Salvage Abdominoperineal Resection for Locally Recurrent or Persistent Anal Squamous Cell Carcinoma after Definitive Chemoradiation

PURPOSE/OBJECTIVE(S)

Initial treatment for patients with squamous cell carcinoma of the anal canal includes definitive chemoradiation. Salvage abdominoperineal resection (APR) is the treatment of choice for recurrent or persistent disease. Older studies suggest approximately 50% successful salvage of recurrent or persistent disease with APR. Risk factors for failure after salvage APR are incompletely characterized.

MATERIALS/METHODS

Using a single institutional database, patients were identified who underwent salvage APR after definitive intensity-modulated radiotherapy-based chemoradiation between 2003 and 2022. Clinical and pathologic variables analyzed included age at APR, sex, race, HIV status, initial cT stage, initial cN stage, radiation dose, recurrent vs persistent disease, recurrent pT stage, recurrent pN stage, the presence of LVSI, PNI or <2mm surgical margins, and the use of either intraoperative radiation or another treatment modality in addition to APR. The log rank test was used to determine differences in time from APR to events (local recurrence, distant metastasis and death) based on clinical and pathologic variables. The Cox Proportional Hazard Model was used to perform multivariable analysis for all factors with a univariate P-value <0.1.

RESULTS

Of 628 patients with anal squamous cell carcinoma, 50 (8.0%) were treated with abdominoperineal resection for locally recurrent (n = 29, 58%) or locally persistent (n = 21, 42%) disease. Median [interquartile range] follow up was 40.0 months [15.2-68.0 months] from APR. Median local recurrence-free survival was not reached; 1- and 2-year local recurrence-free survival was 81% (95% CI 72-92%) and 76% (64-89%). On multivariable analysis, pathologic T-stage of the recurrence (3.85 (1.07-13.9); P = .040), the presence of lymphovascular space invasion (9.1 (1.12-73.62); P = .038) and surgical margins <2mm (8.81 (2.11-36.73); P = .003) were all significantly associated with higher rates of local recurrence. Median distant metastasis-free survival was not reached; 1- and 2-year distant metastasis-free survival was 88% (81-98%) and 79% (67-92%). On multivariable analysis, only persistent (versus recurrent) local disease was significantly associated with higher rates of distant metastasis (1.23 (1.05-5.55) P = .043). Median overall survival was not reached; 1- and 2-year overall survival was 90% (81-98%) and 78% (65-90%). On multivariable analysis, only recurrent pT stage (T3/4 vs T1/2) was associated with higher rates of death (5.87 (1.02-33.65); P = .047).

CONCLUSION

APR is a successful salvage modality for anal squamous cell carcinoma with recurrent or persistent disease after chemoradiation results. Patients with pT3/4 disease, lymphovascular space invasion, surgical margins <2 mm may be associated with higher re-recurrence rates and may benefit from more frequent monitoring or treatment escalation.

Definitive Radiotherapy for Oligometastatic and Oligoprogressive Thyroid Cancer

PURPOSE/OBJECTIVE(S)

Local consolidative radiotherapy (LCT) for oligometastatic disease is a promising paradigm improving outcomes for various malignancies but has been underexplored for metastatic thyroid cancer. We hypothesize that LCT to distant sites with definitive RT doses can yield favorable outcomes and defer systemic therapy escalation for these patients.

MATERIALS/METHODS

We reviewed 96 thyroid cancer patients who received 175 LCT courses from 2010-2022 to 228 metastatic sites, including: thorax (45%), bone (40%), brain (6%), head/neck (5%), and abdomen (3%). Common prescriptions were 50-55Gy/4-5fxs or 56-70Gy/8-10fxs for lung; 52.5-60Gy/15fxs for mediastinum; and 18-24Gy/1fx or 27-30Gy/3fxs for bone. RECIST v1.1 and CTCAE v5.0 were used to define progression and toxicities, respectively. Outcomes were evaluated via Kaplan-Meier and associations examined via Cox proportional hazards modeling.

RESULTS

Median age was 63 years (range: 26-92), with 62 oligometastatic cases (total 1-5 sites) and 34 oligoprogressive (with 1-5 growing sites). Primary disease was controlled in all patients, with 39% receiving post-op RT and 66% prior RAI. Histologies included papillary (40%), anaplastic (25%), follicular (12%), medullary (9%), Hurthle (7%), and poorly-differentiated (7%). Median time from initial diagnosis to LCT was 3 yrs (IQR 1-8), and median follow-up from 1st LCT was 21 mos (IQR 9-51). Patients received an average 2 LCT courses (range 1-8) treating 1-4 sites. Median survival (OS) from 1st LCT was 9 yrs (95% CI = 5-14). On multivariable analysis (MVA), worse OS was associated with anaplastic histology (HR 4.6, p<.01), but longer OS was associated with prior RAI (HR 0.33, p = .02) and oligometastatic disease (HR 0.3, p = .01). For anaplastic histology, median OS was 1.2 years vs. 9.3 years for non-anaplastic; 3-yr OS was 36% vs. 88% (log-rank, p<.01). Five-year OS for oligometastatic cases was 75% vs 53% for oligoprogressive (log-rank, p = .04). Median progression free survival (PFS) from 1st LCT was 15.5 mos (95% C I = 11-20). On MVA for all LCT courses, time to any progression (TTP) was negatively associated with anaplastic histology (HR 1.7, p = .02) and 2nd or higher LCT course (HR 1.45, p = .05), but favorably associated with thoracic site (HR 0.49, p<.01). Following later LCT courses, median TTP was 11 mos vs 17 mos for initial LCT course (log-rank, p = .03). After LCT to lung/chest, TTP was 18.6 mos vs 9.5 mos for non-thoracic sites (log-rank, p<.01). Only 6% of failures occurred at previously treated lesions. Most LCT courses (67%) were without ongoing chemotherapy, while 25% entailed continuing the same regimen and 9% had planned treatment post-RT. There were 2 Grade 3 toxicities (pneumonitis and esophagitis) and no Grade 4-5 events.

CONCLUSION

With high local control rates and minimal toxicity, LCT can be a feasible strategy to defer systemic therapy escalation for oligometastatic and oligoprogressive thyroid cancer.

Patient-Level Savings Using the Mark Cuban Cost Plus Drugs Company for Radiation Oncology Patients

PURPOSE/OBJECTIVE(S)

In 2022, the Mark Cuban Cost Plus Drugs Company (MCCPDC) launched with the goal of offering affordable generic drugs directly to patients through a transparent pricing model. This study aims to evaluate the patient-level potential savings per prescription for patients undergoing radiation oncology treatment, regardless of insurance status.

MATERIALS/METHODS

We analyzed prescription patterns of radiation oncologists in 2019 using the Medicare Part D database and selected the top 100 most frequently prescribed drugs for further analysis. To evaluate potential cost savings, we obtained prescription data from the Medical Expenditure Panel Survey (MEPS) for 2019. We filtered the MEPS data based on the top 100 non-controlled drugs prescribed by radiation oncologists (MCCPDC does not sell controlled substances). We calculated the mode for the scripts of each drug and compared the prices to those offered by MCCPDC then adjusted the prices for inflation using the Consumer Price Index (CPI). We stratified scripts by payor type, including public (Medicare and Medicaid), private, and self-pay, and compared the cash price at MCCPDC to the out-of-pocket costs for patients.

RESULTS

Our analysis included 25,421 prescriptions. Of these, 49% were covered by public payors (Medicare or Medicaid), 25% were covered by private entities (including private insurance), and 26% were self-pay. Savings were defined as the cash price at MCCPDC being lower than the copay. 40% of prescriptions had savings when purchased through MCCPDC regardless of coverage status. Savings were seen on 17% of scripts for patients covered by Medicare or Medicaid, 39% for those with private coverage, and 84% for patients who self-pay. The average savings per script were $8.80 for public payors, $6.33 for private payors, and $11.32 for self-payors. The medication with the highest average potential savings, regardless of coverage, was tadalafil, with savings of $54.63 per prescription. Among public payors, solifenacin had the highest average potential savings, with savings of $37.07 per prescription. For private payors, memantine had the highest potential savings at $62.83 per prescription. For self-pay patients, the medication with the highest potential savings was levetiracetam, with savings of $740.34 per prescription.

CONCLUSION

Our study demonstrates that MCCPDC can provide substantial cost savings to patients when compared to out-of-pocket costs, regardless of insurance status. This is the first analysis to demonstrate such cost-savings at the patient-level. Radiation oncologists should consider discussing MCCPDC with patients when prescribing medications, as it has potential to reduce the financial toxicity burden for many patients.

Addition of Metastasis-Directed Therapy to Standard of Care Systemic Therapy for Oligometastatic Breast Cancer (EXTEND): A Multicenter, Randomized Phase II Trial

PURPOSE/OBJECTIVE(S)

Prior retrospective and prospective evidence have suggested a potential survival benefit of adding metastasis-directed therapy (MDT) to standard of care systemic therapy for oligometastatic breast cancer. This has led to the increased utilization of MDT in this setting despite the lack of randomized evidence to support this approach. Furthermore, the recent presentation of NRG-BR002 has questioned the value of MDT. Thus, we evaluated whether the addition of MDT to systemic therapy improves PFS in oligometastatic breast cancer.

MATERIALS/METHODS

EXTEND (NCT03599765) is a phase II randomized basket trial for multiple solid tumors testing whether the addition of MDT improves PFS. The primary endpoint was pre-specified to be independently assessed and reported for the breast basket when a minimum of 6 months of follow-up had been reached. Patients with ≤5 metastases were randomized to standard of care systemic therapy with or without MDT. The choice of systemic therapy was at the discretion of the treating medical oncologist. Number of metastatic lesions and prior lines of systemic therapy for metastatic disease were used as stratification variables pre-randomization. The primary endpoint was progression-free survival (PFS) defined as time to randomization to date of clinical or radiographic progression or death. The study was designed to have 80% power to detect an improvement in median PFS from 18 to 36 months, with a type I error of 0.1.

RESULTS

Between September 2018 to July 2022, 43 patients were randomized. 22 patients were assigned to the MDT arm, and 21 patients to the no MDT arm. Three patients were not evaluable. The MDT arm patients were older vs the no-MDT arm patients (median 61.5 years vs 48 years, p = 0.01). Otherwise, the arms were well-balanced. Overall, 8 patients had triple negative disease (18.6%), and 12 patients (30%) had de novo metastatic disease. Of those patients with de novo presentation randomized to MDT, all except one had the primary tumor treated with surgery and radiation. At a median follow-up of 19.4 months, 20 events were observed. Among the 40 evaluable patients, there were 5 deaths (3 in the MDT arm and 2 in the no MDT arm). There was no difference in PFS between the MDT and no MDT arms (median 15.6 v 24.9 months, p = 0.66). Similarly, there was no difference in the secondary endpoint of time to new metastatic lesion appearance between the MDT and no MDT arms (median 15.6 months vs not reached, p = 0.09). Two grade 3 toxicities were observed in the MDT arm, and 1 in the no MDT arm. Further analysis of correlative translational biomarkers, including immune markers and ctDNA, are ongoing.

CONCLUSION

The addition of MDT to standard of care systemic therapy did not improve PFS or time to new metastatic lesion in patients with oligometastatic breast cancer. This data coupled with the recently presented NRG-BR002 results, suggests there is no benefit to MDT in an otherwise unselected oligometastatic breast cancer population.

Predictors of Low Anterior Resection Syndrome after Long-Course Chemoradiation for Locally Advanced Rectal Cancer

PURPOSE/OBJECTIVE(S)

Low anterior resection syndrome (LARS) describes disordered bowel function including tenesmus, frequent, clustered, incomplete, urgent or incontinent bowel movements. The impact of clinical and radiation dosimetric factors on LARS score is unknown. We aimed to evaluate the radiation plans for patients who received long course chemoradiation (LC-CRT) to identify potential dosimetric predictors of LARS.

MATERIALS/METHODS

We identified patients with rectal cancer treated with LC-CRT (50.4Gy in 28 fractions) at our institution from 2016-2020 who were alive and without disease. As a part of a larger patient-reported outcome survey, we obtained the Low Anterior Resection Syndrome Score (LARS) for patients without an ostomy at the time of the survey. We utilized clinical and dosimetric variables in a multivariate analysis including age at LC-CRT, body mass index, sex, distance of the tumor from the anal verge (AV), threatened mesorectal fascia (MRF) on staging imaging, T-stage, N-stage, receipt of surgery (vs non-operative management (NOM), radiation technique (3DCRT vs VMAT), mean dose and D0.03ccs for the anal canal (defined as 4cm from the anal verge) and D0.03cc, V30Gy and V45Gy for the small bowel loops. We then created a multiple linear regression model to predict LARS using P>.20 on univariate testing.

RESULTS

Of 110 patients treated with preoperative LC-CRT and who did not have an ostomy, 57 responded (51.8%). The median [interquartile range (IQR)] interval from completion of LC-CRT to survey completion was 38.4 months [26.3-48.9]. Thirty-four patients (60%) were men, the median [IQR] BMI was 28 [24-31.9], the median [IQR] distance of the tumor to the anal verge was 7cm [5-10], 40 (70%) had T3 tumors, 7 (12%) had T4 tumors, 45 (79%) were N+. Forty-one patients (72%) had surgery following LC-CRT, and 16 (28%) had non-operative management. 3D conformal technique was used for 47 (82%) and VMAT used for 10 patients (18%). The median [IQR] LARS score was 32 [24-38] with 35 patients (61%) classified as Major LARS (LARS score = 30-42). On multiple linear regression modeling (Table), only receipt of surgery significantly predicted for higher (worse) LARS score.

CONCLUSION

In our cohort, patients who received surgery after LC-CRT had a significantly higher LARS score. Of the dosimetric parameters tested, D0.03ccs was the best predictor and could potentially be significant with a larger number of patients. Further work is needed to improve bowel function and quality of life for patients treated with LC-CRT for rectal adenocarcinoma.

Assessment of the Spatial Bio-Distribution of NBTXR3 for Locally Advanced or Borderline-Resectable Pancreatic Ductal Adenocarcinoma (LAPC or BRPC) Patients Undergoing Radiation Therapy

PURPOSE/OBJECTIVE(S)

NBTXR3 is a novel radioenhancer composed of functionalized hafnium oxide nanoparticles that are injected directly into the tumor. An ongoing phase I trial is assessing the application of NBTXR3 in the treatment of locally-advanced or borderline-resectable pancreatic ductal adenocarcinoma, with the primary goal of determining the recommended NBTXR3 dose for a subsequent phase II trial. Using patients from the ongoing phase I trial, we evaluated the spatial bio-distribution of NBTXR3 in the pancreas as function of time and assessed if there is migration of the compound during radiation therapy.

MATERIALS/METHODS

Adult patients with LAPC or BRPC were enrolled. Analysis of 8 patients who underwent CT simulation at least 24 hours after receiving the NBTXR3 intratumoral injection in the pancreatic lesion under general anesthesia guided by an endoscopic ultrasound was conducted. Patients were simulated with and without iodinated intravenous contrast under breath hold, with 3mm CT slice thickness and 50-60cm FoV. A contrast-enhanced CT series was chosen for RT planning purposes. All patients were planned for a 15-fraction IMRT course using 6-MV beam energy, with 45Gy and 37.5Gy dose levels (using a simultaneous integrated boost technique) to gross primary tumor and microscopic disease/regional nodes, respectively. Daily image guidance included either cone-beam CT (CBCT, n = 1) or CT-on-Rails (CTOR, n = 7) and were fused to the planning CT images using Velocity, ver. 3.0.1. The NBTXR3 volume was determined by thresholding the images to 165 HU and 300 HU for CTOR and CBCT images, respectively. Bones, stents, and artifacts were manually removed from the NBTXR3 volume. The volumes for the NBTXR3 and the NBTXR3 overlapping with the GTV for each patient were individually fit to a linear model in R, ver. 4.1.3.

RESULTS

One patient from the CTOR cohort was excluded from analysis due to the small volume of NBTXR3 (0.02 cm3) compared to the rest of the cohort (0.716 - 6.917 cm3). The total volume of NBTXR3 in the CBCT images could not be analyzed due the substantial image artifacts, only the volume overlapping the GTV was calculated. There were no statistically significant changes (p > 0.1 Adj-R2 = 0.99) in the raw volume of NBTXR3 for the duration of the treatment in all CTOR patients. For the NBTXR3 volume overlapping with the GTV, five cases did not present with a volume change during the treatment (p > 0.1 Adj-R2 = 0.99), while one CTOR case had a reduction in volume of about 1.5%/day (p = 0.7), and the CBCT case had a reduction of 3%/day (p < 0.001).

CONCLUSION

The raw volume of NBTXR3 injected in the pancreas did not significantly change over the duration of the three weeks of treatment. We also did not observe significant changes in the NBTXR3 volume overlapping the GTV in most cases. The stability of NBTXR3 was demonstrated during RT.

Outcomes and after Hyperfractionated, Accelerated Reirradiation for Recurrent Anal Squamous Cell Carcinoma

PURPOSE/OBJECTIVE(S)

Abdominoperineal resection (APR) is the standard salvage treatment for recurrent or persistent squamous cell carcinoma of the anus (SCCA). However, reirradiation (reRT) can be used preoperatively or for those who are not candidates for surgery.

MATERIALS/METHODS

Using a single institutional database, patients were identified who underwent reRT for SCCA from 2003 to 2022. Response to reRT and outcomes after reRT were recorded. Variables analyzed included age at reRT, sex, reason for reRT (recurrent SCCA vs new SCCA after pelvic radiation for a different malignancy), interval between initial radiation and reRT, reRT dose, concurrent chemotherapy, receipt of APR and the presence of distant metastases at the time of reRT. Cox Proportional Hazard Model was used; multivariable analysis for all factors with a univariate P-value <0.1 on univariable analysis.

RESULTS

A total of 42 patients received reRT, which consisted of 1.5 Gray (Gy) twice daily fractions with ≥6-hour interval to a total dose ranging 30Gy to 54Gy (median [IQR] 39Gy [39-42Gy]. Thirty-eight patients (90.5%) received concurrent chemotherapy; most often with weekly cisplatin and 5-fluorouracil (N = 23, 54.8%). Median [IQR] follow-up after reRT was 11.4 months [4.9-40.8 months]. Median [IQR] initial radiation dose was 54Gy [54-58Gy], and median [IQR] interval between initial radiation and reRT was 3.6 years [2.1-6.0 years]. For 8 patients (19.1%), the initial radiation was given for a different pelvic malignancy prior to being diagnosed with SCCA. Four of these patients received brachytherapy alone or in conjunction with external beam. For the remaining 34 patients, the initial radiation was for SCCA and the reRT was for recurrent SCCA either in the anal canal (N = 23, 67.6%) or regional nodes (N = 11, 32.3%). Four patients (9.5%) had distant disease at the time of reRT. Eleven patients (26.2%) had planned APR after preoperative reRT; 1 patient had a pathologic complete response (pCR), 2 patients had a near pCR (<5% viable cancer). Twenty-nine patients (69.0%) were treated with reRT alone; 15 (51.7%) attained a clinical CR. Two patients (4.8%) were treated with palliative intent and response was not assessed. Median local recurrence free survival (LRFS) was 9.9 months; 2- and 3-year LRFS were both 41%. Median distant metastasis free survival (DMFS) was 11.8 months; 2- and 3-year DMFS were 38% and 34%, respectively. Median overall survival (OS) was 40.5 months; 2- and 3-year OS were 54% and 51%, respectively. On multivariable analysis, only the presence of distant disease at the time of reRT was significantly associated with worse LRFS (HR (95% CI) 4.14 (1.34-12.81); P = .014), worse DMFS (4.06 (1.37-12.06); P = .012) and worse OS (5.73 (1.57-20.9); P = .008).

CONCLUSION

ReRT is an option for patients presenting with either recurrent SCCA or new SCCA after prior pelvic radiation for a different malignancy. ReRT can be given prior to planned salvage APR or alone for patients who are not surgical candidates with an approximate 50% cCR rate.

Phase 1 Trial of SPECT-Guided Liver-Directed Ablative Radiotherapy for Patients with Low Functional Liver Volume

PURPOSE/OBJECTIVE(S)

Traditional liver dose constraints specify that a critical volume of 700 cc of non-tumor liver should be spared from receiving a hepatotoxic dose. We evaluated the safety of liver-directed ablative radiotherapy for patients with hepatocellular carcinoma (HCC), intrahepatic cholangiocarcinoma (iCCA), or liver metastases (LM) with Child-Pugh (CP) A5 liver function at baseline and with low functional liver volume as estimated by Tc-99m sulfur colloid single photon emission computed tomography (SPECT). We hypothesized that functional liver image guidance with SPECT would allow safe delivery of ablative radiotherapy in patients with limited liver volume.

MATERIALS/METHODS

A phase 1 trial with a 3+3 design was conducted to evaluate the safety of comprehensive ablative radiotherapy to the liver disease using escalating functional non-target liver radiation dose constraints. Eligibility criteria included (1) a diagnosis of HCC, iCCA, or LM, (2) prior treatment with irinotecan or oxaliplatin chemotherapy or liver resection, and (3) a minimum functional liver volume of 400 cc as estimated by SPECT using a threshold of 40% maximum intensity. Patients with CP >A5 liver function, prior liver-directed radiotherapy, or prior Yttrium-90 therapy were excluded. The prescription dose was 67.5-75 Gy in 15 fractions or 75-100 Gy in 25 fractions. The volumetric dose constraint for functional non-target liver receiving <24 Gy for 15 fractions or <27 Gy for 25 fractions was determined by the dose level of trial enrollment: level 0 was ≥400 cc and level +1 was ≥300 cc. A level -1 was included if needed. We used standard 15 and 25 fraction dose constraints for other organs at risk. The following dose limiting toxicities (DLTs) were assessed within 6-8 weeks of completing radiotherapy: Grade 3 hypoalbuminemia, increase in INR, increase in bilirubin, or ascites, or Grade 4 hepatic failure or any radiation-related toxicity.

RESULTS

Twelve patients enrolled between February 2016 and June 2022. The median (range) GTV was 36 (2-651) cc. The median CT anatomical non-tumor liver volume was 1584 (764-2699) cc, and the median SPECT functional liver volume was 1117 (570-1928) cc, with a Pearson correlation coefficient of 0.98 (p<0.001). The median non-target SPECT functional liver volume below the volumetric dose constraint was 684 (429-1244) cc. None of the 3 patients treated in dose level 0, and none of the 9 patients treated in dose level +1 experienced any DLTs. The 1-year in-treatment-field control rate was 55%, and 1-year overall survival was 71%.

CONCLUSION

Ablative radiotherapy can be safely delivered using functional SPECT image guidance, which enables sparing lower volumes of functional liver than traditionally accepted in patients with CP A5 liver function. Further evaluation with a phase 2 study is warranted.

Enhancement Patterns of Metastatic Intrahepatic Cholangiocarcinoma and Outcomes after Chemotherapy and Radiation

PURPOSE/OBJECTIVE(S)

Patients with metastatic intrahepatic cholangiocarcinoma (M1-iCCA) have a poor prognosis with a 5-year survival rate of less than 20%. Definitive doses of radiation therapy (RT) after upfront chemotherapy (chemo/RT) in this patient population have shown to prolong survival by reducing the risk of tumor-related liver failure compared to chemotherapy alone. Our group has also identified a baseline radiographic feature, the arterial enhancement pattern, which has pathological and prognostic associations for iCCA. We tested the hypothesis that baseline arterial enhancement is independently associated with survival outcomes for patients who receive chemo/RT or chemo alone.

MATERIALS/METHODS

Patients with M1-iCCA from 2010 to 2021 were included in this retrospective study. Patients were grouped into those who underwent chemo alone and those who underwent chemo/RT. The inclusion criteria included confirmed diagnosis of M1-iCCA, availability of baseline multi-phasic computed tomography (CT), and follow-up for at least six months or until death. Tumor arterial enhancement patterns were categorized as previously described into hypovascular or hypervascular, where the tumors that were hypervascular had either peripheral enhancement or central enhancement. Mean tumor density in Hounsfield units was recorded for each patient. Survival was estimated using the Kaplan Meier method, and Cox proportional models were used to adjust for prognostic variables.

RESULTS

A total of 281 patients with iCCA were identified and 229 had evaluable CT scans. Demographic and baseline characteristics of patient groups are shown in the Table. On univariate analysis, patient age, ECOG performance status (PS) at diagnosis, treatment type, and arterial enhancement patterns associated with overall survival (OS). On multivariable analysis, the arterial enhancement pattern independently associated with OS after accounting for covariates. Patients with hypervascular tumors had prolonged OS compared to those with hypovascular tumors (HR = 0.72, [0.54 - 0.96], p = 0.02). Prolonged OS was also observed in the chemo/RT group compared to the chemo alone group (HR = 0.37, [0.25-0.54], p< 0.0001).

CONCLUSION

Baseline enhancement patterns of M1-iCCA were prognostic in the contexts of chemo alone and chemo/RT. This imaging-based biomarker may improve the ability to stratify patients for therapeutic management.

Herpesvirus replication compartments originate with single incoming viral genomes

Previously we described a method to estimate the average number of virus genomes expressed in an infected cell. By analyzing the color spectrum of cells infected with a mixture of isogenic pseudorabies virus (PRV) recombinants expressing three fluorophores, we estimated that fewer than seven incoming genomes are expressed, replicated, and packaged into progeny per cell. In this report, we expand this work and describe experiments demonstrating the generality of the method, as well as providing more insight into herpesvirus replication. We used three isogenic PRV recombinants, each expressing a fluorescently tagged VP26 fusion protein (VP26 is a capsid protein) under the viral VP26 late promoter. We calculated a similar finite limit on the number of expressed viral genomes, indicating that this method is independent of the promoter used to transcribe the fluorophore genes, the time of expression of the fluorophore (early versus late), and the insertion site of the fluorophore gene in the PRV genome (UL versus US). Importantly, these VP26 fusion proteins are distributed equally in punctate virion assembly structures in each nucleus, which improves the signal-to-noise ratio when determining the color spectrum of each cell. To understand how the small number of genomes are distributed among the replication compartments, we used a two-color fluorescent in situ hybridization assay. Most viral replication compartments in the nucleus occupy unique nuclear territories, implying that they arose from single genomes. Our experiments suggest a correlation between the small number of expressed viral genomes and the limited number of replication compartments.