Abstract 3941: TNG908 is an MTAPnull-selective PRMT5 inhibitor that drives tumor regressions in MTAP-deleted xenograft models across multiple histologies

TNG908 is an investigational PRMT5 inhibitor with a novel MTA-cooperative binding mechanism designed to leverage the synthetic lethal interaction between PRMT5 inhibition and MTAP deletion. MTAP deletion occurs in 10-15% of all human cancer representing multiple histologies. MTA is a negative regulator of PRMT5 that accumulates as a result of MTAP deletion. TNG908 selectively binds the PRMT5-MTA complex driving selective inhibition of PRMT5 in MTAP-null cancers, which is postulated to create a large therapeutic index relative to PRMT5 inhibitors currently in clinical development. TNG908 is 15X selective for MTAPnull cell lines over isogenic MTAPWT cell lines, and has marked selectivity for MTAP-deleted cancer cell lines independent of lineage in a large, diverse cell line panel. In vitro mechanistic studies confirm that MTAPnull-selective PRMT5 inhibitors can selectively target MTAPnull cancer cells in either an admixture of MTAPnull and MTAPWT cells, or with intracellular MTA accumulation 2-5X relative to basal levels in MTAPWT cells. Oral administration of TNG908 drives dose-dependent, MTAPnull-selective antitumor activity in multiple xenograft models, including tumor regressions in models representing non-small cell lung cancer (adenocarcinoma and squamous), cholangiocarcinoma, urothelial carcinoma, and others. Preclinical studies suggest clinical combinations that leverage PRMT5 biology and/or concurrent oncogenic driver mutations, such as KRASG12C. In summary, TNG908 is a novel, potent PRMT5 inhibitor with excellent drug-like properties and strong preclinical activity in multiple xenograft models that has the potential for histology-agnostic clinical development in MTAP-deleted solid tumors.

Citation Format: Kimberly J. Briggs, Kevin M. Cottrell, Matthew R. Tonini, Erik W. Wilker, Lina Gu, Charles B. Davis, Minjie Zhang, Doug Whittington, Deepali Gotur, Matthew J. Goldstein, Heather DiBenedetto, Marc S. Rudoltz, Alan Huang, John P. Maxwell. TNG908 is an MTAPnull-selective PRMT5 inhibitor that drives tumor regressions in MTAP-deleted xenograft models across multiple histologies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3941.

First-in-human study of IM156, a novel potent biguanide oxidative phosphorylation (OXPHOS) inhibitor, in patients with advanced solid tumors

Preclinical models suggest anticancer activity of IM156, a novel biguanide mitochondrial protein complex 1 inhibitor of oxidative phosphorylation (OXPHOS). This first-in-human dose-escalation study enrolled patients with refractory advanced solid tumors to determine the maximum tolerated dose (MTD) or recommended phase 2 dose (RP2D). Eligible patients received oral IM156 every other day (QOD) or daily (QD) and were assessed for safety, dose-limiting toxicities (DLTs), pharmacokinetics, and preliminary signals of efficacy. 22 patients with advanced cancers (gastric, n = 8; colorectal, n = 3; ovarian, n = 3; other, n = 8) received IM156 100 to 1,200 mg either QOD or QD. There were no DLTs. However, 1,200 mg QD was not well tolerated due to nausea; 800 mg QD was determined as the RP2D. The most frequent treatment-related AEs (TRAEs) were nausea (n = 15; 68%), diarrhea (n = 10; 46%), emesis (n = 9; 41%), fatigue (n = 4; 18%) and abdominal pain, constipation, and blood lactate increased (n = 2 each; 9%). Grade 3 nausea (n = 3; 14%) was the only grade ≥ 3 TRAE. Plasma exposures increased dose proportionally; mean Day 27 area under the curve (AUC_0-24) values were higher following QD administration compared to the respective QOD regimen. Stable disease (SD), observed in 7 (32%) patients (confirmed in 2 [9%]), was the best response. To our knowledge, this is the first phase 1 study of an OXPHOS inhibitor that established a RP2D for further clinical development in cancer. Observed AEs of IM156 were manageable and SD was the best response.

Modulation of Oxidative Phosphorylation with IM156 Attenuates Mitochondrial Metabolic Reprogramming and Inhibits Pulmonary Fibrosis

Metabolic reprogramming of the myofibroblast plays a fundamental role in the pathogenesis of fibrosing interstitial lung diseases. Here, we characterized the in vitro and in vivo metabolic and anti-fibrotic effects of IM156, an oxidative phosphorylation (OXPHOS) modulator that acts by inhibiting Protein Complex 1 (PC1). In vitro, IM156 inhibited TGFβ-dependent increases in mitochondrial oxygen consumption rate and expression of myofibroblast markers in human pulmonary fibroblasts without altering cell viability or adding to TGF-β induced increases in the extracellular acidification rate (ECAR). IM156 significantly increased cellular AMPK phosphorylation and was 60-fold more potent than metformin. In vivo, chronic oral administration of IM156 was highly distributed to major peripheral organs (i.e. lung, liver, kidney, heart) and had significant dose-related effects on the plasma metabolome consistent with OXPHOS modulation and AMPK activation. IM156 increased glycolysis, lipolysis, β-oxidation and amino acids, and decreased free fatty acids, TCA cycle activity and protein synthesis. In the murine bleomycin model of pulmonary fibrosis, daily oral administration of IM156 administered 7 days after lung injury, attenuated body/lung weight changes, and reduced lung fibrosis and inflammatory cell infiltration. The plasma exposures of IM156 were comparable to well-tolerated doses in human studies. In conclusion, the metabolic and anti-fibrotic effects of IM156 suggest that OXPHOS modulation can attenuate myofibroblast metabolic reprogramming and support testing IM156 as a therapy for IPF and other fibrotic diseases. Significance Statement Fibrosing Interstitial Lung Diseases (FILD) have a poor prognosis and current anti-fibrotic treatments have significant limitations. This study demonstrates that attenuation of fibrogenic metabolic remodeling, by modulation of OXPHOS with IM156, prevents the myofibroblast phenotype/collagen deposition and is a potentially effective and translational anti-fibrotic strategy.

Abstract CT212: Expanded phase 1/2a study of PLX8394, a novel next generation BRAF inhibitor in patients with advanced, unresectable solid tumors with alterations in BRAF

The authors did not submit an updated abstract. The original abstract should be considered final.

Citation Format: Filip Janku, Eric Sherman, Rona Yaeger, Aparna Parikh, Ryan Sullivan, Lynn Feun, Macarena De La Fuente, Frank Yung-Chin Tsai, Michael Gordon, Carl Allen, Marc S. Rudoltz, Kathe Balinski, Steven Averbuch, Michael Vidne, Gabi Tarcic. Expanded phase 1/2a study of PLX8394, a novel next generation BRAF inhibitor in patients with advanced, unresectable solid tumors with alterations in BRAF [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr CT212.

Phase I study of IM156, a novel potent biguanide oxidative phosphorylation (OXPHOS) inhibitor, in patients with advanced solid tumors

3590

Background: IM156, a novel oral potent biguanide OXPHOS inhibitor of Protein Complex 1 (PC1) of the mitochondrial electron transport chain, causes AMPK phosphorylation, the downstream effects of which are detrimental to OXPHOS-dependent cancer cells prone to energy stress. Preclinical experiments with IM156 demonstrated activity in solid tumor and hematologic malignancy models as a single-agent and in combinations. Methods: This was an open label, first-in-human, multi-center, dose-escalation study ( NCT03272256 ) using a 3+3 design. The primary endpoint was to determine the maximum tolerated dose and/or recommended Phase 2 dose (RP2D) based on dose limiting toxicities (DLT), safety and tolerability. Secondary endpoints included pharmacokinetics (PK), pharmacodynamics (PD) and preliminary signals of efficacy. Eligible patients were adults with advanced solid tumors refractory to standard therapies with ECOG Performance Status <2, adequate organ function, and measurable disease (RECIST 1.1 or RANO [gliomas]). IM156 was administered orally every other day (QOD) or daily (QD) in 28-day cycles. Results: 22 patients (gastric cancer: N = 8; ovarian cancer: N = 3; colorectal cancer: N = 3; endometrial cancer: N = 2; sarcoma: N = 2; other: N = 4) were enrolled in 7 dose cohorts (100, 200, 400, 800, and 1,200 mg QOD; 800 and 1,200 mg QD). The most frequent treatment-related adverse events (TRAEs) were gastrointestinal (nausea [N = 16, 73%], diarrhea [N = 12, 55%], and vomiting N = 11, 50%]). Nausea, reported in 3 (14%) patients, was the only Grade 3 TRAE. No DLTs were reported; the RP2D declared was 800 mg as 1,200 mg QD was associated with Grade 2/3 nausea requiring dose modifications. PK demonstrated dose-proportional increases in Cmax and AUC0-last reaching the expected efficacious range. PD demonstrated a decrease in tumor growth rate in 3 patients (1,200 mg QOD: N = 2; 800 mg QD: N = 1), and a decrease in VEGF and tumor markers in a patient with gastric cancer with neuroendocrine differentiation treated at 800 mg QD who remains on study in Cycle 11. Best response was stable disease in 7 (32%) patients. Conclusions: IM156 is the first PC1 OXPHOS inhibitor to have been successfully tested in patients with cancer with the identification of a RP2D. It was well tolerated at dose levels active in preclinical models, and demonstrated modest clinical activity in an unselected population of patients. Subsequent development will focus on OXPHOS-dependent tumors and in combinations with agents in which OXPHOS metabolism is a mechanism of resistance. Clinical trial information: NCT03272256 .

Repression of LKB1 by miR-17∼92 Sensitizes MYC-Dependent Lymphoma to Biguanide Treatment

Cancer cells display metabolic plasticity to survive stresses in the tumor microenvironment. Cellular adaptation to energetic stress is coordinated in part by signaling through the liver kinase B1 (LKB1)-AMP-activated protein kinase (AMPK) pathway. Here, we demonstrate that miRNA-mediated silencing of LKB1 confers sensitivity of lymphoma cells to mitochondrial inhibition by biguanides. Using both classic (phenformin) and newly developed (IM156) biguanides, we demonstrate that elevated miR-17∼92 expression in Myc+ lymphoma cells promotes increased apoptosis to biguanide treatment in vitro and in vivo. This effect is driven by the miR-17-dependent silencing of LKB1, which reduces AMPK activation in response to complex I inhibition. Mechanistically, biguanide treatment induces metabolic stress in Myc+ lymphoma cells by inhibiting TCA cycle metabolism and mitochondrial respiration, exposing metabolic vulnerability. Finally, we demonstrate a direct correlation between miR-17∼92 expression and biguanide sensitivity in human cancer cells. Our results identify miR-17∼92 expression as a potential biomarker for biguanide sensitivity in malignancies.

Cardiovascular safety profile of VT-464 in patients (pts) with castrate-resistant prostate cancer (CRPC)

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Background: VT-464 is a dual selective inhibitor of CYP17,20 lyase and an androgen receptor antagonist in development for the treatment of CRPC. In early clinical testing, several pts receiving VT-464 in 28-day cycles were noted to have syncopal, pre-syncopal or vaso-vagal episodes with typical prodromes. To further evaluate these events, Holter monitoring (HM) was performed in pts enrolled in two clinical studies. Methods: Continuous HM was performed at Screening, after the first dose of VT-464 C1D8, and C2D1 for study INO-VT-464-CL-001; and at Screening, after the first dose of VT-464, and C2D1 for study INO-VT-464-CL-004. The Screening visit HM data was considered the baseline. Plasma levels of VT-464 (in selected pts) and 12-lead ECGs of 10-seconds duration were extracted in triplicate for each pt from the HM data at Baseline, Day 1 and C2D1 at multiple time points. Results: 57 pt screened for VT-464 treatment, underwent HM. Nonsustained ventricular tachycardia (NSVT) was seen in 6 pts (11%) prior to VT-464, providing a background estimate in this population. 37 pts were treated with VT-464 and had > 1 post-screen HM; 4 pts (11%; all with cardiac disorders) had post-treatment NSVT (all < 5 beats); no episodes of sustained VT were seen. 28 pts had ECG data extracted from HMs that coincided with peak plasma levels of VT-464. There was no QTcF or QRS prolongation; increases in the HR (mean 13.1-19.5 BPM but with a non-significant VT-464 concentration/HR relationship) and small PR increases (mean 32.9 ms; partially driven by several pts) without second degree AV block were observed. Conclusions: VT -464 did not prolong QTcF or QRS intervals and the lack of a significant exposure response HR analysis suggests that the HR increases may not be drug related. The PR prolongation is unlikely to be clinical significance. HM showed a frequency of NSVT consistent with background frequency for this pt population.A detailed examination of study pts experiencing syncope or presyncope revealed these to likely be vasovagal in nature, consistent with the increased vagal tone observed in nonclinical testing. There does not appear to be a pro-arrhythmogenic potential of VT-464 based on data from both nonclinical and clinical assessments. Clinical trial information: NCT02361086.

Abstract PR01: Rebastinib, a selective TIE2 kinase inhibitor, decreases TIE2-expressing macrophages, reduces metastasis, and increases survival in murine cancer models

In the tumor microenvironment, TIE2 expression on tissue macrophages, bone marrow derived TIE2-expressing monocytes (TEMs), osteoclasts, and vascular endothelial cells promotes tumor invasiveness, dissemination, and metastasis. Additionally, a subset of TIE2-expressing macrophages, located within specialized vascular structures known as tumor microenvironment for metastases (TMEMs), are linked to intravasation of cancer cells into circulation and dissemination to metastatic sites. Rebastinib is a picomolar inhibitor of TIE2 kinase, and exhibits an extraordinarily long off-rate from TIE2, measured to be over 24 hours in a cell-based assay. Herein, we examine the efficacy of rebastinib in the polyoma middle-T antigen (PyMT) syngeneic mouse breast cancer model. In this model, PyMT breast cancer cells are implanted in the mammary fat pad, and primary tumor growth leads to lung metastasis, which is known to be modulated by TEMs and TMEM vascular structures. We examined multiple dosing schedules of rebastinib in combination with anti-tubulin agents (ATAs). Rebastinib treatment in this model significantly ablated TEMs in the primary tumor stroma and caused a significant decrease in lung metastases. Furthermore, the combination of rebastinib with ATAs, even with once or twice weekly oral dosing of rebastinib, led to a significant further decrease in lung metastases compared to single-agent treatment with ATAs. Rebastinib also enhanced the activity of ATAs in reducing primary tumor growth and regrowth of tumor post-resection. TIE2 inhibition with targeted therapy represents a novel treatment approach for metastatic breast cancer and other cancers that rely on TEMs and TMEMs for growth and metastasis. As such, rebastinib has been selected for further clinical development in solid tumors with a Phase 1b trial being planned for 2014.

This abstract is also presented as Poster A5.

Citation Format: Daniel L. Flynn, Michael D. Kaufman, Cynthia B. Leary, Molly M. Hood, Wei-Ping Lu, Benjamin A. Turner, Scott C. Wise, Marc S. Rudoltz, Bryan D. Smith. Rebastinib, a selective TIE2 kinase inhibitor, decreases TIE2-expressing macrophages, reduces metastasis, and increases survival in murine cancer models. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr PR01. doi:10.1158/1538-7445.CHTME14-PR01

Phase 1 Study of Weekly Polyethylene Glycol-Camptothecin in Patients with Advanced Solid Tumors and Lymphomas

PURPOSE

To determine the maximal tolerated dose and dose-limiting toxicities (DLT) of pegamotecan (polyethylene glycol-camptothecin) in patients with advanced malignancies when administered in cycles of once weekly for 3 of 4 weeks.

EXPERIMENTAL DESIGN

Eligible patients had advanced solid tumors that failed to respond to standard therapy or for which no standard therapy was available, including also the following criteria: measurable disease, Eastern Cooperative Oncology Group performance status of < or =2, and acceptable organ function. Pegamotecan was administered as a 60-minute infusion, with successive patient cohorts receiving escalating doses from 800 to 4,300 mg/m(2). The primary end point was to determine the maximal tolerated dose. Other end points were toxicity, pharmacokinetics, pharmacodynamics, and efficacy. Pharmacokinetic analysis measured free camptothecin. Pharmacodynamic analysis correlated drug effects with pegamotecan dose and pharmacokinetic variables.

RESULTS

Twenty-seven patients were enrolled. The maximal tolerated dose was 3,240 mg/m(2). Grade 4 neutropenia, the DLT, was noted in two of four patients treated at 4,300 mg/m(2). Other grade 3 and 4 toxicities were anemia, thrombocytopenia, fatigue, prolonged partial thromboplastin time, hemorrhagic cystitis, dysuria, and urinary frequency. Pharmacokinetic analysis showed the apparent terminal elimination half-life to be 46 +/- 12.8 hours. Pharmacodynamic analysis showed that hematuria occurred in 8 of 15 patients with an area under the curve extrapolated to infinity (AUC(0-infinity)) > 20 ng h/mL and 0 of 10 patients with an AUC(0-infinity) < or = 20 ng h/mL. Unconfirmed partial responses were observed in two patients, one with metastatic small bowel adenocarcinoma and the other with metastatic esophageal cancer.

CONCLUSIONS

The maximal tolerated dose of pegamotecan when administered weekly for 3 of 4 weeks is 3,240 mg/m(2). The DLT was neutropenia. Among nonhematologic toxicities, the incidence of gastrointestinal toxicity was low, but genitourinary toxicity seems to occur in the same effective dose range as noted with native camptothecin in earlier trials (27-43 mg/m(2)). The observed antitumor activity suggests that pegamotecan has single-agent activity and merits further investigation in phase 2 studies.

High-dose-rate brachytherapy for primary carcinomas of the oral cavity and oropharynx

OBJECTIVE

Local control for patients treated with primary radiation therapy for tumors of the oral cavity is improved using low-dose-rate brachytherapy. Oropharyngeal carcinomas have also been treated with brachytherapy. The few reports in the literature regarding high-dose-rate brachytherapy (HDRBT) for head and neck cancer involve small numbers of patients and often contain a mix of palliative and curative cases. The purpose of this study is to evaluate the feasibility of HDRBT in the largest reported cohort of primary head and neck cancer patients treated with primary radiation therapy.

STUDY DESIGN

This is a prospective nonrandomized study.

METHODS

Fifty-five patients with primary untreated squamous cell carcinomas of the oral cavity and oropharynx were analyzed. There were 16 patients with T1, 26 with T2, 8 with T3, and 5 with T4 tumors. All patients received external-beam radiotherapy (EBRT) followed by HDRBT. Thirty-eight patients received hyperfractionated (twice daily) EBRT followed by HDRBT two or three times daily. Patients with cervical adenopathy also received hyperthermia and an electron boost to the site(s) of positive nodes. Median follow-up was 2.7 years. Toxicity and local control were analyzed. Data were analyzed by the Kaplan-Meier life-table method with statistical significance determined by the X2 and log-rank tests.

RESULTS

High-dose-rate brachytherapy was extremely well tolerated. Only 9 patients (16%) developed a complication. Four patients developed osteoradionecrosis, and five developed soft tissue necrosis, all of which healed with conservative medical management. No complication required surgical intervention or hospitalization. Actuarial 2-year local control for the entire cohort was 79%. Local control was 87% for patients with T1 (15/16) and T2 (22/26) tumors versus 47% for T3 (5/8) and T4 (2/5) tumors (P < .01).

CONCLUSIONS

High-dose-rate brachytherapy is feasible as a boost for patients with primary squamous cell carcinomas of the oral cavity and oropharynx. Patients with T1 and T2 tumors fared exceptionally well; those with advanced tumors may require more aggressive treatment, such as higher radiation doses, surgical resection, or systemic chemotherapy. The use of HDRBT both shortens the overall treatment time and limits the volume of tissue exposed to high doses of radiation therapy. In the future, as more patients treated with HDRBT are evaluable, we hope to identify potential factors that predict for local control so that we may select patients optimally for this treatment.

Significance of pretreatment hemoglobin level in patients with T1 glottic cancer

Recent reports have suggested that pretreatment hemoglobin level (Hgb) is significantly associated with local control (LC) and overall survival (OS) in patients with T1 and T2 squamous cell carcinoma of the glottic larynx. To further evaluate the association of pretreatment Hgb level and other factors with outcome, we performed a retrospective review limited to patients with T1 squamous cell carcinoma of the glottic larynx treated with external beam radiation therapy. One-hundred thirty-nine patients with T1 squamous cell carcinoma of the glottic larynx were analyzed. Median follow-up was 5 years (range 2-22). Median pretreatment Hgb was 14.4 gm/dl (range 8.2-17.2). The following parameters were analyzed for their impact on LC, OS, and disease specific survival (DSS): age; gender; pretreatment Hgb; tumor grade; anterior commissure involvement; field size; total dose; dose per fraction; and overall treatment time. Five-year actuarial LC was 84%. Pretreatment Hgb was not a significant predictor for LC when assessed as a continuous variable (P = 0.38), nor as a dichotomous variable with a cutoff at 13 gm/dl. Local control was 82% for patients with Hgb >13 vs. 92% for Hgb < or = 13 (P= 0.13). No other factor was significant for LC. Five-year actuarial OS was 74%. Univariate analysis revealed that, pretreatment Hgb, total dose, and patient age were significant factors for OS. Overall survival was 78% for patients with pretreatment Hgb > 13 gm/dl vs. 68% for patients with Hgb < or = 13 gm/dl (P = 0.004). Overall survival was 77% for patients treated with > 66 Gy vs. 67% for those treated with < or =66 Gy (P = 0.0013), and 80% for patients < or =61 years as opposed to 69% for patients older than 61 years (P = 0.017). Multivariate analysis revealed that only age (P = 0.014) and Hgb concentration (P = 0.001) retained significance. Five-year actuarial DSS was 92%. Pretreatment Hgb was not a prognostic factor for DSS, nor were any other analyzed factors. Pretreatment Hgb is not a significant prognostic factor for LC in patients with T1 squamous cell carcinoma of the glottic larynx, but it does predict for a poorer OS without affecting DSS. This suggests that patients with lower pretreatment Hgb may have confounding medical problems that detract from their overall survival.

Second malignant neoplasia in patients with T1 glottic cancer treated with radiation

OBJECTIVE/HYPOTHESIS

To evaluate incidence, site of occurrence and outcome of second malignant neoplasia (SMN) in patients with T1 glottic cancer treated with radiation.

STUDY DESIGN

Retrospective.

METHODS

Between February 1964 and May 1993, 158 patients with T1 squamous carcinoma of the larynx were treated with definitive radiation. Incidence, site (aerodigestive tract or not) and outcome of SMN were analyzed. Median follow-up was 63 months (range, 12-245 mo).

RESULTS

Thirty-four patients developed SMN, for an overall incidence of 22%. Twenty-four (67%) SMNs occurred in an aero-upper-digestive-tract site compared with nine (25%) occurring in a non-aero-upper-digestive tract site. The incidence of SMN observed was higher than would be expected for the general population at risk. The observed-to-expected ratios (OER) for all SMN, aero-upper-digestive SMN and non-aero-upper-digestive SMNs were 1.73, 5.53, and 0.62, respectively. Overall 5- and 10-year survivals were 76% and 57%, respectively, for those who did not develop SMN, as compared with 68% and 26%, for those who developed SMN (P = .003). Overall, 13 patients (8.2%) have died from laryngeal cancer, while 23 (15%) died from SMN (P = .001).

CONCLUSION

This study confirms a higher incidence of SMN in T1 glottic cancer patients, compared with the general population. The majority of cases occur in aero-upper-digestive sites. These patients are more likely to die from their SMN than from glottic cancer. Patients with T1 squamous cell carcinoma of the glottic larynx represent a group of head and neck cancer patients who should be targeted in studies evaluating the potential benefits of chemoprevention, and aggressively counseled for social and/or behavioral modifications.

Multiple causes of cerebrovascular events in children with tumors of the parasellar region

Cerebrovascular arterial occlusion is a rare but devastating event causing long-term morbidity in children with tumors in the parasellar region. While usually associated with radiation therapy, there are a variety of host, tumor and treatment factors which predispose patients to significant vasculopathy. Case reports of 5 patients from St. Jude Children's Research Hospital with tumors in the parasellar region who presented with or developed vascular occlusive disease are summarized. Multiple factors are identified in these cases which probably impacted on the development of cerebral arterial occlusion with or without moyamoya syndrome. These include, but are not limited to, neurofibromatosis, tumor encasement of major cerebral vessels, surgical alterations, and radiation therapy. The literature supports multiple, potentially interactive etiologies for the development of vascular events in these patients, suggesting that their development is not simply a phenomenon related to radiation therapy.

The molecular regulation of apoptosis and implications for radiation oncology

One of the major goals of cancer research is to identify and understand the causes of cellular proliferation. The role of cell death, or lack thereof, in carcinogenesis, tumour growth, metastatic spread and response to treatment has been largely overlooked even though the morphology of apoptosis (programmed cell death) was clearly described over 20 years ago, and its importance in cancer speculated on at that time. Over the last 5 years, however, an explosion of research has focused on delineating the molecular components of the apoptotic pathways and examining the role of apoptosis in a tumour's growth and response to treatment. This review highlights the aspects of apoptosis most relevant to radiation oncologists and radiobiologists. The apoptotic pathways will be described, with attention to the stimuli that initiate apoptosis, the oncogenes and tumour suppressor genes that mediate apoptosis, and the effector enzymes (proteases and endonucleases) responsible for the execution of apoptosis. In addition, we review the effect of classically described radiobiology cell survival parameters-cell cycle stage, dose rate, linear energy transfer, oxygen, total dose, and fractionation-on radiation induced apoptosis.

Regulation of radiation-induced apoptosis in oncogene-transfected fibroblasts: influence of H-ras on the G2 delay

Primary fibroblasts, after serum withdrawal or after irradiation, do not undergo apoptosis. Myc-transfected fibroblasts, in contrast, undergo apoptosis upon serum withdrawal and after irradiation. We have studied the relationship of apoptosis induction to effects on the G2 phase cell cycle in a series of rat embryo cells transformed by rasH plus myc or immortalized by myc alone. In this system, while the presence of rasH had little effect on the extent of apoptosis induction by serum withdrawal, rasH greatly suppressed the apoptotic response of myc-transfected cells to X-rays. The cells into which rasH had been introduced showed a profound G2 arrest associated with suppression of cyclin B1 mRNA expression. In contrast, cells with myc alone had a minimal G2 delay after irradiation and no suppression of cyclin B1 mRNA expression. We hypothesize that rasH, by influencing the G2 response of cells to X-rays, exerts an anti-apoptotic effect. In support of this hypothesis; we found that treatment of cells with caffeine, an agent that relieves the G2 delay after irradiation resulted in increased apoptosis in the irradiated cells, but not in control cells.

Radiotherapy for Merkel cell carcinoma of the skin of the head and neck

BACKGROUND

Merkel cell carcinoma is a relatively rare neuroendocrine carcinoma of the skin. It arises in the head and neck region in approximately 50% of cases. Its aggressive behavior predisposes patients to local-regional recurrence and distant metastases after surgical excision alone. In this article, we describe our experience with Merkel cell carcinoma of the head and neck.

METHODS

Of 18 patients with Merkel cell carcinoma treated in the Department of Radiation Oncology at the University of Florida, 12 patients who had primary tumors in the head and neck region are reported. Eight patients were treated at initial diagnosis (group A), and four were treated at the time of local-regional recurrence (group B).

RESULTS

Local-regional control was achieved in seven of eight patients in group A and all four patients in group B. One patient in group A and all patients in group B developed distant metastases and eventually died of their disease. Bone exposure developed in one patient, requiring surgical debridement and hyperbaric oxygen treatment.

CONCLUSION

Patients with Merkel cell carcinoma of the head and neck should be treated aggressively. Our data suggest that local-regional recurrence is a harbinger of distant metastases. We recommend that these patients receive treatment to both the primary site and draining lymphatics at initial presentation. The role of chemotherapy remains unclear.

Does pathologic node status affect local control in patients with carcinoma of the head and neck treated with radical surgery and postoperative radiotherapy?

PURPOSE

To evaluate the effect of pathologic lymph node status and nodal stage on local control at the primary site in patients with advanced squamous cell carcinomas of the head and neck, treated with radical surgery and postoperative irradiation.

METHODS AND MATERIALS

Fifty-seven patients with advanced squamous cell carcinomas of the oral cavity, oropharynx, hypopharynx, larynx, and supraglottic larynx were analyzed. All patients underwent resection of the primary lesion, neck dissection, and postoperative radiotherapy. Minimum follow-up was 2 years. The median dose to the primary tumor bed was 60.4 Gray (range 39.7-72.0). Besides pathologic nodal status (pN0 vs. pN+) and nodal stage, the following factors were analyzed for their impact on local control: age, gender, T stage, tumor grade, resection margins, interval from surgery to irradiation, dose to the primary site, and overall treatment time.

RESULTS

The 3-year actuarial local control rate was 78%. When all patients were analyzed, nodal status (pN0 vs. pN+) did not affect control at the primary site (71% vs. 82%, p = 0.42). Nodal stage (pN0-N2a va. pN2b-N2c) was also not a significant factor for local control (74% vs. 82%, p = 0.57). When only patients with negative margins were analyzed, nodal status again did not impact on local control (79% vs. 90% for pN0 vs. pN+, p = 0.39). On univariate analysis, only tumor grade, margin status, and elapsed days were significant factors for local control. Local control was 85% for patients with negative margins vs. 60% for those with positive margins (p = 0.016). For patients with moderately and poorly differentiated tumors, local control was 86% as compared to 50% for patients with well-differentiated tumors (p = 0.007). When radiotherapy was completed within 50 days, local control was 93% as opposed to 63% for > 50 days (p = 0.016). On multivariate analysis, only margin status (p = 0.002) and tumor grade (p = 0.007) remained significant.

CONCLUSION

We conclude that neither the presence of pathologically positive nodes nor nodal stage is a prognostically significant factor for local control in patients who have undergone radical surgery and postoperative radiotherapy for advanced squamous cell carcinomas of the head and neck. We do not recommend a change in treatment philosophy, such as an increase in dose to the primary site, based on the pathologic status of the neck.

Prognostic factors for local control and survival in T1 squamous cell carcinoma of the glottis

PURPOSE

To evaluate the effect of host, tumor, and treatment-related variables on local control and survival in patients with T1N0M0 squamous cell carcinoma of the glottis.

MATERIALS AND METHODS

Ninety-one patients with T1N0M0 squamous cell carcinoma of the glottic larynx were analyzed. Median follow-up was 9 years (range 2-25). Patients were treated with daily fractions of 180 cGy to 220 cGy to doses of 5925-7000 cGy (median 6400). The following factors were analyzed: age, sex, histologic grade, disease extent, beam energy, field size, total dose, dose per fraction, and elapsed treatment days.

RESULTS

The 5-year actuarial local control was 80%. On univariate analysis, only elapsed treatment days and dose per fraction were significant factors for local control. Local control was 100% if treatment was completed within 42 days, 91% for 43-46 days, 74% for 47-50 days, 65% for 51-54 days, and 50% for 55-66 days (p = 0.0001). In patients treated at < 200 cGy per fraction, local control was 62% as compared to 87% for > or = 200 cGy per fraction (p = 0.006). On multivariate analysis, only elapsed treatment days was a significant factor for local control (p = 0.0001). The 5-year actuarial survival for the whole group was 92%. Elapsed treatment days was the only variable affecting survival. Survival was 100% if treatment was delivered within 42 days, 96% for 43-46 days, 94% for 47-50 days, 91% for 51-54 days, and 67% for 55-66 days (p = 0.02). The 5-year actuarial disease-specific survival was 95%, with treatment duration again being the only significant prognostic factor. Disease-specific survival was 97% for treatment completed within 39-54 days versus 80% for 55-66 days (p = 0.02). Only three (3.3%) patients experienced moderate or severe complications. None of the evaluated parameters impacted significantly on complications.

CONCLUSION

We conclude that elapsed days is the most prognostically significant factor for local control and survival in patients treated with radiotherapy for T1 squamous cell carcinoma of the glottis. We recommend that these patients be treated with 210 cGy daily fractions to 6300 cGy.

Application of magnetic resonance imaging and three-dimensional treatment planning in the treatment of orbital lymphoma

Radiotherapy for lymphoma of the orbit must be individualized for each patient and clinical setting. Most techniques focus on optimizing the dose to the tumor while sparing the lens. This study describes a technique utilizing magnetic resonance imaging (MRI) and three dimensional (3D) planning in the treatment of orbital lymphoma. A patient presented with an intermediate grade lymphoma of the right orbit. The prescribed tumor dose was 4050 cGy in 18 fractions. Three D planning was carried out and tumor volumes, retina, and lens were subsequently outlined. Dose calculations including dose volume histograms of the target, retina, and lens were then performed. Part of the retina was outside of the treatment volume while 50% of the retina received 90% or more of the prescribed dose. The patient was clinically NED when last seen 2 years following therapy with no treatment-related morbidity. Patients with lymphomas of the orbit can be optimally treated using MRI based 3D treatment planning.