfate, mesalizine or probiotics, can be of aid although some lack of solid evidence of efficacy. Endoscopic treatment can be performed with argon plasma coagulation, bipolar cautery, radiofrequency, laser therapy or dilation. Hyperbaric therapy can be applied in refractory cases and surgery must be reserved to selected patients due to its high morbidity and mortality.

Dose-volume Histogram-based Predictors for Hematuria and Rectal Hemorrhage in Patients Receiving Radiotherapy After Radical Prostatectomy

AIM

The aim of this study was to evaluate the dose-volume histogram parameters for late hematuria and rectal hemorrhage in patients receiving radiotherapy after radical prostatectomy.

PATIENTS AND METHODS

Data of 86 patients treated between January 2006 and June 2019 were retrospectively evaluated. The median radiation dose was 64 Gy in 32 fractions. Receiver operating characteristic (ROC) curves were used to identify optimal cut-off values for late adverse events.

RESULTS

Eleven patients experienced hematuria, and the 5-year cumulative rate was 18%. Four patients experienced rectal hemorrhage, and the 5-year cumulative rate was 7%. ROC curve analysis demonstrated the following significant cut-off values: bladder V50 Gy: 43% (p=0.02) and V40 Gy: 50% (p=0.03) for hematuria, and rectum V60 Gy: 13% (p=0.04) and V50 Gy: 33% (p=0.03) for rectal hemorrhage.

CONCLUSION

This is the first study to identify dose constraints that may reduce hematuria and rectal hemorrhage in patients receiving radiotherapy in the postoperative setting.

[Rectal bleeding: easy to overcome or still a challenge in proctology?]

Rectal bleeding is a frequent symptom in proctology. In most cases frequent causes, such as anal fissures and hemorrhoidal disease can be diagnosed and treated using a structured patient history and basic proctological diagnostic assessment; however, it is not uncommon for proctitis to be the reason for rectal bleeding, which necessitates interdisciplinary diagnostics and treatment. In addition to proctitis associated with chronic inflammatory bowel disease, prolapse-induced, radiogenic, ischemic, infectious types and proctitis associated with sexually transmitted diseases represent important differential diagnoses. Moreover, rectal cancer has to be excluded as the cause of rectal bleeding. Finally, with appropriate diligence most causes of rectal bleeding can be securely identified and effectively managed; however, special circumstances can necessitate interdisciplinary diagnostics and management, including conservative, topical, interventional and surgical treatment options.

Assessment of chronic radiation proctopathy and radiofrequency ablation treatment follow-up with optical coherence tomography angiography: A pilot study

BACKGROUND

Chronic radiation proctopathy (CRP) occurs as a result of pelvic radiation therapy and is associated with formation of abnormal vasculature that may lead to persistent rectal bleeding. While incidence is declining due to refinement of radiation delivery techniques, CRP remains one of the major complications of pelvic radiation therapy and significantly affects patient quality of life. Radiofrequency ablation (RFA) is an emerging treatment modality for eradicating abnormal vasculature associated with CRP. However, questions remain regarding CRP pathophysiology and optimal disease management.

AIM

To study feasibility of optical coherence tomography angiography (OCTA) for investigating subsurface vascular alterations in CRP and response to RFA treatment.

METHODS

Two patients with normal rectum and 8 patients referred for, or undergoing endoscopic RFA treatment for CRP were imaged with a prototype ultrahigh-speed optical coherence tomography (OCT) system over 15 OCT/colonoscopy visits (2 normal patients, 5 RFA-naïve patients, 8 RFA-follow-up visits). OCT and OCTA was performed by placing the OCT catheter onto the dentate line and rectum without endoscopic guidance. OCTA enabled depth-resolved microvasculature imaging using motion contrast from flowing blood, without requiring injected dyes. OCTA features of normal and abnormal microvasculature were assessed in the mucosa and submucosa. Blinded reading of OCTA images was performed to assess the association of abnormal rectal microvasculature with CRP and RFA treatment, and rectal telangiectasia density endoscopic scoring.

RESULTS

OCTA/OCT images are intrinsically co-registered and enabled depth-resolved visualization of microvasculature in the mucosa and submucosa. OCTA visualized normal vascular patterns with regular honeycomb patterns vs abnormal vasculature with distorted honeycomb patterns and ectatic/tortuous microvasculature in the rectal mucosa. Normal arterioles and venules < 200 μm in diameter versus abnormal heterogenous enlarged arterioles and venules > 200 μm in diameter were visualized in the rectal submucosa. Abnormal mucosal vasculature occurred in 0 of 2 normal patients and 3 of 5 RFA-naïve patients, while abnormal submucosal vasculature occurred more often, in 1 of 2 normal patients and 5 of 5 RFA-naïve patients. After RFA treatment, vascular abnormalities decreased, with abnormal mucosal vasculature observed in 0 of 8 RFA-follow-up visits and abnormal submucosal vasculature observed in only and 2 of 8 RFA-follow-up visits.

CONCLUSION

OCTA visualizes depth-resolved microvascular abnormalities in CRP, allowing assessment of superficial features which are endoscopically visible as well as deeper vasculature which cannot be seen endoscopically. OCTA/OCT of the rectum can be performed in conjunction with, or independently from endoscopy. Further studies are warranted to investigate if OCTA/OCT can elucidate pathophysiology of CRP or improve management.

Efficacy and complications of argon plasma coagulation for hemorrhagic chronic radiation proctitis

BACKGROUND

Chronic radiation proctitis (CRP) is a complication which occurs in 1%-5% of patients who undergo radiotherapy for pelvic malignancies. Although a wide range of therapeutic modalities are available, there is no literature to date showing any particularly appropriate therapeutic modality for each disease stage. Argon plasma coagulation (APC) is currently recommended as the first-choice treatment for hemorrhagic CRP, however, its indication based on long-term follow-up is still unclear. On the hypothesis that the long-term efficacy and safety of APC are not fully understood, we reviewed APC treatment for patients with hemorrhagic CRP from a single center.

AIM

To assess the long-term efficacy and safety of APC for hemorrhagic CRP.

METHODS

This is a retrospective study of consecutive patients treated with APC for hemorrhagic CRP from January 2013 to October 2017. Demographics, clinical variables, and typical endoscopic features were recorded independently. Success was defined as either cessation of bleeding or only occasional traces of bloody stools with no further treatments for at least 12 mo after the last APC treatment. We performed univariate and multivariate analyses to identify factors associated with success and risk factors for fistulas.

RESULTS

Forty-five patients with a median follow-up period of 24 mo (range: 12-67 mo) were enrolled. Fifteen (33.3%) patients required blood transfusion before APC. Successful treatment with APC was achieved in 31 (68.9%) patients. The mean number of APC sessions was 1.3 (1-3). Multivariate analysis showed that APC failure was independently associated with telangiectasias present on more than 50% of the surface area [odds ratio (OR) = 6.53, 95% confidence interval (CI): 1.09-39.19, P = 0.04] and ulcerated area greater than 1 cm² (OR = 8.15, 95%CI: 1.63-40.88, P = 0.01). Six (13.3%) patients had severe complications involving rectal fistulation. The only factor significantly associated with severe complications was ulcerated area greater than 1 cm² (P = 0.035).

CONCLUSION

The long-term efficacy of APC for hemorrhagic CRP is uncertain in patients with telangiectasias present on > 50% of the surface area and ulceration > 1 cm².

Rubber Band Ligation of Hemorrhoids is often a Necessary Complement in the Management of Hemorrhagic Radiation Proctitis

BACKGROUND

Management of radiation proctitis presents a treatment challenge. Limited data exist on the management of symptomatic hemorrhoids in radiated patients. This study aims to present a practical approach to the management of radiation proctitis, particularly in patients with synchronous hemorrhoids.

METHODS

A total of 52 consecutive cases of radiation proctitis managed between September 1999 and October 2017 were retrospectively reviewed. The primary treatment was formalin application, plus rubber band ligation in conjunction with formalin when hemorrhoids were a significant component of bleeding, and occasionally argon plasma coagulation.

RESULTS

The primary indication for radiotherapy was for the treatment of prostate cancer (71%), anal squamous cell carcinoma (10%), and gynecological malignancies (18%). More than half of the patients (52%) presented with radiation proctitis and concomitant internal hemorrhoids. The hemorrhoids were managed with rubber band ligation (56%) and stapled hemorrhoidectomy (7%), at the same procedure as formalin application. At a median follow-up of 12 months, no recurrent rectal bleeding occurred, and no further treatment was needed for most patients. One patient experienced a short period of perianal pain, which was treated with analgesics.

CONCLUSION

Formalin application has consistently demonstrated an excellent cure rate and safety profile comparable with the published results as a primary treatment for radiation proctitis. The prolapse of irradiated mucosa over the internal hemorrhoids appears to exacerbate bleeding. Local hemorrhoid treatment is often required as an adjunct in the management of these patients.

Metformin as a Radiation Modifier; Implications to Normal Tissue Protection and Tumor Sensitization

BACKGROUND

Nowadays, ionizing radiation is used for several applications in medicine, industry, agriculture, and nuclear power generation. Besides the beneficial roles of ionizing radiation, there are some concerns about accidental exposure to radioactive sources. The threat posed by its use in terrorism is of global concern. Furthermore, there are several side effects to normal organs for patients who had undergone radiation treatment for cancer. Hence, the modulation of radiation response in normal tissues was one of the most important aims of radiobiology. Although, so far, several agents have been investigated for protection and mitigation of radiation injury. Agents such as amifostine may lead to severe toxicity, while others may interfere with radiation therapy outcomes as a result of tumor protection. Metformin is a natural agent that is well known as an antidiabetic drug. It has shown some antioxidant effects and enhances DNA repair capacity, thereby ameliorating cell death following exposure to radiation. Moreover, through targeting endogenous ROS production within cells, it can mitigate radiation injury. This could potentially make it an effective radiation countermeasure. In contrast to other radioprotectors, metformin has shown modulatory effects through induction of several genes such as AMPK, which suppresses reduction/ oxidation (redox) reactions, protects cells from accumulation of unrepaired DNA, and attenuates initiation of inflammation as well as fibrotic pathways. Interestingly, these properties of metformin can sensitize cancer cells to radiotherapy.

CONCLUSION

In this article, we aimed to review the interesting properties of metformin such as radioprotection, radiomitigation and radiosensitization, which could make it an interesting adjuvant for clinical radiotherapy, as well as an interesting candidate for mitigation of radiation injury after a radiation disaster.

Pelvic Complications After Prostate Cancer Radiation Therapy and Their Management: An International Collaborative Narrative Review

CONTEXT

Radiotherapy used for treating localized prostate cancer is effective at prolonging cancer-specific and overall survival. Still, acute and late pelvic toxicities are a concern, with gastrointestinal (GI) and genitourinary (GU) sequelae being most common as well as other pelvic complications.

OBJECTIVE

To present a critical review of the literature regarding the incidence and risk factors of pelvic toxicity following primary radiotherapy for prostate cancer and to provide a narrative review regarding its management.

EVIDENCE ACQUISITION

A collaborative narrative review of the literature from 2010 to present was conducted.

EVIDENCE SYNTHESIS

Regardless of the modality used, the incidence of acute high-grade pelvic toxicity is low following conventionally fractionated external beam radiotherapy (EBRT). After moderate hypofractionation, the crude cumulative incidences for late grade 3 or higher (G3+) GI and GU complications are as high as 6% and 7%, respectively. After extreme hypofractionation, the 5-yr incidences of G2+ GU and GI toxicities are 3-9% and 0-4%, respectively. Following brachytherapy monotherapy, crude rates of late G3+ GU toxicity range from 6% to 8%, while late GI toxicity is rare. With combination therapy (EBRT and brachytherapy), the cumulative incidence of late GU toxicity is high, between 18% and 31%; however, the prevalence is lower at 4-14%. Whole pelvic radiotherapy remains a controversial treatment option as there is increased G3+ GI toxicity compared with prostate-only treatment, with no overall survival benefit. Proton beam therapy appears to have similar toxicity to photon therapies currently in use. With respect to specific complications, urinary obstruction and urethral stricture are the most common severe urinary toxicities. Rectal and urinary bleeding can be recurrent long-term toxicities. The risk of hip fracture is also increased following prostate radiotherapy. The literature is mixed on the risk of in-field secondary pelvic malignancies following prostate radiotherapy. Urinary and GI fistulas are rare complications. Management of these toxicities may require invasive treatment and reconstructive surgery for refractory and severe symptoms.

CONCLUSIONS

There has been progress in the delivery of radiotherapy, enabling the administration of higher doses with minimal tradeoff in terms of slightly increased or equal toxicity. There is a need to focus future improvements in radiotherapy on sparing critical structures to reduce GU and GI morbidities. While complications such as fistulae, bone toxicity, and secondary malignancy are rare, there is a need for higher-quality studies assessing these outcomes and their management.

PATIENT SUMMARY

In this report, we review the literature regarding pelvic complications following modern primary prostate cancer radiotherapy and their management. Modern radiotherapy technologies have enabled the administration of higher doses with minimal increases in toxicity. Overall, high-grade long-term toxicity following prostate radiotherapy is uncommon. Management of late high-grade pelvic toxicities can be challenging, with patients often requiring invasive therapies for refractory cases.

Management of Radiation Proctitis

Radiation proctitis is radiation-induced rectal mucositis, occurring as a result of radiation therapy for various pelvic malignancies. The management of radiation proctitis is challenging as guidelines are not currently available, and studies of the various treatment modalities are limited. There are various medical, endoscopic, and surgical measures for treating chronic radiation proctitis. Medical options such as anti-inflammatory agents, antioxidants, formalin application, and hyperbaric oxygen may improve bleeding related to chronic radiation proctitis. Endoscopic measures such as argon plasma coagulation are effective and safe. Surgery is considered for refractory or severe cases. A review and discussion of the different treatment modalities is presented.

Role of hemostatic powders in the management of lower gastrointestinal bleeding: A review

Despite the recent advances in endoscopic hemostatic techniques, the management of lower gastrointestinal bleeding could be sometimes challenging. Hemostatic powders such as Hemospray, EndoClot, and Ankaferd Blood Stopper have found their way into digestive endoscopy and are licenced in many countries especially for use in upper gastrointestinal bleeding. We reviewed the literature on the use of these hemostatic powders in different situations in lower gastrointestinal bleeding and looked at the success rate and rebleeding rate. Most of the data are derived from case reports, retrospective and prospective case series with absence of any randomized controlled trials. Hemostatic powders were used as primary or salvage therapy to control bleeding from polypectomy site, colonic tumors, diverticula, arteriovenous malformations, radiation proctitis, ischemic colitis, and surgical intestinal anastomosis. The rate of immediate control of bleeding is in the range of 88-100% with a recurrence rate of 3-13% except for radiation proctitis bleeding where rebleeding rate can be as high as 77%. Although there are many advantages for the use of local hemostatic agents in lower gastrointestinal bleeding, future randomized controlled trials comparing them with conventional methods are needed.

Prevention of Recurrent Lower Gastrointestinal Hemorrhage

This article summarizes current knowledge regarding the incidence of and risk factors associated with recurrent lower gastrointestinal hemorrhage. The literature regarding medical, endoscopic, and surgical methods to prevent rebleeding from diverticulosis, angioectasia, and chronic hemorrhagic radiation proctopathy is reviewed. In addition, the evidence for endoscopic clipping as primary prophylaxis against postpolypectomy bleeding is explored.

Efficacy and Safety of Argon Plasma Coagulation for Hemorrhagic Chronic Radiation Proctopathy: A Systematic Review

Hemorrhagic chronic radiation proctopathy (CRP) is a common complication after pelvic radiotherapy in patients with prostate or gynecological cancers. This systematic review was conducted to evaluate the efficacy and safety of argon plasma coagulation (APC) in treating hemorrhagic CRP. The databases of PubMed, Embase, and Cochrane Library were searched for related studies from inception to July 2017. Finally, 33 studies were identified with a total of 821 hemorrhagic CRP patients. After APC treatment, hemoglobin levels increased from 7.7–13.4 g/L to 11–14 g/L (including 15 studies). All (n = 33) studies reported an effective rate in rectal bleeding, among which five studies had a rate of 100%. Short-term complications were reported in 31 studies, while long-term complications in 33 studies and no complication in 11 studies. As for the severe complications, perforation was reported by 2 out of 33 studies, and the incidences were 3.3% (1/30) and 3.7% (1/27), respectively. As for APC setting, argon gas flow rate (median 1.5 L/min) and electric power (median 50 W) had no significant influence on complications and hemostasis. In conclusion, current literature indicated that APC therapy was an effective and safe strategy for hemorrhagic CRP, and large-scale prospective studies are needed to warrant our study.