Elective irradiation of pelvic lymph nodes during postprostatectomy salvage radiotherapy.

BACKGROUND: Success rates with salvage radiotherapy (SRT) in men who have a postprostatectomy biochemical relapse are suboptimal. One treatment-intensification strategy includes elective irradiation of the pelvic lymph nodes with whole pelvis radiotherapy (WPRT). METHODS: An inter-institutional retrospective cohort study compared outcomes for patients who received SRT at 2 separate academic institutions with disparate treatment paradigms: almost exclusively favoring WPRT (n = 112) versus limiting treatment to the prostate bed (PBRT) (n = 135). Patients were excluded if they had lymph node involvement or if they received androgen-deprivation therapy. The Cox proportional hazards model was used to adjust for potential confounders. RESULTS: In total, 247 patients were analyzed with a median follow-up of 4 years. The pre-SRT prostate-specific antigen (PSA) level (adjusted hazard ratio [HR], 1.58; P < .0001) and a Gleason score of 8 to 10 (adjusted HR, 3.21; P < .0001) were identified as independent predictors of increased risk of biochemical PSA progression after SRT. However, WPRT was not independently associated with biochemical progression-free survival in the multivariate model (adjusted HR, 0.79; P = .20). Neither low-risk patients nor high-risk patients (defined a priori by a preoperative PSA level ≥20 ng/mL, a pathologic Gleason score between 8 and 10, or pathologic T3 tumor classification) benefited from WPRT. Overall survival was similar between treatment groups. When restricting the analysis to patients with pre-SRT PSA levels ≥0.4 ng/mL (n = 139), WPRT was independently associated with a 53% reduction in the risk of biochemical progression (adjusted HR, 0.47; P = .031). CONCLUSIONS: WPRT did not improve outcomes among the entire group but was independently associated with improved biochemical control among patients with pre-SRT PSA levels ≥0.4 ng/mL.

Identifying appropriate patients for early salvage radiotherapy after prostatectomy.

PURPOSE: It remains unclear whether relapsed prostate specific antigen at postprostatectomy salvage radiotherapy impacts outcomes as long it is 1.0 ng/ml or less. MATERIALS AND METHODS: We performed a retrospective cohort study of 197 patients treated with salvage radiotherapy in the setting of detectable relapsed prostate specific antigen 1.0 ng/ml or less. Patients were excluded from analysis if they had lymph node involvement or received androgen deprivation therapy. Freedom from prostate specific antigen progression after salvage radiotherapy was analyzed by a Cox regression model. RESULTS: Median relapsed prostate specific antigen was 0.33 ng/ml (range 0.07 to 1.0). There was 86% freedom from prostate specific antigen progression at a median followup of 52 months. Relapsed prostate specific antigen (HR 1.9, p = 0.004), Gleason score 8-10 (HR 5.2, p <0.001) and negative margin status (HR 2.0, p = 0.02) were independently associated with an increased risk of prostate specific antigen progression after salvage radiotherapy. We identified interaction between relapsed prostate specific antigen and Gleason score (p = 0.04) but not margin status. A significant association was noted between higher relapsed prostate specific antigen and prostate specific antigen progression after salvage radiotherapy in patients with Gleason score 8-10 but not 7 or less. In patients with Gleason score 8-10 the rate of freedom from prostate specific antigen progression at 53 months was 77% vs 26% when salvage radiotherapy was initiated at a relapsed prostate specific antigen of 0.33 or less vs 0.34 to 1.0 ng/ml (log rank p = 0.003). CONCLUSIONS: Different relapsed prostate specific antigen thresholds for unsuccessful salvage radiotherapy may exist based on Gleason score. These data suggest that patients with Gleason score 8-10 should be offered salvage radiotherapy at the earliest detectable relapsed prostate specific antigen, even 0.33 ng/ml or less. Those with Gleason score 7 or less may have the opportunity to be followed with serial prostate specific antigen measurements to improve risk stratification, and delay and/or avoid the potential toxicity of salvage radiotherapy.

Phase 1 Study of Neoadjuvant Short-Course Radiation Therapy Concurrent With Infusional 5-Fluorouracil for the Treatment of Locally Advanced Rectal Cancer.

PURPOSE: To assess the safety and feasibility of neoadjuvant short-course radiation therapy (RT) concurrent with continuous infusion 5-fluorouracil (5-FU) for the treatment of locally advanced rectal cancer. METHODS AND MATERIALS: Patients with cT3-4 or N + rectal adenocarcinoma based on ultrasound or magnetic resonance imaging were prospectively enrolled in this study. Study treatment consisted of continuous infusion 5-FU combined with short-course RT (5 Gy x 5 fractions) followed by 4 cycles of mFOLFOX, total mesorectal excision (TME), and 6 cycles of adjuvant mFOLFOX. To mitigate the potential added toxicity from concurrent 5-FU, intensity modulated RT was used. Using the continual reassessment method, the dose of 5-FU was escalated from 100 to a maximum-tolerated dose of 200 mg/m2/d. RESULTS: Fourteen patients were accrued. All patients completed continuous infusion 5-FU and short-course RT and the 5-FU dose was safely escalated to 200 mg/m2/d with no dose-limiting toxicity. Thirteen patients received the neoadjuvant mFOLFOX, and only 1 patient went straight to surgery after chemoradiation. Clinical response was 21% complete, 63% partial, 14% stable disease, and no patients had progression. Three patients with cCR had negative biopsies and did not have TME. Pathologic response was 64% partial response and 14% stable disease. No patients had pathologic progression. The most common grade 3 and 4 toxicities were cytopenias. The most common grade 1 and 2 toxicities were cytopenia, fatigue, diarrhea, and nausea. CONCLUSIONS: Our findings suggest that concurrent chemotherapy with neoadjuvant short-course RT is feasible and can be safely given with concurrent continuous infusion 5-FU. This works adds to the growing evidence that short-course RT is not only equivalent to long-course RT, but also may provide additional benefits, such as allowing for a transition to full dose systemic therapy in the neoadjuvant setting, selective organ preservation in complete responders, and providing a more convenient and cost-effective way of delivering pelvic RT.

The brain-penetrant clinical ATM inhibitor AZD1390 radiosensitizes and improves survival of preclinical brain tumor models.

Poor survival rates of patients with tumors arising from or disseminating into the brain are attributed to an inability to excise all tumor tissue (if operable), a lack of blood-brain barrier (BBB) penetration of chemotherapies/targeted agents, and an intrinsic tumor radio-/chemo-resistance. Ataxia-telangiectasia mutated (ATM) protein orchestrates the cellular DNA damage response (DDR) to cytotoxic DNA double-strand breaks induced by ionizing radiation (IR). ATM genetic ablation or pharmacological inhibition results in tumor cell hypersensitivity to IR. We report the primary pharmacology of the clinical-grade, exquisitely potent (cell IC50, 0.78 nM), highly selective [>10,000-fold over kinases within the same phosphatidylinositol 3-kinase-related kinase (PIKK) family], orally bioavailable ATM inhibitor AZD1390 specifically optimized for BBB penetration confirmed in cynomolgus monkey brain positron emission tomography (PET) imaging of microdosed 11C-labeled AZD1390 (Kp,uu, 0.33). AZD1390 blocks ATM-dependent DDR pathway activity and combines with radiation to induce G2 cell cycle phase accumulation, micronuclei, and apoptosis. AZD1390 radiosensitizes glioma and lung cancer cell lines, with p53 mutant glioma cells generally being more radiosensitized than wild type. In in vivo syngeneic and patient-derived glioma as well as orthotopic lung-brain metastatic models, AZD1390 dosed in combination with daily fractions of IR (whole-brain or stereotactic radiotherapy) significantly induced tumor regressions and increased animal survival compared to IR treatment alone. We established a pharmacokinetic-pharmacodynamic-efficacy relationship by correlating free brain concentrations, tumor phospho-ATM/phospho-Rad50 inhibition, apoptotic biomarker (cleaved caspase-3) induction, tumor regression, and survival. On the basis of the data presented here, AZD1390 is now in early clinical development for use as a radiosensitizer in central nervous system malignancies.

Orally Bioavailable and Blood-Brain Barrier-Penetrating ATM Inhibitor (AZ32) Radiosensitizes Intracranial Gliomas in Mice.

Inhibition of ataxia-telangiectasia mutated (ATM) during radiotherapy of glioblastoma multiforme (GBM) may improve tumor control by short-circuiting the response to radiation-induced DNA damage. A major impediment for clinical implementation is that current inhibitors have limited central nervous system (CNS) bioavailability; thus, the goal was to identify ATM inhibitors (ATMi) with improved CNS penetration. Drug screens and refinement of lead compounds identified AZ31 and AZ32. The compounds were then tested in vivo for efficacy and impact on tumor and healthy brain. Both AZ31 and AZ32 blocked the DNA damage response and radiosensitized GBM cells in vitro AZ32, with enhanced blood-brain barrier (BBB) penetration, was highly efficient in vivo as radiosensitizer in syngeneic and human, orthotopic mouse glioma model compared with AZ31. Furthermore, human glioma cell lines expressing mutant p53 or having checkpoint-defective mutations were particularly sensitive to ATMi radiosensitization. The mechanism for this p53 effect involves a propensity to undergo mitotic catastrophe relative to cells with wild-type p53. In vivo, apoptosis was >6-fold higher in tumor relative to healthy brain after exposure to AZ32 and low-dose radiation. AZ32 is the first ATMi with oral bioavailability shown to radiosensitize glioma and improve survival in orthotopic mouse models. These findings support the development of a clinical-grade, BBB-penetrating ATMi for the treatment of GBM. Importantly, because many GBMs have defective p53 signaling, the use of an ATMi concurrent with standard radiotherapy is expected to be cancer-specific, increase the therapeutic ratio, and maintain full therapeutic effect at lower radiation doses. Mol Cancer Ther; 17(8); 1637-47. ©2018 AACR.

Dlx3 transcriptional regulation of osteoblast differentiation: temporal recruitment of Msx2, Dlx3, and Dlx5 homeodomain proteins to chromatin of the osteocalcin gene.

Genetic studies show that Msx2 and Dlx5 homeodomain (HD) proteins support skeletal development, but null mutation of the closely related Dlx3 gene results in early embryonic lethality. Here we find that expression of Dlx3 in the mouse embryo is associated with new bone formation and regulation of osteoblast differentiation. Dlx3 is expressed in osteoblasts, and overexpression of Dlx3 in osteoprogenitor cells promotes, while specific knock-down of Dlx3 by RNA interference inhibits, induction of osteogenic markers. We characterized gene regulation by Dlx3 in relation to that of Msx2 and Dlx5 during osteoblast differentiation. Chromatin immunoprecipitation assays revealed a molecular switch in HD protein association with the bone-specific osteocalcin (OC) gene. The transcriptionally repressed OC gene was occupied by Msx2 in proliferating osteoblasts, while Dlx3, Dlx5, and Runx2 were recruited postproliferatively to initiate transcription. Dlx5 occupancy increased over Dlx3 in mature osteoblasts at the mineralization stage of differentiation, coincident with increased RNA polymerase II occupancy. Dlx3 protein-DNA interactions stimulated OC promoter activity, while Dlx3-Runx2 protein-protein interaction reduced Runx2-mediated transcription. Deletion analysis showed that the Dlx3 interacting domain of Runx2 is from amino acids 376 to 432, which also include the transcriptionally active subnuclear targeting sequence (376 to 432). Thus, we provide cellular and molecular evidence for Dlx3 in regulating osteoprogenitor cell differentiation and for both positive and negative regulation of gene transcription. We propose that multiple HD proteins in osteoblasts constitute a regulatory network that mediates development of the bone phenotype through the sequential association of distinct HD proteins with promoter regulatory elements.

Comparative study of late rectal toxicity in prostate cancer patients treated with low-dose-rate brachytherapy: With or without supplemental external beam radiotherapy.

PURPOSE: Supplemental external beam radiation therapy (sEBRT) is often prescribed in men undergoing low-dose-rate (LDR) brachytherapy. A population of patients was analyzed to assess the effect of sEBRT on late rectal toxicity. It was hypothesized that sEBRT + LDR would be associated with a higher risk of late rectal toxicity. METHODS AND MATERIALS: This retrospective cohort study examined LDR brachytherapy patients, treated with or without sEBRT, with a minimum of 5-year followup. Longitudinal assessments were evaluated using the computerized patient record system. The Kaplan-Meier method was used for analysis. RESULTS: Median followup was 7.5 years for 245 patients from 2004 to 2007. sEBRT was administered to 33.5%. Followup beyond 5 years was available for 89%. Overall rates of Grade ≥2 and ≥3 rectal toxicities were 6.9% and 2.9%, respectively. The risk of Grade ≥2 rectal toxicity was 2.8-fold higher for patients receiving sEBRT (95% confidence interval: 1.1-7.2; p = 0.02). The risk of Grade ≥3 rectal toxicity was 11.9-fold higher for patients who received sEBRT (1.5-97.4, 95% confidence interval; p = 0.003). Six of seven patients with a Grade ≥3 rectal toxicity received sEBRT, including one who required an abdominoperineal resection. Median post-LDR D90, V150, V200, and R100 values were 103.3%, 59.4%, 30.1%, and 0.5 cc. CONCLUSIONS: In a cohort of LDR brachytherapy patients with high rates of followup, sEBRT + LDR was associated with significantly higher risk of Grade ≥2 and ≥3 late rectal toxicity. This analysis supports previous findings and maintains concern about the supplemental use of external beam radiation therapy with LDR brachytherapy while its benefit for tumor control has yet to be prospectively validated.

Management of Postprostatectomy Biochemical Relapse With Salvage Radiotherapy: Results of an International Survey.

OBJECTIVES: The management of patients with postprostatectomy salvage radiotherapy (SRT) presents radiation oncologists (ROs) with multiple treatment decisions that may impact outcomes. As the evidence addressing these issues is limited to retrospective data, it was hypothesized that widely disparate treatment paradigms exist. METHODS: A 21-question survey was sent through SurveyMonkey to members of the American Society of Radiation Oncology. RESULTS: A total of 999 ROs responded. Threshold rPSA values to initiate SRT ranged from 0.1 to 1 ng/mL. The highest dose prescribed by ROs ranged from <60 to >70.2 Gy. Elective lymph node irradiation was offered by 74%, and the majority (64%) referenced the Roach formula, Kattan nomogram, or D'Amico risk stratification to decide when it was appropriate. There was variability in pelvic field design with a preference to place the superior field border at either the upper, middle, or lower sacroiliac joint by 57.6%, 28.8%, and 13.6% of respondents, respectively. Adjuvant androgen deprivation therapy (ADT) was offered by 74%. CONCLUSIONS: Disparate treatment paradigms exist for SRT that may impact patient outcomes. Variability includes patient selection, treatment design, and recommendations for ADT. Many reference formulas to predict the benefit of pelvic lymph node irradiation that are not yet validated in the postprostatectomy setting. These data make it clear that well-designed, prospective clinical trials are needed to better evaluate the role of larger treatment fields, dose escalation, and ADT for the thousands of patients who are treated with postprostatectomy SRT each year.

Examining the relationship between pre- and postimplant geometry in prostate low-dose-rate brachytherapy and its correlation with dosimetric quality using the similarity concept.

PURPOSE: This is a retrospective study in which we define multiple metrics for similarity and then inquire on the relationship between similarity and currently used dosimetric quantities describing preimplant and postimplant plans. METHODS AND MATERIALS: We analyzed a unique cohort of 94 consecutively performed prostate seed implant patients, associated with excellent dosimetric and clinical outcomes. For each patient, an ultrasound (US) preimplant and two CT postimplant (Day 0 and Day 30) studies were available. Measures for similarity were created and computed using feature vectors based on two classes of moments: first, invariant to rotation and translation, and the second polar-radius moments invariant to rotation, translation, and scaling. Both similarity measures were calibrated using controlled perturbations (random and systematic) of seed positions and contours in different size implants, thus producing meaningful numerical threshold values used in the clinical analysis. RESULTS: An important finding is that similarity, for both seed distributions and contours, improves significantly when scaling invariance is added to translation and rotation. No correlation between seed and contours similarity was found. In the setting of preplanned prostate seed implants using preloaded needles, based on our data, similarity between preimplant and postimplant plans does not correlate with either minimum dose to 90% of the volume of the prostate or analogous similarity metrics for prostate contours. CONCLUSIONS: We have developed novel tools and metrics, which will allow practitioners to better understand the relationship between preimplant and postimplant plans. Geometrical similarity between a preplan and an actual implant, although useful, does not seem to be necessary to achieve minimum dose to 90% of the volume of the prostate-good dosimetric implants.