Post Radiation Research Articles

Mucinous adenocarcinoma of the prostatic urethra after brachytherapy for prostatic adenocarcinoma: a case series

Mucinous adenocarcinoma of the urethra is extremely rare, even more so in a setting of postradiation therapy, with only 3 cases reported up to date including the first case published by our group in 2011. In the present study, we included the long-term follow-up on our previously reported case and report 3 additional cases. This is the first case series to date of this rare disease entity. The aim of this study is to review the clinicopathologic features of mucinous adenocarcinoma of the prostatic urethra in patients after receiving brachytherapy for prostatic adenocarcinoma. We identified 4 patients with a mean age of 72 years, and a mean interval of 14.8 years from brachytherapy for prostate carcinoma (grade group 1). Patients presented with hematuria or urinary retention. A colonoscopy was performed in three-fourth of patients and was within normal limits. Three patients underwent cystoprostatectomy and 1 had a transurethral resection of the prostate. On gross examination, only tumor formed a 3.5cm tan-gray, ulcerated, friable, and necrotic mass and 2 displayed either irregular red granular or thickened areas within the prostatic urethra. Abundant extracellular mucin pools dissecting the prostatic stroma were present in all tumors, with clusters of tumor cells floating in the mucin. The mucin pools were lined by pleomorphic pseudostratified columnar mucinous epithelium. Tumors were diffusely positive for CK20, CDX2 (4/4), and AMACR (2/2); they focally expressed CK7 (2/4), and lacked nuclear β-catenin expression (3/3). PSA, PSAP, NKX3.1, p63, and GATA3 were negative in the tumors tested. Among the 3 patients who underwent radical surgery, 2 had stage 2 tumors (confined to the prostatic urethra and prostate), and 1 had a stage 3 tumor, with seminal vesicle involvement. All 4 patients were alive without disease with a mean follow-up of 4.9 years. In conclusion, brachytherapy-associated mucinous adenocarcinoma of the prostatic urethra displays intestinal-type features as its non-radiation-related counterpart. It appears to lack a villous adenoma component, displays a different immunohistochemical profile with diffuse CK20 and CDX2 positivity, and is associated with lower stage and less aggressive behavior.

Measuring Indirect Radiation-Induced Perfusion Change in Fed Vasculature Using Dynamic Contrast CT.

Recent functional lung imaging studies have presented evidence of an “indirect effect” on perfusion damage, where regions that are unirradiated or lowly irradiated but that are supplied by highly irradiated regions observe perfusion damage post-radiation therapy (RT). The purpose of this work was to investigate this effect using a contrast-enhanced dynamic CT protocol to measure perfusion change in five novel swine subjects. A cohort of five Wisconsin Miniature Swine (WMS) were given a research course of 60 Gy in five fractions delivered locally to a vessel in the lung using an Accuray Radixact tomotherapy system with Synchrony motion tracking to increase delivery accuracy. Imaging was performed prior to delivering RT and 3 months post-RT to yield a 28–36 frame image series showing contrast flowing in and out of the vasculature. Using MIM software, contours were placed in six vessels on each animal to yield a contrast flow curve for each vessel. The contours were placed as follows: one at the point of max dose, one low-irradiated (5–20 Gy) branching from the max dose vessel, one low-irradiated (5–20 Gy) not branching from the max dose vessel, one unirradiated (<5 Gy) branching from the max dose vessel, one unirradiated (<5 Gy) not branching from the max dose vessel, and one in the contralateral lung. Seven measurements (baseline-to-baseline time and difference, slope up and down, max rise and value, and area under the curve) were acquired for each vessel’s contrast flow curve in each subject. Paired Student t-tests showed statistically significant (p < 0.05) reductions in the area under the curve in the max dose, and both fed contours indicating an overall reduction in contrast in these regions. Additionally, there were statistically significant reductions observed when comparing pre- and post-RT in slope up and down in the max dose, low-dose fed, and no-dose fed contours but not the low-dose not-fed, no-dose not-fed, or contralateral contours. These findings suggest an indirect damage effect where irradiation of the vasculature causes a reduction in perfusion in irradiated regions as well as regions fed by the irradiated vasculature.

Neuroendocrine differentiation in the setting of prostatic carcinoma: contemporary assessment of a consecutive series.

Clinicopathologic characterisation of a contemporary series of neuroendocrine (NE) differentiation in the setting of prostatic carcinoma (PCa) was examined. We reviewed institutional databases for in-house cases with a history of PCa and histopathologic evidence of NE differentiation during the disease course. In all, 79 cases were identified: 32 primary and 47 metastases. Metastatic lesions were in liver (n = 15), lymph node (n = 9), bone (n = 6), lung (n = 3), brain (n = 1), and other sites (n = 13). In all, 63 of 76 (82%) cases with NE differentiation and available history were posttherapy: six postradiation therapy (RT), 24 post- androgen-deprivation therapy (ADT), and 33 post-RT + ADT. Morphologic assessment (n = 79): (i) 23 pure small-cell/high-grade NE carcinoma (HGNEC): 20/23 metastatic; (ii) 10 combined high-grade PCa and small-cell/HGNEC: 9/10 primary; (iii) 15 PCa with diffuse NE immunohistochemistry (IHC) marker positivity/differentiation, associated with nested to sheet-like growth of cells with abundant cytoplasm and prominent nucleoli, yet diffuse positivity for at least one prostatic and one NE IHC marker: all metastatic; (iv) 11 PCa with patchy NE differentiation, displaying more than single-cell positivity for NE IHC: five primary / six metastatic; (v) nine PCa with focal NE marker positive cells: four primary / five metastatic; (vi) 11 PCa with 'Paneth cell-like' change: all primary. In this contemporary series, the majority of NE differentiation in the setting of PCa was seen posttherapy. We highlight the tendencies of small-cell/HGNEC and PCa with diffuse NE differentiation by IHC to occur in metastatic settings, while morphologically combined high-grade PCa + small-cell/HGNEC and 'Paneth cell-like' change occur in primary disease.

Assessment of Tissue Oxygenation and Radiation Dermatitis Pre-, During, and Post-Radiation Therapy in Breast Cancer Patients.

Over 95% of breast cancer patients treated with radiation therapy (RT) undergo an adverse skin reaction known as radiation dermatitis (RD). Assessment of severity or grading of RD is clinically visual and hence subjective. Our objective is to determine sub-clinical tissue oxygenation (oxygen saturation) changes in response to RT in breast cancer patients using near-infrared spectroscopic imaging and correlate these changes to RD grading. A 4-8 week longitudinal pilot imaging study was carried out on 10 RT-treated breast cancer patients. Non-contact near-infrared spectroscopic (NIRS) imaging was performed on the irradiated ipsilateral and the contralateral breast/chest wall, axilla and lower neck regions before RT, across the weeks of RT, and during follow-up after RT ended. Significant changes (p < 0.05) in oxygen saturation (StO2) of irradiated and contralateral breast/chest wall and axilla regions were observed across weeks of RT. The overall drop in StO2 was negatively correlated to RD scaling (in 7 out of 9 cases) and was higher in the irradiated regions when compared to its contralateral region. Differences in the pre-RT StO2 between ipsilateral and contralateral chest wall is a potential predictor of the severity of RD. The subclinical recovery of StO2 to its original state was longer than the visual recovery in RD grading scale, as observed from the post-RT assessment of tissue oxygenation.

Magnetic Resonance Imaging Downstaging, Pathological Response, and Microsatellite Instability Status in Patients with Signet-Ring Cell Carcinoma Rectum Undergoing Preoperative Long-course Chemoradiation

Aim and Objective: To assess the magnetic resonance imaging (MRI) downstaging, pathological response, and the relationship between microsatellite instability (MSI) and radiotherapy response in signet-ring cell carcinoma rectum. Materials and Methods: Twenty two patients were recruited prospectively and retrospectively in this observational study. Six weeks following radiotherapy, the response was assessed using an MRI pelvis, and patients who were operable underwent total mesorectal excision followed by adjuvant chemotherapy. The outcome of radiotherapy was correlated with post radiation MRI downstaging, pathological response, and MSI status. Results: The post radiotherapy response assessment MRI showed tumor regression grading (TRG) 5 in 5 patients. TRG 4 seen in 12, TRG 3 in 3, and TRG 2 in 1 patient. Fifteen patients were operable and post-operativ histopathology showed that 40% had pathological complete response (pCR) and 26.7% had near-complete response. Even those who had no response in MRI had pCR. MSI done 17 patients were stable. Of the 6 patients who had complete pathological response, two were MRI TRG 5, three were MRI TRG 4, and one was MRI TRG 3. The median survival was 23 months. The 2-year and 3-year disease-free survival was 46% and 38%, respectively. Conclusion: The predictive value of MRI downstaging in these tumors following neoadjuvant long-course chemoradiation therapy is not often in concurrence with the histopathological response and needs to be interpreted carefully. Even though the pCR rate seen in this cohort is encouraging, this needs to be evaluated in studies with large cohorts.

Pain control post IMRT for malignant pleural mesothelioma

Purpose: This is retrospective study-reviewing patients with unresectable pleural mesothelioma who received IMRT as part of their treatment course. This work aimed to study pain control and improvement among this group of patients. Methods and Materials: Between 2016 and 2020, 50 patients with unresectable malignant pleural mesothelioma following chemotherapy, of both sex and different age groups, were treated with pleural IMRT to the hemithorax (median dose, 46.8 Gy) at The National Cancer Institute, Cairo University. Results: Of the 30 patients, 38% had stage II, 62 % had stage III, and all received induction chemotherapy (mostly cisplatin and pemetrexed) before IMRT.Patients were evaluable at week 5 post radiotherapy, 17 patients (56.7%) had an improvement of ≥30 % while 6 patients (20 %) had &lt; 30 % pain improvement and 7 patients (23.3%) reported no pain improvement, with overall response rate was 77 %. Conclusion: Treating malignant pleural mesothelioma patients with IMRT is a feasible treatment option with an acceptable rate of pneumonitis.

Smoking and other health factors in patients with head and neck cancer

BackgroundInformation on smoking and other health factors in head and neck cancer (HNC) patients throughout treatment, follow-up and survivorship is limited. This study explores patterns of multiple health factors during radiotherapy (RT) and naturalistic long-term follow-up in a convenience sample of patients with HNC. MethodsSmoking, alcohol use and depression were measured at baseline, 4 and 12 weeks post RT for a sub-group of 99 patients who participated in a randomised controlled trial and completed long-term follow-up. These factors plus healthy eating, physical activity and fatigue are also reported from the long-term follow-up component. Smoking was measured by self-report and biochemically, whilst all other variables were by self-report. Where variables were assessed at multiple time points logistic mixed effects regression models determined within-person changes over time. ResultsThere were important discrepancies between self-reported (4–7%) and biochemically verified (13–29%) rates of smoking. Rates of smoking and hazardous alcohol intake were significantly increased at follow-up compared to baseline. Depression rates were observed to be higher at end of RT compared to baseline. At long-term follow-up, fatigue was common and co-occurred with suboptimal healthy eating and hazardous alcohol use. ConclusionClinically important levels of smoking and alcohol consumption post RT in this sample suggest possible targets for intervention beyond treatment into long-term follow-up of patients.

The role of cesium-131 brachytherapy in brain tumors: a scoping review of the literature and ongoing clinical trials.

Cesium-131 radioactive isotope has favored the resurgence of intracavitary brachytherapy in neuro-oncology, minimizing radiation-induced complications and maximizing logistical and clinical outcomes. We reviewed the literature on cesium-131 brachytherapy for brain tumors. PubMed, Web-of-Science, Scopus, Clinicaltrial.gov, and Cochrane were searched following the PRISMA extension for scoping reviews to include published studies and ongoing trials reporting cesium-131 brachytherapy for brain tumors. We included 27 published studies comprising 279 patients with 293 lesions, and 3 ongoing trials. Most patients had brain metastases (63.1%), followed by high-grade gliomas (23.3%), of WHO Grade III (15.2%) and Grade IV (84.8%), and meningiomas (13.6%), mostly of WHO Grade II (62.8%) and Grade III (27.9%). Most brain metastases were newly diagnosed (72.3%), while most gliomas and meningiomas were recurrent (95.4% and 88.4%). Patients underwent gross-total (91.1%) or subtotal (8.9%) resection, with median postoperative cavity size of 3.5cm (range 1-5.8cm). A median of 20, 28, and 16 seeds were implanted in gliomas, meningiomas, and brain metastases, with median seed activity of 3.8mCi (range 2.4-5mCi). Median follow-up was 16.2months (range 0.6-72months). 1-year freedom from progression rates were local 94% (range 57-100%), regional 85.1% (range 55.6-93.8%), and distant 53.5% (range 26.3-67.4%). Post-treatment radiation necrosis, seizure, and surgical wound infection occurred in 3.4%, 4.7%, and 4.3% patients. Initial data suggest that cesium-131 brachytherapy is safe and effective in primary or metastatic malignant brain tumors. Ongoing trials are evaluating long-term locoregional tumor control and future studies should analyze its role in multimodal systemic tumor management.

DIPG-45. Radiation induces a robust interferon response in Diffuse Midline Glioma (DMG), improving the potential for combination immunotherapy

Diffuse Midline Glioma (DMG), H3K27M altered, confers a dismal survival of 9-15 months and has a non-inflammatory tumor immune microenvironment (TIME). Radiation therapy (RT) is the mainstay treatment for DMG and has been shown in other cancers to recruit an immune component. However, the effect of RT on the DMG TIME has not been explored. In a syngeneic murine model of pontine DMG (PDGFB+, H3.3K27M, p53−/−), mice were treated with single fraction 15Gy RT or sham control, four mice per group. We performed single cell sequencing after CD45 isolation to evaluate the TIME 4 days post RT and compare to untreated tumor (sham control). Unsupervised clustering of 14,848 CD45+ cells revealed 16 immune cell subsets, most abundantly microglia at 75% of cells, with four subtypes representing a spectrum of homeostatic to activated. Microglia from RT are more concentrated in the activated subtypes with an upregulation of interferon response (i.e. Isg15, Ifit3) compared to untreated tumor with an increase in several interferon pathways using REACTOME. Consistent with RT response, RT treated tumors have increase in cell cycle regulatory genes such as Cdkn1a, across all clusters. In non-resident myeloid cells, compared to untreated tumor, RT is associated with a robust upregulation of interferon response genes in both macrophages (Isg15 Fold Change (FC) 2.30; Ifit1 FC 1.64; Ifit3 FC 2.02; Cxcl10 FC 2.29) and dendritic cells (Isg15 FC 2.67; Ifit1 FC 1.72; Ifit3 FC 2.06; Cxcl10 FC 1.50). We also find differential expression of immune checkpoints in RT-treated versus untreated tumor with decreased expression of Lag3, Tim3 (Havcr2), and Csf1R and increased expression of Cd47, Sirpa and Gitr (Tnfrsf18) post RT. In summary, RT stimulates a pro-inflammatory TIME response and alters immune checkpoints in DMG, highlighting the potential for combining RT and immunotherapy in these tumors.

Prospective characterization of circulating tumor cell kinetics in patients treated with radiation therapy per definitive intent oligometastatic paradigm.

3053 Background: Definitive intent oligometastatic paradigm describes a state with limited metastatic sites amenable to comprehensive radiation therapy (RT). We characterized circulating tumor cell (CTC) kinetics in response to definitive RT among patients with oligometastatic cancer and identify a CTC kinetic profile associated with progression free survival (PFS). Methods: In this single-institution prospective correlative biomarker study, we enrolled patients with any solid malignancy, ≤ 5 metastatic sites in ≤3 anatomic organ systems undergoing definitive intent RT to all disease sites. Blood specimens were collected prior to RT (baseline), during RT and at follow up visits up to 24 months post RT. Additional lines of therapy were administered per standard of care. CTCs were captured and enumerated using a previously reported nanotechnology-based assay functionalized with aEpCAM, aHER-2, and aEGFR to facilitate biomimetic cell rolling and dendrimer-mediated multivalent binding. Disease status was assessed per RECIST 1.1 criteria. On exploratory analysis disease status was correlated with CTCs as a continuous and ordinal variable (cut-point upper bound of the 3rd quartile). A favorable CTC clearance profile was defined as a decrease in CTC count between pre-treatment and end of treatment - an unfavorable CTC clearance profile was defined as the opposite. Results: We enrolled 43 patients with median follow up of 14.3 months corresponding to 255 CTC measurements. Median baseline CTC count was 28 CTCs/ml (range 0.17-1085). Thirty four patients (79%) received stereotactic body radiation therapy. On Wilcoxon signed-rank test there was no association between pre-treatment CTC count and number of disease sites (median 1 metastatic site/patient, range 1-5) nor metastases site (bone, brain, visceral), p &gt; 0.05. Thirty one patients (72%) experienced local or systemic progression at subsequent time points. For 90% of patients, a CTC count &lt;15/ml &lt; 100 days post-RT corresponded to durable local control of irradiated lesions. Patients with a favorable versus unfavorable clearance profile had significantly longer PFS (median 13 vs 4 months, log rank test, p = 0.0011). During the post-RT period 24 patients (56%) went on to receive systemic therapy (cytotoxic chemotherapy, hormone therapy, immunotherapy, kinase inhibitors). On logistic regression, CTC &gt; 15/ml at a given time point was associated with clinical disease progression within the subsequent 6 months (odds ratio 3.31, p = 0.007). An increase in CTCs to &gt; 15/ml preceded radiographic or biochemical progression in 8 of 31 (26%) of patients experiencing disease progression. Conclusions: Our data suggests CTCs may serve as a biomarker for disease control in oligometastatic disease and may predict disease progression prior to standard assessments for patients receiving diverse therapies. Clinical trial information: NCT03161821.

RADIATION RECALL PNEUMONITIS COVID-19 INDUCED AFTER ADJUVANT BREAST CANCER RADIOTHERAPY: A CASE REPORT

TYPE: Late Breaking Case Report TOPIC: Chest Infections INTRODUCTION: A radiation recall pneumonitis is an inflammatory reaction within a previous radiation (RT) site. COVID-19 infection in previous irradiated lung could promote a recall pneumonitis as we report herein. CASE PRESENTATION: A 65-year-old woman was diagnosed with invasive stage III A ductal carcinoma of the right breast four years ago. After breast conserving surgery, standard adjuvant RT was provided. Four years later, in March 2020, she complained of mild dyspnea and cough. The COVID-19 swab was positive. The chest CT scan showed a straight and sharp opacity in the right lung miming the previous radiation treatment fields with several ground glass opacities in both lungs. She was admitted in a Covid Unit and treated per protocol. Chest CT scan 3 months later its resolution, a pulmonary fibrosis within the irradiated fields still was observed. DISCUSSION: A radiation recall pneumonitis is an inflammatory reaction localized within a previous irradiation site following the administration of drugs like immunotherapy. Immunity is considered to be an influencing factor, but the mechanism is still unknown. It is known that COVID-19 causes immune system reactions in the lung inducing an alveolar and interstitial damage as occurs in case of radiation induced lung injury. Probably an immune memory response of CD 4+ T cells activated by previous RT may have a role. CONCLUSIONS: We described a case in which radiation recall pneumonitis was observed after COVID-19 pneumonitis four years post adjuvant RT. There are still many uncertainties that are poorly understood about COVID-19 infection and radiation pneumonitis. DISCLOSURE: Nothing to declare. KEYWORD: pneumonitis

Clinical impact of PSMA PET in patients with biochemically recurrent prostate cancer after locoregional definitive therapy.

e17009 Background: [68Ga]-PSMA-11 positron emission tomography (PSMA PET) detects sites of biochemically recurrent prostate cancer (BCR) at higher rates than conventional imaging. We hypothesized that PSMA PET would lead to high change in management (CIM) rates in this setting. Methods: We prospectively recruited patients (pts) with BCR, defined as confirmed PSA &gt; 0.2 ng/mL &gt; 6 weeks post-surgery or PSA ≥2 ng/mL above nadir post-radiation therapy, to undergo Ga-68 PSMA-11 PET. Some also had equivocal lesions on CT, MRI, bone scan, or fluciclovine PET obtained prior to PSMA PET. Pre-PET intended treatment, PSA (ng/mL), and PSA doubling time (PSAdt, months) from most recent 3 values were recorded prior to imaging. Post-PET treatment (intended or actual) was collected from medical record. CIM was categorized as major (change in or addition of treatment modality) vs minor (change within treatment modality, such as altered radiation field). Any lesion with uptake above blood pool was interpreted as positive for prostate cancer by an experienced PET reader (DLC). All values were represented as the median [interquartile range, IQR]. Kruskal Wallis analysis tested for significant differences among groups. Results: 44 pts with BCR age 71 [10] with Gleason scores (GS) at diagnosis of 6 (N = 2), 7 (N = 23), 8 (N = 5), and 9 (N = 13) enrolled, 14/44 with equivocal lesions on conventional imaging. 42 had post-PSMA PET treatment decisions available in medical records for CIM analysis. Time from PSA nadir to PSA at time of PSMA PET was 5 [7.25] months. PSMA PET was positive in 33 (8/33 with equivocal lesions on prior imaging; 7 local disease only; 11 regional nodal metastases, 2/11 also with local disease; and 15 with distant metastases, 4/15 also with local disease, 9/15 with regional nodal metastases), negative in 6, and equivocal in 5 pts. Of those with distant metastases, 8 had oligometastases, defined as 3 or fewer distinct sites (1 site = single nodal region or single bone lesion), 4 in bones and 4 in distant nodes. CIM rate was 71% (30/42) overall, 65.5% (16/29 major, 3/29 minor) in pts with BCR and negative conventional imaging; 84.6% (11/13, all major) in pts with equivocal lesions on conventional imaging. Of the patients with major CIM, a treatment modality was added in 21/27, modality switched in 3/27, and a modality removed in 3/27. PSA was significantly lower (p = 0.04) for those with negative or equivocal PSMA PET (0.5 [2.7]) than those with localized disease (4.1 [2.8]), regional nodal (1.1 [3.4]) or distant metastases (3.8 [5.3]), but not PSAdt (p = 0.2, negative/equivocal PET 5 [6.5], localized 15 [36], regional nodal metastases 11 [13], distant metastases 6 [6]). Conclusions: PSMA PET may impact decision making in pts with BCR after treatment of localized prostate cancer, particularly for those with equivocal findings on conventional imaging, regardless of clinical risk at diagnosis. Clinical trial information: NCT04777071.

Cost-Effectiveness of Single Versus Multifraction SABR for Pulmonary Oligometastases: The SAFRON II Trial

The use of stereotactic ablative body radiation therapy (SABR) in advanced cancer care is increasing, yet the cost-effectiveness of single-fraction (SF) versus multifraction (MF) SABR in pulmonary oligometastases is unknown. A prespecified cost-effectiveness analysis was conducted of the Trans Tasman Radiation Oncology Group 13.01 - SAFRON II - randomized trial comparing SF with MF SABR in 87 patients with 133 pulmonary oligometastases. A partitioned survival model assessed costs and quality-adjusted life-years (QALY) over the within-trial period (4 years) and longer-term (10 years). Costs reflected a societal perspective, expressed in Australian dollars (A$) using 2020 prices and were estimated using patient level data on health care utilization for radiation therapy (including patient time), post-radiation systemic therapy and treatment of adverse effects. Quality of life was assessed using the EuroQoL EQ-5D-5L. The incremental cost-effectiveness ratio (ICER) was expressed as the cost per QALY gained for SF versus MF SABR, with uncertainty assessed using deterministic and probabilistic sensitivity analyses. SF cost less than MF for initial therapy (difference of A$1194/patient). Mean time to initiation of systemic drug therapy did not differ between arms (P=.94). Numerical differences in survival favoring SF resulted in greater overall health care use for the within-trial period. The within-trial ICER was A$15,821/QALY and A$23,265/QALY over the longer term. Results were most sensitive to the cost of postprogression therapies and utility values. The sensitivity analysis indicated that SF SABR has a 97% probability of being cost-effective at a willingness-to-pay of A$50,000/QALY. SF has lower initial costs and is highly likely to be cost-effective. Time to initiation of systemic therapy associated with disease progression is highly patient relevant and is a major driver of cost-effectiveness. Comparisons for SF SABR with nonradiation therapy approaches to the treatment of pulmonary oligometastases warrant further investigation.

Selective Internal Radiation Therapy with Yttrium-90 for Intrahepatic Cholangiocarcinoma: A Systematic Review on Post-Treatment Dosimetry and Concomitant Chemotherapy.

Selective internal radiation therapy (SIRT) with yttrium-90 (90Y)-loaded microspheres is increasingly used for the treatment of Intrahepatic Cholangiocarcinoma (ICC). Dosimetry verifications post-treatment are required for a valid assessment of any dose-response relationship. We performed a systematic review of the literature to determine how often clinics conducted post-treatment dosimetry verification to measure the actual radiation doses delivered to the tumor and to the normal liver in patients who underwent SIRT for ICC, and also to explore the corresponding dose-response relationship. We also investigated other factors that potentially affect treatment outcomes, including the type of microspheres used and concomitant chemotherapy. Out of the final 47 studies that entered our study, only four papers included post-treatment dosimetry studies after SIRT to quantitatively assess the radiation doses delivered. No study showed that one microsphere type provided a benefit over another, one study demonstrated better imaging-based response rates associated with the use of glass-based TheraSpheres, and two studies found similar toxicity profiles for different types of microspheres. Gemcitabine and cisplatin were the most common chemotherapeutic drugs for concomitant administration with SIRT. Future studies of SIRT for ICC should include dosimetry to optimize treatment planning and post-treatment radiation dosage measurements in order to reliably predict patient responses and liver toxicity.

Similar long-term swallowing outcomes for accelerated, mildly-hypofractionated radiotherapy compared to conventional fractionation in oropharyngeal cancer: A multi-centre study

Background and purposeThere is renewed interest in hypofractionated radiotherapy, but limited data and a lack of consensus to support use for head and neck cancer. In this multicentre analysis we compared outcomes for patients with oropharyngeal squamous cell carcinoma (OPSCC) treated with conventional and accelerated, mildly hypofractionated radiotherapy without chemotherapy. Materials and methodsA multi-centre, observational study of consecutive OPSCCs treated between 2015 and 2018. Patients underwent curative-intent radiotherapy (oropharyngeal and bilateral neck) using conventionally fractionated (70 Gy in 35 fractions over 7 weeks, n = 97) or accelerated, mildly hypofractionated (65–66 Gy in 30 fractions over 6 weeks, n = 136) radiotherapy without chemotherapy. Locoregional control (LRC) and overall survival (OS) were compared. Patients alive and cancer-free at a minimum of 2 years post-radiotherapy (n = 151, 65%) were sent an MD Anderson Dysphagia Inventory (MDADI) questionnaire to assess swallow function. ResultsLRC and OS were similar across schedules (p = 0.78 and 0.95 respectively, log-rank test). Enteral feeding rates during radiotherapy appeared higher in the 7-week group though this did not reach statistical significance (59% vs 48%, p = 0.08). Feeding rates were similar at 1 year post radiotherapy for both groups (10% vs 6%, p = 0.27). 107 patients returned MDADI questionnaires (71%); there were no differences between the 6- and 7-week groups for median global (60.0 vs 60.0, p = 0.99) and composite (65.8 vs 64.2, p = 0.44) MDADI scores. ConclusionPatients with OPSCC treated with radiotherapy alone have similar swallowing outcomes, LRC and OS following accelerated, mild hypofractionation and standard fractionation schedules, supporting its use as a standard-of-care option for patients unsuitable for concurrent chemotherapy.

Late-onset retinoblastoma camouflaged with proven chronic uveitis: A case report

A rare case of a 16year old female, diagnosed elsewhere as chronic uveitis in the left eye positive antinuclear antibodies and Anti-SSA antibodies, treated with steroids and referred for cyclocryotherapy for a painful blind eye. On examination, the patient denied perception of light. There was proptosis, limitation of extraocular movements and corneal melting with no view of the posterior segment. Ultrasound B scan showed dense vitritis with doubtful specks of calcification. Magnetic resonance imaging revealed a soft tissue mass obliterating the vitreous and anterior chamber with retroscleral extension and involvement of the optic nerve. Extended enucleation was performed under General anaesthesia. Histopathological examination confirmed a well differentiated retinoblastoma with extrascleral and optic nerve involvement. Metastatic work up was normal. Intravenous Chemotherapy and post surgery radiotherapy to the socket was advised for further management. Late onset retinoblastoma mimicking ocular inflammation with positive antibody serology is rare and the report shows the need for imaging in refractory uveitis.

PD-0573 Protective Effect of Metformin for Biochemical Failure post Radical Prostatectomy or Radiation

PD-0573 Protective Effect of Metformin for Biochemical Failure post Radical Prostatectomy or Radiation

OC-0433 Positive predictive value of post radiotherapy FDG PET-CT is affected by treatment and HPV-status

OC-0433 Positive predictive value of post radiotherapy FDG PET-CT is affected by treatment and HPV-status

MO-0479 Hypofractionation and the risk of post radiation mucosal ulcers in oropharyngeal carcinoma.

MO-0479 Hypofractionation and the risk of post radiation mucosal ulcers in oropharyngeal carcinoma.

Cognitive function after concurrent temozolomide-based chemoradiation therapy in low-grade gliomas.

We sought to evaluate the effects of concurrent temozolomide-based chemoradiation therapy on neurocognitive function in patients with low-grade glioma (LGG). We included adult patients with LGG who were treated postoperatively with radiotherapy (RT) with concurrent and adjuvant temozolomide (TMZ). Patients were evaluated with comprehensive psychometric tests at baseline (prior to RT + TMZ) and at various time intervals following RT + TMZ. Baseline cognitive performance was analyzed by sex, age, education history, history of seizures, IDH mutation status, and 1p/19q codeletion status. Changes in neurocognitive performance were evaluated over time. Thirty-seven LGG patients (mean age 43.6, 59.5% male) had baseline neurocognitive evaluation. Patients with an age > 40years old at diagnosis and those with an education > 16years demonstrated superior baseline verbal memory as assessed by HVLT. No other cognitive domains showed differences when stratified by the variables mentioned above. A total of 22 LGG patients had baseline and post RT + TMZ neurocognitive evaluation. Overall, patients showed no statistical difference between group mean test scores prior to and following RT + TMZ on all psychometric measures (with the exception of HVLT Discrimination). Cognitive function remained stable following RT + TMZ in LGG patients evaluated prospectively up to 2years. The anticipated analysis of RTOG 0424 will provide valuable neurocognitive outcomes specifically for high risk LGG patients treated with RT + TMZ.