Changes of plasma GARP-LTGFβ1 complex during chemoradiotherapy may predict survival in non-small cell lung cancer (NSCLC)

e21042

Background: Glycoprotein-A repetitions predominant protein (GARP), a cell surface docking and activating receptor for latent transforming growth factor β1 (LTGFβ1), has been implicated in promoting oncogenesis. We report recently that GARP-LTGFβ can be clipped by thrombin but its clinical significance remains unclear. Herein, we hypothesized that 1) the baseline plasma GARP-LTGFβ1 complex is associated with clinical stage of cancers; 2) the baseline and/or changes of plasma GARP-LTGFβ1 complex during chemo-radiotherapy is associated with overall survival (OS) in patients with NSCLC. Methods: This is a correlative study for patients with stage I-III NSCLC receiving chemo-radiotherapy. Levels of GARP-LTGFβ1 complex in platelet-poor plasma were determined by a modified ELISA at pre-RT, 2,4 weeks during-RT and post-RT. Values were calculated based on the following formula: (ODtest-ODnegative control)/ODpostive control-ODnegative control). The primary endpoint was OS, analyzed using the Kaplan-Meier method and Cox proportional hazard model. Platelet-poor plasma samples from healthy subjects were used as normal controls. Results: A total of 155 patients were included: 41 stage I-II, 111 stage III. There were 115 male, 50 female with a median age of 66 years. Compared to 13 normal controls (0.638, 95% CI:0.477-0.799), NSCLC patients had a significantly higher plasma GARP-LTGFβ1 (0.965, 95%CI: 0.881-1.048, p = 0.014). The same trend was observed for stage, higher level in more advanced stage (1.037, 95%CI: 0.930-1.145) vs for stage I-II (0.854, 95%CI: 0.720-0.988) (p = 0.0375). Univariate analysis demonstrated that age, gender, clinical stage, smoking history, histology, KPS, and radiation dose were significantly associated with OS. Post/pre RT GARP-LTGFβ1 complex (high vs. low HR = 0.384, p = 0.043) instead of pre-RT (p = 0.538), during RT (p = 0.739 for 2 weeks, p = 0.570 for 4 weeks) or post-RT (p = 0.507) plasma GARP-LTGFβ1 complex during the course of radiation therapy correlated significantly with OS under univariate analysis. On multivariate Cox regression models after adjusting for above significant clinical factors, the changes of plasma GARP-LTGFβ1 level had significance in correlating with OS (HR = 0.359, p = 0.0087). Conclusions: Baseline plasma GARP-LTGFβ1 were significantly associated with presence of cancer and advanced stages in NSCLC patients. Changes of GARP-LTGFβ1 level in plasma could be useful to predict outcomes and reflect the changes of immune status after chemoradiation.

Tolerability of radiation with concurrent temozolomide and effect on survival in chemo-refractory CNS lymphoma

e14554

Background: There is no consensus for the treatment of central nervous system lymphoma (CNSL) refractory to first line high dose methotrexate-based chemotherapy. Whole brain radiation (WBRT) has often been used but may lead to unacceptable neurocognitive dysfunction. We examined our institutional experience with treating CNSL with radiotherapy (RT) and concurrent temozolomide (TMZ) including the resultant acute and long term toxicities. Methods: This single institution IRB approved retrospective study examined treatment, toxicity, and outcome variables in adults with primary or secondary CNS lymphoma. Inclusion criteria were brain-directed RT and development of the treatment plan at our institution. Three main RT field designs were used, including low and high dose WBRT and low dose WBRT with a focal boost to residual disease (WBRT+boost). We assessed relationships between treatment approach (RT field design and concurrent TMZ use) and clinical outcomes and toxicities using multivariable logistic regression models and Kaplan-Meier methods. Toxicity was recorded using the Common Terminology Criteria for Adverse Events version 5. Results: A total of 93 patients with median age of 57 years (range 24 – 86) treated from 2004 – 2019 were included, and 26 patients received concurrent TMZ. The RT field design of low dose WBRT (median dose: 23.4Gy) plus focal boost (median dose: 21.6Gy) was associated with favorable overall survival (OS) and progression free survival (PFS) without any significant difference in Grade 3+ toxicity compared to low dose WBRT (p = 0.20) or WBRT without boost (p = 0.80). Concurrent TMZ with RT was associated with significantly improved OS (HR 0.46, p = 0.025) and CNS PFS (HR 0.49, p = 0.019). Four of nine (44%) Grade 3+ non-hematologic toxicities occurred in patients receiving concurrent TMZ (p = 0.40). The most common non-hematologic toxicities included fatigue and nausea. Long term neurocognitive dysfunction was similar whether or not patients received concurrent TMZ (21% in TMZ group vs 23% in non-TMZ group; OR 0.87, 95% CI 0.25 – 2.68, p = 0.82) and irrespective of RT field design (WBRT+boost vs low dose WBRT p = 0.25, WBRT+boost vs WBRT without boost p = 0.19). Conclusions: Our findings suggest that concurrent TMZ use with brain RT for chemo-refractory CNSL is a promising strategy, with improved survival and no major additional toxicity. Further research that includes rigorous neurocognitive assessments is needed in prospective clinical trials to guide treatment approaches using concurrent TMZ with brain RT in CNSL patients.

DCE-MRI Evaluation of 10 patients with brain metastases treated with RRx-001, a Myc inhibitor and a CD47 and PD-L1 downregulator, in a phase I/II trial called BRAINSTORM

e14509

Background: In a Phase 1/2 trial called BRAINSTORM (NCT02215512) for brain metastases from any histology, quantitative changes in perfusion MRI after administration of RRx-001, a mic inhibitor and CD47 and PD-L1 downregulator with vascular normalizing properties, were determined and correlated with response. Methods: Ten patients with 64 total lesions evaluable at baseline, 24 hours, and end of radiotherapy (RT) that participated in BRAINSTORM were subjected to a correlative dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) examination four days prior to the start of whole brain radiotherapy (WBRT) that evaluated Ktrans (capillary permeability) and Vp (plasma volume). The treatment comprised RRx-001 on Day -4, pre-WBRT then twice weekly during WBRT. Four dose levels were administered (5 mg/m2, 8.4 mg/m2, 16.5 mg/m2, and 27.5 mg/m2. Results: 10 patients underwent DCE-MRI scans and eight patients with 44 total evaluable lesions had available imaging at 1 month, and 6 patients with 29 total evaluable lesions had imaging at 4 months. On univariate analysis, only a decrease in 24-hour Vp from baseline after a single dose of RRx-001 was marginally associated with absolute tumor volume response 1 month after treatment (p-0.07). In a multivariate model, only Vp prior to therapy and 24-hour change in Vp were retained in the model after stepwise selection. A reduction in Vp 24 hours after RRx-001 (prior to WBRT) was associated with reduced tumor volume at 1 month (Estimate 0.88, 95% CI 0.37-1.40, p = 0.001) and 4 months (Estimate 1.51, 95% CI 0.58-2.43, p = 0.003). Likewise, a lower Vp prior to therapy was associated with reduced tumor volume at 1 month (Estimate 0.73, 95% CI 0.29-1.17, p = 0.002) and 4 months (Estimate 1.8, 95% CI 0.95-2.65, p = 0.0002), suggesting anti-angiogenic activity and early potential vascular normalization after a single dose of RRx-001 predictive of longer-term tumor response. Conclusions: RRx-001 induced a reduction in blood plasma volume, which was associated with tumor response and which suggests a vascular normalizing effect that merits further investigation in future planned studies. Clinical trial information: NCT02215512.

ATIM-44. A PHASE I FIRST-IN-HUMAN TRIAL OF TWO ADENOVIRAL VECTORS EXPRESSING HSV1-TK AND FLT3L FOR TREATING NEWLY DIAGNOSED RESECTABLE MALIGNANT GLIOMA: THERAPEUTIC REPROGRAMMING OF THE BRAIN IMMUNE SYSTEM

This is an interim report on a first in human Phase I dose escalation trial of the combination of two adenoviral vectors expressing HSV1-TK or Flt3L for the treatment of newly diagnosed, resectable malignant gliomas. Lack of dendritic cells from the brain precludes anti-glioma immune responses. We combined tumor cytotoxicity (Ad-HSV1TK) with recruitment of dendritic cells to gliomas (Ad-Flt3L) to induce anti-glioma immunity. In experimental models this treatment induces powerful cytotoxic CD8 and CD4 T-dependent anti-glioma immunity, immunological memory, and the capacity to recognize neo-antigens. The trial was approved through a FDA-IND, and all institutional cttees. Treatment was administered intraoperatively following complete glioma resection in newly diagnosed tumors. The trial consisted of vector dose escalation, starting at 1x10^9 v.p., and increasing to 1x10^11 v.p. of each vector, through 6 cohorts of 3 patients each. Two cycles of 14 days of valacyclovir were administered to activate HSV1-TK cytotoxicity. Cycle 1 starts on Day 1–3 post surgery for 14 days, and Cycle 2 on Week 8–12. Standard radiation, i.e., 60 Gy in 2 Gy fractions over 6 weeks, with concurrent temozolomide, was followed by cyclic temozolomide. Examination of tumor samples at primary resection and first recurrence show an increase in the infiltration of inflammatory cells. The experimental treatment was well tolerated. An MTD was not reached. There were approx. 248 AEs, and 26 SAEs; these were not linked to treatment. As secondary outcome, median survival of contemporary controls was 604 days, and median survival of trial patients was 742 days. Our results show for the first time that reprogramming of the host’s brain immune system to recognize gliomas reveals a new approach for the treatment of highly malignant brain tumors. Clinical trial information: NCT01811992.

A mid-treatment break and reassessment maintains tumor control and reduces toxicity in patients with hepatocellular carcinoma treated with stereotactic body radiation therapy

BACKGROUND AND PURPOSE

Patients with hepatocellular carcinoma (HCC) commonly have underlying liver dysfunction with variable tolerance to liver stereotactic body radiation therapy (SBRT). We hypothesized that insertion of a 1-month mid-treatment break would allow us to adapt treatment to the individual patient response, thereby reducing toxicity without compromising local control (LC).

MATERIALS AND METHODS

We analyzed HCC patients receiving 3-5 fraction SBRT at our institution from 2005 to 2017. Over this time, patients were offered enrollment on prospective trials assessing individualized adaptive SBRT. Based on normal tissue complication probability and modeling of changes in liver function following a 1-month treatment break between fractions 3 and 4, patients could receive a total of 3 or 5 fractions. Patients not on trial received 3 or 5 fractions without a break. Toxicity was defined as a ≥2 point rise in Child-Pugh (CP) score within 6 months of SBRT.

RESULTS

178 patients were treated with SBRT to 263 HCCs. Median follow-up was 23 months. 86 treatments had a 1-month break. 1-Year LC was 95.4%; this was not different between patients treated with or without a break (p = 0.14). Controlling for tumor size and dose a break was not associated with inferior LC (HR: 0.58, 95%CI: 0.1-3.34, p = 0.54). 54 patients experienced a ≥2 point rise in CP score. Controlling for the number of prior liver directed therapies and mean liver dose, a treatment break reduced the odds of toxicity (OR: 0.42, 95% CI: 0.17-1.03, p = 0.06).

CONCLUSION

A one-month mid-treatment break and reassessment may reduce the odds of treatment related toxicity without compromising LC.

First-in-human phase I trial of the combination of two adenoviral vectors expressing HSV1-TK and FLT3L for the treatment of newly diagnosed resectable malignant glioma: Initial results from the therapeutic reprogramming of the brain immune system

2019

Background: This is the initial report on a first in human Phase I dose escalation trial of the combination of two adenoviral vectors expressing HSV1-TK or Flt3L for the treatment of newly diagnosed, resectable malignant gliomas. The absence of functional dendritic cells from the brain precludes anti-brain tumor immune responses. We combined tumor cytotoxicity (Ad-HSV1TK) with recruitment of dendritic cells to the brain (Ad-Flt3L) to induce an effective anti-tumor immune response. This strategy induced an efficacious, cytotoxic CD8 and CD4 T-dependent immune response in many animal models of glioma. This immune response also generated anti-tumor memory, and the capacity for neoantigen recognition. Methods: The trial was approved by FDA and all institutional cttees. Treatment was administered intraoperatively following complete glioma resection in newly diagnosed tumors. The trial consisted of vector dose escalation, starting at 1x10^9 i.u., and increasing to 1x10^11 i.u. of each vector. Dose escalation proceeded by increasing the vector dose through a total of 6 combinations administered to 6 cohorts of 3 patients each. Two cycles of 14 days each of valacyclovir were administered to activate HSV1-TK cytotoxicity. Cycle 1 starts on Day 1-3 post surgery for 14 days, and Cycle 2 on Week 8-12. Standard radiation, i.e., 60 Gy in 2 Gy fractions over 6 weeks, with concurrent temozolomide, was followed by cyclic temozolomide. Results: Examination of tumor samples at primary resection and first recurrence show an increase in the infiltration of inflammatory cells. The experimental treatment was well tolerated. At this time the MTD has not been reached. There were approx. 248 AEs, and 26 SAEs; these have not been linked to treatment. At this time the MTD has not been reached. A secondary outcome is overall survival. Preliminary analysis of partial data may suggest that the combined viral vector therapy may provide a clinically significant survival. Conclusions: Our results show for the first time that reprogramming of the host’s brain immune system to recognize gliomas reveals a new approach for the treatment of highly malignant brain tumors. Clinical trial information: NCT01811992.

Early stage hepatocellular carcinoma treated with stereotactic body radiation therapy: A pooled analysis from two North American institutions

350

Background: To report outcomes of pooled data from patients with early stage hepatocellular carcinoma (HCC) treated with stereotactic body radiation therapy (SBRT) at two North American Institutions. Methods: An IRB approved collaborative review of patients with HCC treated with radical intent SBRT was conducted. Inclusion criteria included patients with Stage I-IIIA HCC (UICC/AJCC 7th Ed.) treated with SBRT (≥ 4.5 Gy/ fraction) from June 2003 until Dec 2016. Patients who were treated with SBRT were ineligible for resection, percutaneous ablative or hepatic intravascular therapies. Patients with vascular invasion and those treated with palliative intent (e.g. HCC rupture) were excluded. Overall survival, local control and toxicity of treatment were reviewed retrospectively. Results: Of 310 eligible patients, 23% were Child-Pugh (CP) class B/C (21%/2%), and 40% had failed prior liver directed therapies. The median HCC diameter was 2.4 cm (range 0.5-18.1 cm), and the median prescribed dose was 39 Gray (Gy) in 5 fractions (range: 14 - 60 Gy in 2-6 fractions). Median BED was 78.75 Gy (Range: 23.8-180.0 Gy). 8.4% of patients underwent liver transplant after SBRT. Local control at 1, 3 and 5 years was 91.5%, 82.6% and 82.6%. On multivariable analysis (MVA), the use of breath-hold motion management, but not T stage, size or dose, was significantly associated with local control (p = 0.0098). The 1, 3, and 5 year overall survival (OS) was 77.3%, 37.9% and 23.5%. Factors associated with improved OS on MVA included baseline CP A score (HR = 0.58, p < 0.0045), AFP < 10 µg/L (HR = 0.66, p = 0.0094), and transplant post SBRT (HR = 0.05, p < 0.0001). The median survival of CP A vs. B/C patients was 30.3 and 17.6 months respectively. CTCAE (v4.0) grade 3 or higher luminal gastrointestinal organ toxicity occurred in 2.5% of patients, while a decline in CP score ≥ 2 points was seen in 16.7% of patients at 3 months post SBRT. Grade 3 and above elevated liver enzymes were seen in 12.6% and 8.1% of patients at baseline and at 3 months post SBRT. Conclusions: Similar to Asian series, this North American pooled analysis found high sustained local control and excellent survival in patients with early stage HCC treated with SBRT.

Treatment data and technical process challenges for practical big data efforts in radiation oncology

The term Big Data has come to encompass a number of concepts and uses within medicine. This paper lays out the relevance and application of large collections of data in the radiation oncology community. We describe the potential importance and uses in clinical practice. The important concepts are then described and how they have been or could be implemented are discussed. Impediments to progress in the collection and use of sufficient quantities of data are also described. Finally, recommendations for how the community can move forward to achieve the potential of big data in radiation oncology are provided.

Neoadjuvant FOLFIRINOX and IMRT concurrent with FDR-gemcitabine in patients with borderline resectable pancreatic cancer (BRPC)

381

Background: Preoperative therapy in BRPC is intended to increase the likelihood of R0 resection although an optimal regimen is yet to be defined. Methods: Patients (pts) with BRPC (NCCNv.2.2010 guidelines) and ECOG PS 0-1 were enrolled in a single-institution, phase II trial (NCT01661088). Pts received FOLFIRINOX x 6, followed by IMRT (50 Gy in 25 fractions) concurrent with FDR-gemcitabine 1 g/m2 on days 1, 8, 22, 29. Two additional FDR-gemcitabine infusions completed pre-operative treatment. Pancreatic protocol CT scans (dual phase, 0.65 mm slices) were performed after 4 infusions of FOLFIRINOX, 3 weeks after IMRT, and at treatment completion. Pts without distant disease were offered surgical exploration. The primary objective was to determine R0 resection rate. Secondary objectives included progression free survival (PFS), overall survival (OS), response rate and safety. Results: A total of 25 pts (64% men) median age 60 years (range 47-77) were enrolled from 11/2011 through 01/2017. Twenty-one (84%) pts completed FOLFIRINOX and 19 (76%) all protocol therapy. Treatment-related grade 3-4 adverse events ( > 10%) included neutropenia (40%), nausea/vomiting (28%), diarrhea (16%) and fatigue (12%). One early death and 1 discontinuation due to toxicity occurred during FOLFIRINOX. Response to pre-op therapy included 11 PR, 9 SD, 3 PD and 2 NE. Of 25 treated pts, 18 (72%) had laparotomy and 13 (52%) underwent resection (all R0). The median PFS and OS were 18.1 (95% CI, 10.6 to 25.1) and 24.2 (95% CI, 12.6 to 40.0) months, respectively. The median OS for R0 resected pts was 37.1 (95% CI, 15.4 – not reached) months. Conclusions: Neoadjuvant therapy with FOLFIRINOX, followed by IMRT with concurrent FDR-gemcitabine in BRPC is feasible and tolerated. While R0 resection rate was not obviously improved, OS of the entire cohort and especially in R0 resected pts was favorable. Clinical trial information: NCT01661088.

Phase I study of definitive chemoradiation with gemcitabine and the WEE1 inhibitor AZD1775 in unresectable pancreatic cancer

TPS512

Background: Targeting cell cycle checkpoints has the potential to enhance the efficacy of chemoradiation therapy. Tumor cells commonly have an abnormal G1 checkpoint due to mutations in the p53 pathway making them reliant on the G2 checkpoint to repair DNA damage. In our preclinical studies, WEE1 inhibition with AZD1775 abrogates the G2 checkpoint and sensitizes pancreatic cancer cell lines and xenografts to chemoradiation. Additionally, AZD1775 attenuates homologous recombination repair and promotes replication stress in cancer cells. Given our preclinical findings, we designed a phase I dose escalation study of the WEE1 inhibitor AZD1775 with gemcitabine and radiation in patients with unresectable pancreatic cancer (NCT02037230). Methods: The primary objective of our phase I study is to determine the MTD (maximum tolerated dose) of AZD1775 when combined with gemcitabine and radiation in patients with locally advanced pancreatic cancer. Our secondary objectives are to estimate the efficacy of this regimen at the target dose and to determine if WEE1 is inhibited by AZD1775 at or below its target dose in surrogate tissues (hair follicles). Patients with unresectable, non-metastatic pancreatic cancer are eligible for the study. Protocol therapy consists of the administration of AZD1775 and gemcitabine at the assigned dose levels in accordance with a Time-to-Event Continual Reassessment Method. All patients on the study are treated with four cycles of therapy consisting of AZD1775 given orally on days 1, 2 and 8, 9 of a 21 day cycle with gemcitabine given intravenously over 30 minutes on day 1 and day 8. Cycles 2 and 3 are administered with concurrent radiation therapy, 52.5 Gy in 25 fractions to the primary pancreatic tumor. The MTD will be determined by the development of dose limiting toxicities (DLT) within the first 4 cycles of therapy with a target DLT rate of 25%. Blood samples obtained at baseline and after cycles 1, 2, and 4 will be used for correlative studies on circulating tumor cells and tumor derived exosomes. Our estimated accrual is 36 patients. To date we have enrolled 21 patients. Supported by P50 CA130810, R01 CA163895, Cancer Center Core grant P30 CA46592, and the Taubman Institute. Clinical trial information: NCT02037230.

Adjuvant stereotactic body radiotherapy (SBRT) for resected primary and metastatic liver cancers

487

Background: Stereotactic body radiotherapy (SBRT) has been shown to be a safe and effective treatment for hepatobiliary cancers. However, little is known about the efficacy of adjuvant SBRT for resected liver tumors with positive margins. We examined the characteristics and outcomes of patients who received adjuvant SBRT for both primary and metastatic cancers of the liver. Methods: We retrospectively reviewed the charts of patients who had received liver SBRT from 2009-2015 at our institution. During that time frame, 11 patients were identified as having received adjuvant SBRT post resection. Patient data such as age, gender, portal vein thrombosis, cirrhosis, ECOG performance status, prior liver directed therapies, and SBRT dose were collected. Descriptive statistics were used for analysis given the small number of patients in this series. Results: Median age at the time of treatment was 63 years (range 51-79), and the majority of patients (72.7%) were male. Seven tumors (63.6%) were hepatocellular carcinomas, and 4 (36.4%) were adenocarcinomas. Of the tumors with adenocarcinoma histology, 3 were cholangiocarcinomas and one was metastatic colorectal cancer. Ten patients (90.9%) were treated for positive margins, and one was treated for inferior vena cava (IVC) invasion. Seven patients (63.6%) had no other liver-directed treatment prior to adjuvant SBRT. Two patients received systemic therapy prior to SBRT. Median EQD2 was 83.3 Gy (range 60-126), and 81.8% of patients received 5 fractions. There were no grade 3 or above late toxicities from treatment. Median follow-up was 14.1 months (range 5.4-38.1). None of the treated tumors progressed locally. Six patients (54.5%) progressed elsewhere in the liver, and one patient experienced distant metastatic progression. One patient experienced both intrahepatic progression and distant metastatic progression. Conclusions: Adjuvant SBRT appears to be a safe and feasible adjuvant treatment in patients with primary liver resection for either primary liver cancer or metastatic disease who are at high risk of recurrence.

The use of plasma microRNAs to predict toxicty following liver stereotactic body radiation therapy

245

Background: Stereotactic body radiation therapy (SBRT) is an effective treatment for patients with hepatocellular carcinoma or liver metastases. Predictive biomarkers for liver toxicity would allow for careful patient selection and the adaptation of therapy. Prior studies have shown specific miRNAs are elevated prior to clinical signs of toxin induced liver injury. We hypothesized that miRNAs can be used to predict radiation induced liver toxicity prior to clinical manifestations. Methods: As part of an IRB approved clinical trial (NCT01522937) patients with liver tumors underwent a split course of SBRT. All patients underwent liver function testing using indocyanine green clearance (ICG) followed by three SBRT fractions. One month later ICG was reassessed and two more fractions were given if the patient did not have a decline in liver function. Plasma samples were obtained at baseline and 1 month after finishing three of five SBRT fractions for 89 patients. For this exploratory analysis, we selected the 10 patients that had a 2+ point increase in Child-Turcotte-Pugh score within 6 months of completing therapy and 19 additional patients without toxicity. The levels of 752 miRNAs were quantified for each sample using qPCR. We then used a univariate tree based classifier and the elastic net with 10-fold cross validation to calculate the AUC for predicting liver toxicity in individual and small groups of miRNAs, respectively. Results: Several miRNAs were found to be potentially predictive of toxicity on univariate tree based classifier analysis including the liver specific microRNA miR.122.3p, the epithelial specific miR.141.3p and miR.200b.3p, the neuroendocrine related miR.375 and miR.217, and miR.125a.5p which plays a role in hepatitis and regulates ERBB2 and ERBB3 signaling. The elastic net model achieved a conservative AUC estimate of 0.74 +/- 0.04 using 69 baseline miRNAs and 0.76 +/- 0.06 using 11 mid-treatment miRNAs to predict toxicity. Conclusions: Our preliminary analysis of the miRNAome from 29 patients receiving liver SBRT shows promising results for the ability of these markers to select patients at risk for radiation induced liver toxicity. Further validation in a larger patient cohort is needed. Clinical trial information: NCT01522937.

Phase II study of individualized adaptive stereotactic body radiotherapy (SBRT) for patients at high risk for liver damage

424

Background: Patients (Pts) with pre-existing liver dysfunction are at high risk for further damage after SBRT. We completed a phase 2 study of individualized SBRT, utilizing pre- and during-treatment indocyanine green (ICG) clearance to adapt treatment and maximize both safety and efficacy. Methods: From 5/10-10/14, pts with hepatocellular carcinoma (HCC) or metastases (mets) were enrolled and underwent SBRT planning up to a target dose of 50-60 Gy or as limited by a 15% normal tissue complication probability for radiation-induced liver disease (RILD). ICG retention at 15 minutes (ICGR15) was measured prior to and 1 month after 3 of 5 planned treatments. Using a Bayesian adaptive model, RT dose was scaled down as necessary for the final 2 treatments to keep ICGR15 < 44% after the full treatment and thus minimize toxicity. Follow up was every 3 months for 2 years. Results: 90 pts received SBRT to 116 tumors and had at least 1 year of potential follow up. Median age was 62 years, range 34-85. 69 had HCC, 4 intrahepatic cholangiocarcinoma, and 17 mets. 62 had cirrhosis, most commonly HCV and alcoholic. Median Child-Pugh (CP) score was 6, range 5-9. 20 pts were CP B/C. Median pre-RT ICGR15 was 22, range 4-75, normal 4-10. Pts had a median of 1.5 (range 0-6) prior liver-directed therapies, most commonly transarterial chemoembolization (70), prior RT (36), and radiofrequency ablation (13). Median tumor size was 3 cm, and 12 had portal vein involvement. 63 received all 5 fractions (48 full dose, 15 with dose reduction due to elevated ICGR15); 27 received only 3 treatments. Median prescription dose was 47 Gy. Treatment was well tolerated with no classical RILD and a lower complication rate than expected without adaptation. 4 pts had grade 3 ascites. 2 pts had GI bleed after SBRT. 14% and 10% of pts experienced at least a 1 or 2 point increase in CP 6 months post SBRT. Local control (95%CI) at 1 and 2 yrs was 99 (96,100)% and 90 (81,100)%. 4 recurrent tumors were 3 HCC and 1 met, measuring 26, 12, 30, 38mm; treated to 30, 50, 33, 30 Gy. Conclusions: Individualized adaptive SBRT, based on ICG clearance is a promising method of allowing pts to receive the maximally aggressive dose based on each pt’s individual tolerance to RT. Funded by P01 CA59827

Association between equivalent uniform dose (EUD) and rates of local progression in liver tumors treated with stereotactic body radiation therapy (SBRT)

380

Background: When tumors are near organs at risk such as bowel or heart, this results in partial underdosing relative to prescribed dose. We hypothesized that equivalent uniform dose (EUD) may better capture the biologic effect than other dose metrics. Methods: In this IRB-approved retrospective study, 257 primary and metastatic liver tumors from 168 patients treated with SBRT at the University of Michigan Health System between 2005 and 2014 were identified. Univariate analysis and multivariate Cox regression models were used to correlate patient, tumor, and treatment characteristics with rates of LC. Results: 1 and 2 year LC were 93% and 75% for all. Of the 156 primary liver tumors, 1 and 2 year LC were 94% and 76%, compared to 83% and 61%, for patients with colorectal metastases (CRM). 22 tumors locally progressed in 17 patients of which 9 were CRM, 5 hepatocellular carcinomas (HCC), and 3 other. Tumors that locally progressed received a median prescribed dose of 50 Gy (24 - 60), GTV EUD (a=-10) 49 Gy (23 - 72), and PTV EUD 46 Gy (17 - 69). Median gross tumor volume (GTV) was 21 cc (1-103). Tumors that did not locally progress received a median prescribed dose of 50 Gy (19 - 60), GTV EUD (a=-10) 52 Gy (17 - 86), and PTV EUD 47 Gy (7 - 76). Median GTV was 10 cc (0.2 - 2092). On univariate analysis, CRM (p = 0.005) was correlated with higher progression, while high GTV and PTV EUD (a=-10) (p = 0.01, 0.05) were correlated with lower progression. HCC (p = 0.06) was borderline for low progression. Age, gender, primary or metastatic, prescribed dose, biologically equivalent dose (BED), minimum GTV or PTV dose and GTV did not predict for progression. In a multivariable model including age, gender, histology, prescribed dose, BED, GTV EUD and GTV size, only GTV EUD predicted for LC, HR = 0.947, 95% CI = 0.901 - 0.996, p = 0.036. Every 1 Gy increase in EUD decreased the risk of local failure by 5%. Conclusions: EUD was predictive of local progression even when accounting for histology, size, and dose as measured by prescribed dose and BED. GTV EUD (a=-10) over 47.64 Gy yielded a >95% local control. EUD may be the preferred dose metric in future tumor control studies.

Evaluation of liver toxicity using Child-Pugh, MELD, and MELD-Na following stereotactic body radiation therapy (SBRT) of hepatocellular carcinomas

365

Background: Radiation-induced liver disease (RILD) has been tracked when assessing the safety of fractionated liver radiotherapy. However, due to the rarity and severity of events, a more sensitive measure of liver damage is necessary. This study characterizes the time course of changes in generalizable measures of liver function as potential toxicity metrics. Methods: In this IRB-approved retrospective study, the records of 63 patients with 87 HCC tumors treated with SBRT at the University of Michigan between 2006 and 2012 were reviewed. Changes in Child-Pugh (CP), MELD, and MELD-Na were analyzed using the Student t test and chi-squared test. Results: 83% of the patients had cirrhosis, 62% hepatitis (hep) C, 7% hep B, 25% alcoholic, and 13% other. 83% had prior liver-directed therapy. 24% had >1 tumor concurrently treated with SBRT. Median tumor size was 2.3 cm (0.7-10), gross tumor volume was 9.2 cc (0.6-469), and mean liver dose-GTV was 4.4 Gy (0-17.6 Gy). Prior to SBRT, 73% were CP A, 25% CP B, and 2% CP C. Median baseline CP, MELD, and MELD-Na were 5, 9, and 10. Mean CP increases after 3, 6, 9, and 12 months were 0.84, 1.79, 1.72, and 1.33; increases in MELD 1.47, 2.88, 5.38, and 3.91; increases in MELD-Na 1.45, 2.03, 4.24, and 2.48. All changes were significantly increased from baseline. On univariate analysis, >1 tumor and cirrhosis predicted for a 1+ point increase in CP and >1 tumor and higher mean liver dose-GTV for a 2+ point increase in CP. Older age, >1 tumor, smaller GTV, and smaller max tumor dimension predicted for a 10+ point increase in MELD and >1 tumor, hep C cirrhosis, and higher baseline MELD-Na for MELD-Na. Patients treated concurrently to >1 tumor had greater increases in CP (3.60 vs. 0.81), MELD (9.33 vs. 1.97), and MELD-Na (8.47 vs. 2.19), p < 0.0001 for all, compared to those with 1 tumor. No differences were seen with gender, portal vein thrombosis, number of prior treatments and baseline Child-Pugh classifications. Conclusions: We describe a time course and predictive factors for change in CP, MELD, and MELD-Na scores after SBRT for HCCs. These should be investigated further for potential use in toxicity modeling after incorporating dosimetric parameters.

Patterns of relapse after concurrent temozolomide and dose-escalated intensity-modulated radiation therapy (IMRT) in newly diagnosed glioblastoma (GBM)

2052

Background: We hypothesized that IMRT would permit us to safely escalate the dose of radiation with concurrent temozolomide substantially above the current standard of 60 Gy and that this increased dose would more adequately control local disease leading to an alteration in the patterns of relapse in patients with GBM. Methods: Between 2003 and 2012 a total of 69 patients were treated with dose-escalated IMRT with concurrent temozolomide. 39 patients were initially treated in a combined phase I/II trial with IMRT doses of 66 to 81 Gy over 6 weeks with concurrent daily temozolomide (75 mg/m2) followed by adjuvant cyclic temozolomide (200 mg/m2 d1-5 q28d for 6 or more cycles). Subsequently, 30 additional patients were treated to 66-72 Gy based on the reported efficacy and safety of the initial phase I/II study. Results: All 69 patients were assessed to evaluate the effect of dose escalation on late toxicity and patterns of progression. Median RT dose was 72 Gy and median overall survival was 19.0 months. Late CNS grade III toxicity was observed at 78 (2 of 7 patients) and 81 Gy (1 of 9 patients). 0 of 53 patients receiving 75 or less Gy developed necrosis. 64% (44/69) of patients had progression of their disease after dose-escalated chemoradiotherapy. The patterns of progression differ, however, from previous studies which identify in-field relapse of 72-80% with standard dose radiation (Brandes AA, Tosoni A, Franceschi E, et al: J Clin Oncol. 27:1275-9, 2009). In this cohort, 41% (18/44) of patients developed marginal or distant relapse compared to 59% (26/44) who developed local, in-field relapse. Conclusions: Patients with GBM can safely receive standard temozolomide with up to 75 Gy in 30 fractions, delivered using IMRT. Dose-escalated chemoradiotherapy improves local control and leads to an increased percentage of patients progressing distally, highlighting the need for improved tumor targeting with newer imaging modalities to identify the initial extent of tumor involvement as well as the need for more effective systemic treatment. I/II study.

A phase II trial of mid-treatment FDG-PET adaptive, individualized radiation therapy plus concurrent chemotherapy in patients with non-small cell lung cancer (NSCLC)

7522

Background: We have found that FDG-PET response during chemoradiation for patients with NSCLC is heterogeneous and predicts outcome. We hypothesized that dose escalated treatment targeted to the FDG-avid tumor would improve local tumor control. Methods: This is a phase II trial for patients with locally advanced, inoperable/unresectable NSCLC. Conformal radiotherapy (RT) was given in 30 daily fractions. RT dose was individualized to a fixed risk of lung toxicity and adaptively escalated to the residual tumor on mid-tx FDG-PET up to a total physical dose of 86 Gy. Patients had concurrent weekly followed by consolidation carboplatin/paclitaxel. The primary endpoint was local-regional tumor control (LRTC) at 2 years. Survival was calculated from RT start. Results were compared to stage-matched patients treated during the same time period with standard RT dosing (60-66 Gy). The data are presented as median (95% CI) unless otherwise specified. Results: 42 patients were enrolled: median age 63 years (range 45-83); 28 (67%) male; 39 (93%) smokers; 39 (93%) stage III; and 45% squamous cell. The mean gross tumor volume was 154 cc (range 10-617 cc). Median physical dose reached was 84 Gy (range 63-86 Gy), equivalent to 90 Gy in 2 Gy fractions (biological effective dose 108 Gy). 8 patients (19%) had RT-induced lung toxicity and 13 (31%) grade ≥2 esophagitis. Minimum and median follow-up were 10 and 25 months, respectively. The 2-year rates of in-field LRTC, overall LRTC, and LR-PFS were 84% (63-94%), 68% (47-82%), and 43% (27-58%), respectively. 14 patients progressed: 7 (50%) first at distant sites; 5 (36%) at nodal regions; 2 (14%) at primary tumor. Median overall survival was 26 months and 2-year overall survival rate was 51% (34-65%). These results compared favorably to stage-matched patients treated with standard-dose RT [2-year overall survival 23% (8-41%)]. Conclusions: These results support our hypothesis that adapting RT by escalating dose to the FDG avid region detected mid-tx improves 2-year local-regional tumor control. Adaptive RT may also improve overall survival. RTOG 1106 is currently testing this regimen in a randomized fashion. Clinical trial information: NCT01190527.

Definitive chemoradiation with full-dose gemcitabine for unresectable pancreatic cancer: A single-institution experience

331

Background: Definitive chemoradiotherapy (chemoRT) for unresectable pancreatic cancer has traditionally involved 5-FU-based chemotherapy. We have a long-history of combining gemcitabine and radiotherapy and performed a retrospective review of patients (pts) treated in this manner over the past 13 years. Methods: After IRB approval, the records of pts who underwent definitive treatment with radiotherapy (RT) and concurrent gemcitabine-based chemotherapy at the University of Michigan from February 1999 – May 2012 were reviewed. 193 pts were identified. Mean radiation dose was 40.5 Gy (median 36 Gy, range 24-60 Gy) in 2.2 Gy fractions (range 1.6 to 2.8), and targeted only radiographically apparent disease. 32% of pts received ≥50 Gy, and IMRT was used for 33%. The majority (97.9%) of pts were treated with concurrent full-dose weekly gemcitabine at 1000mg/m2. 48% of pts received at least 1 cycle of chemotherapy prior to chemoRT, and 13% received 2+ cycles. 85% of pts received additional chemotherapy after RT. Cox proportional hazard models were used for survival analysis. Results: Treatment was well-tolerated, with 91% of pts completing RT without a toxicity-related treatment break. With a median follow-up of 10 months, median overall survival (OS) was 13.5 months. 1, 2, and 5 year OS was 57%, 25%, and 5%, respectively. On univariate analysis, pre-treatment CA 19-9 and KPS predicted for OS (p=0.02 and 0.04). Tumor diameter was marginally associated (p=0.06). Age, gender, comorbidities, RT dose, and change in CA 19-9 before or after RT did not predict for OS. With regards to local response to treatment, 1 pt achieved a radiographic complete response (CR) and 30% of pts had a partial response (PR). Distant disease relapse occurred in 52% of all pts, including metastatic disease in the liver in 30%, peritoneum 15%, and lung 14%. 11 pts (6%) had late gastric or duodenal bleeds. Conclusions: Definitive chemoRT utilizing full dose gemcitabine is well-tolerated and achieves survival outcomes which compare favorably with reported series on 5-FU based therapy.

Phase I trial of dose escalated whole liver irradiation (WLRT) with hepatic arterial (HA) fluorodeoxyuridine (FUDR)/leucovorin (LV)/streptozotocin (STZ) chemotherapy followed by chemoembolization with mitomycin C (MMC) for patients with neuroendocrine hepatic metastases

e14603

Background: Phase I trial combining HA chemotherapy, chemoembolization and dose-escalated WLRT was conducted to determine if the maximum safe dose of 32 Gy in 2 Gy fractions could be delivered to patients (pts) with neuroendocrine (NE) hepatic metastases. Methods: Pts with symptomatic liver metastases from NE tumors who failed somatostatin analog therapy were eligible. HA FUDR (3 mg/m2/d) and LV (300 mg/m2/d) were given for 12 days; STZ (500 mg/m2/d) was given on days 5,8,10. Concurrent WLRT was prescribed in 2 Gy/day with doses escalated from 24 Gy to 32 Gy using the time-to-event continual reassessment method for dose allocation with a target rate of dose-limiting grade ≥3 radiation-induced liver disease (RILD) of 10%. 8 weeks later, for patients without RILD and other grade ≥4 toxicities, 72-h infusion with HA FUDR (3 mg/m2/d) and LV (300 mg/m2/d) was given, followed by chemoembolization with mitomycin C (20 mg) and polyvinyl alcohol. Results: 19 pts were enrolled in the trial, 11 pts completed the entire protocol. 7 pts received 24 Gy, 2 - 26 Gy, 1 - 28 Gy, 2 - 30 Gy and 6 - 32 Gy. One pt stopped at 14 Gy because of STZ-induced grade 4 renal failure. No pts developed RILD at any dose level; 4 - had grade 3-4 increased liver function tests, 4 - had other grade 4 toxicities during or after the first part of the treatment; 1 - had other grade 4 toxicity during the second part. Posterior estimates of probabilities of RILD were all <10% (table). Three pts (14%) had partial response, 16 (84%) - stable disease. Median freedom from local progression for all pts was 35.3 (9.3-58.9) months. Conclusions: The study showed that chemotherapy can be safely combined with a full dose of WLRT and subsequent chemoembolization without producing RILD. [Table: see text]

SBRT as an alternative to RFA for the treatment of primary and metastatic liver tumors

158

Background: Radiofrequency ablation (RFA) is a widely used local therapy for small, unresectable liver tumors (LT). Stereotactic body radiotherapy (SBRT) has been used for similar patients, and has the advantage that it can be used when lesions are adjacent to blood vessels, are difficult to reach and cannot be imaged on ultrasound. We examined RFA and SBRT outcomes for treating primary and metastatic LT at our institution and identified predictive factors for local control.

Methods: This study included 62 patients (pts) with 106 LT (69 metastatic, 37 primary) treated with SBRT and 127 pts with 206 LT (80 metastatic, 126 primary) treated with RFA from 2000 to 2010. 42 lesions were ablated intra-operatively while 164 were ablated percutaneously. Mean tumor size by maximum diameter was 2.2 cm (0.4-11) and 2.3 cm (0.6-6.2) for RFA- and SBRT-treated LT, respectively. Freedom from local progression (FFLP) for SBRT was defined as absence of progressive LT within or at the PTV margin while FFLP for RFA was defined as recurrence within or immediately adjacent to the ablation zone.

Results: With a median follow-up of 29.4 months (0.46 to 120.8), 1- and 2-yr FFLP rates for all SBRT- vs RFA-treated LT were 93% and 84% vs 86% and 83%. There were 14 cases of residual LT after RFA, 6 of which were re-ablated; these were not counted as RFA failures. Significantly more pts in the SBRT group had received prior systemic therapy (54% vs 31%, p=0.0001) and had active extrahepatic disease at treatment start (36% vs 23%, p=0.01). For SBRT, neither LT size nor dose predicted for FFLP. For RFA, tumor size ≥3 cm had worse FFLP (HR: 5.3, p<0.0001) but an intraoperative approach had better FFLP (HR: −2.2, p=0.01). For tumors >3cm, SBRT had significantly better FFLP than percutaneous RFA (HR: 0.32, p=0.018). In the RFA group, there were 9 complications, including pneumothorax, hemothorax, and small bowel injury, 2 of which resulted in death. In the SBRT group, there was 1 case of radiation-induced liver disease in a Child-Pugh Class B pt but no other significant toxicities.

Conclusions: SBRT is a safe alternative to RFA, can be used in a wider variety of patients, and may be more effective than percutaneous RFA at locally controlling larger liver tumors.

Whole-liver irradiation with hepatic arterial floxuridine/leucovorin/streptozotocin followed by hepatic arterial floxuridine/leucovorin and chemo-embolization with mitomycin C for patients with metastatic neuroendocrine tumors

339

Background: Neuroendocrine tumors metastatic to liver are incurable with limited treatments. We conducted a phase I trial combining hepatic arterial (HA) chemotherapy, chemoembolization and dose-escalated whole liver radiotherapy (WLRT) to determine if the maximum safe dose of 32 Gy in 2 Gy fractions could be achieved.

Methods: Patients (pts) with liver metastases from neuroendocrine tumors who failed somatostatin analog therapy were eligible. First, floxuridine (FUDR, 3 mg/m2/d) and leucovorin (LV, 300 mg/m2/d) were given by continuous hepatic artery infusion for 12 days; streptozotocin (500 mg/m2/d) was given over 3 h on days 5, 8 and 10. Concurrent WLRT was prescribed in 2 Gy/day with doses escalated from 24 Gy to 32 Gy using the time-to-event continual reassessment method for dose allocation with a target rate of dose-limiting grade (gr.) ≥ 3 radiation-induced liver disease (RILD) of 10%. 8 weeks later, for pts without RILD and other gr. ≥ 4 toxicities, continuous 72-h infusion with HA FUDR (3 mg/m2/d) and LV (300 mg/m2/d) was given, followed by chemoembolization with mitomycin C (20 mg) and polyvinyl alcohol foam.

Results: 19 pts were enrolled in the trial. 8 pts received 24 Gy, 2 - 26 Gy, 1 - 28 Gy, 2 - 30 Gy and 6 - 32 Gy. 8 pts received only the first part of the treatment, 11 completed the entire protocol. No pts developed dose-limiting RILD; 5 - had gr. 3-4 increased liver function tests (LFT), 4 - had other gr. 4 toxicities after the first part of the treatment, primarily chemotherapy and embolization-related; 3 - had gr. 3 increased LFT, and 1 - had other gr. 4 toxicities after the second part of the treatment. 4 pts (21%) had partial response, 14 (74%) - stable disease and one pt (5%) receiving only part 1 had progressive disease. Median progression free survival for all pts was 20.6 (8.4-45.4) months (m); 15.4 (3.4-67.8) m for pts who received the first part of the treatment only, and 27.9 (8.4 – infinite) m for pts who received both parts of treatment.

Conclusions: This study showed that chemotherapy can be safely combined with a full dose of WLRT and subsequent chemoembolization without producing RILD.

Metabolic alterations: a biomarker for radiation-induced normal brain injury-an MR spectroscopy study

PURPOSE

To assess if interval changes in metabolic status in normal cerebral tissue after radiation therapy (RT) can be detected by 2D CSI (chemical shift imaging) proton spectroscopy.

MATERIALS AND METHODS

Eleven patients with primary brain tumors undergoing cranial radiation therapy (RT) were included. 2D-CSI MRS was performed before, during, and after the course of RT with the following parameters: TE/TR 144/1500 ms, field of view (FOV) 24, thickness 10 mm, matrix 16 x 16. The metabolic ratios choline/creatine (Cho/Cr), N-acetylaspartate (NAA)/Cr, and NAA/Cho in normal brain tissue were calculated.

RESULTS

NAA/Cr and Cho/Cr were significantly decreased at week 3 during RT and at 1 month and 6 months after RT compared to values prior to RT (P < 0.01). The NAA/Cr ratio decreased by -0.19 +/- 0.05 (mean +/- standard error [SE]) at week 3 of RT, -0.14 +/- 0.06 at the last week of RT, -0.14 +/- 0.05 at 1 month after RT, and -0.30 +/- 0.08 at 6 months after RT compared to the pre-RT value of 1.43 +/- 0.04. The Cho/Cr ratio decreased by -0.27 +/- 0.05 at week 3 of RT, -0.11 +/- 0.05 at the last week of RT, -0.26 +/- 0.05 at 1 month after RT and -0.25 +/- 0.07 at 6 months after RT from the pre-RT value of 1.29 +/- 0.03. Changes in Cho/Cr were correlated with the interaction of the radiation dose and dose-volume at week 3 of RT, during the last week of RT (P < 0.005), and at 1 month after RT (P = 0.017).

CONCLUSION

The results of this study suggest that MRS can detect early metabolic changes in normal irradiated brain tissue.

Radiation improves gene delivery by a novel transferrin-lipoplex nanoparticle selectively in cancer cells

Selective gene transfer to tumor is critical in cancer gene therapy. We previously used ionizing radiation to improve adenovirus uptake in intrahepatic tumors but liver cytotoxicity associated with the viral administration still occurred. Here, we explore the potential of radiation for improving gene delivery by a virus-mimicking nanoparticle, transferrin (Tf)-cationic liposome-DNA complex (Tf-lipoplex). Transduction by Tf-lipoplex was highly efficient in various cell lines and further increased by radiation in a dose- and time-dependent manner. This radiation induction, which was associated with an increase in Tf-lipoplex uptake (3- to 4-folds in hepatocytes WB and lung cancer cells, LLC1), was absent when a Tf-deficient complex was used or abolished by the presence of free Tf, suggesting that Tf receptor (TfR) interaction is required for radiation induction. Radiation (10-20 Gy) markedly induced transgene (LacZ) expression in LLC1 xenografts (3.5- to 7.4-folds), correlating with increased plasmid content and TfR expression in irradiated tumors. Moreover, Tf-lipoplex-mediated gene expression was not observed in the liver or other normal tissues regardless of radiation treatment. We conclude that radiation improves Tf-lipoplex gene delivery selectively to tumor cells both in vitro and in vivo. Our findings may provide insight in developing ligand-specific lipoplex for molecularly targeted cancer gene therapy.

Role of epidermal growth factor receptor degradation in gemcitabine-mediated cytotoxicity

We have recently reported that treatment with gemcitabine, a potent chemotherapeutic agent and radiation sensitizer, stimulates phosphorylation of the epidermal growth factor receptor (EGFR). Because phosphorylation of EGFR is known to precede receptor degradation, we hypothesized that gemcitabine treatment may also result in EGFR degradation. In two human head and neck cancer cell lines, UMSCC-1 and UMSCC-6, we demonstrated an approximately 80% decrease in total EGFR levels at 72 h after a 2-h treatment with 1 muM gemcitabine. Neither cisplatin nor 5-fluorouracil, which are used to treat head and neck cancer, caused EGFR degradation. EGFR downregulation did not occur at the level of transcription, as assessed by reverse transcription-polymerase chain reaction (RT-PCR), but instead occurred via phosphorylation and ubiquitination of the receptor along a proteosome/lysosome-mediated pathway. Inhibition of EGFR degradation, by either pretreatment with the EGFR tyrosine kinase inhibitor gefitinib or by exposure to the proteosome/lysosome inhibitor MG132, significantly reduced gemcitabine-induced cell death. These results suggest that EGFR degradation may be a novel mechanism for gemcitabine-mediated cell death. These findings also indicate that caution should be exercised when combining gemcitabine with agents that may prevent EGFR degradation, such as EGFR tyrosine kinase inhibitors administered in a suboptimal sequence or proteosome inhibitors.

The role of Bcl-X(S) in radiation sensitivity

Bcl-X(S) is a pro-apoptosis member of the Bcl2 family that has been shown to induce cell death and enhance chemosensitivity. We have investigated the effect of Bcl-X(S) overexpression on radiation sensitivity. Using a tetracycline-repressible system, we found that removal of tetracycline for 16 h induced Bcl-X(S) and reduced the surviving fraction of NIH 3T3 cells to 25%. However, radiation sensitivity was not significantly affected by Bcl-X(S) expression; the mean inactivation doses for Bcl-X(S) repressed and Bcl-X(S) induced cells were 2.7 +/- 0.3 and 2.3 +/- 0.1 Gy, respectively. We conclude that Bcl-X(S) induces cell death without affecting radiation sensitivity. These results suggest that mitochondrial pathways to apoptosis may not have a significant role in survival after irradiation.

The potential of 5-fluorocytosine/cytosine deaminase enzyme prodrug gene therapy in an intrahepatic colon cancer model

Colorectal cancer can metastasize to the liver, but remain liver confined for years. A critical step in developing treatments for intrahepatic cancer involves assessment in an orthotopic intrahepatic model. The purpose of this study was to develop a noninvasive intrahepatic tumor model to study the efficacy of 5-flucytosine/yeast cytosine deaminase (5FC/yCD)-based gene therapy for liver tumors. Luciferase expressing human colorectal carcinoma (HT-29luc) cells were generated by retroviral infection and implanted in the left liver lobe of nude mice. The bioluminescence was measured every week for a period of 1 month, then animals were killed and tumors were measured by calipers. After we found a correlation between photon counts and tumor size, animals were implanted with tumors composed of either 0%, 10%, or 100% yCD/HT-29luc cells, and treated with 5FC. Tumor bioluminescence was measured during treatment and tumor histology examined at the time of death. We found that 5FC caused significant regression of yCD expressing tumors. Furthermore, visible tumors at the time of death, which emitted little bioluminescence, contained little or no viable tumor. We then developed an adenoviral vector for yCD. Intraperitoneal administration of adenovirus containing yCD led to the production of yCD enzyme within intrahepatic tumors. These results suggest that (1) intrahepatic cancer responds to 5FC when cells express yCD; (2) the luciferin-luciferase system permits non-invasive real time imaging of viable intrahepatic cancer; and (3) this system can be used to carry out gene therapy experiments using yCD adenovirus.

The reproducibility of organ position using active breathing control (ABC) during liver radiotherapy

PURPOSE

To evaluate the intrafraction and interfraction reproducibility of liver immobilization using active breathing control (ABC).

METHODS AND MATERIALS

Patients with unresectable intrahepatic tumors who could comfortably hold their breath for at least 20 s were treated with focal liver radiation using ABC for liver immobilization. Fluoroscopy was used to measure any potential motion during ABC breath holds. Preceding each radiotherapy fraction, with the patient setup in the nominal treatment position using ABC, orthogonal radiographs were taken using room-mounted diagnostic X-ray tubes and a digital imager. The radiographs were compared to reference images using a 2D alignment tool. The treatment table was moved to produce acceptable setup, and repeat orthogonal verification images were obtained. The positions of the diaphragm and the liver (assessed by localization of implanted radiopaque intra-arterial microcoils) relative to the skeleton were subsequently analyzed. The intrafraction reproducibility (from repeat radiographs obtained within the time period of one fraction before treatment) and interfraction reproducibility (from comparisons of the first radiograph for each treatment with a reference radiograph) of the diaphragm and the hepatic microcoil positions relative to the skeleton with repeat breath holds using ABC were then measured. Caudal-cranial (CC), anterior-posterior (AP), and medial-lateral (ML) reproducibility of the hepatic microcoils relative to the skeleton were also determined from three-dimensional alignment of repeat CT scans obtained in the treatment position.

RESULTS

A total of 262 fractions of radiation were delivered using ABC breath holds in 8 patients. No motion of the diaphragm or hepatic microcoils was observed on fluoroscopy during ABC breath holds. From analyses of 158 sets of positioning radiographs, the average intrafraction CC reproducibility (sigma) of the diaphragm and hepatic microcoil position relative to the skeleton using ABC repeat breath holds was 2.5 mm (range 1.8-3.7 mm) and 2.3 mm (range 1.2-3.7 mm) respectively. However, based on 262 sets of positioning radiographs, the average interfraction CC reproducibility (sigma) of the diaphragm and hepatic microcoils was 4.4 mm (range 3.0-6.1 mm) and 4.3 mm (range 3.1-5.7 mm), indicating a change of diaphragm and microcoil position relative to the skeleton over the course of treatment with repeat breath holds at the same phase of the respiratory cycle. The average population absolute intrafraction CC offset in diaphragm and microcoil position relative to skeleton was 2.4 mm and 2.1 mm respectively; the average absolute interfraction CC offset was 5.2 mm. Analyses of repeat CT scans demonstrated that the average intrafraction excursion of the hepatic microcoils relative to the skeleton in the CC, AP, and ML directions was 1.9 mm, 0.6 mm, and 0.6 mm respectively and the average interfraction CC, AP, and ML excursion of the hepatic microcoils was 6.6 mm, 3.2 mm, and 3.3 mm respectively.

CONCLUSION

Radiotherapy using ABC for patients with intrahepatic cancer is feasible, with good intrafraction reproducibility of liver position using ABC. However, the interfraction reproducibility of organ position with ABC suggests the need for daily on-line imaging and repositioning if treatment margins smaller than those required for free breathing are a goal.

Phase I trial of radiation dose escalation with concurrent weekly full-dose gemcitabine in patients with advanced pancreatic cancer

PURPOSE

The primary objective of this phase I trial was to determine the maximum-tolerated dose of radiation that could be delivered to the primary tumor concurrent with full-dose gemcitabine in patients with advanced pancreatic cancer.

PATIENTS AND METHODS

Thirty seven patients with unresectable (n = 34) or incompletely resected pancreatic cancer (n = 3) were treated. Gemcitabine was administered as a 30-minute intravenous infusion at a dose of 1,000 mg/m(2) on days 1, 8, and 15 of a 28-day cycle. Radiation therapy was initiated on day 1 and directed at the primary tumor alone, without prophylactic nodal coverage. The starting radiation dose was 24 Gy in 1.6-Gy fractions. Escalation was achieved by increasing the fraction size in increments of 0.2 Gy, keeping the duration of radiation constant at 3 weeks. A second cycle of gemcitabine alone was intended after a 1-week rest.

RESULTS

Two of six assessable patients experienced dose-limiting toxicity at the final planned dose level of the trial (42 Gy in 2.8-Gy fractions), one with grade 4 vomiting and one with gastric/duodenal ulceration. Two additional patients at this dose level experienced late gastrointestinal toxicity that required surgical management.

CONCLUSION

The final dose investigated (42 Gy) is not recommended for further study considering the occurrence of both acute and late toxicity. However, a phase II trial of this novel gemcitabine-based chemoradiotherapy approach, at a radiation dose of 36 Gy in 2.4-Gy fractions, is recommended on the basis of tolerance, patterns of failure, and survival data.

The investigational new drug XK469 induces G(2)-M cell cycle arrest by p53-dependent and -independent pathways

PURPOSE

XK469 (2-[4-(7-chloro-2-quinoxalinyloxy) phenoxy]propionic acid), a synthetic quinoxaline phenoxypropionic acid derivative, has broad activity against murine tumors and is entering Phase I clinical development as a topoisomerase IIbeta inhibitor. This study investigated the underlying molecular mechanism of XK469's effects on the cell cycle.

EXPERIMENTAL DESIGN

Growth inhibition, cell cycle arrest, induction of p53 and p21 mRNA and protein, and cdc2 phosphorylation and kinase activity were studied in treated cells from the H460 lung cancer line and p21 and p53 knockout cells of the HCT 116 colon cancer line.

RESULTS

XK469 arrested H460 cells at G(2)-M, which was associated with cdc2 phosphorylation and decreased cdc2 kinase activity. Moreover, XK469 stabilized p53 and subsequently increased p21(WAF1/CIP1). Furthermore, HCT116 p21(-/-) cells were less sensitive than wild-type cells to XK469-induced growth inhibition, but p53(+/+) and p53(-/-) cells were equally sensitive despite the absence of p21 induction in the p53(-/-) cells.

CONCLUSIONS

When considered with published data, our study suggests a complex mechanism of XK469-mediated anticancer activity involving multiple pathways, including p53-dependent and -independent G(2)-M arrest via inactivation of cdc2-cyclin B1 kinase activity.

Profiling of cancer cells using protein microarrays: discovery of novel radiation-regulated proteins

The advent of DNA microarray technology will likely have a major impact on the molecular classification and understanding of human cancer. Obtaining a global perspective of proteins expressed in cancer cells is considerably more challenging. Here we describe a microarray-based platform that can be used to measure protein levels and activities in a complex biological milieu such as a cellular lysate. Using a protein microarray made up of 1920 elements (146 distinct antibodies) we were able to monitor alterations of protein levels in LoVo colon carcinoma cells treated with ionizing radiation. The protein microarray approach revealed radiation-induced up-regulation of apoptotic regulators including p53, DNA fragmentation factor 40/caspase activated DNase, DNA fragmentation factor 45/inhibitor of caspase activated DNase, tumor necrosis factor-related apoptosis-inducing ligand, death receptor 5, decoy receptor 2, FLICE-like inhibitory protein, signal transducers and activators of transcription 1alpha, and uncoupling protein 2, among others. Consistent with this observation, an increased percentage of apoptosis was observed in irradiated LoVo cells. Interestingly, we also observed radiation-induced down-regulation of carcinoembryonic antigen, a prototypic cancer biomarker. Selected proteins assessed by microarray were validated by traditional immunoblotting. Taken together, our work suggests that protein/antibody microarrays will facilitate high-throughput proteomic studies of human cancer and carcinogenesis.

Recent advances in the use of radiosensitizing nucleosides

Chemotherapeutic drugs that perturb nucleotide metabolism have the potential to produce substantial sensitization of tumor cells to radiation treatment. The clinical effectiveness of fluoropyrimidines as radiosensitizers has been proven in multiple randomized trials. The development of oral fluoropyrimidine formulations may allow protracted exposure without the need for indwelling intravenous lines and infusion pumps. These agents may also provide more selective radiosensitization and are likely to be widely incorporated into chemoradiotherapy regimens for patients with gastrointestinal malignancies. Gemcitabine has been well studied in the laboratory, with respect to mechanisms of radiosensitization and strategies that may increase the therapeutic index. Clinical trials based on these studies are now defining the role of this radiosensitizing nucleoside. Issues regarding the use oral fluoropyrimidines and gemcitabine need to be viewed in the context of both local and distant disease control, given the potential systemic activity of these agents.

Partial irradiation of the liver

The use of three-dimensional radiotherapy (RT) and the prospective follow-up of patients for radiation-induced liver disease (RILD) have led to a more quantitative understanding of the partial organ tolerance of the liver compared with previous estimates based on clinical judgment alone. Parameters of both the Lyman normal tissue complication probability (NTCP) model and a local damage-organ injury (D-I) NTCP model have been fit to clinical data from patients who have received hepatic radiation. Based on analyses of over 180 patients, the liver exhibits a large volume effect and a low threshold volume for RILD. Mean liver dose is associated with RILD, and no cases of RILD have been reported in patients with a mean liver dose of less than 31 Gy. Most recent estimates of the partial liver tolerance to RT suggest that if less than 25% of the normal liver is treated with RT, then there may be no upper limit on dose associated with RILD. Estimates of the liver doses associated with a 5% risk of RILD for uniform irradiation of one third, two thirds, and the whole liver are 90 Gy, 47 Gy, and 31 Gy, respectively.

Selective radioprotection of hepatocytes by systemic and portal vein infusions of amifostine in a rat liver tumor model

PURPOSE

The tolerance of the liver to radiation is too low to permit an effective dose to be delivered to patients who have diffuse intrahepatic cancer. In this study we evaluated whether systemic or portal venous administration of the aminothiol compound, amifostine, could protect the normal liver from the effects of ionizing radiation without compromising tumor cell kill in a rat liver tumor model.

METHODS AND MATERIALS

Rats implanted with liver tumors were infused with 200 mg/kg amifostine over 15 min via the femoral or portal vein. The livers were irradiated with a single 6-Gy fraction 15-20 min after the termination of amifostine infusion. Protection of the liver was assessed by an in vitro hepatocyte micronucleus assay and tumor protection by an in vivo-in vitro clonogenic survival assay. Tissue levels of the active metabolite, free WR-1065, were determined in the tumor and in the normal liver using a specific HPLC assay with electrochemical detection.

RESULTS

After a 6-Gy fraction, the frequency of hepatocyte micronuclei after administration of saline, systemic amifostine, and portal venous amifostine was 18.7+/-1%, 6.8+/-1%, and 9.9+/-2%, respectively, corresponding to a radiation equivalent effect of 6 Gy +/- 0.5, 1.8 Gy +/- 0.3, and 2.5 Gy +/- 1.3, respectively. Both amifostine conditions showed considerably less radiation effect than saline-treated controls (p < 0.01); the two amifostine conditions did not differ (p = 0.3). The surviving fraction of tumor cells was not affected by amifostine treatment and was 0.03+/-0.02 and 0.05+/-0.03 for systemic and portal venous delivery and 0.06+/-0.02 for control animals (ANOVA analysis showed no significant difference of the means p = 0.34). Portal venous delivery produced significantly less WR-1065 in the tumor compared to systemic administration (54 microM +/- 36 vs. 343 microM +/- 88, respectively, p = 0.03).

CONCLUSIONS

Both systemic and portal venous administration of amifostine effectively protect hepatocytes from ionizing radiation without compromising tumor cell kill in a clinically relevant animal model. These findings suggest that amifostine may be a selective normal tissue radioprotectant in liver cancer and that regional/portal infusions may be preferable to systemic dosing.

The role of apoptosis in 2',2'-difluoro-2'-deoxycytidine (gemcitabine)-mediated radiosensitization

The nucleoside analogue Gemcitabine [2',2'-difluoro-2'-deoxycytidine (dFdCyd)] is active against a wide variety of solid tumors and is a potent radiation sensitizer. Because apoptosis has been shown to be an important mechanism of cell death for many cancers, we wished to investigate the role of apoptosis in dFdCyd-mediated radiosensitization. We evaluated HT29 colon cancer cells, UMSCC-6 head and neck cancer cells, and A549 lung cancer cells, which differ substantially in the ability to undergo radiation-induced apoptosis. We hypothesized that if dFdCyd produced radiosensitization by potentiating preexisting death pathways, then only the apoptotic-prone HT29 cells would show a substantial increase in apoptosis when treated with the combination of dFdCyd and radiation and that UMSCC-6 cells and A549 cells would be radiosensitized through nonapoptotic mechanisms. We found that the radiosensitization of HT29 cells (enhancement ratio, 1.81 +/- 0.16) was accompanied by an increase in apoptosis and by caspase activation and that inhibition of this activation by the caspase inhibitor Z-Asp-Glu-Val-Asp-fluoromethylketone (DEVD) significantly decreased radiosensitization (to 1.36 +/- 0.24; P < 0.05). In contrast, UMSCC-6 cells and A549 cells were modestly radiosensitized (enhancement ratio, 1.47 +/- 0.24 and 1.31 +/- 0.04, respectively) via a nonapoptotic mechanism. These findings suggest that although apoptosis can contribute significantly to dFdCyd-mediated radiosensitization, the role of apoptosis in dFdCyd-mediated radiosensitization depends on the cell line rather than representing a general property of the drug.

Radiation concurrent with gemcitabine for locally advanced head and neck cancer: a phase I trial and intracellular drug incorporation study

PURPOSE

To examine the feasibility and dose-limiting toxicity (DLT) of once-weekly gemcitabine at doses predicted in preclinical studies to produce radiosensitization, concurrent with a standard course of radiation for locally advanced head and neck cancer. Tumor incorporation of gemcitabine triphosphate (dFdCTP) was measured to assess whether adequate concentrations were achieved at each dose level.

PATIENTS AND METHODS

Twenty-nine patients with unresectable head and neck cancer received a course of radiation (70 Gy over 7 weeks, 5 days weekly) concurrent with weekly infusions of low-dose gemcitabine. Tumor biopsies were performed after the first gemcitabine infusion (before radiation started), and the intracellular concentrations of dFdCTP were measured.

RESULTS

Severe acute and late mucosal and pharyngeal-related DLT required de-escalation of gemcitabine dose in successive patient cohorts receiving dose levels of 300 mg/m(2)/wk, 150 mg/m(2)/wk, and 50 mg/m(2)/wk. No DLT was observed at 10 mg/m(2)/wk. The rate of endoscopy- and biopsy-assessed complete tumor response was 66% to 87% in the various cohorts. Tumor dFdCTP levels were similar in patients receiving 50 to 300 mg/m(2) (on average, 1.55 pmol/mg, SD 1.15) but were barely or not detectable at 10 mg/m(2).

CONCLUSION

A high rate of acute and late mucosa-related DLT and a high rate of complete tumor response were observed in this regimen at the dose levels of 50 to 300 mg/m(2), which also resulted in similar, subcytotoxic intracellular dFdCTP concentrations. These results demonstrate significant tumor and normal tissue radiosensitization by low-dose gemcitabine. Different regimens of combined radiation and gemcitabine should be evaluated, based on newer preclinical data promising an improved therapeutic ratio.

Yeast cytosine deaminase improves radiosensitization and bystander effect by 5-fluorocytosine of human colorectal cancer xenografts

The efficacy of cancer gene therapy using bacterial cytosine deaminase (bCD)/5-fluorocytosine (5-FC) enzyme/prodrug strategy is limited by the inefficiency of cytosine deaminase (CD)-catalyzed conversion of 5-FC into 5-fluorouracil (5-FU). We have shown previously that yeast CD (yCD) is more efficient at the conversion of 5-FC than bCD. In the current study, we hypothesized that the increased production of 5-FU by yCD would enhance the efficacy of the CD/5-FC treatment strategy by increasing the bystander effect as well as the efficacy of radiotherapy because of the radiosensitizing capacity of 5-FU. To test this hypothesis, we generated stable HT29 human colon cancer cell lines expressing either bCD (HT29/bCD) or yCD (HT29/yCD). The amount of 5-FU produced in HT29/yCD tumors after a single injection of 5-FC (1000 mg/kg, i.p.) was 15-fold higher than that produced in HT29/bCD tumors. In tumor-bearing nude mice, the average minimum relative tumor size (compared with pretreatment values) of HT29/bCD tumors treated with 5-FC and radiation (500 mg/kg i.p. and 3 Gy, 5 days a week for 2 weeks) was 0.55+/-0.1, compared with 0.01+/-0.01 in HT29/yCD tumors (P = 0.002). Moreover, an increased cytotoxic and radiosensitizing effect of 5-FC on bystander cells was observed in vitro and in vivo when yCD was expressed in HT29 cells instead of bCD. In mice bearing HT29 tumors containing 10% HT29/yCD cells, the combined treatment resulted in a minimum tumor size of 0.20+/-0.07 compared with 0.60+/-0.1 in 10% HT29/bCD cells (P < 0.001). These results demonstrate that the use of yCD in the CD/5-FC strategy has a high potential to improve the therapeutic outcome of combined gene therapy and radiotherapy in cancer patients.

Lack of effect of TP53 status on fluorodeoxyuridine-mediated radiosensitization

Substantial evidence suggests that TP53 (also known as p53) status can influence the response of cells to chemotherapy and radiation. We wished to determine if TP53 function affected the response of cells to fluoropyrimidines and radiation, a combination used for tens of thousands of patients each year. To assess the role of TP53 in fluoropyrimidine-mediated radiosensitization, we carried out experiments using RKO parental cells (wild-type TP53) and RKO cells overexpressing mutant TP53 (which blocks TP53 function) or expressing E6 (which degrades TP53). We found that TP53 function had no effect on the ability of fluorodeoxyuridine to increase radiation sensitivity. These findings are consistent with the hypothesis that the late G(1)-phase checkpoint, which is mediated by TP53, is not crucial to radiosensitization. Rather, the ability of cells to progress in to S phase in the presence of the drug, which is independent of TP53, is more closely associated with increased radiation sensitivity.

The role of p53 in gemcitabine-mediated cytotoxicity and radiosensitization

PURPOSE

We compared the cytotoxic and radiosensitizing effects of gemcitabine (2',2'-difluoro-2'-deoxycytidine, dFdCyd), a clinically valuable radiosensitizer, in colon cancer RKO cells which differed in their p53 status. The parental RKO cells, RKO-P, contain wild-type p53 protein. In RKO-E6 cells, the p53 function has been disrupted by transfection of the cells with the human papillomavirus type-16 E6 gene.

RESULTS

We found that the RKO-P cells were significantly more sensitive to dFdCyd-mediated cytotoxicity and apoptosis than RKO-E6 cells (IC10 39.3 +/- 5.3 nM and 62.0 +/- 6.9 nM, respectively). The cytotoxic effect of dFdCyd in RKO-P cells was accompanied by induction of the proapoptotic protein Bax at the time when p53 was induced. In contrast, similar treatment of RKO-E6 cells with dFdCyd resulted in only limited expression of Bax, suggesting that the cytotoxic effect of dFdCyd was mediated, in part, by a p53-dependent apoptosis pathway. We also studied the effect of dFdCyd on radiation sensitivity. We found that at minimally cytotoxic concentrations dFdCyd failed to radiosensitize either RKO-P or RKO-E6 cells, whereas at cytotoxic concentrations equal sensitization was produced. Finally, we assessed the influence of dFdCyd on cell cycle distribution. We found that dFdCyd synchronized RKO-P cells, whereas synchrony was not produced in p53-disrupted RKO-E6 cells.

CONCLUSION

These results suggest that p53 status may influence dFdCyd-mediated apoptosis, cytotoxicity, and cell cycle progression but do not support an important role for p53 in radiosensitization.

Escalated focal liver radiation and concurrent hepatic artery fluorodeoxyuridine for unresectable intrahepatic malignancies

PURPOSE

To evaluate the response, time to progression, survival, and impact of radiation (RT) dose on survival in patients with intrahepatic malignancies treated on a phase I trial of escalated focal liver RT.

PATIENTS AND METHODS

From April 1996 to January 1998, 43 patients with unresectable intrahepatic hepatobiliary cancer (HB; 27 patients) and colorectal liver metastases (LM; 16 patients) were treated with high-dose conformal RT. The median tumor size was 10 x 10 x 8 cm. The median RT dose was 58.5 Gy (range, 28.5 to 90 Gy), 1.5 Gy twice daily, with concurrent continuous-infusion hepatic arterial fluorodeoxyuridine (0.2 mg/kg/d) during the first 4 weeks of RT.

RESULTS

The response rate in 25 assessable patients was 68% (16 partial and one complete response). With a median potential follow-up period of 26.5 months, the median times to progression for all tumors, LM, and HB were 6, 8, and 3 months, respectively. The median survival times of all patients, patients with LM, and patients with HB were 16, 18, and 11 months, respectively. On multivariate analyses, escalated RT dose was independently associated with improved progression-free and overall survival. The median survival of patients treated with 70 Gy or more has not yet been reached (16.4+ months), compared with 11.6 months in patients treated with lower RT doses (P =.0003).

CONCLUSION

The excellent response rate, prolonged intrahepatic control, and improved survival in patients treated with RT doses of 70 Gy or more motivate continuation of dose-escalation studies for patients with intrahepatic malignancies.

Radiosensitization produced in vivo by once- vs. twice-weekly 2'2'-difluoro-2'-deoxycytidine (gemcitabine)

PURPOSE

Gemcitabine (2'2'-difluoro-2'-deoxycytidine, dFdCyd) is a potent radiosensitizer of rodent and human tumor cells. Our Phase I clinical trial using once-weekly dFdCyd as a radiosensitizer in the treatment of patients with Stage IV squamous cell head and neck cancer has produced a high rate of tumor response and significant normal mucosal toxicity. These findings raised the question of whether we are using dFdCyd in the optimal dose and schedule. In vitro studies suggest that twice-weekly dFdCyd has the potential to be more effective than once-weekly dFdCyd when administered in combination with radiation (RT) given 5 days per week. Therefore, we have used a mouse model to assess whether the therapeutic ratio of combined modality therapy may be improved by using a twice-weekly drug regimen. We asked two questions: 1) Does a once-weekly or twice-weekly dFdCyd regimen cause more normal tissue radiosensitization? 2) Does a once-weekly or twice-weekly dFdCyd + RT regimen produce a better therapeutic index?

METHODS AND MATERIALS

To assess normal tissue toxicity, C3H mice underwent mouth (60)Co RT (27.5 Gy in 5 daily fractions) +/- dFdCyd delivered intraperitoneally (IP) either once or twice weekly 6 hours prior to irradiation. Acute lip reactions were quantified according to a standard scoring system, and weight loss was measured. We measured tumor control using squamous cell carcinoma (SCC) VII murine squamous cell flank tumors (50-125 mm(3)) treated with the same regimens used in the mouth irradiation model.

RESULTS

We found that dFdCyd delivered 800 mg/kg once weekly or 150 mg/kg twice weekly caused similar (and maximal tolerable) weight loss; therefore these regimens were chosen to test which schedule produced more acute lip radiosensitization. Twice-weekly dFdCyd + RT was somewhat more toxic by weight loss (800 mg/kg once weekly: 11.9%; 150 mg/kg twice weekly: 17.7%; p = 0.09). To assess therapeutic index, we treated SCC VII flank tumors with RT combined with isotoxic drug/RT regimens (dFdCyd 800 mg/kg once weekly or 100 mg/kg twice weekly). Tumors treated with twice-weekly dFdCyd + RT were significantly smaller than tumors treated with once-weekly drug + RT at 28 days from the start of treatment (p < 0.03).

CONCLUSIONS

These findings demonstrate that equitoxic once- versus twice-weekly dFdCyd regimens cause differing levels of oral mucosal radiosensitization. This would suggest that each radiation-dFdCyd schedule will require its own dFdCyd dose escalation trial (which cannot be determined by the maximum tolerated dose (MTD) for dFdCyd alone using that schedule). In addition, our findings suggest that for head and neck cancers twice-weekly dFdCyd may have a higher therapeutic index compared with once-weekly dFdCyd when combined with daily RT.

Interaction between gemcitabine and mitomycin-C in vitro

Both gemcitabine (2',2'-difluorodeoxycytidine; dFdCyd) and mitomycin-C (MMC) are active against several solid malignancies. dFdCyd is an attractive agent for use in combination with drugs which damage DNA and with radiation therapy because of its ability to inhibit DNA replication and repair as well as its radiosensitizing effect. We hypothesized that the repair of MMC adducts in DNA might be inhibited by dFdCyd leading to a synergistic effect. To test this possibility, we studied the effect of combining dFdCyd and MMC in HT29 human colon carcinoma cells in vitro. The cells were exposed to a variety of drug concentration ratios and schedules, then assessed for clonogenic survival. D50 values (drug concentration at which clonogenicity is inhibited by 50%) were calculated, and the interactive effects of the two drugs were evaluated using median effect analysis. In this approach, if the calculated combination index (CI) is < 1, 1, or > 1, it indicates synergism, additivity, or antagonism, respectively (Chou and Talalay 1984). We found that marked synergy (CI of 0.5-0.7) was produced by concurrent exposure to mitomycin and gemcitabine. In contrast, sequential treatment led only to additivity. These findings suggest that, when combined in an appropriate schedule, the chemosensitizing effect of gemcitabine may be beneficial in the treatment of malignancies which are sensitive to MMC.

Decreased 13-S-hydroxyoctadecadienoic acid levels and 15-lipoxygenase-1 expression in human colon cancers

13-S-Hydroxyoctadecadienoic acid (13-S-HODE), the product of 15-lipoxygenase (15-LOX) metabolism of linoleic acid, enhances cellular mitogenic responses to certain growth factors. Other observations have questioned whether 13-S-HODE has tumorigenic effects. Our study evaluated the hypothesis that 15-LOX-1 is overexpressed in colon cancers resulting in an increase in intracellular 13-S-HODE. 15-LOX-1 and 13-S-HODE were quantified using western blots, ELISA and immunohistochemistry in 18 human colon cancers with paired normal colonic mucosa. Additionally, 15-LOX-1 expression was measured by western blots in three transformed colonic cell lines and in a human umbilical vein endothelial cell line. Next, we evaluated 13-S-HODE effects on cellular proliferation, cell cycle distribution and apoptosis in a transformed colonic cell line (RKO). Cell cycle distributions were measured by flow cytometry and apoptosis was assessed by phase contrast microscopy, electron microscopy, flow cytometry and DNA fragmentation assay. 15-LOX-1 immunohistochemistry staining scores were reduced in tumor tissues (P </= 0.0001) and 15-LOX-1 expression was absent in three transformed colonic cell lines. 13-S-HODE levels were also reduced in tumors tissues compared with normal controls by ELISA (median 3.3-fold, P = 0.02) and by immunohistochemistry (P </= 0.0001). In vitro 13-S-HODE inhibited RKO cell proliferation and induced cell cycle arrest and apoptosis. 13-S-HODE produced similar effects in HT-29 cells. Our observations indicate that: (i) human colon cancers are associated with a down-regulation in 15-LOX-1 expression and a reduction in 13-S-HODE intracellular levels; (ii) 13-S-HODE can suppress cell proliferation and induce apoptosis in transformed colonic epithelial cells.

Radiosensitization by gemcitabine

Gemcitabine is a potent radiosensitizer in both laboratory studies and in the clinic. Initial laboratory studies showed that gemcitabine radiosensitizes a wide variety of rodent and human tumor cells in culture. Maximum radiosensitization occurs in cells that demonstrate concurrent redistribution into S phase and d-adenosine triphosphate pool depletion. Although the mechanism of sensitization is not yet clear, recent evidence from our laboratory suggests that gemcitabine lowers the threshold for radiation-induced apoptosis. Our preclinical data were used to design gemcitabine dose-escalation trials in combination with standard radiation for patients with unresectable head and neck cancer and pancreatic cancer. In head and neck cancer, we have found that gemcitabine doses far below the maximum tolerated dose for the drug when used alone significantly potentiate the toxicity of treatment. Comparatively, normal tissue sensitization has not been as marked in the treatment of pancreatic tumors. These findings have led us to conduct experiments using an animal model to improve the therapeutic index of treatment. We conclude that gemcitabine is a promising radiation sensitizer that will need to be developed cautiously if excessive normal tissue toxicity is to be avoided.