Increasing anticarcinoma activity of an anti-erbB2 recombinant immunotoxin by the addition of an anti-EpCAM sFv

PURPOSE

erbB2, the product of the Her2-neu gene, is a well-established therapeutic target for antibody-based biologicals, but anti-erbB2 antibody-toxin fusion proteins are limited in their activity. The goal of this study was to determine if genetically adding an sFv targeting epithelial cell adhesion molecule (EpCAM) to an anti-Her2 sFv immunotoxin would result in enhanced antitumor activity.

EXPERIMENTAL DESIGN

In vitro studies were done in which the new bispecific immunotoxin DTEpCAM23 was compared with monospecific immunotoxins (DTEpCAM and DT23) to quantitate immunotoxin activity. Mixtures of monospecific immunotoxins were tested to determine if they were as effective as the bispecific immunotoxin. Binding and internalization studies were also done. In vivo, bispecific immunotoxins were given i.t. to athymic nude mice bearing HT-29 human colon cancer flank tumors and i.p. to mice with i.p. tumors.

RESULTS

DTEpCAM23 bispecific immunotoxins showed far greater activity than monospecific immunotoxin (sometimes over 2,000-fold) against most tumor lines. Bispecific immunotoxin was superior and selective in its activity against different carcinoma cell lines. Bispecific immunotoxin had greater activity than monospecific immunotoxin indicating an advantage of having both sFv on the same single-chain molecule. Binding and internalization studies did not explain the differences between bispecific immunotoxin and monospecific immunotoxin activity. Orientation of the sFvs on the molecule had a significant effect on in vitro and in vivo properties. The bispecific immunotoxins were more effective than the monospecific immunotoxin in the flank tumor mouse model.

CONCLUSIONS

The synthesis of bispecific immunotoxin created a new biological agent with superior in vitro and in vivo activity (over monospecific immunotoxin), more broad reactivity, more efficacy against tumors in vivo, and diminished toxic effects in mice.

A novel reduced immunogenicity bispecific targeted toxin simultaneously recognizing human epidermal growth factor and interleukin-4 receptors in a mouse model of metastatic breast carcinoma

PURPOSE

To develop a targeted biological drug that when systemically injected can penetrate to metastatic breast cancer tumors, one needs a drug of high potency and reduced immunogenicity. Thus, we bioengineered a novel bispecific ligand-directed toxin (BLT) targeted by dual high-affinity cytokines with a PE(38)KDEL COOH terminus. Our purpose was to reduce toxin immunogenicity using mutagenesis, measure the ability of mutated drug to elicit B-cell antitoxin antibody responses, and show that mutated drug was effective against systemic breast cancer in vivo.

EXPERIMENTAL DESIGN

A new BLT was created in which both human epidermal growth factor (EGF) and interleukin 4 cytokines were cloned onto the same single-chain molecule with truncated Pseudomonas exotoxin (PE(38)). Site-specific mutagenesis was used to mutate amino acids in seven key epitopic toxin regions that dictate B-cell generation of neutralizing antitoxin antibodies. Bioassays were used to determine whether mutation reduced potency, and ELISA studies were done to determine whether antitoxin antibodies were reduced. Finally, a genetically altered luciferase xenograft model was used; this model could be imaged in real time to determine the effect on the systemic malignant human breast cancer MDA-MB-231.

RESULTS

EGF4KDEL 7mut was significantly effective against established systemic human breast cancer and prevented metastatic spread. Mutagenesis reduced immunogenicity by approximately 90% with no apparent loss in in vitro or in vivo activity.

CONCLUSIONS

Because EGF4KDEL 7mut was highly effective even when we waited 26 days to begin therapy and because immunogenicity was significantly reduced, we can now give multiple drug treatments for chemotherapy-refractory breast cancer in clinical trials.

A bispecific recombinant cytotoxin (DTEGF13) targeting human interleukin-13 and epidermal growth factor receptors in a mouse xenograft model of prostate cancer

PURPOSE

Overexpressed cytokine receptors are considered valid targets for new biologicals targeting prostate cancer. However, current reagents are limited in efficacy. Our goal was to determine the advantages of simultaneously targeting two established targets, epidermal growth factor receptor and interleukin-13 (IL-13) receptor, with a new bispecific cytotoxin in which both EGF and IL-13 cytokines were cloned onto the same single-chain molecule with truncated diphtheria toxin (DT(390)).

EXPERIMENTAL DESIGN

In vitro experiments measured the potency of bispecific DTEGF13 and compared its activity to its monospecific counterparts, DTEGF and DTIL13. We determined whether the presence of both cytokine ligands on the same molecule was responsible for its superior activity. In vivo, DTEGF13 was given i.t. to athymic nude mice with established PC-3 human prostate cancer tumor xenografts on their flanks.

RESULTS

In vitro, DTEGF13 was more potent than the monospecific cytotoxins against human prostate cancer lines. Enhanced activity was related to the presence of both cytokines on the same single-chain molecule and was not attributed to enhanced binding capacity. Killing was receptor specific. Cytotoxicity could be blocked with anti-EGF and anti-IL-13 antibodies. In vivo, DTEGF13, but not monospecific DTEGF or DTIL13, significantly inhibited the growth of established PC-3 tumors in nude mice (P < 0.0001).

CONCLUSIONS

These data show for the first time that simultaneous targeting of cytokine receptors with two ligands on the same molecule has pronounced anticancer advantages. In an animal model in which human DTEGF13 is cross-reactive with mouse, DTEGF13 was highly effective in checking aggressive prostate tumor progression and was reasonably tolerated.

Design and modification of EGF4KDEL 7Mut, a novel bispecific ligand-directed toxin, with decreased immunogenicity and potent anti-mesothelioma activity

BACKGROUND

Potency, immunogenicity, and toxicity are three problems that limit the use of targeted toxins in solid tumour therapy.

METHODS

To address potency, we used genetic engineering to develop a novel bispecific ligand-directed toxin (BLT) called EGF4KDEL, a novel recombinant anti-mesothelioma agent created by linking human epidermal growth factor (EGF) and interleukin-4 (IL-4) to truncated pseudomonas exotoxin (PE38) on the same single-chain molecule. Immunogenicity was reduced by mutating seven immunodominant B-cell epitopes on the PE38 molecule to create a new agent, EGF4KDEL 7Mut.

RESULTS

In vitro, bispecific EGF4KDEL showed superior anti-mesothelioma activity compared with its monospecific counterparts. Toxicity in mice was diminished by having both ligands on the same molecule, allowing administration of a 10-fold greater dose of BLT than a mixture of monomeric IL4KDEL and EGFKDEL. EGF4KDEL 7Mut, retained all of its functional activity and induced about 87% fewer anti-toxin antibodies than mice given the parental, non-mutated form. In vivo, intraperitoneal (IP) injection of the BLT showed significant (P<0.01) and impressive effects against two aggressive, malignant IP mesothelioma models when treatment was begun 14-16 days post tumour innoculation.

CONCLUSION

These data show that EGF4KDEL 7Mut is a promising new anti-mesothelioma agent that was developed to specifically address the obstacles facing clinical utility of targeted toxins.

Genetically designing a more potent antipancreatic cancer agent by simultaneously co-targeting human IL13 and EGF receptors in a mouse xenograft model

OBJECTIVE

Investigators are currently interested in the epidermal growth factor receptor (EGFR) and interleukin 13 receptor (IL13R) as potential targets in the development of new biologicals for pancreatic cancer. Attempts to develop successful agents have met with difficulty. The novel approach used here was to target these receptors simultaneously with EGF and IL13 cloned on the same bispecific single-chain molecule with truncated diphtheria toxin (DT(390)) to determine if co-targeting with DTEGF13 had any advantages.

DESIGN

Proliferation experiments were performed to measure the potency and selectivity of bispecific DTEGF13 and its monospecific counterparts against pancreatic cancer cell lines PANC-1 and MiaPaCa-2 in vitro. DTEGF13 was then administered intratumourally to nude mice with MiaPaCa-2 flank tumours to measure efficacy and toxicity (weight loss).

RESULTS

In vitro, bispecific DTEGF13 was 2800-fold more toxic than monospecific DTEGF or DTIL13 against PANC-1. A similar enhancement was observed in vitro when MiaPaCa-2 pancreatic cancer cells or H2981-T3 lung adenocarcinoma cells were studied. DTEGF13 activity was blockable with recombinant EGF13. DTEGF13 was potent (IC(50) = 0.00017 nM) against MiaPaCa-2, receptor specific and significantly inhibited MiaPaCa-2 tumours in nude mice (p<0.008).

CONCLUSIONS

In vitro studies show that the presence of both ligands on the same bispecific molecule is responsible for the superior activity of DTEGF13. Intratumoural administration showed that DTEGF13 was highly effective in checking aggressive tumour progression in mice. Lack of weight loss in these mice indicated that the drug was tolerated and a therapeutic index exists in an "on target" model in which DTEGF13 is cross-reactive with native mouse receptors.

Preliminary Analysis of a Phase II Trial of Stereotactic Body Radiation Therapy for Prostate Cancer With High-Risk Features After Radical Prostatectomy

Purpose

There are limited data regarding using stereotactic body radiation therapy (SBRT) in the postprostatectomy setting. Here, we present a preliminary analysis of a prospective phase II trial that aimed to evaluate the safety and efficacy of postprostatectomy SBRT for adjuvant or early salvage therapy.

Materials and Methods

Between May 2018 and May 2020, 41 patients fulfilled inclusion criteria and were stratified into 3 groups: group I (adjuvant), prostate-specific antigen (PSA) < 0.2 ng/mL with high-risk features including positive surgical margins, seminal vesicle invasion, or extracapsular extension; group II (salvage), with PSA ≥ 0.2 ng/mL but < 2 ng/mL; or group III (oligometastatic), with PSA ≥ 0.2 ng/mL but < 2 ng/mL and up to 3 sites of nodal or bone metastases. Androgen deprivation therapy was not offered to group I. Androgen deprivation therapy was offered for 6 months for group II and 18 months for group III patients. SBRT dose to the prostate bed was 30 to 32 Gy in 5 fractions. Baseline-adjusted physician reported toxicities (Common Terminology Criteria for Adverse Events), patient reported quality-of-life (Expanded Prostate Index Composite, Patient-Reported Outcome Measurement Information System), and American Urologic Association scores were evaluated for all patients.

Results

The median follow-up was 23 months (range, 10-37). SBRT was adjuvant in 8 (20%) patients, salvage in 28 (68%), and salvage with the presence of oligometastases in 5 (12%) patients. Urinary, bowel, and sexual quality of life domains remained high after SBRT. Patients tolerated SBRT with no grade 3 or higher (3+) gastrointestinal or genitourinary toxicities. The baseline adjusted acute and late toxicity grade 2 genitourinary (urinary incontinence) rate was 2.4% (1/41) and 12.2% (5/41). At 2 years, clinical disease control was 95%, and biochemical control was 73%. Among the 2 clinical failures, 1 was a regional node and the other a bone metastasis. Oligometastatic sites were salvaged successfully with SBRT. There were no in-target failures.

Conclusions

Postprostatectomy SBRT was very well tolerated in this prospective cohort, with no significant effect on quality of life metrics postirradiation, while providing excellent clinical disease control.

An artificial intelligence-enabled analysis of ECG changes after androgen deprivation therapy (ADT) for prostate cancer

e17535

Background: Androgen Deprivation Therapy (ADT) is commonly used to treat prostate cancer (PC), but has been associated with cardiac morbidity and mortality. The exact mechanisms of this association are unclear. We sought to use an artificial intelligence (AI) enabled algorithm to identify ECG changes in PC patients who received ADT compared to PC patients who did not receive ADT. Methods: From 1,000,000 ECGs performed on 210,414 patients between 1993 and 2017 at our institution, a convolutional neural network was developed to detect predictive signatures for cardiac pathologies. During this process, the ability to predict “estimated sex” of the patient was developed, with output values ranging from 0 (female) to 1 (male). We applied this algorithm to 8,619 ECGs performed on 1,057 men age 75 or younger treated with radiation for high-risk or recurrent PC at our institution, and compared estimated sex after receiving ADT (n = 1,065) to ADT-naive ECGs (n = 7,554). We correlated ECG-identified estimated sex with serum testosterone levels using Spearman rank correlation. Results: Patients who had received ADT had a mean (SD) estimated sex value of 0.81 (0.26) compared to 0.92 (0.17) for those who did not (p < 0.001). Difference between estimated sex in post-ADT ECGs and ADT-naive ECGs remained significant across age groups (Table). Decreased serum total testosterone correlated with decreased estimated sex values in men receiving ADT (R = .57, p < 0.001). Conclusions: ADT for prostate cancer is associated with changes in AI-identified ECG parameters, including lower estimated male sex after receiving ADT. Lower ECG male sex estimate was associated with decreased serum testosterone. In this study, we provide preliminary proof of concept for a potential non-invasive means of monitoring treatment effect and physiologic change using ECGs. [Table: see text]

Thoracic radiotherapy for renal cell carcinoma metastases

409

Background: For patients with metastatic renal cell carcinoma (RCC), metastasis-directed local therapies can delay progression and need to initiate/switch systemic therapy. We examined our experience treating lung or mediastinal metastases from RCC with radiotherapy (RT). Methods: We reviewed patients with lung or mediastinal metastases from RCC treated with RT. Overall survival (OS) and local control (LC) was measured from the start of RT using the Kaplan-Meier method. Results: Seventy-one patients were treated with RT for 89 lung or mediastinal metastases. Median follow-up was 2.0 years (range 0.02-11.4 years) after RT for surviving patients. Most patients were male (n=53, 74.6%). Median age was 58.4 years at initial diagnosis. Histology was most frequently clear cell carcinoma (n=62, 89.9%). At the time of treatment, 18 patients (25.4%) had 1-3 metastases, and the remainder (74.6%) had 4 or more metastases. Forty-one patients (57.5%) received systemic therapy prior to thoracic radiation. Initial systemic therapy was most commonly sunitinib (45%) or pazopanib (32.5%). Median time from starting systemic therapy to initiation of radiation was 2.0 years. Fifty-eight lung metastases and 31 mediastinal metastases were treated with a median 5 fractions (range 1-40), to a median total dose of 4800 cGy (range 400-7000), with a median fraction size of 500 cGy (range 150-2000). Thirty-three lesions were treated with concurrent systemic therapy, which was most commonly nivolumab (n=16). Of 89 treated lesions, 11 (12%) had local tumor recurrence, at a median of 1.6 years (range 0.4-2.9 years) after initiation of radiation. 1, 3, and 5 year MC (metastasis control) were 96.6%, 83.5% and 67.9%, respectively. Nine patients were treated with radiation in order to delay initiation of systemic therapy. Of these, 3 eventually received systemic therapy, initiated at a median 2.5 years after radiation. At last follow-up, 41 patients (57.7%) had died. Median OS was 2.6 years. Survival at 1, 3, and 5 years was 65.2%, 48.5%, and 38%, respectively. Conclusions: Radiation achieves high metastasis control rates for lung and mediastinal metastases from RCC, potentially delaying the need for systemic therapy.

Use of Focal Radiotherapy Boost for Prostate Cancer and Perceived Barriers toward its Implementation: A Survey

PURPOSE/OBJECTIVE(S)

In a recent phase III randomized control trial (FLAME), delivering a focal radiotherapy (RT) boost to tumors visible on MRI was shown to improve outcomes for prostate cancer patients without increasing toxicity. The aim of this study was to assess how widely this technique is being applied in current practices worldwide as well as physicians' perceived barriers toward its implementation.

MATERIALS/METHODS

An online survey assessing the use of intraprostatic focal boost was conducted in December 2022 and February 2023. The survey link was distributed to radiation oncologists worldwide via email list, group text platform, and social media. Survey questions included how many prostate cancer cases participants treat in a typical month; how often they use focal boost, if at all; the degree to which their practice is genitourinary (GU)-subspecialized; main barriers to implementing focal boost more often in their practice; and demographic information. Subgroup analyses were also conducted for participants from high-income or low-to-middle-income countries, as defined by the World Bank.

RESULTS

The survey initially collected 205 responses from various countries over a two-week period in December 2022. The survey was then reopened for one week in February 2023 to allow for more participation, leading to a total of 263 responses. The highest-represented countries were the United States (42%), Mexico (13%), and the United Kingdom (8%). The majority of respondents worked at an academic medical center (52%) and considered their practice to be at least partially GU-subspecialized (74%). 57% of participants overall reported not routinely using intraprostatic focal boost. Even among complete subspecialists, a substantial proportion (39%) do not routinely use focal boost. Less than half of participants in both high-income and low-to-middle-income countries were shown to routinely use focal boost. Perceived barriers to implementation are shown in Table 1.

CONCLUSION

Despite the promising level 1 results of the FLAME trial, many radiation oncologists worldwide are not routinely offering focal RT boost. Adoption of this technique might be accelerated by increased access to high-quality MRI, better registration algorithms of MRI to CT simulation images, physician education on benefit-to-harm ratio, automated planning algorithms, and physician training on contouring prostate lesions on MRI.

Role of metastases-directed therapy (MDT) in the management of solitary metastatic prostate cancer

143

Background: Systemic treatment in the management of metastatic prostate cancer is inevitable. However, there is a growing interest in metastases-directed therapy (MDT). We sought to investigate the efficacy of MDT in treating patients with solitary metastatic prostate cancer and hence, delaying initiation of systemic treatment (i.e., Androgen deprivation therapy or chemotherapy). Methods: We retrospectively identified 61 patients treated with targeted therapy in the form of surgery (n = 30), stereotactic body radiation therapy (SBRT) (n = 25), or cryotherapy (n = 7) for their solitary metastases prostate cancer. Complete response was defined by achieving a PSA value of ≤0.2 ng/ml plus resolution of the solitary metastatic lesion on C-11 choline PET choline scan, while incomplete response was defined by a residual PSA of > 0.2 ng/ml and/or radiographic evidence of disease following metastases-targeted therapy. Results: Mean (±SD) age was 68.4 (±7.8) yrs., median (IQR) primary Gleason Score was 7 (7-9) and median (IQR) pre-MDT PSA was 2 (1.3-3.8) ng/ml. Median (IQR) time from primary treatment of the prostate to MDT was 5.1 (2.7-10.1) years. None of the patients were on hormone therapy at the time of presentation with solitary metastases prostate cancer. 30 patients had bone metastases, 29 patients had lymph node metastases, 1 patient had soft tissue metastasis (pelvic metastatic mass), and another patient had visceral metastasis (to the lung). 42% of the patients (n = 26) achieved complete response to targeted therapy. Median time to initiation of 2nd line systemic treatment following MDT was 17.8 months for the complete responders versus 9.3 months for incomplete responders. 11% of the patients (n = 7) did not require 2nd line therapy after their MDT for a mean (±SD) time of 56.9 (±22.5) months. Conclusions: The use of targeted therapy in the management of patients with solitary metastatic disease or low-volume metastatic disease can provide comparable outcomes to those of systemic treatment. Further studies are warranted.

Consolidative Radiotherapy for Residual PET-Avid Disease on Day +30 Post CAR T-Cell Therapy in Non-Hodgkin Lymphoma

PURPOSE/OBJECTIVE(S)

Up to30% of non-Hodgkin lymphoma (NHL) patients achieve a partial response (PR) to anti-CD19 Chimeric Antigen Receptor T-cell Therapy (CART) on day +30. Most PR patients relapse and only 30% achieve spontaneous complete response (CR) without additional therapies. This study is the first to report on the role of consolidative radiotherapy (cRT) for PR PET-avid disease on day +30 post-CART in NHL.

MATERIALS/METHODS

Aretrospective review across 3 institutions from 2018 to 2022 identified 60 patients with B-cell NHL who received CART and achieved PR (Deauville 4-5) with <5 PET-avid disease sites on day +30. Progression-free survival (PFS) was defined from CART infusion to any disease progression. Overall survival (OS) was defined from CART infusion to death. Local relapse-free survival (LRFS), calculated based on the total number of PR sites, was defined from CART infusion to local relapse (LR) in the PR site identified on day +30. cRT was defined as comprehensive (compRT) - treated all PR PET-avid sites - or focal (focRT).

RESULTS

Followingday +30 PET scan, 45 PR patients were observed and 15 received cRT. Only one patient received consolidative systemic therapy and belonged to the cRT group. Prior to CART, bridging RT was given to 13 patients (9 in observation group and 4 in cRT group). There were no significant differences in the pre-CART and day +30 baseline characteristics, including the median size and SUVmax of the PR sites, between the two groups. However, the median number of PR sites on day +30 was higher in the cRT group (2 [range 1-3] vs 1 [range 1-3], p = 0.003). The median equivalent 2 Gy dose was 39.1 (Interquartile range 36.8-41) Gy, and the most common cRT regimen was 37.5 Gy in 15 fractions. The median follow-up was 21 months. Among the observed patients, 15 (33%) achieved spontaneous CR, and 27 (60%) experienced disease progression with all relapses involving the initial PR sites. Among patients who received cRT, 10 (67%) achieved CR, and 3 (20%) had disease progression with no relapses in the radiated PR sites. None of the 10 cRT patients achieving CR relapsed or required subsequent therapies. The 2-year PFS was 80% and 37% (p = 0.012) and the 2-year OS was 78% and 43% (p = 0.12) in the cRT and observation groups, respectively. Patients consolidated with compRT (n = 12) had superior 2-year PFS (92% vs 37%, p = 0.003) and 2-year OS (86% vs 43%, p = 0.048) compared to observed or focRT patients (n = 48). There were no grade 3+ RT-related toxicities. A total of 90 PR sites were identified; 64 were observed and 26 received cRT. Fourteen (22%) observed PR sites achieved spontaneous sustained CR and 42 (66%) experienced LR. Twenty-four (92%) PR sites consolidated with cRT achieved sustained CR and none experienced LR. The 2-year LRFS was 100% in the cRT sites and 31% in the observed sites (p<0.001).

CONCLUSION

NHL patients who achieve PR by PET to CART are at high risk of local progression. cRT for residual PET-avid disease on day +30 post-CART appears to alter the pattern of relapse and improve LRFS and PFS.

Predictors of Local Control with Palliative Radiotherapy for Multiple Myeloma

PURPOSE/OBJECTIVE(S)

Palliative radiotherapy (RT) is employed for patients with multiple myeloma to improve or prevent symptoms. However, the optimal dose fractionation is not well defined. The role of cytogenetics in informing RT warrants further study. We performed an institutional analysis of patients with multiple myeloma receiving palliative RT and assessed factors associated with local progression, with a focus on dose fractionation and cytogenetic abnormalities.

MATERIALS/METHODS

We queried a prospectively maintained, departmental database for consecutive patients who received palliative RT for multiple myeloma at our institution from 2015 to 2020. Double- and triple-hit were defined as the presence of two and three high-risk cytogenetic abnormalities. RT dose fractionation data were extracted from the database. Follow-up imaging was used to evaluate for progression.

RESULTS

A total of 239 patients with 362 treated lesions were included. Twenty-five patients (10.4%) with 39 lesions had double-hit cytogenetics, and 4 patients (1.7%) with 7 lesions were triple-hit. Patients had the following number of lesions treated with RT: 1 (156, 65.3%), 2 (53, 22.2%), 3 (17, 7.1%), or >3 (13, 5.4%). The most commonly targeted sites were spine (125, 34.5%), abdomen/pelvis (67, 18.5%), and lower extremity (53, 14.6%). Most lesions received doses of 20 Gy/5 fx (132, 36.5%), 8 Gy/1 fx (93, 25.7%), or 30 Gy/10 fx (48, 13.3%). RT equivalent dose in 2 Gray fractions (EQD2) was <2000 cGy for 126 lesions (34.8%) and ≥2000 cGy for 236 lesions (65.2%). At a median follow-up of 4.3 years, the risk of local progression on a per lesion basis at 1 and 4 years was 7.8% (95% CI: 5.5-11.1) and 13.4% (10.3-17.5), respectively. No cytogenetic abnormalities were correlated with local progression. Factors significant on univariate analysis included female sex [hazard ratio (HR): 1.94 (1.02-3.71), p = .045], LDH at diagnosis [HR per 10 units/liter: 1.04 (1.09-1.08), p = .016], and number of treated lesions [HR per lesion: 1.38 (1.02-1.89), p = .039]. These three covariates were included on multivariable analysis, and the only covariate to approach significance was number of treated lesions [HR for >3 versus 1: 2.43 (0.88-6.74), p = .059]. In the overall cohort, EQD2 did not impact risk of progression. Among those with >3 treated lesions, EQD2 ≥2000 cGy was associated with a significantly lower risk of progression [HR: 0.05 (0.01-0.23), p<.001]. Double- and triple-hit status were not correlated with progression. Median overall survival in all patients was 4.1 years versus 1.5 and 0.6 years in those with double- and triple-hit disease, respectively.

CONCLUSION

In this large, institutional study of patients with multiple myeloma, palliative RT achieves durable long-term local control. Patients with high disease burden may be at increased risk of progression at treated sites. This group may benefit from an EQD ≥2000 cGy. Cytogenetics, including double- and triple-hit status, do not appear to influence RT response.

In-field recurrences in relapsed/refractory (R/R) B-cell non-Hodgkin lymphoma (NHL) bridged with radiation prior to CD19 chimeric antigen receptor T-cell therapy (CART)

7556

Background: The majority of R/R NHL progressions after CART involve pre-existing sites, suggesting a promising role for bridging radiotherapy (bRT). We assessed the local control rate of disease sites bridged with radiotherapy prior to CART and identified predictors of in-field recurrence. Methods: We retrospectively reviewed 35 patients with aggressive B-cell NHL who received bRT between leukapheresis and CART infusion between 2018 and 2021 at a multi-site single institution. bRT local control rate (LC), calculated based on the total number of irradiated sites, was defined from bRT end date. Progression-free survival (PFS) and overall-survival (OS) were defined from the date of CART infusion. In-field recurrence was defined as disease relapse occurring within the radiation planning target volume. Kaplan-Meier plots and cox regression modeling were used to estimate the desired output. Results: Median age of the cohort at time of CART infusion was 59 (range 19-73). The median equivalent 2 Gy dose (EQD2) administered was 23.3 Gy (range 4-41 Gy). The median time from end of bRT to CART infusion was 14 days (range 6-42). Five (14%) patients also received bridging chemotherapy with bRT. Among the 34 evaluable patients, 30 (88%) achieved an objective response (59% complete response and 29% partial response). At a median follow-up of 12 months, 1-year PFS was 48% and 1-year OS was 72%. No progression occurred beyond 240 days. On review of treatment plans and pre-treatment PET/CT scans, 59 sites were identified that received bRT prior to CART infusion. The median size and SUVmax of the irradiated sites were 8.7cm (range 1.5-22) and 13 (range 4-46), respectively. Of the 59 irradiated sites, 8 sites (13.6%) in 7 patients had in-field local recurrence, translating to 1-year LC of 84%. No in-field recurrence occurred beyond 180 days. Moreover, no local recurrence occurred in patients who received radiation to all known sites of active disease to EQD2> 30 Gy (n = 4 patients); these patients remained in remission except for 1 who experienced progression outside the bRT field. On univariate analysis, triple hit lymphoma (THL) (OR 22.8, 95% CI: 3.8-138.3; p < 0.001), tumor size (OR 1.25, 95% CI: 1.1-1.4; p < 0.001), specifically ≥ 9cm (OR 9.4, CI: 1.2-77.3; p = 0.036) and SUVmax (OR 1.1, CI: 1.02-1.15; p = 0.008), specifically ≥ 20 (OR 5.6, CI: 1.3-23.7; p = 0.018), were significantly associated with increased risk of in-field recurrence. On multivariate analysis, THL (OR 32.9, CI: 3.2-336.0; p = 0.03) and tumor size (OR 1.3, CI: 1.1-1.6; p = 0.01) retained significant association with in-field recurrence. Conclusions: Bridging radiotherapy prior to CART provides excellent and durable in-field local control for R/R B-cell NHL. Patients with triple hit histology and bulky disease are likely at higher risk of in-field recurrence and may benefit from higher doses of bRT.

A phase II trial of hypofractionated radiation therapy over five treatments for prostate cancer with high-risk features after radical prostatectomy: MC1754

248

Background: Hypofractionated prostate cancer radiation has showed similar results in several prior phase III studies (PCG GU 003, PACE-B, and Hypo PC RT). However, prospective phase II-III clinical trial data testing 5 tx after prostatectomy is scarce. Methods: Between 2018 and 2019, 41 patients were treated after postprostatectomy for high risk features. 5 patients were treated adjuvantly, 36 for salvage including 8 with oligometastatic disease. Indications for adjuvant RT included a PSA < 0.2 and +margins, SVI, or EPE. Salvage RT was offered for PSA ≥0.2. Oligometastatic RT for patients with ≤5 RT targets. Staging included C11 PET for all cases. Total dose to the prostate bed was 30-32 Gy in 5tx QOD with IMRT, conebeam IGRT, and MRI registration. All salvage patients received ADT for 6 months and oligometastatic patients for 18 months. Dose to the metastatic sites was 30 in 5tx QOD. Of the 41 patients 8 also received SBRT to the sites of oligometastatic disease. We looked at clinical outcomes defining biochemical failure as a PSA > 0.2 after treatment, baseline adjusted CTC AE V5.0, baseline adjusted patient reported toxicities (PRO CTC AE), QOL (EPIC, PROMIS), and AUA was used for all cases. Results: Median follow up was 23 months (range 10-37). Pre-RT T stage was T2-T3b, with 47% being T3a-b; Pre RT Median PSA of 0.4 (range < 0.1-1.9); Median GS 8 (6-9); and (+) margins in 48.8%. Sites of oligometastatic disease radiated included the LN and bone. Treatment related AE were grade 0-1 in all cases, except for one patient with G2 GU incontinence. Overall QOL remained high during follow including Promis 10 overall, mental, and physical scores; urinary bother, irritative/obstructive, and AUA scores; bowel overall, bowel bother, and bowel function scores; and overall sexual, sexual function, and sexual bother scores remained at baseline levels during follow up. Only hormonal overall, hormonal function, and hormonal bother had lower scores at 3 months that recovered by 12 months in patients treated with ADT for 6 months and by 24 months in patients treated with ADT for 18 months. A total of 3 clinical failure have been seen; 2 patients with regional failures alone; and one with axial skeleton bony failures for 93% clinical control at median follow up of 23 months. All 3 patients with clinical failure were salvaged successfully with SBRT and all patients remain disease free at last follow up. A total 5 patients with raising PSAs alone have been seen. All patients have been re-staged with C11 PET. No failures in the prostate bed or previously radiated sites have been seen. Conclusions: Toxicity for RT over 5tx is lower than expected with only one case of grade 2 urinary incontinence. QOL scores remained high during follow up, minor changes in hormonal scores were seen during ADT, but recovered after. 30-32 Gy over 5 tx provided 100% control in radiated targets and metastatic sites. Clinical trial information: NCT03570827.

Impact of Prostate Cancer Treatment with Low Dose Rate Brachytherapy on Testosterone: A Retrospective Analysis

PURPOSE/OBJECTIVE(S)

Decrease in serum testosterone counts have been reported in the literature following external beam radiotherapy (EBRT), with a suggested association to low dose irradiation of the testes occurring with historical and modern external techniques. Low dose rate (LDR) brachytherapy has been described as exposing the testes to between 2 and 19 cGy compared with 196-220 cGy with EBRT. This decrease in excess dose is hypothesized to spare post-treatment testosterone decrease and subsequent change in patient-perceived quality of life. Here, we retrospectively evaluate LDR-treated prostate cancer patient testosterone change in a single-institution patient cohort.

MATERIALS/METHODS

Patients with prostate cancer who had previously received LDR brachytherapy were identified, and patients with prior baseline total testosterone lab values as well as a lab value within one year post-treatment were identified. Patients receiving concurrent androgen deprivation therapy or EBRT were excluded. The closest baseline values prior to and after LDR treatment were used for before/after comparison. Samples were compared using the paired t-test.

RESULTS

A total of 1,463 patients receiving LDR were identified with data available for analysis between 1998 and 2023; of these, 139 patients met the above criteria for analysis. Mean age was 66 (median 67; range: 47 - 79). 5 patients received 110 Gy, 2 received 120 Gy, and the remainder 145 Gy, all conducted with I-125. Total mCi delivered ranged from 20.3 mCi to 56.7 mCi (median 37.6 mCi). Approximately 57% were GS6, 42% G7, and < 1% G8. Approximately 80% of patients had T1c disease, with 19% T2 and < 1% T3a. All patients were cN0M0. Mean pre- and post-treatment testosterone were 385.5 ng/dL and 382.9 (SD: 170.9, 150.9; mean difference 2.65 [95% CI: -15.6, 20.9]), respectively, with no statistical change noted (p = 0.774).

CONCLUSION

Testosterone levels have been reported to drop following definitive EBRT owing to excess dose delivery to the testes. On review of our institutional experience in definitive LDR brachytherapy for patients treated without ADT administration, no change in testosterone levels were noted.

Genomic attributes of prostate cancer across primary and metastatic noncastrate and castrate resistant disease states: a next generation sequencing study of 183 patients

Primary prostatic adenocarcinoma (pPC) undergoes genomic evolution secondary to therapy-related selection pressures as it transitions to metastatic noncastrate (mNC-PC) and castrate resistant (mCR-PC) disease. Next generation sequencing results were evaluated for pPC (n = 97), locally advanced disease (involving urinary bladder/rectum, n = 12), mNC-PC (n = 21), and mCR-PC (n = 54). We identified enrichment of TP53 alterations in high-grade pPC, TP53/RB1 alterations in HGNE disease, and AR alterations in metastatic and castrate resistant disease. Actionable alterations (MSI-H phenotype and HRR genes) were identified in approximately a fifth of all cases. These results help elucidate the landscape of genomic alterations across the clinical spectrum of prostate cancer.

Assessment of Minimum Dose as a Strong Predictor of Local Failure after Spine SBRT

PURPOSE/OBJECTIVE(S)

Stereotactic body radiation therapy (SBRT) has demonstrated robust clinical benefits in carefully selected patients, improving local control and even overall survival (OS). Even so, a wide range of dose-fractionation schemes are used in clinical practice. We seek to assess a large database to determine clinical and dosimetric predictors of local failure after spine SBRT.

MATERIALS/METHODS

From a large institutional database, spine SBRT treatments with subsequent imaging follow-up to assess local control were identified. Patients were treated with a simultaneous integrated boost technique using 1 or 3 fractions, generally delivering 20-24 Gy in 1 fraction to the high dose volume and 16 Gy to the low dose volume (or 30-36 Gy and 24 Gy for 3 fraction treatments). Exclusions included: lack of imaging follow-up, proton therapy, and benign primary histologies. Statistical analyses included Cox proportional hazards analyses and the robust log-rank statistic for cut-point analysis. The cumulative incidence of local failure with death as a competing risk was considered as the primary endpoint.

RESULTS

A total of 522 eligible spine SBRT treatments (68% single fraction) were identified in 377 unique patients. Patients had a median OS of 43.7 months (95% confidence interval: 34.3-54.4). The cumulative incidence of local failure was 19.3% (15.3-23.2) at 1 year and 25.6% (21.1-29.9) at 2 years. Univariate analysis identified that the minimum dose (normalized for the prescription dose) was a strong predictor of local failure (p = 0.0093). Among patients treated with a single fraction, statistical significance was maintained (p = 0.024). No other dosimetric factors were predictive of local failure. In a cut point analysis, the log-rank statistic was maximized at 15.8 Gy minimum dose for single-fraction treatment (HR = 0.51, 95% CI: 0.34 - 0.75, p = 0.0009). Cumulative incidence of local failure was 15.1% (9.8-20.2) vs. 24.7% (17.2-31.5) at 1 year using this cut-off. Comparable local control was demonstrated with a minimum dose of 14 Gy (HR = 0.57, 95%: 0.37 - 0.87, p = 0.009), with reduced local control with lower minimum doses. Among a range of clinical factors assessed, only epidural and soft tissue involvement were predictive of local failure (HR = 1.80 and 1.98, respectively). Multivariable analyses incorporating soft tissue involvement, epidural extension, and multilevel disease confirmed the 15.8 Gy cutoff for single fraction cases (HR = 0.58, 95% CI: 0.38-0.88, p = 0.011).

CONCLUSION

Spine SBRT offers favorable local control using a range of dose-fractionation schemes; however, minimum dose has a strong association with local control, unlike any other dosimetric factors tested. Furthermore, statistical significance was maintained even when considering epidural extension and potential limitations from dose to the spinal cord. Our data suggests that the minimum dose should be prioritized during treatment planning, ideally to at least 14 - 15.8 Gy for single fraction.

Multi-Institutional Analysis of Metastasis Directed Therapy with or without Androgen Deprivation Therapy in Oligometastatic Castration Sensitive Prostate Cancer

PURPOSE/OBJECTIVE(S)

Several prospective trials in oligometastatic castration sensitive prostate cancer (omCSPC) have shown metastasis-directed therapy (MDT) can delay time to progression and initiation of androgen deprivation therapy (ADT) compared to observation. However, the optimal integration of ADT with MDT remains unclear. Here we report a multi-national, multi-institutional retrospective cohort of omCSPC treated with MDT to characterize the long-term outcomes of patients treated with MDT alone or in combination with ADT.

MATERIALS/METHODS

Patients with a controlled primary site and omCSPC (defined as ≤ 5 lesions on conventional imaging) treated with MDT with or without concurrent ADT and with at least 36 months follow-up were retrospectively screened across 13 institutions. The primary endpoints included biochemical progression free survival (bPFS) and radiographic progression free survival (rPFS) calculated using Kaplan-Meier method and stratified by treatment group (MDT alone vs MDT + ADT). Multivariable Cox regression was performed adjusted for variables found to be prognostic on univariate analysis.

RESULTS

Among 414 patients screened, a total of 263 patients treated between 2003 and 2018 met inclusion criteria and included. Of these, 105 received MDT alone and 158 received MDT+ADT, with median follow-up of 49.5 and 54.5 months, respectively. The majority were metachronous (90%) and had bone lesions (60%). Median ADT duration was 21.3 months (IQR 12.0- 31.9). Patients who received ADT vs. no ADT had poorer prognostic features including 23% vs. 1% synchronous (p<0.001), and 55% vs 40% Gleason 8-10 (p = 0.012). ADT use was associated with a better 5-year bPFS 24% vs 11% (p<0.0001) and rPFS 41% vs 29% (p<0.001). On multivariable Cox regression adjusting for post-MDT PSA nadir and salvage therapy, ADT use maintained significance for both bPFS (HR 0.51 (0.36, 0.71), p<0.001) and rPFS (HR 0.67, 95% CI 0.46-0.96, p = 0.03).

CONCLUSION

Long-term outcomes with MDT alone suggest a small proportion of patients experience sustained disease control. The addition of ADT appears to improve rPFS, however prospective studies are needed in order to allow for personalization of care in patients with omCSPC.

Sensitivity of the PROMIS-10 for Capturing Radiation-Related Quality of Life Changes

PURPOSE/OBJECTIVE(S)

Patient reported outcomes (PROs) are becoming more common when assessing the effects of radiotherapy (RT). The aim of this study was to assess the sensitivity of the Mental and Physical domains of the Patient-Reported Outcomes Measurement Information System 10 (PROMIS-10) to radiotherapy and determine what predictors were associated with change in quality of life.

MATERIALS/METHODS

Patients, regardless of cancer type, were enrolled on a multi-site prospective registry. Inclusion criteria included curative radiotherapy and completion of the PROMIS-10 prior to treatment (Baseline) and at End of Treatment (EOT). To assess the strongest predictors of change in the T score of mental and physical health, we included 14 demographic characteristics and treatment variables in a multivariable stepwise regression.

RESULTS

A total of 7,586 patients were eligible for the analysis. The median age was 65 (range 18-94), 54% were males, and 94% were white. A majority received photons (62.5%) and the others received protons (37.5%) with an average dose of 52.3 Gy (range 20-80 Gy) over an average of 22.6 fractions (range 1-66). Patient disease sites were sub-grouped into 12 categories: Breast (25.5%), GU (23.0%), H&N (11.1%), CNS (8.5%), Pancreas-Biliary (6.7%), Thoracic (5.7%), Soft Tissue/Bone (5.0%), Esophagus-Gastric (4.7%), Colorectal-Anus (4.4%), Heme/Lymph (2.6%), GYN (1.8%), and Skin/Melanoma (1.0%). For both outcomes, the model selected disease group as an important predictor and it explained the most variance in the outcome compared to the rest of the predictors. When probing the effect of disease group, H&N, Esophagus-Gastric, Skin/Melanoma, and Colorectal-Anus had the largest mean decrease in quality of life for both domains. For mental health, the model also selected radiation type. Patients treated with protons indicated a bigger decrease in mental health compared to patients treated with photons (b = 0.43, 95% CI: -0.01, 0.69). For physical health, the model selected total fractions, ethnicity, and T stage. As number of fractions increased, the physical health change scores became more negative, on average (b = -0.03, 95% CI: -0.05, -0.01). Hispanic/Latino patients indicated a smaller decrease in physical health compared to White (b = -1.50, 95% CI: -2.60, -0.40) and Unknown ethnicity patients (b = -1.82, 95% CI: -3.36, -0.27). Finally, patients with a T stage of 3 or greater indicated a smaller decrease in physical health than patients with a T stage less than 3 (b = 0.76, 95% CI: 0.35, 1.16).

CONCLUSION

The PROMIS-10 did not capture significant change for patients undergoing curative radiotherapy except for patients with Head & Neck, Esophagus-Gastric, Skin, and Colorectal-Anus cancer. Further analyses should explore which patients experience the greatest change in quality of life within disease group.

Impact of initial treatment selection on clinical outcomes after biochemical failure in radiorecurrent high-risk prostate cancer

208

Background: Treatment of high risk prostate cancer (HRPCa) with external beam radiotherapy (EBRT) plus brachytherapy (BT) boost (EBRT+BT) has been prospectively associated with lower rates of BCR, albeit potentially with increased toxicity, and retrospectively linked to decreased distant metastasis (DM) and PCa-specific mortality (PCSM) compared to EBRT alone. However, it is unclear whether patients who develop BCR following either approach have similar downstream oncologic outcomes. Methods: We identified 706 out of 3820 men with HRPCa treated at 13 institutions from 1998-2015 with EBRT (n=468/2134) or EBRT+BT (n=238/1686) who developed BCR. We compared rates of DM, PCSM, and all-cause mortality (ACM) after BCR between treatment groups using Fine-Gray competing risk regression. Models were adjusted for age, Gleason grade group, initial PSA (iPSA), clinical T stage, time-dependent use of systemic salvage, and interval to BCR using inverse probability of treatment weighting. Results: Median follow-up was 9.9 years from RT and 4.8 years from BCR. Groups were similar in age, iPSA, presence of ≥2 HR features, and median interval to BCR (3.3 years). Most men received neoadjuvant/concurrent androgen deprivation therapy (ADT), 92.5% and 91.0% for EBRT and EBRT+BT, respectively, though for a longer duration with EBRT (median 14.7 vs. 9.0 months, p=0.0012). Local and systemic salvage rates were 2.3% and 36.3% after EBRT, and 2.6% and 43.6% after EBRT+BT, respectively. Initial EBRT+BT was associated with significantly lower rates of DM after BCR (HR 0.48, 95% CI 0.36-0.64, p<0.001). Rates of PCSM and ACM did not significantly differ (HR 0.93, 95% CI 0.67-1.30, p=0.93, and HR 0.8, 95% CI 0.6-1.1, p=0.11, respectively). Conclusions: In this large retrospective series of radiorecurrent HRPCa, initial treatment with EBRT+BT was associated with significantly lower rates of DM after BCR compared with EBRT, despite shorter ADT use and a similar median interval to BCR. Local salvage was widely underutilized in both groups. In the absence of salvage for local failure after EBRT, upfront treatment intensification with BT may reduce DM, though not PCSM or ACM, even after development of BCR.

Long-Term Patient-Reported Bowel and Urinary Quality of Life in Patients Treated with Intensity-Modulated Radiotherapy and Intensity-Modulated Proton Therapy for Localized Prostate Cancer

PURPOSE/OBJECTIVE(S)

To assess long-term differences in patient-reported outcomes in bowel and urinary domains between intensity-modulated radiotherapy (IMRT) and intensity-modulated proton therapy (IMPT) for prostate cancer.

MATERIALS/METHODS

Bowel function (BF), urinary irritative/obstructive symptoms (UO), and urinary incontinence (UI) domains of EPIC-26 were collected in patients with T1-T2 prostate cancer receiving IMRT or IMPT at a tertiary cancer center (2015-2018). Mean changes in domain scores were analyzed from pretreatment to 24 months post-radiotherapy for each modality. A clinically meaningful change was defined as a score change >50% of the standard deviation of a baseline score.

RESULTS

A total of 82 patients treated with IMRT (52.2%) and 56 patients treated with IMPT (53.3%) completed the questionnaire at baseline and 24 months post-RT. There were no baseline differences in domain scores between treatment modalities. At 24 months post-radiotherapy, there was significant and clinically meaningful decline of BF mean score in the IMRT cohort (-4.52 [range -50, 29.17], p = 0.003), whereas the decline in BF score did not reach statistical significance (-1.88 [range -37.5,50], p = 0.046) when accounting for the Bonferroni adjustment nor clinical relevance in the IMPT cohort. A higher proportion of patients treated with IMRT had a clinically relevant reduction in BF when compared with IMPT (47.37% vs 25.93%, p = 0.017). The mean changes in UI and UO scores of the IMRT and IMPT cohorts were neither statically significant nor clinically relevant.

CONCLUSION

IMPT has less decrement in BF than IMRT at 24 months post-RT, while there was no differential effect on UO and UI.