Pre-clinical Research on Bladder Toxicity After Radiotherapy for Pelvic Cancers: State-of-the Art and Challenges

Maintaining Serum Hemoglobin Levels Within the Physiological Range Prevented Bladder Tamponade Recurrence Due to Radiation-Induced Hemorrhagic Cystitis: A Case Report

Radiation-induced hemorrhagic cystitis is a refractory disease that can cause severe hematuria and bladder tamponade. Bladder tamponade due to radiation-induced hemorrhagic cystitis can often recur repeatedly and markedly reduce the quality of life. However, no blood test parameter has been studied yet regarding the prevention of bladder tamponade recurrence. An 84-year-old patient with a history of radiation therapy for cervical cancer was repeatedly hospitalized for bladder tamponade due to radiation-induced hemorrhagic cystitis. At each hospitalization, blood transfusions were performed to treat severe anemia as the first treatment, resulting in hematuria improvement, and the patient was discharged without invasive treatments such as transurethral coagulation. However, anemia developed gradually after each discharge. The anemia progression was obviously unrelated to macrohematuria because macrohematuria did not appear during that period. When the serum hemoglobin level decreased below the physiological range, bladder tamponade recurred. Based on these findings, we posited that the monitoring of the serum hemoglobin level could be useful to predict the occurrence of bladder tamponade. We hypothesized that if the serum hemoglobin level did not fall below the physiological range, bladder tamponade would not occur. We treated chronic anemia after determining its cause and kept serum hemoglobin levels within the physiological range. Since the treatment was initiated, bladder tamponade has not recurred in over 27 months. In this case, the monitoring of the serum hemoglobin level was useful to predict the occurrence of bladder tamponade due to radiation-induced hemorrhagic cystitis. By maintaining serum hemoglobin levels within the physiological range, we successfully prevented the recurrence of bladder tamponade due to radiation-induced hemorrhagic cystitis.

Complications after Prostate Cancer Treatment: Pathophysiology and Repair of Post-Radiation Urethral Stricture Disease

Radiation therapy (RT) in the management of pelvic cancers remains a clinical challenge to urologists given the sequelae of urethral stricture disease secondary to fibrosis and vascular insults. The objective of this review is to understand the physiology of radiation-induced stricture disease and to educate urologists in clinical practice regarding future prospective options clinicians have to deal with this condition. The management of post-radiation urethral stricture consists of conservative, endoscopic, and primary reconstructive options. Endoscopic approaches remain an option, but with limited long-term success. Despite concerns with graft take, reconstructive options such as urethroplasties in this population with buccal grafts have shown long-term success rates ranging from 70 to 100%. Robotic reconstruction is augmenting previous options with faster recovery times. Radiation-induced stricture disease is challenging with multiple interventions available, but with successful outcomes demonstrated in various cohorts including urethroplasties with buccal grafts and robotic reconstruction.

Risk and prognosis of secondary malignant neoplasms after radiation therapy for bladder cancer: A large population-based cohort study

Objective

To investigate the association between radiotherapy and the risk of second malignant neoplasm (SMN) development among patients with bladder cancer (BC). Overall survival (OS) is compared among patients developing SMN and without.

Method

We identified patients diagnosed with BC from the Surveillance, Epidemiology, and End Results (SEER) database. The development of an SMN is defined as any SMN occurring more than 5 years after the diagnosis of BC. The Fine-Gray competing risk regression is used to estimate the probability of SMN. The radiotherapy-associated risk (RR) for SMNs is assessed by Poisson regression. The Kaplan–Meier method was used to evaluate the OS of patients with SMNs. Propensity score matching (PSM) is performed.

Results

A total of 76575 BC patients are enrolled in our study. The probability of SMNs in the radiotherapy cohort is statistically higher than in the non-radiotherapy cohort. In competing risk regression analysis, radiotherapy is proven to be associated with a higher risk of SMN (Hazard ratio: 1.23; 95% CI: 1.102–1.368). The radiotherapy-associated risks significantly increase in the radiotherapy cohort (RR: 1.28; 95% CI: 1.14–1.43). In site-specific analysis, statistically significant results are observed in lung and bronchus (LAB) cancer and hematological malignancies. The OS rate in patients developing SMN is significantly lower than that among matched patients with primary BC.

Conclusion

Radiotherapy for BC is associated with SMN. Radiotherapy increases the risk of secondary low-dose area cancer development, including LAB cancer or hematological malignancies. Notably, this effect is not observed in the high-dose area involving pelvic tumors. Patients developing SMN showed poorer OS.

CyberKnife radiation therapy as a platform for translational mouse studies

PURPOSE

Radiation therapy (RT) is a common nonsurgical treatment in the management of patients with cancer. While genetically engineered mouse models (GEMM) recapitulate human disease, conventional linear particle accelerator systems are not suited for state-of-the-art, imageguided targeted RT (IGRT) of these murine tumors. We employed the CyberKnife (CK; Accuray) platform for IGRT of GEMM-derived non-small cell lung cancer (NSCLC) lesions.

MATERIAL AND METHODS

GEMM-derived Kras^LSL-G12D/+/Trp53^fl/fl -driven NSCLC flank tumors were irradiated using the CK RT platform. We applied IGRT of 2, 4, 6, and 8 Gy using field sizes of 5-12.5 mm to average gross tumor volumes (GTV) of 0.9 cm3 using Xsight Spine Tracking (Accuray).

RESULTS

We found that 0 mm planning target volume (PTV) margin is sufficient for IGRT of murine tumors using the CK. We observed that higher RT doses (6-8 Gy) decreased absolute cell numbers of tumor infiltrating leukocytes (TIL) by approximately half compared to low doses (2-4 Gy) within 1 h, but even with low dose RT (2 Gy) TIL were found to be reduced after 8-24 h.

CONCLUSION

We here demonstrate that the CK RT system allows for targeted IGRT of murine tumors with high precision and constitutes a novel promising platform for translational mouse RT studies.

Impact of prostatic radiation therapy on bladder contractility and innervation

AIMS

To determine the effect of prostatic radiation therapy (RT) on bladder contractility and morphology, and axon, or neuron profiles within the detrusor and major pelvic ganglia (MPG) in male rats.

METHODS

Male Sprague-Dawley rats (8 weeks) received a single dose of prostatic RT (0 or 22 Gy). Bladders and MPG were collected 2- and 10-weeks post-RT. Detrusor contractile responses to carbachol and electrical field stimulation (EFS) were measured. Bladders were stained with Masson's trichrome, and antibodies for nonspecific neuronal marker, cholinergic nerve marker choline acetyltransferase (ChAT), and alpha-smooth muscle actin. MPG gene expression was assessed by quantitative polymerase chain reaction for ubiquitin carboxy-terminal hydrolase L1 (Uchl1) and Chat.

RESULTS

At 2 weeks post-RT, bladder smooth muscle, detrusor cholinergic axon profiles, and MPG Chat gene expression were increased (p < .05), while carbachol and EFS-mediated contractions were decreased (p < .05). In contrast, at 10 weeks post-RT, nerve-mediated contractions were increased compared with control (p < .05), while bladder smooth muscle, detrusor cholinergic axon profiles, MPG Chat expression, and carbachol contractions had normalized. At both 2- and 10-weeks post-RT, there was no change in detrusor nonspecific axon profiles and MPG Uchl1 expression.

CONCLUSION

In a rat model, RT of the prostate and MPG was associated with early changes in MPG Chat gene expression, and bladder cholinergic axon profiles and smooth muscle content which resolved over time. After RT recovery, bladder contractility decreased early and increased by 10 weeks. Long-term changes to the MPG and increased bladder cholinergic axons may contribute to RT-induced bladder dysfunction in prostate cancer survivors.

Regional Responses in Radiation-Induced Normal Tissue Damage

Normal tissue side effects remain a major concern in radiotherapy. The improved precision of radiation dose delivery of recent technological developments in radiotherapy has the potential to reduce the radiation dose to organ regions that contribute the most to the development of side effects. This review discusses the contribution of regional variation in radiation responses in several organs. In the brain, various regions were found to contribute to radiation-induced neurocognitive dysfunction. In the parotid gland, the region containing the major ducts was found to be critical in hyposalivation. The heart and lung were each found to exhibit regional responses while also mutually affecting each other's response to radiation. Sub-structures critical for the development of side effects were identified in the pancreas and bladder. The presence of these regional responses is based on a non-uniform distribution of target cells or sub-structures critical for organ function. These characteristics are common to most organs in the body and we therefore hypothesize that regional responses in radiation-induced normal tissue damage may be a shared occurrence. Further investigations will offer new opportunities to reduce normal tissue side effects of radiotherapy using modern and high-precision technologies.