A phase I trial of the dual farnesyltransferase and geranylgeranyltransferase inhibitor L-778,123 and radiotherapy for locally advanced pancreatic cancer

PURPOSE

Preclinical and clinical studies have demonstrated that inhibition of prenylation can radiosensitize cell lines with activation of Ras and produce clinical response in patients with cancer. The aim of this study was to determine the maximally tolerated dose of the dual farnesyltransferase and geranylgeranyltransferase I inhibitor L-778,123 in combination with radiotherapy for patients with locally advanced pancreatic cancer.

EXPERIMENTAL DESIGN

L-778,123 was given by continuous intravenous infusion with concomitant radiotherapy to 59.4 Gy in standard fractions. Two L-778,123 dose levels were tested: 280 mg/m2/day over weeks 1, 2, 4, and 5 for dose level 1; and 560 mg/m2/day over weeks 1, 2, 4, 5, and 7 for dose level 2.

RESULTS

There were no dose-limiting toxicities observed in the eight patients treated on dose level 1. Two of the four patients on dose level 2 experienced dose-limiting toxicities consisting of grade 3 diarrhea in one case and grade 3 gastrointestinal hemorrhage associated with grade 3 thrombocytopenia and neutropenia in the other case. Other common toxicities were mild neutropenia, dehydration, hyperglycemia, and nausea/vomiting. One patient on dose level 1 showed a partial response of 6 months in duration. Both reversible inhibition of HDJ2 farnesylation and radiosensitization of a study patient-derived cell line were demonstrated in the presence of L-778,123. K-RAS mutations were found in three of the four patients evaluated.

CONCLUSIONS

The combination of L-778,123 and radiotherapy at dose level 1 showed acceptable toxicity in patients with locally advanced pancreatic cancer. Radiosensitization of a patient-derived pancreatic cancer cell line was observed.

Treatment optimisation using external beam radiation in gynaecological cancers

The majority of patients with gynaecological cancers present with advanced stages in which external beam radiation forms a major component of the treatment. These patients undergo simulation for treatment planning prior to radiation. Currently the lower extent of the disease is evaluated by vaginal examination and marked using a lead wire on the anterior abdominal wall in the pelvic region. A 2 cm margin inferior to this level is used as the lower border of the treatment field. The suggested modified technique includes the placement of an indigenously designed perspex vaginal obturator with graduations at 1 cm distance from its tip. Following vaginal examination the obturator can be inserted into the vagina and fixed at the predefined length using a fixation device. The radio-opaque markers can be seen even in the lateral films. Twentyfive consecutive patients underwent the procedure and the differences between the two methods of marking the lower border were calculated. The external lead wire was inferior to the internal obturator in 19 patients (76%) ranging from 0.5 cm to 3 cm (median 1.5 cm, mean 1.37 cm). It was at the same level in 4 patients (16%) and 1 cm superior to the internal obturator in 2 (8%). With the modified technique using the internal obturator application for delineating the lower border of vaginal disease or vault, it was possible to decrease the length of field thereby reducing the chances of treatment-related toxicity, especially groin and vulval reactions, as well as avoiding treatment interruptions.

Vertebral height as the measure of lesion length in carcinoma of the oesophagus - is it accurate?

No abstract available.

Stereotatic radiosurgery of 468 brain metastases < or =2 cm: implications for SRS dose and whole brain radiation therapy

PURPOSE

The national standard stereostatic radiosurgery (SRS) dose for brain metastases < or =2 cm is 24 Gy as established by the Radiation Therapy Oncology Group study 90-05, in which planned whole brain radiotherapy (WBRT) was not used. On the basis of our institutional experience, the goal of this study was to determine the optimal SRS dose and influence of WBRT on local tumor control among 468 < or =2-cm metastases.

METHODS AND MATERIALS

Between October 1992 and May 2001, 468 newly diagnosed or recurrent < or =2-cm brain metastases, among 160 patients, were treated with SRS (dose range, 7-30 Gy; median, 20). A total of 240 metastases received planned WBRT (range, 6.75-50.4 Gy; median, 40.5) vs. 228 metastases that did not. The variables tested by multivariate analysis for their potential effect on tumor control included histologic type, site of metastasis, primary diagnosis, tumor volume, SRS dose, newly diagnosed vs. recurrent metastasis, and planned WBRT vs. no planned WBRT.

RESULTS

Follow-up ranged from 1 to 82 months (median 7). On multivariate analysis, the addition of WBRT was the most significant predictor of local tumor control. Overall, patients who received WBRT had superior local tumor control rates (97% vs. 87% in those who did not receive WBRT; p = 0.0001). Patients receiving WBRT and SRS > or =20 Gy achieved local control rates of 99% compared with 91% control rates when treated with WBRT and SRS <20 Gy (p = 0.0029). Increasing the SRS dose to >20 Gy resulted in no improvement in local tumor control and a higher rate of Grade 3 and 4 neurotoxicity, approaching statistical significance (5.9% vs. 1.9%, p = 0.078).

CONCLUSION

First, optimal control of brain metastasis < or =2 cm was seen with 20-Gy SRS combined with planned WBRT. Second, SRS doses >20 Gy resulted in no obvious improvement in local control and appeared to be associated with a greater rate of complications.

Low-dose fractionated radiation as a chemopotentiator of neoadjuvant paclitaxel and carboplatin for locally advanced squamous cell carcinoma of the head and neck: results of a new treatment paradigm

PURPOSE

Current therapies for locally advanced squamous cell carcinoma of the head and neck (SCCHN) result in 50% long-term remission. Low-dose radiotherapy (<100 cGy) induces enhanced cell killing in vitro via the hyper-radiation sensitivity phenomenon but has not been used in the clinical setting. On the basis of the demonstrated synergy between chemotherapy and low-dose fractionated RT, a novel neoadjuvant therapy was designed using low-dose fractionated RT as a chemopotentiator for locally advanced SCCHN.

METHODS AND MATERIALS

Forty patients with locally advanced SCCHN received paclitaxel (225 mg/m2), carboplatin (area under the curve of 6), and four 80-cGy fractions of radiotherapy (two each on Days 1 and 2). This sequence was repeated on Days 22 and 23.

RESULTS

Of the 40 patients enrolled, 39 were assessable. Grade 3 or worse toxicities included neutropenia (50%), infection (13%), arthralgias/myalgias (3%), skin (8%), lung (3%), and allergic reaction (3%), with no Grade 5 toxicity. The response was assessed radiographically and by panendoscopy. At the primary site, 11 patients (28%) had a complete response, 24 (62%) had a partial response, and 4 (10%) had stable disease. Of those with lymph node involvement, 10 (31%) had a complete response, 12 (38%) a partial response, 9 (28%) had stable disease, and 1 (3%) had progressive disease. The overall response rate was 82%.

CONCLUSION

Low-dose fractionated RT combined with paclitaxel and carboplatin is effective in SCCHN and has a similar toxicity profile to chemotherapy alone. This novel approach provided a response rate of 90% at the primary site and a nodal response rate of 69%. Additional scientific investigation of this new treatment paradigm is warranted.

Low dose fractionated radiation potentiates the effects of taxotere in nude mice xenografts of squamous cell carcinoma of head and neck

This study evaluated the combined effect of Low Dose Fractionated Radiation (LDFRT) and Taxotere (TXT) therapy on the growth of SCCHN (squamous cell carcinoma of head and neck; SQ-20B, a p53 mutant SCCHN cell line) tumors in a nude mouse model to exploit the increased hyper radiation sensitivity (HRS) phenomenon present in G(2)/M cell cycle phase when induced by low doses of radiation that was demonstrated in in vitro settings. Seventy-eight animals were randomized into one control group and 5 treatment groups (treatments were administered weekly for six weeks). Tumor regression was observed in all the groups, however, tumor regression was not significant in 2 Gy or TXT or 2 Gy plus TXT treated groups when compared to control group. The tumor regression was significant in both the LDFRT group (p < 0.0043) and LDFRT + TXT group (p < 0.0006) when compared to other groups. A significantly prolonged tumor growth delay was observed in LDFRT group (p < 0.0081). Importantly, in combination of TXT and LDFRT, no tumor regrowth was observed in 12 out of 13 mice since LDFRT + TXT treatment caused a sustained regression of tumors for 9 weeks. Molecular analysis of resected tumor specimens demonstrated that Bax levels were elevated with concomitant increase in cytochrome c release to the cytosol of the treatment Group VI. These findings strongly suggest that LDFRT can be used in combination with TXT to potentiate the effects of drug on tumor regression through an apoptotic mode of death. Furthermore, the G(2)/M cell cycle arrest by TXT appears to be an important component of the enhanced apoptotic effect of TXT + LDFRT combined treatment.

Therapeutic advantage of grid irradiation for large single fractions

PURPOSE

In the present work, we used model calculations of cell survival to compare the effects of single fraction high-dose grid therapy with those of uniform dose delivery on tumor and normal tissues.

METHODS AND MATERIALS

The grid consisted of a hexagonal pattern of divergent holes in a Cerrobend block. A linear-quadratic model was used to find the surviving fraction of tumor and normal tissue cells after high-dose irradiation. Equivalent uniform doses were determined according to the tumor cell kill. The ratio of the normal tissue surviving fraction under grid irradiation to that obtained under equivalent uniform dose irradiation was taken as a measure of therapeutic gain.

RESULTS

The therapeutic ratio varied from 0.80 to 13.22 for the range of cell sensitivities investigated, with single fraction doses of 10.0-20.0 Gy. Optimization studies showed no significant dependence of therapeutic gain on hole spacing.

CONCLUSION

With high, single-fraction doses, grid irradiation revealed a therapeutic advantage over uniform dose irradiation whenever the tumor and surrounding normal tissues cells were equally radiosensitive, or, particularly, if the tumor cells were more radioresistant than the normal cells. The therapeutic gain did not appear to be a strong function of grid design.

Low-dose fractionated radiation potentiates the effects of Paclitaxel in wild-type and mutant p53 head and neck tumor cell lines

This study was designed to: (a) evaluate the induction of hyper-radiation sensitivity (HRS), a phenomenon observed at low doses of radiation (<1 Gy); (b) compare the potentiating effects of single dose radiation (2 Gy) versus the effect of low-dose fractionated radiation (LDFRT; <1 Gy) on Paclitaxel; and (c) understand the molecular mechanism of LDFRT-mediated chemo-potentiating effects, in wild-type p53 SCC-61 and p53 mutant SQ-20B head and neck squamous cell carcinoma cell lines. Both cell lines exhibited the HRS phenomenon at low radiation doses. Compared with SCC-61 cells, SQ-20B cells were resistant to radiation and Paclitaxel alone. A significant enhancement of radiation sensitization by Paclitaxel (0.5 or 1 nM) was observed in both cell lines. Chemo-potentiation of Paclitaxel by single 2-Gy radiation was observed in SCC-61 cells but not in SQ-20B cells. However, LDFRT (0.5 Gy in four fractions) significantly chemo-potentiated the effect of Paclitaxel in both cell lines. The cell cycle regulator p53 and its target genes p21(waf1/cip1) and BAX were induced in SCC-61 cells treated with 2 Gy, Paclitaxel, or in combination, but not in SQ-20B cells. These treatments elevated the antiapoptotic BCL-2 protein in SQ-20B cells but not in SCC-61 cells. Interestingly, LDFRT treatment in both cell lines with or without Paclitaxel down-regulated nuclear factor kappa B activity and BCL-2 protein expression and simultaneously up-regulated BAX protein. These findings strongly suggest that LDFRT (at these doses, HRS phenomenon is observed) can be used in combination with Paclitaxel to overcome the antiapoptotic effects of BCL-2 and nuclear factor kappa B.

Race and survival of men treated for prostate cancer on radiation therapy oncology group phase III randomized trials

PURPOSE

We assessed the impact of race on survival in men treated with external beam radiotherapy with or without hormonal therapy for localized prostate cancer in Radiation Therapy Oncology Group randomized trials.

MATERIALS AND METHODS

Between 1975 and 1992, 2,048 men were treated for clinically localized prostate cancer in 1 of 4 consecutive prospective phase III randomized trials. After excluding nonblack and nonwhite men 2,012 remained for analysis. Patients were included in this analysis if they were deemed evaluable and eligible for the trial, and followup information and centrally reviewed pathological results were available. Short-term hormonal therapy consisted of goserelin acetate and flutamide administered 2 months before and during radiotherapy. Long-term hormonal therapy consisted of adjuvant goserelin acetate, which was generally given for 2 years or more. Pretreatment prostate specific antigen (PSA) findings were available in 430 cases (21%), including 213 treated with radiotherapy alone, 60 treated with short-term hormonal therapy and 157 on long-term hormonal therapy. Mean pretreatment PSA was 68.8 and 35.2 ng./ml. in black and white patients, respectively. Cox proportional hazards models were used to identify the impact of previously defined risk groups on overall and disease specific survival. Multivariate analysis was done for the significance of race using a stratified Cox model. Median followup in patients treated in early and late studies exceeded 11 and 6 years, respectively.

RESULTS

On univariate analysis black race was associated with lower overall and disease specific survival (p = 0.04, RR = 1.24 and p = 0.016, RR = 1.41, respectively). After adjusting for risk group and treatment type (with or without short-term or long-term hormonal therapy) race was no longer associated with outcome (p >0.05). The trend for a persistent difference in survival was likely due to the higher tumor burden in black men, as reflected in higher PSA.

CONCLUSIONS

As previously reported, tumor grade (Gleason score), palpation T stage, lymph node status, pretreatment PSA and treatment type are major predictors of overall and disease specific survival. We noted no evidence that race has independent prognostic significance in patients treated for prostate cancer in Radiation Therapy Oncology Group prospective randomized trials.

Dosimetric characteristics with spatial fractionation using electron grid therapy

Recently, promising clinical results have been shown in the delivery of palliative treatments using megavoltage photon grid therapy. However, the use of megavoltage photon grid therapy is limited in the treatment of bulky superficial lesions where critical radiosensitive anatomical structures are present beyond tumor volumes. As a result, spatially fractionated electron grid therapy was investigated in this project. Dose distributions of 1.4-cm-thick cerrobend grid blocks were experimentally determined for electron beams ranging from 6 to 20 MeV. These blocks were designed and fabricated at out institution to fit into a 20 x 20-cm(2) electron cone of a commercially available linear accelerator. Beam profiles and percentage depth dose (PDD) curves were measured in Solid Water phantom material using radiographic film, LiF TLD, and ionometric techniques. Open-field PDD curves were compared with those of single holes grid with diameters of 1.5, 2.0, 2.5, 3.0, and 3.5 cm to find the optimum diameter. A 2.5-cm hole diameter was found to be the optimal size for all electron energies between 6 and 20 MeV. The results indicate peak-to-valley ratios decrease with depth and the largest ratio is found at Dmax. Also, the TLD measurements show that the dose under the blocked regions of the grid ranged from 9.7% to 39% of the dose beneath the grid holes, depending on the measurement location and beam energy.

Farnesyltransferase inhibitor (L-744,832) restores TGF-beta type II receptor expression and enhances radiation sensitivity in K-ras mutant pancreatic cancer cell line MIA PaCa-2

Activated ras is known to dysregulate TGF-beta signaling by altering the expression of TGF-beta type II receptor (RII). It is well documented that tumor cells harboring mutant ras are more resistant to radiation than cells with wild-type ras. In this study, we hypothesized that the use of farnesyltransferase inhibitor (FTI, L-744,832) may directly restore TGF-beta signaling through RII expression via ras dependent or independent pathway leading to induction of radiation sensitivity. Two pancreatic cancer cell lines, BxPC-3 and MIA PaCa-2 were used in this study. FTI inhibited farnesylation of Ras protein more significantly in MIA PaCa-2 than BxPC-3 cells. In contrast, MIA PaCa-2 cells were resistant to radiation when compared to BxPC-3 cells. BxPC-3 cells were more resistant to FTI than MIA PaCa-2 cells. In combination treatment, no significant radiosensitizing effect of FTI was observed in BxPC-3 cells at 5 or 10 microM. However, in MIA PaCa-2 cells, a significant radiosensitizing effect was observed at both 5 and 10 microM concentrations (P>0.004). The TGF-beta effector gene p21(waf1/cip1) was elevated in combination treatment in MIA PaCa-2 but not in BxPC-3 cells. In MIA PaCa-2 cells, FTI induced TGF-beta responsive promoter activity as assessed by 3TP-luciferase activity. A further induction of luciferase activity was observed in MIA PaCa-2 cells treated with radiation and FTI. Induction of TGF-beta signaling by FTI was mediated through restoration of the RII expression, as demonstrated by RT-PCR analysis. In addition, re-expression of RII by FTI was associated with a decrease in DNA methyltransferase 1 (DNMT1) levels. Thus, these findings suggest that the L-744,832 treatment restores the RII expression through inhibition of DNMT1 levels causing induction of TGF-beta signaling by radiation and this forms a novel molecular mechanism of radiosensitization by FTI.

Didox (a novel ribonucleotide reductase inhibitor) overcomes Bcl-2 mediated radiation resistance in prostate cancer cell line PC-3

In this study, we investigated the influence of Bcl-2 overexpression on the radiosensitizing potential of Didox (DX; 3,4-Dihydroxybenzohydroxamic acid), a novel ribonucleotide reductase inhibitor, in p53-null prostate cancer cell line PC-3. The PC-3 cells were transfected with vector alone or ectopically overexpressed with CMV-Bcl-2 construct. The effect of radiation (IR) or DX alone and in combination (pre and post IR exposure of DX) on cell survival was determined by colony-forming assay. The impact of these two treatments on the cell cycle was determined by flow cytometry. To further understand the molecular mechanism of DX-mediated radiosensitization, induction of pro-survival and pro-apoptotic factors were determined by Western blot and gel-shift assays respectively. When compared to PC-3/Bcl-2 cells (SF(2)=0.84; D(0)=437cGy), the PC-3/vector cells (SF(2)=0.4; D(0)=235cGy) were significantly sensitive to ionizing radiation (p<0.001). Exposure of DX at 5 microM concentration prior or post to radiation in both PC-3/vector and PC-3/Bcl-2 transfectants caused an increase in radiation enhancement ratios. A significant reduction in G(2)M phase was observed in cells exposed to DX post IR when compared to cells exposed to IR alone. Exposure to DX after radiation in PC-3/vector significantly abrogated radiation-induced Bcl-2 upregulation, with a concomitant induction of bax protein. In PC-3/Bcl-2 transfectants, DX exposure after IR caused an induction of bax protein. Gel shift assays indicated that in PC-3/vector cells when exposed to IR caused an induction of NFkappa-B activity however, DX down regulated the NFkappa-B activity. Radiation-induced NFkappa-B activity was abrogated in pre and post DX exposure in combination with IR. These findings indicate that DX mediates a potent radiosensitizing effect in p53 null prostate cancer cells by overcoming radiation induced NFkappa-B activity and Bcl-2 expression.

Long-term results of reirradiation for patients with recurrent rectal carcinoma

BACKGROUND

The current study was conducted to assess the long-term results of reirradiation in patients with recurrent rectal carcinoma.

METHODS

One hundred and three patients with recurrent adenocarcinoma of the rectum underwent reirradiation with concurrent 5-fluorouracil-based chemotherapy. The initial radiation dose to the pelvis ranged from 3000 to 7400 centigrays (cGy) with a median dose of 5040 cGy. The median time from initial treatment to recurrence was 19 months. Irradiation techniques consisted of two lateral fields with/without a posterior pelvic field to include recurrent tumor with a margin of 2-4 cm only. The reirradiation doses ranged from 1500 to 4920 cGy with a median dose of 3480 cGy. Total cumulative doses ranged from 7060 to 1080 cGy with a median total dose of 8580 cGy. After the reirradiation, 34 patients also underwent surgical resection for residual disease. Fourteen patients underwent pelvic exenteration, 11 patients underwent abdominoperineal resection, 4 patients underwent transanal transabdominal proctosigmoidectomy, 2 patients underwent full thickness local excision, and 3 patients underwent a Hartmann resection.

RESULTS

Follow-up ranged from 3 84 months with a median follow-up of 2 years. The median survival for the whole group was 26 months and the 5-year actuarial survival rate was 19%. The median interval and 5-year survival rate of patients undergoing surgical resection after reirradiation was 44 months and 22% compared with 14 months and 15% for patients treated with reirradiation only (P = 0.001). Treatment was generally well tolerated. Fifteen patients required a treatment break and early termination of treatment for Grade 3 and higher diarrhea, moist desquamation, or mucositis. Late complications were seen in 22 patients, including persistent severe diarrhea in 18 patients with 10 patients requiring long-term parental support, small bowel obstruction was seen in 15 patients, fistula formation in 4 patients, and coloanal stricture in 2 patients. There was no difference in incidence of acute or long-term complications by the total radiation dose delivered.

CONCLUSIONS

In patients with recurrent rectal carcinoma, high doses of reirradiation can be delivered with acceptable risks without prohibitive long-term side effects. Surgical salvage and long-term survival of patients are possible.

Increased expression of PSA mRNA during brachytherapy in peripheral blood of patients with prostate cancer

OBJECTIVES

To determine the extent of iatrogenic tumor cell dissemination during brachytherapy by assessing prostate-specific antigen (PSA) mRNA expression in circulating prostate tumor cells using reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. The instrumentation used in the radioisotope seed placement of the prostate causes trauma to blood vessels and provides a vascular access for tumor cells that can lead to potential iatrogenic dissemination and systemic failure.

METHODS

Twenty-five patients treated for brachytherapy were recruited in the study. Controls included 4 normal men and 1 woman; case controls included 4 patients who underwent prostate biopsy for prostate cancer diagnosis. Peripheral blood (10 mL) was collected before, during, and after the brachytherapy procedure. Total RNA was isolated from mononuclear cells and phosphorus-32 RT-PCR was performed to analyze the mRNA expression of PSA and G6PDH genes.

RESULTS

Of 25 patients, 23 were negative for PSA mRNA expression and 2 were positive for PSA mRNA expression before brachytherapy. Of the 23 patients who were negative for PSA mRNA expression before treatment, 15 patients (65%) turned positive during or after brachytherapy and the remaining 8 patients remained negative throughout the treatment. Eight of the 25 patients developed rising serum PSA levels. Of these 8 patients, 1 (12.5%) did not have PSA mRNA expression in the peripheral blood before, during, or after brachytherapy; the remaining 7 patients who developed rising serum PSA levels had PSA mRNA expression after brachytherapy (P = 0.03).

CONCLUSIONS

These findings strongly suggest that iatrogenic shedding of prostate cells occurs as a result of brachytherapy and raises the concern that these cells liberated at the time of brachytherapy increase the risk of metastatic deposits and results in systemic failure, as measured by serum PSA levels.