Impact of Relative Biologic Effectiveness for Proton Therapy for Head and Neck and Skull-Base Tumors: A Technical and Clinical Review.

Proton therapy has emerged as a crucial tool in the treatment of head and neck and skull-base cancers, offering advantages over photon therapy in terms of decreasing integral dose and reducing acute and late toxicities, such as dysgeusia, feeding tube dependence, xerostomia, secondary malignancies, and neurocognitive dysfunction. Despite its benefits in dose distribution and biological effectiveness, the application of proton therapy is challenged by uncertainties in its relative biological effectiveness (RBE). Overcoming the challenges related to RBE is key to fully realizing proton therapy's potential, which extends beyond its physical dosimetric properties when compared with photon-based therapies. In this paper, we discuss the clinical significance of RBE within treatment volumes and adjacent serial organs at risk in the management of head and neck and skull-base tumors. We review proton RBE uncertainties and its modeling and explore clinical outcomes. Additionally, we highlight technological advancements and innovations in plan optimization and treatment delivery, including linear energy transfer/RBE optimizations and the development of spot-scanning proton arc therapy. These advancements show promise in harnessing the full capabilities of proton therapy from an academic standpoint, further technological innovations and clinical outcome studies, however, are needed for their integration into routine clinical practice.

Elective Irradiation of Retropharyngeal Lymph Nodes as an Indication for Adjuvant Radiation Therapy After Transoral Surgery for Tonsil Cancer.

Treatment of squamous cell carcinoma of the tonsil involves primary radiation therapy (RT) or surgical resection. Historically, if RT was the primary or adjuvant treatment modality, most of the bilateral retropharyngeal lymph nodes (RPLNs) were treated electively with a therapeutic dose for subclinical disease, regardless of whether radiographically pathologic lymph nodes were seen on initial diagnostic imaging. De-escalation strategies include the incorporation of transoral surgery with the goal to either eliminate or reduce the dose of adjuvant RT or chemotherapy. Transoral surgery does not include elective removal of the RPLNs, and no guideline or outcome paper recommends adjuvant RT specifically to electively treat RPLNs. In this Topic Discussion, we discuss pertinent literature and suggest management decisions. The management decisions discussed in this Topic Discussion pertain to only tonsillar primaries and not those of the soft palate or base of the tongue.

Local and distant brain control in melanoma and NSCLC brain metastases with concurrent radiosurgery and immune checkpoint inhibition.

INTRODUCTION: The treatment of brain metastases with stereotactic radiosurgery (SRS) in combination with immune checkpoint inhibitors (ICI) has become more common in recent years, but there is a lack of prospective data on cancer control outcomes when these therapies are administered concurrently. METHODS: Data were retrospectively reviewed for patients with non-small cell lung cancer (NSCLC) and melanoma brain metastases treated with SRS at a single institution from May 2008 to January 2017. A parametric proportional hazard model is used to detect the effect of concurrent ICI within 30, 60, or 90 days of ICI administration on local control and distant in-brain control. Other patient and lesion characteristics are treated as covariates and adjusted in the regression. A frailty term is added in the baseline hazard to capture the within-patient correlation. RESULTS: We identified 144 patients with 477 total lesions, including 95 NSCLC patients (66.0%), and 49 (34.0%) melanoma patients. On multivariate analysis, concurrent SRS and ICI (SRS within 30 days of ICI administration) was not associated with local control but was associated with distant brain control. When controlling for prior treatment to lesion, number of lesions, and presence of extracranial metastases, patients receiving this combination had a statistically significant decrease in distant brain failure compared to patients that received non-concurrent ICI or no ICI (HR 0.15; 95% CI 0.05-0.47, p = 0.0011). CONCLUSION: Concurrent ICI can enhance the efficacy of SRS. Prospective studies would allow for stronger evidence to support the impact of concurrent SRS and ICI on disease outcomes.

Establishing Cost-Effective Allocation of Proton Therapy for Patients With Mediastinal Hodgkin Lymphoma.

PURPOSE: For curative treatment of Hodgkin lymphoma, radiation therapy benefit must be weighed against toxicity. Although more costly, proton radiation therapy reduces dose to healthy tissue, potentially improving the therapeutic ratio compared with photons. We sought to determine the cost-effectiveness of proton versus photon therapy for mediastinal Hodgkin lymphoma (MHL) based on reduced heart disease. METHODS AND MATERIALS: Our model approach was 2-fold: (1) Use patient-level dosimetric information for a cost-effectiveness analysis using a Markov cohort model. (2) Use population-based data to develop guidelines for policymakers to determine thresholds of proton therapy favorability for a given photon dose. The HD14 trial informed relapse risk; coronary heart disease risk was informed by the Framingham risk calculator modified by the mean heart dose (MHD) from radiation. Sensitivity analyses assessed model robustness and identified the most influential model assumptions. A 30-year-old adult with MHL was the base case using 30.6-Gy proton therapy versus photon intensity modulated radiation therapy. RESULTS: Proton therapy was not cost-effective in the base case for male ($129,000/ quality-adjusted life years [QALYs]) or female patients ($196,000/QALY). A 5-Gy MHD decrease was associated with proton therapy incremental cost-effectiveness ratio <$100,000/QALY in 40% of scenarios. The hazard ratio associating MHD and heart disease was the most influential clinical parameter. CONCLUSIONS: Proton therapy may be cost-effective a select minority of patients with MHL based on age, sex, and MHD reduction. We present guidance for clinicians using MHD to aid decision-making for radiation therapy modality.

Isocitrate dehydrogenase 1 mutant glioblastomas demonstrate a decreased rate of pseudoprogression: a multi-institutional experience.

BACKGROUND: Pseudoprogression (psPD) represents false radiologic evidence of tumor progression and is observed in some glioblastoma (GBM) patients after postoperative chemoradiation (CRT) with temozolomide (TMZ). The ambiguity of the psPD diagnosis confounds identification of true progression and may lead to unnecessary interventions. The association between psPD and isocitrate dehydrogenase 1 (IDH1) mutational (mut) status is understudied, and its incidence may alter clinical decision making. METHODS: We retrospectively evaluated 120 patients with IDH1-mut (n = 60) and IDH1-wild-type (IDH-WT; [n = 60]) GBMs who received postoperative CRT with TMZ at 4 academic institutions. Response Assessment in Neuro-Oncology criteria were used to identify psPD rates in routine brain MRIs performed up to 90 days after CRT completion. RESULTS: Within 90 days of completing CRT, 9 GBM patients (1 [1.7%] IDH1-mut and 8 [13.3%] IDH1-WTs) demonstrated true progression, whereas 17 patients (3 [5%] IDH1-muts and 14 [23.3%] IDH1-WTs) demonstrated psPD (P = .004). IDH1-mut GBMs had a lower probability of psPD (hazard ratio: 0.173, 95% CI, 0.047-0.638, P = .008). Among the patients with radiologic signs suggestive of progression (n = 26), psPD was found to be the cause in 3 of 4 (75.0%) of the IDH1-mut GBMs and 14 of 22 (63.6%) of the IDH1-WT GBMs (P = .496). Median overall survival for IDH1-mut and IDH1-WT GBM patients was 40.3 and 23.0 months, respectively (P < .001). CONCLUSIONS: IDH1-mut GBM patients demonstrate lower absolute rates of psPD expression. Irrespective of GBM subtype, psPD expression was more likely than true progression within 90 days of completing CRT. Continuing adjuvant treatment for IDH1-mut GBMs is suggested if radiologic progression is suspected during this time interval.

Using the Radiosensitivity Index (RSI) to Predict Pelvic Failure in Endometrial Cancer Treated With Adjuvant Radiation Therapy.

PURPOSE: Variability exists in the adjuvant treatment for endometrial cancer (EC) based on surgical pathology and institutional preference. The radiosensitivity index (RSI) is a previously validated multigene expression index that estimates tumor radiosensitivity. We evaluate RSI as a genomic predictor for pelvic failure (PF) in EC patients treated with adjuvant radiation therapy (RT). METHODS AND MATERIALS: Using our institutional tissue biorepository, we identified EC patients treated between January 1999 and April 2011 with primarily endometrioid histology (n = 176; 86%) who received various adjuvant therapies. The RSI 10-gene signature was calculated for each sample using the previously published algorithm. Radiophenotype was determined using the previously identified cutpoint where RSI ≥ 0.375 denotes radioresistance (RR) and RSI < 0.375 describes radiosensitivity. RESULTS: A total of 204 patients were identified, of which 83 (41%) were treated with adjuvant RT. Median follow-up was 38.5 months. All patients underwent hysterectomy with bilateral salpingo-oophorectomy with the majority undergoing lymph node dissection (n = 181; 88%). In patients treated with radiation, RR tumors were more likely to experience PF (3-year pelvic control 84% vs 100%; P = .02) with worse PF-free survival (PFFS) (3-year PFFS 65% vs 89%; P = .04). Furthermore, in the patients who did not receive RT, there was no difference in PF (P = .87) or PFFS (P = .57) between the RR/radiosensitive tumors. On multivariable analysis, factors that continued to predict for PF included the RR phenotype (hazard ratio [HR], 12.2; P = .003), lymph node involvement (HR, 4.4; P = .02), and serosal or adnexal involvement (HR, 5.3; P = .01). CONCLUSIONS: On multivariable analysis, RSI was found to be a significant predictor of PF in patients treated with adjuvant RT. We propose using RSI to predict which patients are at higher risk for failing in the pelvis and may be candidates for treatment escalation in the adjuvant setting.

Novel Dose Escalation Approaches for Stereotactic Body Radiotherapy to Adrenal Oligometastases: A Single-Institution Experience.

OBJECTIVES: The role of local disease control in the oligometastatic setting is evolving. Stereotactic body radiation therapy (SBRT) is a noninvasive treatment option for oligometastases; however, using ablative radiation doses for adrenal metastases raises concern given the proximity to radiosensitive organs. Novel treatment techniques may allow for selective dose escalation to improve local control (LC) while minimizing dose to nearby critical structures. MATERIALS AND METHODS: We retrospectively reviewed patients with adrenal oligometastases treated with SBRT from 2013 to 2018. LC, disease-free survival, and overall survival were estimated using Kaplan-Meier methods. Predictors of outcomes were evaluated by log-rank and Cox proportional hazard analyses. RESULTS: We identified 45 adrenal oligometastases in 41 patients treated with SBRT. The median age at treatment was 67 years (range, 40 to 80). The most common primary histologies were non-small cell lung cancer (51%), renal cell carcinoma (24%), and small cell lung cancer (10%). The median prescription dose was 50 Gy (range, 25 to 60 Gy), with 30 (67%) lesions receiving ≥50 Gy and 14 (31%) receiving 60 Gy. In total, 26 (58%) lesions received a simultaneous-integrated boost. Of the 42 treatment simulations, 26 (62%) were supine, 5 (12%) prone, and 11 (26%) in the left lateral decubitus position. At a median follow-up of 10.5 months, there were 3 local failures with a 12-month LC rate of 96%. CONCLUSIONS: Adrenal SBRT for oligometastatic disease is a feasible, noninvasive option with excellent LC and minimal toxicity. Lesions in close proximity to radiosensitive organs may benefit from dynamic patient positioning and selective simultaneous-integrated boost techniques to allow for dose escalation, while also limiting toxicity risks.

CDK 4/6 inhibitors and stereotactic radiation in the management of hormone receptor positive breast cancer brain metastases.

PURPOSE: Cyclin-dependent kinase (CDK) 4/6 inhibitors are becoming increasingly utilized in the setting of advanced, hormone receptor (HR+) positive breast cancer. Pre-clinical data suggests a potential synergy between radiation therapy (RT) and CDK4/6 inhibitors. We assessed clinical outcomes of patients treated at our institution with the use of CDK4/6 inhibitors and stereotactic radiation in the management of HR+ breast brain metastases. METHODS: A retrospective analysis of patients who received stereotactic radiotherapy for HR+ brain metastases within 6 months of CDK4/6 inhibitor administration was performed. The primary endpoint was neurotoxicity during or after stereotactic radiation. Secondary endpoints were local brain control, distant brain control, and overall survival (OS). RESULTS: A total of 42 lesions treated with stereotactic radiation in 15 patients were identified. Patients received either palbociclib (n = 10; 67%) or abemaciclib (n = 5; 33%). RT was delivered concurrently, before, or after CDK4/6 inhibitors in 18 (43%), 9 (21%), and 15 (36%) lesions, respectively. Median follow-up following stereotactic radiation was 9 months. Two lesions (5%) developed radionecrosis, both of which received four prior RT courses to the affected lesion prior to onset of radionecrosis and subsequently managed with steroids and bevacizumab. Six- and 12-month local control of treated lesions was 88% and 88%, while 6- and 12-month distant brain control was 61% and 39%, respectively. Median OS was 36.7 months from the date of brain metastases diagnosis. CONCLUSIONS: Stereotactic radiation to breast brain metastases was well tolerated alongside CDK4/6 inhibitors. Compared to historical data, brain metastases control rates are similar whereas survival appears prolonged.

Clinical outcomes of breast leptomeningeal disease treated with intrathecal trastuzumab, intrathecal chemotherapy, or whole brain radiation therapy.

PURPOSE: Leptomeningeal disease is a rare presentation of advanced metastatic breast cancer. The purpose of this study was to evaluate craniospinal progression between intrathecal (IT) trastuzumab, IT chemotherapy, and whole brain radiation therapy (WBRT) in leptomeningeal disease. METHODS: A total of 56 patients were identified with breast cancer leptomeningeal disease at our institution treated with IT trastuzumab (n = 18; 32%), single-agent IT chemotherapy (methotrexate n = 14 or thiotepa n = 1; 27%), or WBRT alone (n = 23; 41%). Patients were treated beginning November 2012 and followed until November 2018. RESULTS: Median time from breast cancer diagnosis to development of leptomeningeal disease was 4.3 years. There were no significant differences noted between IT trastuzumab, IT chemotherapy, or WBRT groups in age (p = 0.4), Karnofsky Performance Status (KPS) (p = 0.07), or receipt of systemic therapy at time of leptomeningeal disease treatment (p = 0.47). Median follow-up of patients from leptomeningeal diagnosis was 5 months (range 0.2-81.1 months). Significant differences were noted in Kaplan-Meier (KM) craniospinal progression-free survival (CS-PFS) with 6-month rates of 44%, 18%, and 26% (p = 0.04) between IT trastuzumab, IT chemotherapy, and WBRT, respectively. Craniospinal control > 10 months was achieved in four patients treated with IT trastuzumab. Twelve-month KM OS rates were 54%, 10%, and 19% (p = 0.01) between IT trastuzumab, IT chemotherapy, and WBRT groups, respectively. IT therapy was adequately tolerated with three patients undergoing treatment-related hospitalizations. CONCLUSIONS: In our institutional series, significant differences were noted in CS-PFS and OS by treatment modality. IT trastuzumab should be considered in the management HER2+ breast leptomeningeal disease.

Novel Genomic-Based Strategies to Personalize Lymph Node Radiation Therapy.

Current standard radiotherapy doses have been derived from empiric methods rather than a scientific framework. Subclinical nodal dosing remains relatively uniform across most disease sites, despite heterogeneity in patient and tumor biology. It is now clear that there are subsets of patients who will benefit from genomically-informed radiotherapy planning, and there are increasing efforts toward prescribing radiation dose to match the radiosensitivity of the tumor. By using novel genomic biomarkers to personalize delivery of radiotherapy, there is an opportunity to improve loco-regional control and cure rates. We survey the current landscape of personalized radiation oncology across commonly treated disease sites.

Using the Albumin-Bilirubin (ALBI) grade as a prognostic marker for radioembolization of hepatocellular carcinoma.

BACKGROUND: The Child-Pugh (CP) class is a commonly used scoring system to measure liver function in patients with hepatocellular carcinoma (HCC). We correlate the Albumin-Bilirubin (ALBI) grading system and CP to overall survival in our HCC patients receiving radioembolization. METHODS: We retrospectively evaluated patients who received radioembolization for HCC between the years 2009-2014. We evaluated the albumin and bilirubin levels in our patients prior to receiving their first (n=124) radioembolization. The ALBI grades were calculated from these data with the formula (log10 bilirubin ×0.66) + (albumin × -0.085) and correlated to outcomes using Mantel-Cox Log analysis. These statistical comparisons were duplicated with CP classes. RESULTS: Median survival differences between CP class A and B and between ALBI grade 1 and 2 were 4.7 and 9.9 months, respectively. A subset of ALBI grades 1 and 2 were identified within our CP class A patients with a median survival difference of 9.9 months. CONCLUSIONS: ALBI is a more sensitive marker of liver function than CP in the setting of mild dysfunction. Using ALBI, we identified a subset of patients that have significantly better outcomes from Y-90 radioembolization than previously identified with CP.

Cardiovascular effects of radiation therapy.

Radiation therapy (RT) plays a prominent role in the treatment of many cancers. With increasing use of RT and high overall survival rates, the risks associated with RT must be carefully considered. Of these risks, the cardiovascular and autonomic toxicities have been of significant concern. In fact, cardiovascular disease is the leading cause of nonmalignancy-related death in cancer survivors. The manifestations of radiation induced cardiac injury include the acute toxicities of myopericarditis and late toxicities including constrictive pericarditis, restrictive cardiomyopathy, coronary artery disease, valvular heart disease, heart failure, and conduction abnormalities. Neck and cranial RT have also been associated with significant long-term toxicities including accelerated occlusive carotid artery disease, autonomic dysfunction due to baroreceptor damage, and development of metabolic syndromes due to damage to the hypothalamic-pituitary axis. The clinical manifestations of radiation induced disease may not present until several years following the delivery of radiation. We review the adverse effects of RT on these organ systems and discuss risk reduction strategies that may effectively mitigate some of these adverse outcomes.

Brainstem metastases treated with Gamma Knife stereotactic radiosurgery: the Indiana University Health experience.

Brainstem metastases offer a unique challenge in cancer treatment, yet stereotactic radiosurgery (SRS) has proven to be an effective modality in treating these tumors. This report discusses the clinical outcomes of patients with brainstem metastases treated at Indiana University with Gamma Knife (GK) radiosurgery from 2008 to 2016. 19 brainstem metastases from 14 patients who had follow-up brain imaging were identified. Median tumor volume was 0.04 cc (range: 0.01-2.0 cc). Median prescribed dose was 17.5 Gy to the 50% isodose line (range: 14-22 Gy). Median survival after GK SRS treatment to brainstem lesion was 17.2 months (range: 2.8-45.6 months). The experience at Indiana University confirms the safety and efficacy of range of GK SRS prescription doses (14-22 Gy) to brainstem metastases.

Does lymphocyte-to-monocyte ratio before, during, or after definitive chemoradiation for locally advanced pancreatic cancer predict for clinical outcomes?

BACKGROUND: Elevated pre-treatment lymphocyte (L) to monocyte (M) ratio (LMR) in peripheral blood has been suggested to correlate with improved survival in some malignancies, but data in the context of pancreatic cancer (PC) is limited. The aim of this study was to evaluate the prognostic significance of LMR before, during and after definitive chemoradiotherapy (CRT) for locally advanced pancreatic cancer (LAPC). METHODS: We retrospectively reviewed 57 patients with LAPC treated with definitive CRT at a single institution from 2005 to 2013. Complete blood counts were obtained before (TP1), during the third week (TP2) and at the end of CRT (TP3). Univariate analysis (UVA) included gender, age, body mass index, pre-treatment CA19-9, T stage, N stage, induction chemotherapy (ICT), absolute L count (TP1, TP2, TP3), absolute M count (TP1, TP2, TP3), LMR (TP1, TP2, TP3), and relative LMR changes (TP2 ÷ TP1, TP3 ÷ TP1, TP3 ÷ TP2). RESULTS: Median follow-up was 14 months. Twelve patients received ICT. Median LMR was 2.7 (range, 0.8-5.25), 1.4 (range, 0.3-5) and 0.98 (range, 0.3-3.4) at TP1, TP2 and TP3, respectively. Superior PFS was significantly associated with an absolute M count during CRT <0.1 (P=0.04) while pre-CRT L count ≥1.1 trended towards significance (P=0.09). Superior OS was significantly associated with change in LMR (TP3 ÷ TP2) > 0.32 (P<0.0001) while pre-CRT LMR ≥2.6 trended towards significance (P=0.06). CONCLUSIONS: Factors significantly associated with overall survival (OS) and progression-free survival (PFS) were change in LMR at the end of CRT and absolute M count during CRT. This analysis suggests treatment-time-specific immune system parameters may affect clinical outcomes and warrant continued investigation.

Factors Associated With Survival Following Radium-223 Treatment for Metastatic Castration-resistant Prostate Cancer.

BACKGROUND: Radium-223 (223Ra) improves survival in patients with metastatic castration-resistant prostate cancer (mCRPC). This retrospective analysis was performed to better understand its efficacy in routine clinical practice and identify factors associated with survival. MATERIALS AND METHODS: Sixty-four patients with mCRPC who received 223Ra between 2013 and 2015 were the basis of this retrospective study. Clinical outcomes and patient characteristics were obtained. Potential prognostic factors for survival were evaluated by univariate analysis using the log-rank test and multivariate analysis using the Cox proportional hazard method. RESULTS: The median survival was 12.9 months. Twenty-one patients (33%) developed a skeletal event, and the median time to the first skeletal event was 4.4 months. In univariate analysis, factors significantly associated with survival included: no prior chemotherapy, ≤ 5 bone metastases, baseline prostate-specific antigen (PSA) ≤ 36 ng/mL, baseline alkaline phosphatase (ALP) < 115 U/L, baseline hemoglobin > 12 g/dL, ALP response after 223Ra treatment, PSA decrease during 223Ra treatment, and absence of > 25% PSA increase during 223Ra treatment. In multivariate analysis, 4 factors remained significant: no prior chemotherapy, ≤ 5 bone metastases, baseline ALP < 115 U/L, and ALP response after 223Ra treatment. CONCLUSION: When 223Ra is administered in routine clinical practice, clinical outcomes can be more variable than those reported in the randomized study owing to patient heterogeneity. Four factors were identified to be significantly associated with survival after 223Ra treatment. These pretreatment factors may be used as stratification factors in future studies to investigate whether 223Ra would be more effective for patients with newly diagnosed metastatic disease that is sensitive to androgen deprivation therapy.

Triple-acting Lytic Enzyme Treatment of Drug-Resistant and Intracellular Staphylococcus aureus.

Multi-drug resistant bacteria are a persistent problem in modern health care, food safety and animal health. There is a need for new antimicrobials to replace over used conventional antibiotics. Here we describe engineered triple-acting staphylolytic peptidoglycan hydrolases wherein three unique antimicrobial activities from two parental proteins are combined into a single fusion protein. This effectively reduces the incidence of resistant strain development. The fusion protein reduced colonization by Staphylococcus aureus in a rat nasal colonization model, surpassing the efficacy of either parental protein. Modification of a triple-acting lytic construct with a protein transduction domain significantly enhanced both biofilm eradication and the ability to kill intracellular S. aureus as demonstrated in cultured mammary epithelial cells and in a mouse model of staphylococcal mastitis. Interestingly, the protein transduction domain was not necessary for reducing the intracellular pathogens in cultured osteoblasts or in two mouse models of osteomyelitis, highlighting the vagaries of exactly how protein transduction domains facilitate protein uptake. Bacterial cell wall degrading enzyme antimicrobials can be engineered to enhance their value as potent therapeutics.