Abstract: Proton radiation therapy is an effective modality for cancer treatments, but the cost of proton therapy is much higher compared to conventional radiotherapy and this presents a formidable barrier to most clinical practices that wish to offer proton therapy. Little attention in literature has been paid to the costs associated with collimators, range compensators and hypofractionation. The objective of this study was to evaluate the feasibility of cost-saving modifications to the present standard of care for proton treatments for prostate cancer. In particular, we quantified the dosimetric impact of a treatment technique in which custom fabricated collimators were replaced with a multileaf collimator (MLC) and the custom range compensators (RC) were eliminated. The dosimetric impacts of these modifications were assessed for 10 patients with a commercial treatment planning system (TPS) and confirmed with corresponding Monte Carlo simulations. We assessed the impact on lifetime risks of radiogenic second cancers using detailed dose reconstructions and predictive dose-risk models based on epidemiologic data. We also performed illustrative calculations, using an isoeffect model, to examine the potential for hypofractionation. Specifically, we bracketed plausible intervals of proton fraction size and total treatment dose that were equivalent to a conventional photon treatment of 79.2 Gy in 44 fractions. Our results revealed that eliminating the RC and using an MLC had negligible effect on predicted dose distributions and second cancer risks. Even modest hypofractionation strategies can yield substantial cost savings. Together, our results suggest that it is feasible to modify the standard of care to increase treatment efficiency, reduce treatment costs to patients and insurers, while preserving high treatment quality.
Abstract: Background: Androgen deprivation therapy (ADT) for prostate cancer (PCa) is associated with multiple metabolic complications, previously predominantly evaluated in the white population. Methods: A chart-based retrospective review was conducted on black patients with PCa, considered for ADT, from September 2007 to July 2010. Baseline data were collected on body mass index (BMI), vitamin-D status, bone mineral density (BMD), dyslipidemia and diabetes. Overweight and obesity were classified as BMI ≥ 25 and BMI ≥ 30, respectively. Vitamin-D sufficiency was defined as levels ≥30 ng/mL, insufficiency as <30 ng/mL and deficiency as ≤20 ng/mL. Osteopenia was defined as T scores between −1 to −2.5 and osteoporosis when T scores ≤−2.5. Results: Of the initial cohort of 130 black men, 111 (85.4%) patients underwent ADT. At baseline, average BMI was 28.1 ± 5.9 with 43.3% of men being overweight and 30.8% obese. More than one-third of the patients had pre-existing dyslipidemia while 28.8% were diabetics. 50% were vitamin-D deficient while 41% had low bone mass. Conclusions: Black men with PCa presenting for consideration of ADT have a high prevalence of existing metabolic risk factors. Close monitoring of this patient population is needed during ADT to prevent and treat metabolic complications.
Abstract: Melanoma and prostate cancer are the fifth and first most common cancers in men within the United States, respectively. The association between the two cancers lies in the mutual androgen-dependence. However, the relationship between prostate cancer history and melanoma development remains to be further elucidated. We aim to determine the odds of history of prostate cancer among men with melanoma as compared to time-frame, clinic, and provider-matched controls without melanoma within a single academic surgical center. We present a case-control study comparing men treated for melanoma and non-melanoma cancer by a single provider between 2010 and 2014 within an academic dermatologic surgical center. Overall, there were nine cases of prostate cancer among the melanoma group and two cases amongst the controls—a statistically significant difference in both uni- and multivariable analyses (p = 0.057 [95% CI 1, 23.5], p = 0.042 [95% CI 1.1, 129], respectively). Body mass index, alcohol use, and skin type II were significant risk factors for melanoma (p = 0.011 [95% CI 1, 1.3], 0.005 [95% CI 1.4, 7], 0.025 [95% CI 1.1, 3.3], respectively). There were more immunosuppressed controls (p = 0.002); however, the melanoma patients had a significantly longer duration of immunosuppression (11.6 vs. 1.9 years, p < 0.001 [95% CI 0.03, 0.5]). Melanoma screenings for men should include questions on prostate cancer history. Prostate cancer patients may benefit from more frequent and comprehensive melanoma screening.
Abstract: Protein Phosphatase 2A (PP2A) is a major serine/threonine phosphatase in cells. It consists of a catalytic subunit (C), a structural subunit (A), and a regulatory/variable B-type subunit. PP2A has a critical role to play in homeostasis where its predominant function is as a phosphatase that regulates the major cell signaling pathways in cells. Changes in the assembly, activity and substrate specificity of the PP2A holoenzyme have a direct role in disease and are a major contributor to the maintenance of the transformed phenotype in cancer. We have learned a lot about how PP2A functions from specific mutations that disrupt the core assembly of PP2A and from viral proteins that target PP2A and inhibit its effect as a phosphatase. This prompted various studies revealing that restoration of PP2A activity benefits some cancer patients. However, our understanding of the mechanism of action of this is limited because of the complex nature of PP2A holoenzyme assembly and because it acts through a wide variety of signaling pathways. Information on PP2A is also conflicting as there are situations whereby inactivation of PP2A induces apoptosis in many cancer cells. In this review we discuss this relationship and we also address many of the pertinent and topical questions that relate to novel therapeutic strategies aimed at altering PP2A activity.
Abstract: An intensity-modulated proton therapy (IMPT) patient-specific quality assurance (PSQA) program based on measurement alone can be very time consuming due to the highly modulated dose distributions of IMPT fields. Incorporating independent dose calculation and treatment log file analysis could reduce the time required for measurements. In this article, we summarize our effort to develop an efficient and effective PSQA program that consists of three components: measurements, independent dose calculation, and analysis of patient-specific treatment delivery log files. Measurements included two-dimensional (2D) measurements using an ionization chamber array detector for each field delivered at the planned gantry angles with the electronic medical record (EMR) system in the QA mode and the accelerator control system (ACS) in the treatment mode, and additional measurements at depths for each field with the ACS in physics mode and without the EMR system. Dose distributions for each field in a water phantom were calculated independently using a recently developed in-house pencil beam algorithm and compared with those obtained using the treatment planning system (TPS). The treatment log file for each field was analyzed in terms of deviations in delivered spot positions from their planned positions using various statistical methods. Using this improved PSQA program, we were able to verify the integrity of the data transfer from the TPS to the EMR to the ACS, the dose calculation of the TPS, and the treatment delivery, including the dose delivered and spot positions. On the basis of this experience, we estimate that the in-room measurement time required for each complex IMPT case (e.g., a patient receiving bilateral IMPT for head and neck cancer) is less than 1 h using the improved PSQA program. Our experience demonstrates that it is possible to develop an efficient and effective PSQA program for IMPT with the equipment and resources available in the clinic.
Abstract: Cancer of the brain and central nervous system (CNS) is the second most common of all pediatric cancers. Treatment of many of these cancers includes radiation therapy of which radiation induced cerebral necrosis (RICN) can be a severe and potentially devastating side effect. Risk factors for RICN include brain volume irradiated, the dose given per fraction and total dose. Thirteen pediatric patients were selected for this study to determine the difference in predicted risk of RICN when treating with volumetric modulated arc therapy (VMAT) compared to passively scattered proton therapy (PSPT) and intensity modulated proton therapy (IMPT). Plans were compared on the basis of dosimetric endpoints in the planned treatment volume (PTV) and brain and a radiobiological endpoint of RICN calculated using the Lyman-Kutcher-Burman probit model. Uncertainty tests were performed to determine if the predicted risk of necrosis was sensitive to positional errors, proton range errors and selection of risk models. Both PSPT and IMPT plans resulted in a significant increase in the maximum dose to the brain, a significant reduction in the total brain volume irradiated to low doses, and a significant lower predicted risk of necrosis compared with the VMAT plans. The findings of this study were upheld by the uncertainty analysis.