ImmunoPET and near-infrared fluorescence imaging of CD105 expression using a monoclonal antibody dual-labeled with (89)Zr and IRDye 800CW

CD105 (endoglin) is an independent marker for poor prognosis in more than 10 solid tumor types. The goal of this study was to develop a CD105-specific agent for both positron emission tomography (PET) and near-infrared fluorescence (NIRF) imaging, which has potential clinical applications in the diagnosis and imaged-guided resection of solid tumors. TRC105, a chimeric anti-CD105 monoclonal antibody, was conjugated to a NIRF dye (800CW) and p-isothiocyanatobenzyl-desferrioxamine (Df-Bz-NCS) before (89)Zr-labeling. Another chimeric antibody, cetuximab, was used as an isotype-matched control. FACS analysis revealed no difference in CD105 binding affinity/specificity between TRC105 and Df-TRC105-800CW. Serial PET imaging revealed that the 4T1 tumor uptake of (89)Zr-Df-TRC105-800CW was 6.3 ± 1.9, 12.3 ± 1.3, and 11.4 ± 1.1 %ID/g at 4, 24, and 48 h post-injection (p.i.) respectively (n = 3), higher than all organs starting from 24 h p.i., which provided excellent tumor contrast. Tumor uptake as measured by both in vivo and ex vivo NIRF imaging had a linear correlation with the %ID/g values obtained from PET, corroborated by biodistribution studies. Blocking experiments, control studies with (89)Zr-Df-cetuximab-800CW, and histology all confirmed the CD105 specificity of (89)Zr-Df-TRC105-800CW. In conclusion, herein we report dual-modality PET and NIRF imaging of CD105 expression in a breast cancer model, where CD105-specific uptake of (89)Zr-Df-TRC105-800CW in the tumor was observed.

Multimodality imaging of breast cancer experimental lung metastasis with bioluminescence and a monoclonal antibody dual-labeled with 89Zr and IRDye 800CW

Metastatic breast cancer is incurable. The goal of this study was to develop a positron emission tomography (PET)/near-infrared fluorescent (NIRF) probe for imaging CD105 expression in breast cancer experimental lung metastasis. TRC105, a chimeric anti-CD105 antibody, was dual-labeled with a NIRF dye (IRDye 800CW) and (89)Zr to yield (89)Zr-Df-TRC105-800CW. Luciferase-transfected 4T1 murine breast cancer cells were injected intravenously into female mice to establish the tumor model. Bioluminescence imaging (BLI) was carried out to noninvasively monitor the lung tumor burden. PET imaging revealed that 4T1 lung tumor uptake of (89)Zr-Df-TRC105-800CW was 8.7 ± 1.4, 10.9 ± 0.5, and 9.7 ± 1.1% ID/g at 4, 24, and 48 h postinjection (n = 4), with excellent tumor contrast. Biodistribution studies, blocking, control studies with (89)Zr-Df-cetuximab-800CW, ex vivo BLI/PET/NIRF imaging, and histology all confirmed CD105 specificity of the tracer. Broad clinical potential of TRC105-based agents was shown in many tumor types, which also enabled early detection of small metastasis and intraoperative guidance for tumor removal.

A phase I first-in-human study of TRC105 (Anti-Endoglin Antibody) in patients with advanced cancer

PURPOSE

TRC105 is a chimeric IgG1 monoclonal antibody that binds CD105 (endoglin). This first-in-human, phase I, open-label study assessed safety, pharmacokinetics, and antitumor activity of TRC105 in patients with advanced refractory solid tumors.

PATIENTS AND METHODS

Patients received escalating doses of intravenous TRC105 until disease progression or unacceptable toxicity using a standard 3 + 3 phase I design.

RESULTS

Fifty patients were treated with escalating doses of TRC105. The maximum tolerated dose (MTD) was exceeded at 15 mg/kg every week because of dose-limiting hypoproliferative anemia. TRC105 exposure increased with increasing dose, and continuous serum concentrations that saturate CD105 receptors were maintained at 10 mg/kg weekly (the MTD) and 15 mg/kg every 2 weeks. Common adverse events including anemia, telangiectasias, and infusion reactions reflected the mechanism of action of the drug. Antibodies to TRC105 were not detected in patients treated with TRC105 from Chinese hamster ovary cells being used in ongoing phase Ib and phase II studies. Stable disease or better was achieved in 21 of 45 evaluable patients (47%), including two ongoing responses at 48 and 18 months.

CONCLUSION

TRC105 was tolerated at 10 mg/kg every week and 15 mg/kg every 2 weeks, with a safety profile that was distinct from that of VEGF inhibitors. Evidence of clinical activity was seen in a refractory patient population. Ongoing clinical trials are testing TRC105 in combination with chemotherapy and VEGF inhibitors and as a single agent in prostate, ovarian, bladder, breast, and hepatocellular cancer.

Dose-specific clearance of TRC105 (anti-CD105 antibody) in advanced solid tumor patients

3042^

Background: CD105 is an endothelial cell membrane receptor highly expressed on angiogenic tumor vessels. TRC105 is an anti-CD105 monoclonal antibody that inhibits angiogenesis and tumor growth by endothelial cell growth inhibition, ADCC and apoptosis. Methods: Patients with advanced solid tumors and normal organ function were treated with escalating doses of intravenously administered TRC105 and assessed for safety and pharmacokinetics (PK). PK parameters for determining dose-linearity were estimated following single doses on in 16 patients at 3, 10 and 15 mg/kg and correlated with safety. Results: TRC105 was tolerated at 10 mg/kg weekly and 15 mg/kg every 2 weeks, but hyproliferative anemia was dose-limiting at 15 mg/kg weekly and was associated with TRC105 accumulation in serum from target saturation. Preliminary evidence of activity was observed with 21 of 45 evaluable patients progression-free at 2 months, including two ongoing responders. The AUC-single dose relationship of TRC105 revealed supra-proportionality in serum exposure at 15 mg/kg compared to 3 and 10 mg/kg. Dose proportionality using a power model revealed a nonlinear pharmacokinetic process (log[AUC] = 0.125*Dose+2.67, r2 = 0.92, ANOVA p<0.0035). The steady state volume of distribution was low (≈ 5.40 L/70kg) indicating TRC105 was confined to the vasculature with a low capacity target (i.e., low relative abundance) making it susceptible to saturation. The post-infusion Cmax however was linearly related to dose (r = 0.85) which suggested the nonlinearity in clearance was attributed to target-mediated disposition. The nonlinear disposition in the presence of low distribution indicated TRC105 bound avidly to endothelial cells. Concentrations expected to saturate CD105 binding were achieved continuously at 15 mg/kg dosed every 2 weeks and 10 mg/kg/wk. TRC105 accumulated at 15 mg/kg/wk as the accumulation factor at 56 days was 1.77-fold over single doses on C1D1. Conclusions: TRC105 clearance decreased above the MTD resulting in drug accumulation and hypoproliferative anemia with weekly dosing. The nonlinearity in clearance was attributed to saturating target-mediated disposition, consistent with binding to proliferating endothelial cells.

A phase Ib dose-escalation study of TRC105 in combination with bevacizumab for advanced solid tumors

3034

Background: CD105 (endoglin) is an endothelial cell membrane receptor highly expressed on angiogenic tumor vessels that is essential for angiogenesis and upregulated by hypoxia and VEGF inhibition. TRC105 is a human/mouse chimeric anti-CD105 monoclonal antibody that completed phase I testing and is being studied in multiple phase II trials. Methods: Pts with advanced solid tumors (non-CNS), ECOG PS 0-1, and normal organ function were treated with escalating doses of intravenously administered TRC105 plus bevacizumab (BEV) at 15 mg/kg q3wk or 10 mg/kg q2wk and assessed for safety, PK, and response. Results: Twelve pts were treated (3 with TRC105 at 3 mg/kg q1wk + BEV at 15 mg/kg q3wk, 5 with TRC105 at 6 mg/kg q1wk + BEV at 15 mg/kg q3wk, and 4 with TRC105 at 6 mg/kg q1wk + BEV at 10 mg/kg q2wk), and 10 have completed the DLT evaluation period. TRC105 at 6 mg/kg q1wk + BEV at 15 mg/kg q3wk resulted in grade 1-3 headaches with sinus congestion following the cycle 1 day 1 (C1D1) dose in 5 of 5 pts that improved with continued dosing. Treatment with BEV 10 mg/kg q2wk and sequential dosing with Bev starting on C1D1 and TRC105 on C1D8 resulted in decreased frequency and severity of headaches, allowing dose escalation to continue. TRC105 serum concentrations that saturate CD105 binding sites (>200 ng/mL) were achieved continuously at 6 mg/kg q1wk. At 3 mg/kg q1wk TRC105 + 15 mg/kg q3wk BEV, one pt with BEV-resistant ovarian cancer had stable disease for 6 cycles and one pt with refractory hepatocellular cancer who failed sorafenib and sunitinib had an AFP decrease from 1578 at baseline to 179 at the end of cycle 3. Two of three evaluable pts at 6 mg/kg q1wk TRC105 + 15 mg/kg q3wk BEV with VEGF-refractory tumors (HCC and CRC) are ongoing in C4 with stable disease. Dose escalation continues and TRC105 dose levels of 8 and 10 mg/kg are planned. Conclusions: The combination of TRC105 and BEV was tolerated with early evidence of activity in VEGF-refractory pts by sequential administration during initial dosing in C1.

Modulation of angiogenic biomarkers in patients receiving high-dose TRC105

e21038

Background: TRC105, an anti-CD105 monoclonal antibody, has completed phase 1 testing and is being studied in multiple phase 2 trials. We previously reported that low dose TRC105 (0.01-1.0 mg/kg) modulated the expression of soluble angiogenic biomarkers in patients [J Clin Oncol 29: 2011 (suppl; abstr 10565)]. In this report, we evaluated angiogenic biomarkers in patients receiving higher doses of TRC105 including the recommended phase 2 dose. Methods: Patients with advanced refractory solid tumors were treated with escalating doses of TRC105 until disease progression. Serial plasma samples were analyzed via an optimized multiplex ELISA platform. 36 biomarkers related to tumor growth, angiogenesis, and inflammation were assayed at baseline (BL), after 1 month (C2D1), concurrent with radiological restaging near the end of cycle 2 (C2D22), and at end of study (EOS). Results: 32 patients treated with TRC105 at doses of 0.3 to 15 mg/kg were evaluated for biomarker expression. Wilcoxon signed rank tests indicated that the following analytes were significantly different at C2D1 when compared with baseline (p<0.05): Ang-2, IGFBP-3, total PAI-1, PDGF-AA, PDGF-BB, TSP-1, VEGF-D were all down-regulated; and E-Cadherin, soluble CD105, E-Selectin, IL-6, OPN, TSP-2, vWF were all up-regulated. At EOS, significant increases from C2D1 were observed for the following analytes: Ang-2, CRP, ICAM-1, IGFBP-1, IL-6, TSP-2, and VCAM-1 (p<0.05). Additionally, dose-dependent increases in soluble CD105 at C2D1 were observed (p<0.0001, r=0.9), suggesting direct target modulation by TRC105. Conclusions: TRC105 therapy is associated with early down-regulation of certain key angiogenic biomarkers and a dose-dependent increase in sCD105. Increases in many initially down-regulated angiogenic factors were observed at the time of progression, suggesting possible mechanisms for acquired resistance to TRC105. Further analysis of TRC105 in specified patient populations is underway and may provide more insight into the biological effects of this drug.

Positron emission tomography imaging of CD105 expression with a 64Cu-labeled monoclonal antibody: NOTA is superior to DOTA

Optimizing the in vivo stability of positron emission tomography (PET) tracers is of critical importance to cancer diagnosis. In the case of ⁶⁴Cu-labeled monoclonal antibodies (mAb), in vivo behavior and biodistribution is critically dependent on the performance of the bifunctional chelator used to conjugate the mAb to the radiolabel. This study compared the in vivo characteristics of ⁶⁴Cu-labeled TRC105 (a chimeric mAb that binds to both human and murine CD105), through two commonly used chelators: 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) and 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). Flow cytometry analysis confirmed that chelator conjugation of TRC105 did not affect its CD105 binding affinity or specificity. PET imaging and biodistribution studies in 4T1 murine breast tumor-bearing mice revealed that ⁶⁴Cu-NOTA-TRC105 exhibited better stability than ⁶⁴Cu-DOTA-TRC105 in vivo, which resulted in significantly lower liver uptake without compromising the tumor targeting efficiency. In conclusion, this study confirmed that NOTA is a superior chelator to DOTA for PET imaging with ⁶⁴Cu-labeled TRC105.

Positron emission tomography imaging of CD105 expression with 89Zr-Df-TRC105

PURPOSE

High tumor microvessel density correlates with a poor prognosis in multiple solid tumor types. The clinical gold standard for assessing microvessel density is CD105 immunohistochemistry on paraffin-embedded tumor specimens. The goal of this study was to develop an (89)Zr-based PET tracer for noninvasive imaging of CD105 expression.

METHODS

TRC105, a chimeric anti-CD105 monoclonal antibody, was conjugated to p-isothiocyanatobenzyl-desferrioxamine (Df-Bz-NCS) and labeled with (89)Zr. FACS analysis and microscopy studies were performed to compare the CD105 binding affinity of TRC105 and Df-TRC105. PET imaging, biodistribution, blocking, and ex-vivo histology studies were performed on 4T1 murine breast tumor-bearing mice to evaluate the pharmacokinetics and tumor-targeting of (89)Zr-Df-TRC105. Another chimeric antibody, cetuximab, was used as an isotype-matched control.

RESULTS

FACS analysis of HUVECs revealed no difference in CD105 binding affinity between TRC105 and Df-TRC105, which was further validated by fluorescence microscopy. (89)Zr labeling was achieved with high yield and specific activity. Serial PET imaging revealed that the 4T1 tumor uptake of (89)Zr-Df-TRC105 was 6.1 ± 1.2, 14.3 ± 1.2, 12.4 ± 1.5, 7.1 ± 0.9, and 5.2 ± 0.3 %ID/g at 5, 24, 48, 72, and 96 h after injection, respectively (n = 4), higher than all organs starting from 24 h after injection, which provided excellent tumor contrast. Biodistribution data as measured by gamma counting were consistent with the PET findings. Blocking experiments, control studies with (89)Zr-Df-cetuximab, and ex-vivo histology all confirmed the in vivo target specificity of (89)Zr-Df-TRC105.

CONCLUSION

We report here the first successful PET imaging of CD105 expression with (89)Zr as the radiolabel. Rapid, persistent, CD105-specific uptake of (89)Zr-Df-TRC105 in the 4T1 tumor was observed.

Abstract B62: A phase 1 study of oral TRC102 (methoxyamine), an inhibitor of base-excision repair, to potentiate the therapeutic effects of pemetrexed in patients with advanced refractory cancer

Background: TRC102 is a small molecule inhibitor of base-excision repair (BER) that is highly water soluble and nearly completely bioavailable after oral administration. TRC102 potentiates the cytotoxicity of alkylator and antimetabolite chemotherapy and reverses chemotherapy resistance by rapidly and covalently binding to chemotherapy-induced abasic sites. TRC102-bound DNA is no longer a substrate for BER enzymes and is instead cleaved by topoisomerase II resulting in double-strand breaks that trigger apoptosis.

Methods: This Phase 1 trial evaluated the safety, PK, and PD of oral TRC102 combined with intravenous pemetrexed in patients with advanced refractory cancer. Patients were required to have ECOG PS ≤ 1 and adequate organ function. TRC102 was escalated in cohorts of 3–6 evaluable patients in combination with standard-dose pemetrexed. All patients received TRC102 alone on Days 1–4 of a 2-week cycle followed by the combination of TRC102 (D1–4) and pemetrexed (D1) every 3 weeks thereafter.

Results: 20 patients were treated with a total of 65 cycles of TRC102 at 15 mg/m2 (n=4), 30 mg/m2 (n=7), 60 mg/m2 (n=3) and 100 mg/m2 (n=6). 18 of the 20 patients were evaluable for safety. No adverse events were attributed to TRC102 alone up to 60 mg/m2. One of six patients treated at 100 mg/m2 experienced dose-limiting Grade 3 anemia with TRC102 alone in Cycle 1. The patient remains on study in Cycle 3 with a 50% dose-reduction of TRC102. Adverse events considered possibly related to the combination of TRC102 + pemetrexed included Grade 3–4 neutropenia without fever, Grade 3 thrombocytopenia, and Grade 1–2 fatigue and asthenia. The only other DLT was Grade 3 anemia in a patient who received 30 mg/m2 TRC102 + pemetrexed in Cycle 2. The patient remained on study through Cycle 5 with a 50% dose-reduction of TRC102. Clinical PK analyses indicated that TRC102 plasma concentrations required for in vivo activity were achieved with daily oral administration at all dose levels (Cmax &gt; 50 ng/mL, t½ &gt; 24 hr). PD studies confirmed that TRC102 binds pemetrexed-induced abasic sites in these patients. One patient with squamous cell carcinoma of the tonsillar fossa recurrent in the right lung and right hilum had RECIST-defined partial response after 2 cycles of 30 mg/m2 TRC102 + pemetrexed that is ongoing in Cycle 10. One patient with epithelial clear cell cancer of the ovary metastatic to the liver had a mixed response after 2 cycles of 30 mg/m2 TRC102 + pemetrexed. Stable disease for 9 cycles was observed in a patient with metastatic squamous cell lung cancer at 30 mg/m2 TRC102 + pemetrexed as 3rd line therapy.

Conclusion: Daily oral TRC102 for 4 days is tolerated at doses that may potentiate the clinical activity of pemetrexed in patients with advanced refractory cancer. Phase 2 studies are planned in multiple indications.

Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B62.

Phase II Study of Consolidation Paclitaxel After Concurrent Chemoradiation in Poor-Risk Stage III Non–Small-Cell Lung Cancer: SWOG S9712

Purpose

A previous Southwest Oncology Group (SWOG) study (S9429) demonstrated efficacy and tolerability of concurrent chemoradiotherapy in poor-risk stage III non–small-cell lung cancer (NSCLC). This study evaluated adding consolidation paclitaxel after chemoradiotherapy for a similar patient cohort.

Patients and Methods

Patients with histologically/cytologically determined stage III NSCLC were eligible based on performance status (PS) 2 and either low albumin or weight loss more than 10%, poor pulmonary function, or comorbidities precluding cisplatin use. Treatment was carboplatin 200 mg/m2 days 1, 3, 29, and 31, and etoposide 50 mg/m2 days 1 through 4, and 29 to 32. Beginning day 1, thoracic radiation was delivered at 1.8 Gy in 25 fractions plus 16-Gy boost (total dose, 61 Gy). Patients without disease progression received paclitaxel 175 mg/m2 every 21days for three cycles.

Results

Characteristics of 87 eligible patients were age 51 to 82 years; 57% PS 0 to 1, 43% PS 2; and 51% stage IIIA, 49% stage IIIB. Toxicities of concurrent chemoradiotherapy included grade 3 esophagitis (7%) and grade 3/4 neutropenia (43%). Fifty-four assessable patients received paclitaxel consolidation. Four treatment-related deaths occurred during chemoradiotherapy and four occurred during consolidation. Overall response rate was 53%. Median progression free- and overall survival were 6.1 and 10.2 months, respectively. One- and 2-year survival rates were 43% and 25%.

Conclusion

Compared with a previous SWOG trial in a similar patient population, the addition of consolidation paclitaxel after chemoradiotherapy resulted in increased toxicity without a survival advantage. More PS 2 patients (43% v 18%) enrolled onto S9712, which may explain increased toxicity and lack of benefit. The optimal chemoradiotherapy approach for poor-risk patients remains to be defined.

Phase I/II Study of Galiximab, an Anti-CD80 Antibody, for Relapsed or Refractory Follicular Lymphoma

Purpose

This multicenter, dose-escalation study evaluates the safety, pharmacokinetics, and efficacy of galiximab (anti-CD80 monoclonal antibody) in patients with relapsed or refractory follicular lymphoma.

Patients and Methods

Patients had follicular lymphoma that had relapsed or failed to respond to primary therapy; the majority (90%) presented with stage III or IV disease. Four weekly intravenous infusions of galiximab were administered at doses of 125, 250, 375, or 500 mg/m2.

Results

Thirty-seven patients received galiximab treatment and were evaluated for safety; 35 were assessable for response. Antibody infusions were safe and well tolerated with no dose-limiting toxicities. A total of 22 (60%) of 37 patients experienced adverse events related to galiximab. All but one of the events were grade 1 or 2; the most common were fatigue, nausea, and headache. Cytopenias were rare; only one patient experienced anemia and febrile neutropenia, which were unrelated to galiximab and resolved after treatment. No patient developed antigaliximab antibody formation. The mean serum half-life ranged from 13 to 24 days. The overall response rate was 11% (two complete responses and two partial responses). Time to best response was delayed (months 3, 6, 9, and 12). Twelve patients (34%) maintained stable disease. Nearly half of all patients (49%) had a decrease in indicator lesions. Two responders remain on study without progression (22 and 24.4 months).

Conclusion

The favorable safety profile of galiximab and evidence of single-agent biologic activity and dose-dependent pharmacokinetics support further evaluation of galiximab as a treatment for follicular lymphoma, possibly in combination with other lymphoma therapies.

Radioimmunotherapy of non-Hodgkin’s lymphoma: Clinical development of the Zevalin regimen

Zevalin (ibritumomab tiuxetan; IDEC Pharmaceuticals Corporation, San Diego, CA, USA) was approved by the United States Food and Drug Administration on February 19, 2002, following 9 years of clinical development. Six clinical studies supported the Zevalin Biologics License Application. The Zevalin regimen is indicated for the treatment of patients with relapsed or refractory low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma (NHL), and for those with follicular NHL refractory to Rituxan (rituximab, MabThera; IDEC Pharmaceuticals Corporation, San Diego, CA and Genentech, South San Francisco, CA). In the year following FDA approval, approximately 1300 patients were treated in clinical trials or with the commercially available product.

Consolidation docetaxel after concurrent chemoradiotherapy in stage IIIB non-small-cell lung cancer: phase II Southwest Oncology Group Study S9504

PURPOSE

To test the concept of taxane sequencing in combined-modality therapy, this phase II trial (S9504) evaluated consolidation docetaxel after concurrent chemoradiotherapy in patients with pathologically documented stage IIIB non-small-cell lung cancer (NSCLC). Results were compared with those of the predecessor study (S9019) with identical eligibility, staging criteria, and treatment, excepting docetaxel consolidation.

PATIENTS AND METHODS

Treatment consisted of cisplatin 50 mg/m2 on days 1, 8, 29, and 36, etoposide 50 mg/m2 on days 1 through 5 and 29 through 33, and concurrent thoracic radiotherapy (total dose of 61 Gy). Consolidation docetaxel started 4 to 6 weeks after chemoradiotherapy at an initial dose of 75 mg/m2.

RESULTS

Stage subsets (tumor-node-metastasis system) in 83 eligible patients were as follows: T4N0/1, 31 patients (37%); T4N2, 22 patients (27%), and T1-3N3, 30 patients (36%). Concurrent chemoradiotherapy was generally well tolerated, but two patients died from probable radiation-associated pneumonitis. Neutropenia during consolidation docetaxel was common (57% with grade 4) and most frequent during escalation to 100 mg/m2. Median progression-free survival was 16 months, median survival was 26 months, and 1-, 2-, and 3-year survival rates were 76%, 54%, and 37%, respectively. Brain metastasis was the most common site of failure. In S9019, median survival was 15 months and 1-, 2-, and 3-year survival rates were 58%, 34%, and 17%, respectively.

CONCLUSION

Consolidation docetaxel after concurrent chemoradiotherapy in stage IIIB NSCLC is feasible and generally tolerable, and results compare favorably with the predecessor trial S9019. Nevertheless, this study remains hypothesis-generating and does not provide definitive evidence of the benefit of this approach. Phase III trials evaluating the S9504 regimen have been initiated to validate these results.

Additional radiation absorbed dose estimates for Zevalin radioimmunotherapy

Zevalin (ibritumomab tiuxetan) radioimmunotherapy is a novel treatment for non-Hodgkin's lymphoma (NHL). The Zevalin regimen includes 5 mCi (111)In-labeled Zevalin on Day 1, followed by serial anterior and posterior planar gamma images for imaging or dosimetry. On Day 8, patients receive 0.4 mCi/kg (90)Y Zevalin for radioimmunotherapy. Both Zevalin doses are preceded by 250 mg/m(2) rituximab to clear peripheral B cells and improve biodistribution of the radiolabeled antibody. In a 143-patient, Phase III, randomized study, the Zevalin regimen produced a significantly higher overall response rate than rituximab for relapsed or refractory, low-grade, follicular, or transformed NHL (80% versus 56%, p = 0.02). Fifteen patients from the Zevalin arm of this study were randomly selected for additional radiation dosimetry. (90)Y residence times were calculated from (111)In image analysis data. MIRDOSE3.1 radiation absorbed dose estimates to normal tissues were highest for spleen, testes, and liver, with considerably lower doses reaching heart, lung, intestines, red marrow, and kidneys. Radiation absorbed doses to organs and marrow were within a safe range following administration of 0.4 mCi/kg (90)Y Zevalin.

Radiation dosimetry results from a Phase II trial of ibritumomab tiuxetan (Zevalin) radioimmunotherapy for patients with non-Hodgkin's lymphoma and mild thrombocytopenia

This was a 30-patient Phase II trial of reduced-dose (90)Y ibritumomab tiuxetan (Zevalin) RIT for patients with low-grade, follicular, or transformed B-cell NHL and mild thrombocytopenia. Patients were given an imaging dose of (111)In-labeled ibritumomab tiuxetan for dosimetry measurements. One week later, patients were administered a therapeutic dose of 0.3 mCi/kg (11 MBq/kg) (90)Y ibritumomab tiuxetan. Both (111)In- and (90)Y-labeled ibritumomab tiuxetan doses were preceded by an infusion of 250 mg/m(2) rituximab (Rituxan, MabThera) an unlabeled chimeric anti-CD20 antibody, to clear peripheral blood B cells and improve biodistribution of the radiolabeled antibody. For all 30 patients, normal organ and red marrow radiation absorbed doses were well below protocol-defined limits of 2000 cGy and 300 cGy, respectively. Median radiation absorbed doses were 48 cGy to red marrow (range: 6.5-95 cGy), 393 cGy to liver (range: 92-1581 cGy), 522 cGy to spleen (range: 165-1711 cGy), 162 cGy to lungs (41-295 cGy), and 14 cGy to kidneys (0.03-65 cGy). Though most correlative analyses were negative, certain analyses demonstrated a statistically significant correlation between the severity or duration of thrombocytopenia and pharmacokinetic or dosimetric parameters. These correlations were not consistent across the total patient population, and therefore, could not be exploited to predict hematologic toxicity.

Antiproliferative properties of toremifene on AIDS-related Kaposi's sarcoma cells

BACKGROUND

Kaposi's sarcoma (KS) is the most common neoplastic apoptosis manifestation of acquired immunodeficiency syndrome. Toremifene is known to upregulate transforming growth factor beta-1 (TGF-beta1), which is a growth-inhibitory factor for KS. We investigated the in vitro effect of toremifene on KS cells.

METHODS

MTT assay was used to measure the growth of four KS cell lines and a human umbilical vein endothelial (HUVE) cell line after incubation with toremifene. Reverse transcription polymerase chain reaction and ELISA were used to measure the level of TGF-beta1.

RESULTS

The IC(50) for the KS cells ranged from 2.2 to 3.2 microM, and 80% of the growth inhibition occurred within 24 h. Toremifene enhanced TGF-beta1 mRNA expression, and the level of TGF-beta1 increased from 103 to 473 pg/ml after 48 h of incubation. Toremifene had no effect on the growth of HUVE cells.

CONCLUSION

Toremifene has a specific antiproliferative effect on KS cells. The stimulation of TGF-beta1 production may play a role in the antiproliferative process.

Choosing an optimal radioimmunotherapy dose for clinical response

Clinical trials have documented the single-agent efficacy of radioimmunotherapy (RIT) in lymphoma, and several combination therapy studies are now in progress. RIT agents are currently becoming generally available for clinical use in lymphoma therapy. Solid tumors, which are notoriously less responsive to any single agent, have demonstrated clinically useful responses, albeit temporary, and multimodality studies have been instituted. However, a sincere debate continues regarding the basic parameters to be used to define appropriate therapeutic dosing when using this modality in clinical cancer care. It is a good time to reevaluate relevant dose response information from preclinical and clinical RIT. Preclinical studies have demonstrated abundant evidence of dose response in tumor and normal tissue in homogenous model systems; however, substantive variation occurs between the dose responses of tumors with low and variable (or shed) antigen expression, as well as between histologically different tumor models. Clinical studies of various heavily pretreated patient populations given several very different RIT pharmaceuticals have led to disparate conclusions regarding patient dosing methods and dosimetric predictions of toxicity and efficacy. Single-study data on previously untreated lymphoma patients with similar histology has demonstrated a correlation of imaging dosimetry with toxicity and tumor response. High-dose therapy with bone marrow support has also demonstrated a high tumor response rate and nonmarrow normal organ toxicities that correlate with the calculated dose to those organs from imaging. In iodine-131 ((131)I)--anti-CD20 studies, (131)I was demonstrated to have variable excretion, and estimated total-body radiation dose from tracer study proved a predictive surrogate for marrow toxicity. Yttrium-90 ((90)Y)--anti-CD20, which has little (90)Y excretion from the body, demonstrated the injected dose per body weight to be more predictive of marrow toxicity than indium-111 ((111)In) tracer dosimetry methods in heavily pretreated patients, and showed maximal safety with standard mCi/kg therapy dosing. Variations in clinical RIT choices, dosing methods, and dosimetry methods emphasize the need to review the relevant information to date. Future clinical trial designs, the sophistication of dosimetry, treatment planning, and clinical treatment decisions should all be focused on achieving the best benefit-risk relationship for each patient.

Biodistribution and dosimetry results from a phase III prospectively randomized controlled trial of Zevalin radioimmunotherapy for low-grade, follicular, or transformed B-cell non-Hodgkin's lymphoma

Radiation dosimetry studies were performed in patients with non-Hodgkin's lymphoma (NHL) treated with 90Y Zevalin (90yttrium ibritumomab tiuxetan, IDEC-Y2B8) on a Phase III open-label prospectively randomized multicenter trial. The trial was designed to evaluate the efficacy and safety of 90Y Zevalin radioimmunotherapy compared to rituximab (Rituxan, MabThera) immunotherapy for patients with relapsed or refractory low-grade, follicular, or transformed NHL. An important secondary objective was to determine if radiation dosimetry prior to 90Y Zevalin administration is required for safe treatment in this patient population.

METHODS

Patients randomized into the Zevalin arm were given a tracer dose of 5 mCi (185 MBq) (111)In Zevalin (111indium ibritumomab tiuxetan) on Day 0, evaluated with dosimetry, and then administered a therapeutic dose of 0.4 mCi/kg (15 MBq/kg) 90Y Zevalin on Day 7. Both Zevalin doses were preceded by an infusion of 250 mg/m(2) rituximab to clear peripheral B-cells and improve Zevalin biodistribution. Following administration of (111)In Zevalin, serial anterior and posterior whole-body scans were acquired and blood samples were obtained. Residence times for 90Y were estimated for major organs, and the MIRDOSE3 computer software program was used to calculate organ-specific and total body radiation absorbed dose. Patients randomized into the rituximab arm received a standard course of rituximab immunotherapy (375 mg/m(2) weekly x 4).

RESULTS

In a prospectively defined 90 patient interim analysis, the overall response rate was 80% for Zevalin vs. 44% for rituximab. For all patients with Zevalin dosimetry data (N=72), radiation absorbed doses were estimated to be below the protocol-defined upper limits of 300 cGy to red marrow and 2000 cGy to normal organs. The median estimated radiation absorbed doses were 71 cGy to red marrow (range: 18-221 cGy), 216 cGy to lungs (94-457 cGy), 532 cGy to liver (range: 234-1856 cGy), 848 cGy to spleen (range: 76-1902 cGy), 15 cGy to kidneys (0.27-76 cGy) and 1484 cGy to tumor (range: 61-24274 cGy). Toxicity was primarily hematologic, transient, and reversible. The severity of hematologic nadir did not correlate with estimates of effective half-life (half-life) or residence time of 90Y in blood, or radiation absorbed dose to the red marrow or total body.

CONCLUSION

90Y Zevalin administered to NHL patients at non-myeloablative maximum tolerated doses delivers acceptable radiation absorbed doses to uninvolved organs. Lack of correlation between dosimetric or pharmacokinetic parameters and the severity of hematologic nadir suggest that hematologic toxicity is more dependent on bone marrow reserve in this heavily pre-treated population. Based on these findings, it is safe to administer 90Y Zevalin in this defined patient population without pre-treatment (111)In-based radiation dosimetry.

Acute toxicity of three-dimensional conformal radiotherapy in prostate cancer patients eligible for implant monotherapy

PURPOSE

To assess the acute toxicity of three-dimensional conformal radiotherapy (3D-CRT) in prostate cancer patients eligible for implant monotherapy.

METHODS AND MATERIALS

Between December 1991 and June 1998, 198 prostate cancer patients were treated with 3D-CRT at the University of California Davis Medical Center. Fifty-two of these patients had a prostate-specific antigen (PSA) level </= 10.0 ng/ml, Gleason score </= 6, and a 1997 AJCC clinical stage T1bN0-T2bN0. Eleven (21%) patients received radiotherapy to the prostate and seminal vesicles; the remaining patients were treated to the prostate only. The 3D-CRT treatment planning guidelines in Radiation Therapy Oncology Group (RTOG) 9406 were followed after 1994 (similar treatment planning was used before the protocol became available). Typically, 4 oblique and 2 lateral fields were treated. All patients were seen at least weekly while under treatment, 1 month postirradiation and then every 3 months. Total radiation doses ranged from 66.0-79.2 Gy, with a median dose of 73.8 Gy in 41 fractions over 8 weeks. Acute toxicity is described according to the RTOG acute toxicity scoring system.

RESULTS

Overall, 3D-CRT was well-tolerated: 29% of patients experienced RTOG Grade 1 and 27% experienced Grade 2 acute lower gastrointestinal (GI) toxicity. Forty percent and 33% of patients experienced Grade 1 and 2 acute genitourinary (GU) toxicity, respectively. As expected, more acute morbidity, especially GI, was observed with a larger clinical target volume (prostate and seminal vesicles versus prostate only; p = 0. 05). Neoadjuvant hormonal therapy did not increase the incidence or severity of radiation-induced side effects. No acute toxicity >/= Grade 3, e.g., hourly nocturia, gross hematuria, diarrhea requiring parenteral support, narcotics for pain control, or catheterization for acute urinary retention, was observed.

CONCLUSION

Although relatively high doses of radiation are delivered to prostate cancers with 3D-CRT compared with conventional radiotherapy, 3D-CRT is surprisingly well-tolerated. No patients in the cohort eligible for implant monotherapy experienced acute toxicity >/= Grade 3.

Neovascular targeting with cyclic RGD peptide (cRGDf-ACHA) to enhance delivery of radioimmunotherapy

Radioimmunotherapy (RIT) has been hampered by delivery of only a small fraction of the administered dose of radiolabeled MAb to tumor. A strategy for creating and controlling tumor vascular permeability would enable more effective RIT. The alpha v beta 3 integrin receptor is an appealing target for strategies designed to enhance permeability of tumor vessels because it is highly and preferentially expressed in most tumors. In human tumor mouse models, apoptosis of neovascular endothelial cells has been demonstrated after treatment with alpha v beta 3 antagonists. Since this apoptotic effect could transiently increase permeability of tumor blood vessels, radiolabeled antibodies (MAb) circulating during this period would have increased access to extravascular tumor. To determine if this hypothesis was correct, a pharmacokinetic study of an immunospecific MAb given after an alpha v beta 3 antagonist was performed in nude mice bearing human breast cancer xenografts. The alpha v beta 3 antagonist, cyclic RGD pentapeptide (c-RGDf-ACHA; cyclo arginine glycine aspartic acid D-phenylalanine -1 amino cyclohexane carboxylic acid), inhibits alpha v beta 3 binding to its vitronectin ligand at nanomolar levels. Cyclic RGD peptide (250 micrograms i.p.) given 1 hour before 111In-ChL6 MAb resulted in a 40-50% increase in tumor uptake (concentration), when compared to the control tumor uptake, of MAb 24 hours after administration. When cyclic RGD peptide was given as a continuous infusion (17.5 micrograms/hr) for 1 or 24 hours before 111In-ChL6, tumor uptake of 111In-ChL6 was increased less, and, these data were not statistically different from the control data. There were no differences for any of the groups in the groups in the concentrations of 111In-ChL6 in normal organs or blood when compared to the control group. The results suggest that cyclic RGD peptide provided a temporary, selective increase in tumor vascular permeability, that allowed a larger fraction of the 111In-ChL6 to accumulate in the tumor.

Radioimmunotherapy of acquired immunodeficiency syndrome (AIDS) associated lymphoma

Standard therapy for AIDS associated NHL (AANHL) is toxic and often ineffective. Radioimmunotherapy (RIT) is an appealing alternative to chemotherapy because of the radiosensitivity of NHL and the ability of the Lym-1 monoclonal antibody to target therapeutic irradiation to NHL while relatively sparing normal tissue. A Phase I/II study of 90Y-2IT-BAD-Lym-1 was designed specifically for RIT of AANHL. The first patient has been treated with 15 mCi (7.5 mCi/m2) of 90Y-2IT-BAD-Lym-1, after an imaging dose of 111In-2IT-BAD-Lym-1. Before RIT, AANHL in the maxillary sinus extended into the oral cavity and axillary adenopathy was present. Imaging showed excellent accumulation of 111In-2IT-BAD-Lym-1 in the tumors. Substantial shrinkage of the oral lymphoma was observed 18 hours after the therapy dose of 90Y-2IT-BAD-Lym-1 and axillary adenopathy had disappeared by one week after RIT. Transient Grade IV myelosuppression was the only notable toxicity. Further RIT cycles were precluded by development of an antibody response (HAMA) against Lym-1. This novel preliminary study has shown that Lym-1 can target AANHL and produce significant tumor regression thereby providing encouragement to proceed with additional patients.

Preclinical evaluation of chimeric L6 antibody for the treatment of Kaposi's sarcoma with radioimmunotherapy

L6 is a murine IgG2a monoclonal antibody with panadenocarcinoma reactivity. Chimeric L6 (ChL6), the variable region of murine L6 combined with a human IgG1 constant region, has been used in clinical trials for the delivery of radioimmunotherapy to patients with breast cancer. AIDS-associated Kaposi's sarcoma (KS), a malignancy of vascular endothelium, may be an excellent candidate for systemic radioimmunotherapy because KS is well vascularized and radioresponsive. Because ChL6 has been noted to bind vascular endothelium, our hypothesis was that ChL6 will recognize and bind KS tumors making this a potentially useful antibody for the treatment of KS with radioimmunotherapy. To test this hypothesis, 4 human KS spindle cell cultures established from cutaneous punch biopsy specimens (KS-MR, KS-NO, KS-JD and KS 6-3E) and one well-characterized human KS cell line (KS Y-1) were assessed for L6 immunoreactivity. All 5 cell cultures were L6 positive by immunohistochemistry. KS Y-1 cells grown as nude mouse xenografts were also L6 positive by immunohistochemistry. Competitive binding assays performed on the KS Y-1 and KS 6-3E cell cultures showed high density and high affinity cell binding. Biodistribution experiments performed on nude mice with KS Y-1 xenografts demonstrate tumor targeting by ChL6. These findings indicate that ChL6 may be a useful antibody for the radioimmunotherapy of KS. Future experiments will assess the therapeutic efficacy of radiolabeled ChL6 with and without concurrent systemic radiosensitizing chemotherapy.

Severe esophageal toxicity after thoracic radiation therapy for lung cancer associated with the human immunodeficiency virus: a case report and review of the literature

This case report documents severe esophagitis and rapid esophageal stricture formation in a man infected with the human immunodeficiency virus (HIV) who was treated with standard thoracic irradiation for locally advanced non-small-cell lung cancer. Severe late esophageal toxicity is a rare complication of radiation therapy in patients who are HIV negative, but those who are HIV positive may be at increased risk. This article reviews the literature suggesting that HIV infection may lead to unusually severe radiation-induced mucosal injury. High-dose chest irradiation should be performed with caution in this group of patients.

Solitary extramedullary plasmacytoma five years after successful cardiac transplantation: case report and review of the literature

We document the occurrence of a solitary extramedullary plasmacytoma (SEP) in a cardiac transplant patient. The diagnosis of plasma cell malignancy was confirmed by histopathologic and immunohistochemical examination of a nodular skin lesion. A complete systemic evaluation showed no evidence of metastatic disease. The patient was treated locally with radiation therapy (RT), but disseminated multiple myeloma developed 4 months after diagnosis. A variety of tumors have been reported to develop in the cardiac or renal transplant recipient, although plasma cell malignancies are rare. To our knowledge, this is the first reported case of an SEP in an organ transplant recipient.

Effects of stem cell factor on the growth and radiation survival of tumor cells

Recombinant human stem cell factor (SCF) binds to the c-kit receptor on human bone marrow progenitor cells and enhances their survival following irradiation. Since the c-kit receptor has also been detected on malignant cells, experiments were performed to study the effect of SCF on the proliferation and radiation survival of a variety of both c-kit-positive and -negative human tumor cell lines using [3H]thymidine incorporation and colony formation assays. The addition of SCF to both c-kit-positive and -negative cell line cultures had no significant effect on the stimulation index (in [3H]thymidine assay). In contrast, colony formation by H69 (small cell lung cancer cell line), H128 (small cell lung cancer cell line), and HEL (erythroid leukemia cell line) cells was enhanced by SCF in a dose-dependent manner, but SCF did not promote the in vivo growth of H128 xenograft tumors in terms of graft rate, time from implantation to tumor detection, or tumor size. Furthermore, SCF did not significantly increase the surviving fraction of either c-kit-positive or -negative cell lines following radiation, and there were no statistically significant differences between D0 [defined by the slope of the terminal exponential region of the two-component (single-hit multitarget model) survival curve where slope = 1/D0], Dq (quasithreshold dose), n (extrapolation number), alpha, and beta values for any of the cell lines studied that were irradiated with and without SCF. Finally, nude mice with transplanted human LG425 cutaneous T-cell lymphoma (c-kit positive) were treated with 10 Gy with or without SCF (100 micrograms/kg i.p. 20 h before, 2 h before, and 4 h after irradiation). There were no significant differences in the median tumor quadrupling time between groups that received either no treatment or SCF alone, or between groups treated with 10 Gy and SCF or 10 Gy alone (P > 0.05). These results are encouraging and suggest that SCF does not stimulate tumor cell proliferation in vivo or enhance the survival of tumor cells following irradiation.

Stem cell factor enhances the survival of murine intestinal stem cells after photon irradiation

Recombinant rat stem cell factor (SCF) has been shown to decrease lethality in mice exposed to total-body irradiation (TBI) in the lower range of lethality through radioprotection of hematopoietic stem cells and acceleration of bone marrow repopulation. This study evaluates the effect of SCF on the survival of the intestinal mucosal stem cell after TBI. This non-hematopoietic stem cell is clinically relevant. Gastrointestinal toxicity is common during and after abdominal and pelvic radiation therapy and limits the radiation dose in these regions. As observed with bone marrow, the administration of SCF to mice prior to TBI enhanced the survival of mouse duodenal crypt stem cells. The maximum enhancement of survival was seen when 100 micrograms/kg of SCF was given intraperitoneally 8 h before irradiation. This regimen increased the survival of duodenal crypt stem cells after 12.0 Gy TBI from 22.5 +/- 0.7 per duodenal cross section for controls to 30.0 +/- 1.7 after treatment with SCF (P = 0.03). The TBI dose producing 50% mortality at 6 days (LD50/6) was increased from 14.9 Gy for control mice to 19.0 Gy for mice treated with SCF (dose modification factor = 1.28). These findings demonstrate that SCF has radioprotective effects on a non-hematopoietic stem cell population and suggest that SCF may be of clinical value in preventing radiation injury to the intestine.

Clinical hyperthermia with a new device: the current sheet applicator

PURPOSE

The current sheet applicator (CSA) is a newly developed microwave hyperthermia device. Advantages over commercial microwave applicators include its small size and high ratio of heating area to physical aperture area. These physical characteristics make the CSA excellent for heating constricted areas and allow the use of arrays of CSAs over large surfaces. This study examines the clinical efficacy of the CSA for heating superficial malignant tumors.

METHODS AND MATERIALS

From December 1989 through October 1991, 19 patients with recurrent or metastatic superficial malignant tumors were treated once or twice weekly to 30 hyperthermia fields using one to four CSAs. Each field received from one to four hyperthermia treatments for a total of 74 treatments. The treatment objective was to elevate the tumor temperature to a minimum of 42.5 degrees C for 30 min (2 patients) or 60 min (17 patients). Intratumor temperatures were measured with percutaneous fiberoptic thermometry probes. All patients received concurrent fractionated radiation therapy with total dose ranging from 20 to 65 Gy (median 46 Gy). Seventeen of the 30 fields had been previously irradiated to a median dose of 50 Gy.

RESULTS

Mean values for the maximum temperature, average temperature, and minimum temperature were 43.6 degrees C +/- 1.0, 42.2 degrees C +/- 1.4, and 41.0 degrees C +/- 1.5, respectively. Mean values for T50 and T90 were 42.2 degrees C +/- 1.1 and 41.0 degrees C +/- 1.3, respectively. The overall response rate for all assessable fields was 96%. Only Only three responding tumors have progressed with a median follow-up period of 6 months. Treatment related morbidity was generally mild and self-limited.

CONCLUSION

The CSA is a promising new microwave hyperthermia device capable of heating superficial tumors to therapeutic temperatures. When used in combination with radiotherapy, response rates are excellent without excessive toxicity.

Radiation-induced angiosarcoma of the breast. Case report and review of the literature

Angiosarcoma is a rare, highly malignant soft tissue sarcoma that sometimes occurs in the breast as a late sequela of treatment for breast cancer. The conventional treatment for radiation-induced angiosarcoma is surgery, which is associated with a poor overall prognosis. We report a case of radiation-induced angiosarcoma of the intact breast that occurred 6 years after breast conservation therapy. Simple mastectomy was performed; however, rapid chest wall recurrence of angiosarcoma ensued. After salvage therapy with combined radiotherapy and hyperthermia, the patient has been disease-free for more than 3 years.

Stem cell factor enhances the survival of irradiated human bone marrow maintained in SCID mice

The effect of recombinant human stem cell factor (SCF) on the response of human fetal bone marrow progenitor cells to irradiation was studied using immunodeficient mice with human fetal bone grafts (SCID/Hu mice). SCID/Hu mice were treated with three intraperitoneal injections of 500 micrograms/kg SCF at 20 h before, two h before, and four h after 100 cGy total body irradiation. Fourteen days following irradiation, the fetal bone grafts were harvested and studied. Most of the isolated bone marrow cells were human, as determined by flow cytometry. Colony forming assays were performed on the bone marrow to determine the survival of erythroid (BFU-E) and myeloid (CFU-GM) precursor cells. A statistically significant increase in BFU-E and CFU-GM survival after irradiation was observed for bone marrow maintained in the SCF treated mice when compared to bone marrow from mice not treated with SCF. The enhancement in colony forming unit survival after irradiation ranged from 4.3-fold for BFU-E (p = 0.05) to 13.1-fold for CFU-GM (p = 0.002). These findings suggest that SCF may be of potential clinical value for the prevention of radiation-induced myelosuppression.

Radiation therapy salvage of Hodgkin's disease following chemotherapy failure

PURPOSE

This study evaluates the efficacy of comprehensive salvage radiation therapy, with or without chemotherapy, in selected patients with Hodgkin's disease who have failed primary combination chemotherapy.

METHODS AND MATERIALS

Between 1972 and 1991, 28 patients with advanced Hodgkin's disease failing intensive combination chemotherapy in previously unirradiated nodal and/or pulmonary sites were treated with salvage radiotherapy with curative intent. Treatment consisted of comprehensive extended field radiotherapy to all known areas of disease. Total radiation doses ranged from 17.0 to 50.0 Gy, with only five patients (18%) receiving < 30.0 Gy to any field. Twelve patients also received chemotherapy as part of their salvage regimen.

RESULTS

Twenty-six patients (93%) achieved a complete response and 14 (50%) remain in continuous complete remission at 14 to 133 months. In addition, three patients (11%) who failed salvage radiotherapy are now without evidence of disease following additional therapy. With a median follow-up of 47 months (range 14+ to 198+), actuarial median relapse-free survival and overall survival are 46 and 97 months, respectively. Actuarial 5-year relapse-free survival and overall survival are 40% and 63%, respectively. Patients with an initial complete response to chemotherapy had a significantly longer actuarial relapse-free survival than those with an initial partial response (p = 0.02). Salvage therapy was generally well-tolerated and resulted in no treatment-related deaths.

CONCLUSION

Comprehensive salvage radiotherapy is of significant benefit in selected patients and should be considered an option for patients with advanced Hodgkin's disease following chemotherapy failure.

The effect of stem cell factor on irradiated human bone marrow

This study evaluates the effect of recombinant human stem cell factor (SCF) on the in vitro response of human bone marrow progenitor cells to irradiation. Light density nonadherent mononuclear cells were isolated from human bone marrow and resuspended in either semisolid culture or liquid culture with or without 100 ng/ml SCF. After 24 h in culture, cells were irradiated and assessed for survival of erythroid burst-forming unit, granulocyte colony-forming unit(s), or granulocyte-macrophage colony-forming unit precursors in the presence of erythropoietin, granulocyte colony-stimulating factor, or granulocyte-macrophage colony-stimulating factor, respectively. Incubation with SCF prior to irradiation (0-300 cGy) resulted in an increase in both absolute colony number and surviving fraction for erythroid burst-forming units, granulocyte colony-forming units, and granulocyte-macrophage colony-forming units as compared to cultures that did not contain SCF. The mean surviving fraction enhancement ratio after 100 cGy ranged from 1.2 to 3.7. An increased fraction of CD34+ progenitors in S-phase after exposure to SCF may explain in part the apparent radioprotective effect of SCF on human bone marrow progenitor cells.

Radiation therapy for the palliation of multiple myeloma

PURPOSE

This reviews the experience at the University of Arizona in an effort to define the minimum effective radiation dose for durable pain relief in the majority of patients with symptomatic multiple myeloma.

METHODS AND MATERIALS

The records of 101 patients with multiple myeloma irradiated for palliation at the University of Arizona between 1975 and 1990 were reviewed. Three hundred sixteen sites were treated. Ten sites were asymptomatic, including six hemibody fields with advanced disease unresponsive to chemotherapy and four local fields with impending pathological fractures. Three hundred six evaluable symptomatic sites remained. The most common symptom was bone pain. Other symptoms included neurological impairment and a palpable mass.

RESULTS

Total tumor dose ranged from 3.0 to 60 Gy, with a mean of 25 Gy. Symptom relief was obtained in 297 of 306 evaluable symptomatic sites (97%). Complete relief of symptoms was obtained in 26% and partial relief in 71%. Symptom relief was obtained in 92% of sites receiving a total dose less than 10 Gy (n = 13) and 98% of sites receiving 10 Gy or more (n = 293). No dose-response could be demonstrated. The likelihood of symptom relief was not influenced by the location of the lesion or the use of concurrent chemotherapy. Of the 297 responding sites, 6% (n = 19) relapsed after a median symptom-free interval of 16 months. Neither the probability of relapse nor the time to relapse was related to the radiation dose. Retreatment of relapsing sites provided effective palliation in all cases.

CONCLUSION

Radiation therapy is effective in palliating local symptoms in multiple myeloma. A total dose of 10 Gy should provide durable symptom relief in the majority of patients.