Rutenberg, Michael S.

10 Background: Cell-free circulating tumor tissue modified viral DNA (ctDNA) has been used as a biomarker to detect recurrence for anal squamous cell carcinoma (ASCC). However, its value in informing treatment modification during definitive chemoradiation (CRT) has yet to be explored. We evaluated ctDNA response during and at completion of definitive CRT to establish patterns of disease response and inform future studies to personalize treatment. Methods: From 11/2022 to 6/2024, 13 consecutive patients with biopsy proven, non-metastatic ASCC received definitive CRT and had ctDNA testing using a commercially available droplet digital quantitative PCR assay. ctDNA testing was done at baseline (pre-CRT), week 4 of CRT, and/or end of CRT, 1-3 months post-CRT, and every 6 months thereafter. CRT included concurrent 5FU/MMC (or capecitabine/MMC) and radiotherapy according to RTOG 0529. Treatment response assessment included: physical exam, anoscopy, and imaging with PET/CT, CT C/A/P +/- MRI abdomen and pelvis. Results: 13 patients had ctDNA testing and 11 patients had HPV-positive ASCC and tested positive for ctDNA. The 11 patients with detectable baseline ctDNA were included in this analysis. The median age at diagnosis was 63 years old. Staging included: 1- Stage IIA, 7- Stage IIB, 1- Stage IIIA, 2- Stage IIIC. 1 patient was cN0, while 11 were cN1. With a median follow-up from completion of CRT of 13 months, 4 patients have persistent or recurrent disease: 2 with distant metastases, 1 with persistent local disease (1 month post-CRT), and 1 with local and distant recurrence. Baseline value of ctDNA did not correlate to stage at diagnosis, rate of clearance during CRT, or likelihood of recurrence. 5 of 11 patients cleared ctDNA by week 4 of CRT. Of 5 patients who cleared ctDNA by week 4 of CRT, 4 remain NED and 1 developed distant metastases. Of 6 patients with persistent ctDNA at week 4 of CRT, 3 have persistent or recurrent disease- 1 local persistence 1 month post-CRT, 1 local and distant recurrence 6 months post-CRT, and 1 with distant recurrence 12 months post- CRT. Among 6 patients who cleared ctDNA by the final week of CRT, 1 patient developed recurrent disease. Among the 4 patients in the series with residual/recurrent disease, 3 of them had not cleared ctDNA by the end of CRT. Of 10 patients with ctDNA testing at 1 month post-CRT, 8 had no detectable ctDNA. 2 patients with persistent (1) or recurrent (1) ctDNA at 1 month post-CRT developed disease recurrence- 1 with distant recurrence and 1 with local and distant recurrence. Conclusions: ctDNA assessment during CRT may provide insight into disease response that can predict patterns of failure and facilitate personalized therapy- treatment intensification, deintensification, or additional testing to detect early metastatic disease. Larger studies and clinical validation are needed.

Abstract Background Adult onset medulloblastoma (aMB) is a rare tumor with limited available evidence. We present a large multi-institutional retrospective cohort of aMB patients treated in the modern era, with an emphasis on understanding the role of chemotherapy at initial diagnosis. Methods We included 267 consecutive patients with aMB treated at 7 different institutions from 2000-present, controlling for chemotherapy regimen and cycles received. Results Treatment factors were highly intercorrelated with one another and with treating institution. Concurrent chemotherapy was not associated with overall survival (OS). Adjuvant chemotherapy was associated with OS on univariable analyses (HR = 0.55, P = .029) and on multivariable analysis when adjusting for risk status (HR 0.55, P = .026) but not when also adjusting for treating institution. Proton craniospinal irradiation was associated with improved survival on univariable (HR = 0.50, P = .019) and multivariable analysis adjusting for risk status (HR = 0.51, P = .024) but not when treating institution was also considered. On subgroup analysis, adjuvant chemotherapy was associated with improved survival in M0 (HR = 0.55, P = .043) but not M1 disease, in patients with subtotal resection (HR = 0.43, P = .048) but not those with GTR. Similarly, progression-free survival was improved with chemotherapy in patients with M0 (HR = 0.57, P = .032) but not M1 disease, and in patients with subtotal (HR = 0.50, P = .054) but not gross total resection. Conclusions There was no benefit of concurrent chemotherapy. Adjuvant chemotherapy was associated with improved overall survival and this effect was driven by select subgroups, specifically those with M0 disease and those with residual tumor. We could not confirm that these associations are independent of the treating institution.

Abstract Purpose: Squamous cell carcinoma of the anus (SCCA) is primarily driven by human papillomavirus (HPV) infection. Up to 30% of patients experience recurrence, necessitating improved surveillance strategies. Liquid biopsies have shown promise as a tool in oncology. This study investigates the clinical performance of circulating tumor tissue modified viral (TTMV)- HPV DNA in the post-treatment surveillance of SCCA. Patients and methods: This central IRB-approved retrospective cohort study included 117 patients diagnosed with HPV-driven SCCA from seven U.S. centers who had ≥1 TTMV-HPV DNA tests (NavDx®, Naveris, Inc., Waltham, MA) performed between March 2020 and June 2024. TTMV-HPV DNA for HPV subtypes 16, 18, 31, 33, and 35 were analyzed using droplet digital PCR. The diagnostic accuracy of TTMV-HPV DNA was evaluated by comparing test results with clinical evidence of SCCA recurrence determined through anoscopy, radiology, and/or tissue biopsy. Recurrence is defined as either a positive biopsy or subsequent salvage therapy. Results: Patients were primarily female (73%) with a median age 63 years. Median follow-up after initial treatment was 19 months. Forty-seven patients (40%) had pretreatment TTMV-HPV DNA testing, with a baseline detectability of 85.1% (40/47, 95% CI: 74.9–95.3). Of these, 24 were re-tested within 3 months post-treatment and 18 had undetectable TTMV-HPV DNA (75%). Those patients whose scores became undetectable had significantly longer recurrence-free survival than those whose scores remained detectable (log-rank test, p=0.01). One hundred and four patients (89%) underwent post-treatment testing, of which 91 provided relevant data for the analysis. Of these 91 patients, 27 (29.7%) experienced recurrence. Post-treatment testing demonstrated a per- patient sensitivity of 85.7% (24/28, 95% CI: 72.8-98.7). Of four patients with a false negative test, only one had biopsy-confirmed recurrence, whereas the remaining recurrences were not biopsied prior to starting salvage treatment. The positive predictive value of a single positive test was 97.6% (40/41; 95% CI: 92.8–100.0). One patient remains in active follow-up. Of the true positive post-treatment tests, 58% (14/24) predicted recurrence before clinical detection, with a median lead time of 59 days (range: 10–536). There were 141 negative post-treatment tests across 66 patients. This yielded a per-test specificity and negative predictive value of 99.3% (136/137, 95% CI: 97.8-100.0) and 97.2% (136/140, 95% CI: 94.9-99.9), respectively. Indeterminate TTMV-HPV DNA tests were rare (5/268,1.9%). However, clinically indeterminate findings (CIFs) were common, with 141 post-treatment CIFs identified across 52/117 patients (44.4%). TTMV-HPV DNA testing was able to correctly predict recurrence status in 94.3% of CIF cases. Conclusion: TTMV-HPV DNA testing is a sensitive and specific surveillance method for detecting early recurrence of HPV-driven SCCA. Citation Format: Shane Lloyd, Rafi Kabarriti, James Jabalee, Tyler Slater, Corbin Jacobs, Sean Inocencio, Michael Rutenberg, Chance Matthiesen, Kasha Neff, Gene-Fu F Liu, Tiffany M Juarez, Catherine DV Fitz, Stanley Liauw. Plasma-based circulating tumor tissue modified viral (TTMV)-HPV DNA for detection of recurrent HPV-driven anal cancer [abstract]. In: Proceedings of the AACR Special Conference: Liquid Biopsy: From Discovery to Clinical Implementation; 2024 Nov 13-16; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(21_Suppl):Abstract nr B018.

AbstractPurposeSkin collimation is a useful tool in electron beam therapy (EBT) to decrease the penumbra at the field edge and minimize dose to nearby superficial organs at risk (OARs), but manually fabricating these collimation devices in the clinic to conform to the patient's anatomy can be a difficult and time intensive process. This work compares two types of patient‐specific skin collimation (in‐house 3D printed and vendor‐provided machined brass) using clinically relevant metrics.MethodsAttenuation measurements were performed to determine the thickness of each material needed to adequately shield both 6 and 9 MeV electron beams. Relative and absolute dose planes at various depths were measured using radiochromic film to compare the surface dose, flatness, and penumbra of the different skin collimation materials.ResultsClinically acceptable thicknesses of each material were determined for both 6 and 9 MeV electron beams. Field width, flatness, and penumbra results between the two systems were very similar and significantly improved compared to measurements performed with no surface collimation.ConclusionBoth skin collimation methods investigated in this work generate sharp penumbras at the field edge and can minimize dose to superficial OARs compared to treatment fields with no surface collimation. The benefits of skin collimation are greatest for lower energy electron beams, and the benefits decrease as the measurement depth increases. Using bolus with skin collimation is recommended to avoid surface dose enhancement seen with collimators placed on the skin surface. Ultimately, the appropriate choice of material will depend on the desire to create these devices in‐house or outsource the fabrication to a vendor.

Skull-base chordoma and chondrosarcoma are rare radioresistant tumors treated with surgical resection and/or radiotherapy. Because of the established dosimetric and biological benefits of heavy particle therapy, we performed a systematic and evidence-based review of the clinical outcomes of patients with skull-base chordoma and chondrosarcoma treated with carbon ion radiotherapy (CIRT). A literature review was performed using a MEDLINE search of all articles to date. We identified 227 studies as appropriate for review, and 24 were ultimately included. The published data illustrate that CIRT provides benchmark disease control outcomes for skull-base chordoma and chondrosarcoma, respectively, with acceptable toxicity. CIRT is an advanced treatment technique that may provide not only dosimetric benefits over conventional photon therapy but also biologic intensification to overcome mechanisms of radioresistance. Ongoing research is needed to define the magnitude of benefit, patient selection, and cost-effectiveness of CIRT compared to other forms of radiotherapy.