Permanent prostate brachytherapy: a century of technical evolution

RNA biomarkers in cancer therapeutics: The promise of personalized oncology

Cancer therapy is a rapidly evolving and constantly expanding field. Current approaches include surgery, conventional chemotherapy and novel biologic agents as in immunotherapy, that together compose a wide armamentarium. The plethora of choices can, however, be clinically challenging in prescribing the most suitable treatment for any given patient. Fortunately, biomarkers can greatly facilitate the most appropriate selection. In recent years, RNA-based biomarkers have proven most promising. These molecules that range from small noncoding RNAs to protein coding gene transcripts can be valuable in cancer management and especially in cancer therapeutics. Compared to their DNA counterparts which are stable throughout treatment, RNA-biomarkers are dynamic. This allows prediction of success prior to treatment start and can identify alterations in expression that could reflect response. Moreover, improved nucleic acid technology allows RNA to be extracted from practically every biofluid/matrix and evaluated with exceedingly high analytic sensitivity. In addition, samples are largely obtained by minimally invasive procedures and as such can be used serially to assess treatment response real-time. This chapter provides the reader insight on currently known RNA biomarkers, the latest research employing Artificial Intelligence in the identification of such molecules and in clinical decisions driving forward the era of personalized oncology.

Biological effective dose in analysis of rectal dose in prostate cancer patients who underwent a combination therapy of VMAT and LDR with hydrogel spacer insertion

This study aimed to evaluate rectal dose reduction in prostate cancer patients who underwent a combination of volumetric modulated arc therapy (VMAT) and low‐dose‐rate (LDR) brachytherapy with insertion of hydrogel spacer (SpaceOAR). For this study, 35 patients receiving hydrogel spacer and 30 patients receiving no spacer were retrospectively enrolled. Patient was treated to doses of 45 Gy to the primary tumor site and nodal regions over 25 fractions using VMAT and 100 Gy to the prostate using prostate seed implant (PSI). In VMAT plans of patients with no spacer, mean doses of rectal wall were 43.6, 42.4, 40.1, and 28.8 Gy to the volume of 0.5, 1, 2, and 5 cm³, respectively. In patients with SpaceOAR, average rectal wall doses decreased to 39.0, 36.9, 33.5, and 23.9 Gy to the volume of 0.5, 1, 2, and 5 cm³, respectively (p < 0.01). In PSI plans, rectal wall doses were on average 78.5, 60.9, 41.8, and 14.8 Gy to the volume of 0.5, 1, 2, and 5 cm³, respectively, in patients without spacer. In contrast, the doses decreased to 34.5, 28.4, 20.6 (p < 0.01), and 8.5 Gy (p < 0.05) to rectal wall volume of 0.5, 1, 2, and 5 cm³, respectively, in patient with SpaceOAR. To demonstrate rectal sum dose sparing, dose‐biological effective dose (BED) calculation was accomplished in those patients who showed >60% overlap of rectal volumetric doses between VMAT and PSI. In patients with SpaceOAR, average BED_sum was decreased up to 34%, which was 90.1, 78.9, 65.9, and 40.8 Gy to rectal volume of 0.5, 1, 2, and 5 cm³, respectively, in comparison to 137.4, 116.7, 93.0, and 50.2 Gy to the volume of 0.5, 1, 2, and 5 cm³, respectively, in those with no spacer. Our result suggested a significant reduction of rectal doses in those patients who underwent a combination of VMAT and LDR with hydrogel spacer placement.

Development and Preliminary Evaluation of an Anthropomorphic Trans-rectal Ultrasound Prostate Brachytherapy Training Phantom

The quality of the trans-rectal ultrasound (TRUS) image, and thus seed placement during the prostate brachytherapy (PBT) procedure, relies on the user's technical and clinical competency. Simulation-based medical education can provide a structured approach for the acquisition of clinical competencies, but the efficacy of the training relies on the fidelity of the training simulators. In this work, the design, development and preliminary evaluation of an anthropomorphic training phantom for TRUS PBT is described. TRUS clinical patient data informed the design of 3-D printed moulds to fabricate prostate targets. Tissue-mimicking materials were included that had the sonographic characteristics of the prostate and overlying tissues, as well as the clinically relevant physical response, to provide haptic feedback to the user. Through an iterative design process, prototypes were constructed. These prototypes were quantitatively evaluated using a specification list and evaluated by an experienced clinical brachytherapy oncologist; their feedback was implemented, and the results of this evaluation are presented.

Reduced dose to urethra and rectum with the use of variable needle spacing in prostate brachytherapy: a potential role for robotic technology

Purpose

Several robotic delivery systems for prostate brachytherapy are under development or in pre-clinical testing. One of the features of robotic brachytherapy is the ability to vary spacing of needles at non-fixed intervals. This feature may play an important role in prostate brachytherapy, which is traditionally template-based with fixed needle spacing of 0.5 cm. We sought to quantify potential reductions in the dose to urethra and rectum by utilizing variable needle spacing, as compared to fixed needle spacing.

Material and methods

Transrectal ultrasound images from 10 patients were used by 3 experienced planners to create 120 treatment plans. Each planner created 4 plan variations per patient with respect to needle positions: ¹²⁵I fixed spacing, ¹²⁵I variable spacing, ¹⁰³Pd fixed spacing, and ¹⁰³Pd variable spacing. The primary planning objective was to achieve a prostate V₁₀₀ of 100% while minimizing dose to urethra and rectum.

Results

All plans met the objective of achieving prostate V₁₀₀ of 100%. Combined results for all plans show statistically significant improvements in all assessed dosimetric variables for urethra (U_max, U_mean, D₃₀, D₅) and rectum (R_max, R_mean, R_V100) when using variable spacing. The dose reductions for mean and maximum urethra dose using variable spacing had p values of 0.011 and 0.024 with ¹⁰³Pd, and 0.007 and 0.029 with ¹²⁵I plans. Similarly dose reductions for mean and maximum rectal dose using variable spacing had p values of 0.007 and 0.052 with ¹⁰³Pd, and 0.012 and 0.037 with ¹²⁵I plans.

Conclusions

The variable needle spacing achievable by the use of robotics in prostate brachytherapy allows for reductions in both urethral and rectal planned doses while maintaining prostate dose coverage. Such dosimetric advantages have the potential in translating to significant clinical benefits with the use of robotic brachytherapy.

Rectal injury during permanent seed implantation for prostate brachytherapy

Serious complications have not been previously reported during seed implantation for prostate brachytherapy. We present an unreported case of rectal injury caused by an ultrasound probe. A 67-year-old male presented with a serum prostate-specific antigen level of 5.50 ng/ml, a Gleason score of 7 (3 + 4) and clinical T2a adenocarcinoma of the prostate. A transperineal permanent prostate brachytherapy implantation was performed. The patient subsequently complained of abdominal pain postoperatively. A gastrointestinal perforation was suspected based on an abdominal X-ray obtained on the day after the brachytherapy. Rectal injury was recognized during an exploratory laparotomy, and a primary closure and temporary diversion ileostomy were performed. The healing of the injury was confirmed by colonoscopy and an ileostomy closure was performed 2 months after the temporary diversion. The investigating committee for this accident concluded that the ultrasound probe had perforated the rectum. This is the first case of a rectal injury during seed implantation for prostate brachytherapy.

Therapeutic effects of survivin dominant negative mutant in a mouse model of prostate cancer

PURPOSE

Patients with localized prostate cancer can usually achieve initial response to conventional treatment. However, most of them will inevitably progress to advanced disease stage. There is a clear need to develop innovative and effective therapeutics for prostate cancer. Mouse survivin T34A (mS-T34A) is a phosphorylation-defective Thr34 → Ala dominant negative mutant, which represents a potential promising target for cancer gene therapy. This study was designed to determine whether mS-T34A plasmid encapsuled by DOTAP-chol liposome (Lip-mS) has the anti-tumor activity against prostate cancer, if so, to further investigate the possible mechanisms.

METHODS

In vitro, TRAMP-C1 cells were transfected with Lip-mS and examined for apoptosis by PI staining and flow cytometric analysis. In vivo, subcutaneous prostate cancer models were established in C57BL/6 mice, which were randomly assigned into three groups to receive i.v. administrations of Lip-mS, pVITRO2-null plasmid complexed with DOTAP-chol liposome (Lip-null) or normal saline every 2 days for eight doses. Tumor volume was measured. Tumor tissues were inspected for apoptosis by TUNEL assay. Microvessel density (MVD) was determined by CD31 immunohistochemistry. Alginate-encapsulated tumor cell test was conducted to evaluate the treatment effect on angiogenesis.

RESULTS

Administration of Lip-mS resulted in significant inhibition in the growth of mouse TRAMP-C1 tumors. The anti-tumor response was associated with increased tumor cell apoptosis and decreased microvessel density.

CONCLUSIONS

The present study may be of importance in the exploration of the potential application of Lip-mS in the treatment of a broad spectrum of tumors.

Imaging in radiation oncology: a perspective

This paper reviews the integration of imaging and radiation oncology, and discusses challenges and opportunities for improving the practice of radiation oncology with imaging.

An inherent goal of radiation therapy is to deliver enough dose to the tumor to eradicate all cancer cells or to palliate symptoms, while avoiding normal tissue injury. Imaging for cancer diagnosis, staging, treatment planning, and radiation targeting has been integrated in various ways to improve the chance of this occurring. A large spectrum of imaging strategies and technologies has evolved in parallel to advances in radiation delivery. The types of imaging can be categorized into offline imaging (outside the treatment room) and online imaging (inside the treatment room, conventionally termed image-guided radiation therapy). The direct integration of images in the radiotherapy planning process (physically or computationally) often entails trade-offs in imaging performance. Although such compromises may be acceptable given specific clinical objectives, general requirements for imaging performance are expected to increase as paradigms for radiation delivery evolve to address underlying biology and adapt to radiation responses. This paper reviews the integration of imaging and radiation oncology, and discusses challenges and opportunities for improving the practice of radiation oncology with imaging.

Analysis of dose to patient, spouse/caretaker, and staff, from an implanted trackable radioactive fiducial for use in the radiation treatment of prostate cancer

PURPOSE

A fiducial tracking system based on a novel radioactive tracking technology is being developed for real-time target tracking in radiation therapy. In this study, the authors calculate the radiation dose to the patient, the spouse/caretaker, and the medical staff that would result from a 100 microCi Ir192 radioactive fiducial marker permanently implanted in the prostate of a radiation therapy patient.

METHODS

Local tissue dose was calculated by Monte Carlo simulation. The patient's whole body effective dose equivalent was calculated by summing the doses to the sensitive organs. Exposure of the spouse/caretaker was calculated from the NRC guidelines. Exposure of the medical staff was based on estimates of proximity to and time spent with the patient.

RESULTS

The local dose is below 40 Gy at 5 mm from the marker and below 10 Gy at 10 mm from the marker. The whole body effective dose equivalent to the patient is 64 mSv. The dose to the spouse/caretaker is 0.25 mSv. The annual exposures of the medical staff are 0.2 mSv for a doctor performing implantations and 0.34 mSv for a radiation therapist positioning patients for therapy.

CONCLUSIONS

The local dose is not expected to have any clinically significant effect on the surrounding tissue which is irradiated during therapy. The dose to the patient is small in comparison to the whole body dose received from the therapy itself. The exposure of all other people is well below the recommended limits. The authors conclude that there is no radiation exposure related contraindication for use of this technology in the radiation treatment of prostate cancer.

Partial cystectomy does not undermine cancer control in appropriately selected patients with urothelial carcinoma of the bladder: a population-based matched analysist

OBJECTIVES

Cancer control outcomes after partial cystectomy (PC) are not well studied. We compared the population-based rates of overall (OS) and cause-specific survival (CSS) in patients with urothelial carcinoma of the urinary bladder (UCB) treated with PC or radical cystectomy (RC).

METHODS

Within the Surveillance Epidemiology and End Results-9 database, we identified 7243 patients treated with PC (n = 1573) or RC (n = 5670), who had pathologic T(1-4)N(1-2)M(0) UCB. Matched Kaplan-Meier survival analyses compared the effect of PC vs RC on OS and CSS.

RESULTS

In the entire cohort, the OS and CSS estimates at 5 years were 57.2% and 76.4%, respectively, for PC patients and 50.2% and 65.8%, respectively, for RC patients (P < .001). In the cohort matched for age, race, pT stage, pN stage, tumor grade, and year of surgery, at 5 years the OS and CSS estimates were 56.0% and 73.5%, respectively, for PC patients, and 50.9% and 67.5%, respectively, for RC patients (OS, P = .03 and CSS, P < .001). When the number of removed lymph nodes was added to the matching criteria, the 5-year OS and CSS estimates were 57.2% and 70.3%, respectively, for PC patients, and 54.6% and 69.2%, respectively, for RC patients (HR 1.1, P = .3 and HR 1.1, P = .5).

CONCLUSIONS

Partial cystectomy does not undermine cancer control in appropriately selected patients with UCB.

Cytoreductive partial nephrectomy does not undermine cancer control in metastatic renal cell carcinoma: a population-based study

OBJECTIVES

We examined the population-based rates of cancer-specific survival in patients with metastatic renal cell carcinoma (MRCC) treated with either partial (PN) or radical cytoreductive nephrectomy (RN).

METHODS

Patients diagnosed with MRCC and treated with either PN or RN were identified within nine SEER cancer registries. Matched and unmatched Kaplan-Meier survival analyses, as well as multivariable Cox regression models compared the effect of RN (n = 1997, 97.8%) vs. PN (n = 46, 2.2%) on cancer-specific survival (CSS). Covariates consisted of age, gender, community type (rural vs urban), race, Surveillance, Epidemiology, and End Results (SEER) registry, tumor size and year of diagnosis.

RESULTS

In multivariable unmatched Cox regression analyses, no statistically significantly difference was found in CSS between the two groups (hazard ratio [HR] 1.40, P = .16). Similarly, no difference in CSS was found in the matched analyses (HR 1.35, log rank P = .34).

CONCLUSION

Cytoreductive PN does not appear to undermine survival in patients with MRCC.

Effects of sustained antiangiogenic therapy in multistage prostate cancer in TRAMP model

Antiangiogenic therapy is a promising alternative for prostate cancer growth and metastasis and holds great promise as an adjuvant therapy. The present study evaluated the potential of stable expression of angiostatin and endostatin before the onset of neoplasia and during the early and late stages of prostate cancer progression in transgenic adenocarcinoma of mouse prostate (TRAMP) mice. Groups of 5-, 10-, and 18-week-old male TRAMP mice received recombinant adeno-associated virus-6 encoding mouse endostatin plus angiostatin (E+A) by i.m. injection. The effects of therapy were determined by sacrificing groups of treated mice at defined stages of tumor progression and following cohorts of similarly treated mice for long-term survival. Results indicated remarkable survival after recombinant adeno-associated virus-(E+A) therapy only when the treatment was given at an earlier time, before the onset of high-grade neoplasia, compared with treatment given for invasive cancer. Interestingly, early-stage antiangiogenic therapy arrested the progression of moderately differentiated carcinoma to poorly differentiated state and distant metastasis. Immunohistochemical analysis of the prostate from treated mice indicated significantly lower endothelial cell proliferation and increased tumor cell apoptosis. Vascular endothelial growth factor receptor (VEGFR)-2 expression was significantly down-regulated in tumor endothelium after treatment but not VEGFR-1. Analysis of the neuroendocrine marker synaptophysin expression indicated that antiangiogenic therapy given at an early-stage disease reduced neuroendocrine transition of the epithelial tumors. These studies indicate that stable endostatin and angiostatin gene therapy may be more effective for minimally invasive tumors rather than advanced-stage disease.