Radiation and taxol effects on synchronized human cervical carcinoma cells

Additive Damage Models for Cellular Pharmacodynamics of Radiation-Chemotherapy Combinations

Many cancer patients receive combination treatments with radiation and chemotherapy. Available mathematical models for cellular pharmacodynamics have limited ability to represent observed in vitro responses to radiochemotherapy. Here, a family of additive damage models is proposed to describe cell kill resulting from radiochemotherapy with fixed schedule and variable doses. The pathways by which the agents produce cellular damage are assumed to converge in a single cell death process, so that survival depends on total damage, which can be represented as a sum of contributions from the various damage pathways. Heterogeneity in response across the cell population is ascribed to variations in the damage threshold for cell kill. The family of proposed models includes effects of one or two pathways of damage for each agent, saturation in drug responses, and cooperative or antagonistic interactions between agents. Models from this family with 4-7 unknown parameters are tested for their ability to fit 218 in vitro literature data sets for a range of drugs and cell lines. Overall, the additive damage models are found to outperform models based on the existing concept of independent cell kill, according to the corrected Akaike Information Criterion. The results are used to assess the importance of the various effects included in the models. These additive damage models have potential applications to the optimization of treatment and to the analysis and interpretation of in vitro screening data for new drug-radiation combinations.

Timed, sequential administration of paclitaxel improves its cytotoxic effectiveness in a cell culture model

Paclitaxel (taxol) is a chemotherapeutic agent frequently used in combination with other anti-neoplastic drugs. It is most effective during the M phase of the cell-cycle and tends to cause synchronization in malignant cells lines. In this study, we investigated whether timed, sequential treatment based on the cell-cycle characteristics could be exploited to enhance the cytotoxic effect of paclitaxel. We characterized the cell-cycle properties of a rapidly multiplying cell line (Sp2, mouse myeloma cells) by propidium-iodide DNA staining such as the lengths of various cell cycle phases and population duplication time. Based on this we designed a paclitaxel treatment protocol that comprised a primary and a secondary, timed treatment. We found that the first paclitaxel treatment synchronized the cells at the G2/M phase but releasing the block by stopping the treatment allowed a large number of cells to enter the next cell-cycle by a synchronized manner. The second treatment was most effective during the time when these cells approached the next G2/M phase and was least effective when it occurred after the peak time of this next G2/M phase. Moreover, we found that after mixing Sp2 cells with another, significantly slower multiplying cell type (Jurkat human T-cell leukemia) at an initial ratio of 1:1, the ratio of the two different cell types could be influenced by timed sequential paclitaxel treatment at will. Our results demonstrate that knowledge of the cell-cycle parameters of a specific malignant cell type could improve the effectivity of the chemotherapy. Implementing timed chemotherapeutic treatments could increase the cytotoxicity on the malignant cells but also decrease the side-effects since other, non-malignant cell types will have different cell-cycle characteristic and be out of synch during the treatment.

The effects of narrow-band middle infrared radiation in enhancing the antitumor activity of paclitaxel

Paclitaxel is used as an adjuvant to enhance the effectiveness of ionization radiation therapy; however, high-energy radiation often damages the healthy cells surrounding cancer cells. Low-energy, middle-infrared radiation (MIR) has been shown to prevent tissue damage, and recent studies have begun combining MIR with paclitaxel. However, the cytotoxic effects of this treatment combination remain unclear, and the mechanism underlying its effects on HeLa cells has yet to be elucidated. This study investigated the effectiveness of treating HeLa human cervical cancer cells with a combination of paclitaxel for 48 h in conjunction with narrow-band MIR from 3.0 to 5.0 μm. This combined treatment significantly inhibited the growth of HeLa cells. Specifically, results from Annexin V-FITC/PI apoptosis detection and cell mitochondrial membrane potential analyses revealed an increase in apoptotic cell death and a collapse of mitochondrial membrane potential. One possible mechanism underlying cellular apoptosis is an increase in oxidative stress. These preliminary findings provide evidence to support the combination of narrow-band MIR with paclitaxel as an alternative approach in the treatment of human cervical cancer.

Comparison of chemotherapy regimens for concurrent chemoradiotherapy in unresectable stage III non-small cell lung cancer

BACKGROUND

The purpose of this study was to retrospectively compare the survival and toxicities associated with chemoradiotherapy using full-dose and weekly regimens in patients with stage III non-small cell lung cancer.

METHODS

Consecutive patients who received concurrent chemoradiotherapy between October 2002 and June 2006 at our institution were enrolled. The prescribed dose for thoracic radiotherapy was 60 Gy in 30 fractions for all the patients.

RESULTS

Fifty-nine patients were enrolled; 36% of the patients were treated with full-dose regimens and 64% with weekly regimens. The patient characteristics were similar in the two groups. In both univariate and multivariate analyses, treatment with weekly regimens was associated with a better overall survival than that with full-dose regimens (2-year survival rates: 75% for weekly regimens vs 41% for full-dose regimens). The toxicities and compliance in the two groups were comparable.

CONCLUSION

Weekly regimens exhibited more favorable overall survival as compared to full-dose regimens in this retrospective study. Confirmation of the results by a randomized phase III trial is warranted.

Acid ceramidase upregulation in prostate cancer: role in tumor development and implications for therapy

Bioactive sphingolipids, such as ceramide, sphingosine and sphingosine-1-phosphate are known bio-effector molecules which play important roles in various aspects of cancer biology including cell proliferation, growth arrest, apoptosis, metastasis, senescence and inflammation. Therefore, enzymes involved in ceramide metabolism are gaining recognition as being critical regulators of cancer cell growth and/or survival. We previously observed that the ceramide metabolizing enzyme, acid ceramidase (AC) is upregulated in tumor tissues. Studies have now concluded that this creates a dysfunctional ceramide pathway, which is responsible for tumor progression and resistance to chemotherapy and radiation. This suggests that development of small-molecule drugs that inhibit AC enzyme activity is a promising approach for improving standard cancer therapy and patient's clinical outcomes.

Comparison of concurrent chemoradiotherapy with cisplatin plus 5-fluorouracil versus cisplatin plus paclitaxel in patients with locally advanced cervical carcinoma

OBJECTIVE

The aim of this study was to compare survival outcomes and toxicities between concurrent radiotherapy with cisplatin plus 5-fluorouracil and that with cisplatin plus paclitaxel in patients with locally advanced cervical carcinoma.

METHODS

We retrospectively reviewed data from 93 locally advanced cervical carcinoma patients (stage IB to IVA) who had been treated by concurrent radiotherapy with cisplatin plus 5-fluorouracil (CF, n=45) vs. cisplatin plus paclitaxel (CP, n=48) as primary therapy. Toxicities and survival outcomes were compared.

RESULTS

In the CP group, there were higher frequencies of severe (grade 3 or 4) leukopenia (79.2%, as compared to 11.1% in the CF group), severe neutropenia (77.1%, as compared to 8.9% in the CF group) and severe peripheral neuropathy (12.5%, as compared to 2.2% in the CF group). In the CF group, there were higher frequencies of severe nausea (33.3%, as compared to 14.6% in the CP group) and severe hyponatremia (11.1%, as compared to 0% in the CP group). Five-year DFS of the CF and CP groups was 67.4% and 79.1%, respectively (p=NS). Five year OS of the CF and CP groups was 79.6% and 80.9%, respectively (p=NS).

CONCLUSION

Concurrent radiotherapy with cisplatin plus paclitaxel showed increased leukopenia, neutropenia and peripheral neuropathy, but less gastrointestinal toxicity (nausea) than that with cisplatin plus 5-fluorouracil. Survival outcome between these two groups was not statistically different in this study. Large prospective randomized controlled studies will be needed to confirm this result.

Acid ceramidase upregulation in prostate cancer cells confers resistance to radiation: AC inhibition, a potential radiosensitizer

Radiation resistance in a subset of prostate tumors remains a challenge to prostate cancer radiotherapy. The current study on the effects of radiation on prostate cancer cells reveals that radiation programs an unpredicted resistance mechanism by upregulating acid ceramidase (AC). Irradiated cells demonstrated limited changes of ceramide levels while elevating levels of sphingosine and sphingosine-1-phosphate. By genetically downregulating AC with small interfering RNA (siRNA), we observed radiosensitization of cells using clonogenic and cytotoxicity assays. Conversely, AC overexpression further decreased sensitivity to radiation. We also observed that radiation-induced AC upregulation was sufficient to create cross-resistance to chemotherapy as demonstrated by decreased sensitivity to Taxol and C(6) ceramide compared to controls. Lower levels of caspase 3/7 activity were detected in cells pretreated with radiation, also indicating increased resistance. Finally, utilization of the small molecule AC inhibitor, LCL385, sensitized PPC-1 cells to radiation and significantly decreased tumor xenograft growth. These data suggest a new mechanism of cancer cell resistance to radiation, through upregulation of AC that is, in part, mediated by application of the therapy itself. An improved understanding of radiotherapy and the application of combination therapy achieved in this study offer new opportunities for the modulation of radiation effects in the treatment of cancer.

Impact of hemoglobin on survival of cervical carcinoma patients treated with concurrent chemoradiotherapy is dependent on lymph node metastasis findings by magnetic resonance imaging

The objective of this study was to confirm whether hemoglobin (Hb) levels during chemoradiotherapy are associated with survival in patients with locally advanced cervical carcinoma and to assess impact of the Hb level on survival according to lymph node (LN) metastasis. A retrospective review of 85 cervical carcinoma patients treated with concurrent chemoradiotherapy was conducted. The stage of disease ranged between FIGO stage IB and stage IVA. Disease-free and overall survivals were evaluated by univariate and multivariate analyses. After median follow-up of 35.7 months, 24 patients developed recurrence of disease and 14 patients died from their disease. Stage, LN metastasis, and squamous cell carcinoma antigen and Hb levels during chemoradiation were correlated significantly with survival (P < 0.05). Maintenance of Hb above 10.0 g/dL was associated with better survival (P < 0.05). However, no such benefits were observed in patients with LN metastasis by magnetic resonance imaging (MRI). Multivariate Cox regression hazard model showed that Hb levels during chemoradiation were an independent prognostic factor in patients without LN metastasis by MRI. Maintenance of Hb during chemoradiation is of benefit in cervical carcinoma patients without LN metastasis but not with LN metastasis by MRI.

High-dose radioimmunotherapy combined with fixed, low-dose paclitaxel in metastatic prostate and breast cancer by using a MUC-1 monoclonal antibody, m170, linked to indium-111/yttrium-90 via a cathepsin cleavable linker with cyclosporine to prevent human anti-mouse antibody

PURPOSE

Although radioimmunotherapy alone is effective in lymphoma, its application to solid tumors will likely require a combined modality approach. In these phase I studies, paclitaxel was combined with radioimmunotherapy in patients with metastatic hormone-refractory prostate cancer or advanced breast cancer.

EXPERIMENTAL DESIGN

Patients were imaged with indium-111 (111In)-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid-peptide-m170. One week later, yttrium-90 (90Y)-m170 was infused (12 mCi/m2 for prostate cancer and 22 mCi/m2 for breast cancer). Initial cohorts received radioimmunotherapy alone. Subsequent cohorts received radioimmunotherapy followed 48 hours later by paclitaxel (75 mg/m2). Cyclosporine was given to prevent development of human anti-mouse antibody.

RESULTS

Bone and soft tissue metastases were targeted by 111In-m170 in 15 of the 16 patients imaged. Three prostate cancer patients treated with radioimmunotherapy alone had no grade 3 or 4 toxicity. With radioimmunotherapy and paclitaxel, two of three prostate cancer patients developed transient grade 4 neutropenia. Four breast cancer patients treated with radioimmunotherapy alone had grade 3 or 4 myelosuppression. With radioimmunotherapy and paclitaxel, both breast cancer patients developed grade 4 neutropenia. Three breast cancer patients required infusion of previously harvested peripheral blood stem cells because of neutropenic fever or bleeding. One patient in this trial developed human anti-mouse antibody in contrast to 12 of 17 patients in a prior trial using m170-radioimmunotherapy without cyclosporine.

CONCLUSIONS

111In/90Y-m170 targets prostate and breast cancer and can be combined with paclitaxel with toxicity limited to marrow suppression at the dose levels above. The maximum tolerated dose of radioimmunotherapy and fixed-dose paclitaxel with peripheral blood stem cell support has not been reached. Cyclosporine is effective in preventing human anti-mouse antibody, suggesting the feasibility of multidose, "fractionated" therapy that could enhance clinical response.

G2/M cell cycle checkpoint is functional in cervical cancer patients after initiation of external beam radiotherapy

PURPOSE

To investigate changes in cancer of the uterine cervix during radiotherapy (RT) with respect to G2/M transition in relation to tumor cell apoptosis and changes in the tumor vasculature in cervical carcinoma.

METHODS AND MATERIALS

A total of 40 consecutive patients with Stage IIA-IIIB cervical cancer underwent RT without any chemotherapy. Tumor biopsy was obtained before RT and after five fractions of 1.8 Gy. The tumor samples were stained for cyclin B1, cdc2, and Ki-67, the apoptotic index, using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling staining. The tumor vasculature density was assessed. In 38 cases, the tissue samples were informative.

RESULTS

Cyclin B1 was positive in all biopsies before and after initiation of RT, and staining for cdc2 was positive in 35 (92%) of 38 biopsies before and 33 (87%) of 38 after 1 week of RT. Nuclear staining for cyclin B1 was observed in 92% of patients, staining an average of 15% of cells before RT. After initiating RT, 73% of patients showed positive staining on about 5% of tumor cells (p < 0.01). Nuclear staining for cdc2 was detected in 89% of patients, staining an average of 21% of cells before RT. After initiating RT, 79% of patients showed positive staining on 9% of cells (p < 0.01). The apoptotic index of the tumor cells increased after initiating RT, and a slight decrease in the vascular density after 1 week of RT was noted (p = 0.08). Changes in G2/M were associated with the clinical response, but changes in apoptosis or tumor vasculature were not.

CONCLUSION

RT leads to significant changes in the cell cycle in cervical cancer indicating intact G2/M checkpoint function. Targeting G2/M with compounds interfering with G2/M transition may further enhance the effect of RT in cervical cancer patients.

Hyperfractionated radiotherapy with concurrent chemotherapy for para-aortic lymph node recurrence in carcinoma of the cervix

PURPOSE

To evaluate efficacy, toxicity, and patterns of relapse in patients treated with hyperfractionated radiotherapy (HFRT) with concurrent chemotherapy for para-aortic lymph node (PALN) recurrence of cervical carcinoma.

METHODS AND MATERIALS

Between September 1997 and October 2000, 12 cervical carcinoma patients with isolated PALN recurrence who had previously received radical or postoperative radiotherapy were treated with HFRT and concurrent chemotherapy. The initial FIGO stage was Stage IB in 4 (33%) patients, Stage IIA in 2 (17%), and Stage IIB in 6 (50%). The radiation field encompassed the gross recurrent PALN with the superior margin at the upper end of the T12 body and the inferior margin between L5 and S1. The fractionated dose was 1.2 Gy in 2 daily fractions, and the median total dose was 60 Gy. The weekly concurrent chemotherapy consisted of paclitaxel in 11 patients and cisplatin in 1. The median number of cycles of chemotherapy was 5.

RESULTS

The latent period to PALN recurrence from the time of initial treatment for all patients ranged from 2 to 92 months (median: 12 months). One month after treatment, the clinical tumor response evaluated was complete in 33% (4/12) and partial in 67% (8/12). The 3-year overall survival rate and median survival were 19% and 21 months, respectively. The latent period to PALN recurrence was the only significant prognostic factor; the median survival of patients who relapsed in < or =24 months from the initial treatment of cervical carcinoma was 13 months vs. 45 months for those relapsed at >24 months (p = 0.026). Grade 3-4 hematologic toxicity developed in 2 patients. Six (50%) patients experienced Grade 2 nausea. There were no late gastrointestinal or neurologic complications during the follow-up period. Subsequent distant metastases after PALN treatment developed in 58% (7/12).

CONCLUSION

HFRT of 60 Gy to PALN with concurrent chemotherapy could be regarded as an effective treatment modality without significant acute or late toxicity. Patients with a latent period >24 months until PALN recurrence had a more favorable survival rate than those with a latent period </=24 months. Subsequent distant metastasis after PALN recurrence was the main cause of death and is a problem to overcome in the future.

Paclitaxel combined with fractionated radiation in vitro: a study with vulvar squamous cell carcinoma cell lines

Concurrent paclitaxel and radiation has given promising results in the treatment of a variety of solid tumors. We wanted to test the efficacy of this combination for vulvar carcinoma, which currently has a poor outcome in advanced stages. The radiation sensitivity, sublethal damage repair (SLDR) capacity and effect of paclitaxel during fractionated radiation were assessed in our study on 7 vulvar inherently radioresistant squamous cell carcinoma (SCC) cell lines. The 96-well plate clonogenic assay was used. Survival data were fitted to the linear quadratic model. The area under the curve (AUC), equivalent to mean inactivation dose (D), was obtained with numerical integration. AUC ratios between single-dose radiation and fractionated radiation with or without paclitaxel were used to determine the SLDR of the cell lines and the effect of paclitaxel on it. Seven currently tested vulvar SCC cell lines were found to have a limited capacity of repairing sublethal damage (SLD). Only 3 of them presented SLDR of significance. The effect of concurrent radiation and paclitaxel was clearly additive when the radiation dose was fractionated in most of the cell lines. In addition, 2 of the cell lines having SLDR exhibited a trend toward losing the repair capacity when paclitaxel was present during the irradiation. In addition, the survival curve of the UM-SCV-1A cell line gave the impression of a true paclitaxel effect on SLDR. Paclitaxel used concurrently with fractionated radiation showed effectiveness on vulvar carcinoma. The effect was at least additive and could even be expected to abrogate the SLDR during split-dose radiation.

Biological basis for chemo-radiotherapy interactions

For over 10 years, chemo-radiotherapeutic combinations have been used to treat locally advanced epithelial tumours. The rationale for these combinations relies on spatial cooperation or interaction between modalities. Interactions may take place (i) at the molecular level, with altered DNA repair or modification of the lesions induced by drugs or radiation, (ii) at the cellular level, notably through cytokinetic cooperation arising from differential sensitivity of the various compartments of the cell cycle to the drug or radiation, and (iii) at the tissue level, including reoxygenation, increased drug uptake or inhibition of repopulation or angiogenesis. Some mechanisms underlying interaction of radiation with cis-diammino-platinum (II) (cis-Pt), 5-fluoro-2'-deoxyuridine (5-FU), taxanes and gemcitabine are described. It is shown how various mechanisms including cell synchronisation and reoxygenation concur to paclitaxel-induced radiosensitisation. In the future, specific targeting of tumours, for example, with the epidermal growth factor receptor (EGFR) or angiogenesis inhibitors, should be achieved in order to increase the therapeutic index.

The novel taxane analogs, BMS-184476 and BMS-188797, potentiate the effects of radiation therapy in vitro and in vivo against human lung cancer cells

PURPOSE

To evaluate the novel taxane analogs, BMS-184476 and BMS-188797, as potential radiosensitizers in vitro and in vivo.

METHODS AND MATERIALS

Human H460 lung cancer cells were incubated with either paclitaxel or a taxane analog and irradiated at various times. Surviving fractions were then determined using a clonogenic assay. Three different schedules were used: (A) 1-h drug incubation with radiation at t = 8 h, (B) 1-h drug incubation with radiation at t = 24 h, (C) 24-h drug incubation with radiation immediately after. Cell cycle redistribution by taxanes alone was measured with propidium iodide and flow cytometry. Percent apoptosis was also measured using 7-aminoactinomycin D (7-AAD) staining with flow cytometry. For in vivo studies, H460 cell xenografts were used in nude mice. Tumors were grown s.c. on the flank and then treated with BMS-184476 (10 mg/kg i.p. injection, Days 0, 2, and 4) and/or radiation (2 Gy/day, Days 0-4). Tumor growth delay was then measured for each treatment group.

RESULTS

The mean in vitro radiation dose enhancement ratios of BMS-184476, BMS-188797, and paclitaxel were 1.76, 1.49, and 1.31 for Schedules A, B, and C, respectively. Isobologram analysis showed that BMS-184476 was synergistic with radiation using Schedule A. Treatment with taxanes caused an increase in the percentage of G2/M cells at the time of irradiation. The mean fold increases in the %G2/M above control values for all three drugs were 5.6, 2.5, and 1.7 for Schedules A, B, and C, respectively. The combined effects of taxanes plus radiation on the induction of apoptosis were additive for all three drugs. In vivo studies showed that BMS-184476 can enhance the effects of fractionated radiotherapy, with an average enhancement factor of 1.66 obtained from three independent experiments.

CONCLUSIONS

These results demonstrated that the novel taxane analogs, BMS-184476 and BMS-188797, can enhance the effects of radiation in human lung cancer cells both in vitro and in vivo. These data also support the hypothesis that a G2/M block is involved in the radiosensitization caused by the taxanes.

Taxanes in combined modality therapy for solid tumors

The taxanes, paclitaxel and docetaxel, are novel antimitotic agents that are under extensive investigation in clinical trials. Both taxanes have demonstrated significant activity against many solid tumors as single agents and in combination with other chemotherapeutic agents. In addition, taxanes arrest cells at the G2/M phase of the cell cycle, which is the most radiosensitive phase. These properties are exploited in clinical trials combining this taxane with radiation therapy. Most studies included patients with non-small cell lung cancer (NSCLC) and cancers of the head and neck and there are a few studies with concurrent taxane/RT in esophageal, gastric, pancreatic, brain and breast cancer. Information concerning the tolerability and possible utility of docetaxel is also becoming available. This manuscript will review some of the more prominent trials of the taxanes in combination with radiation therapy for solid tumors.

Predictors of response and survival after concurrent chemotherapy and radiation for locally advanced squamous cell carcinomas of the head and neck

BACKGROUND

The objective of this study was to determine prognostic factors for response and survival on three consecutive institutional trials utilizing concurrent chemotherapy and radiation for locally advanced squamous cell carcinomas of the head and neck (SCCHN).

METHODS

Since 1985, patients with locally advanced SCCHN at the University of Maryland have been managed with concurrent chemotherapy and radiation therapy (RT). Three consecutive pilot studies have been performed evaluating the utility of weekly chemotherapy with standard fractionated RT. Chemotherapy consisted of carboplatin either alone (28 patients) or in combination with bleomycin (23 patients) or paclitaxel (60 patients). In all three studies, RT was given to 70.2 gray (Gy) at 1.8 Gy/fraction/day to the primary site. All patients had locally advanced SCCHN and were believed to be poor surgical candidates. Sixty-seven percent of patients had T4 disease, and 21% had T3 disease. Seventy-five percent of patients had N2-N3 disease. One hundred eleven patients were examinable for toxicity, response, and survival analysis. Factors including age, race, gender, primary site location, histologic grade, T classification, N classification, and treatment regimen were evaluated to identify predictors of these endpoints.

RESULTS

The median follow-up for patients treated on study 1 (carboplatin and RT) and study 2 (carboplatin and bleomycin [C + B]/RT) was 98 months, and it was 30 months for study 3 (carboplatin and paclitaxel [C + P]/RT). The complete response rates were 54%, 52%, and 70% respectively (P = 0.01). Multivariate analysis identified length of treatment break (< 1 week vs. > 1 week) as the only predictor of complete response to therapy. The local control for the entire group was 50%. The local control for C + P/RT was 63%, versus 32% and 36% for C/RT and C + B/RT respectively (P = 0.004). The 2-, 3-, and 5-year disease free and overall survivals for the entire population were 41%, 41%, and 35% and 42%, 36%, and 33%, respectively. The 3-year overall survival rates by treatment regimen were 18% (C/RT), 35% (C + B/RT), and 47% (C + P/RT; P = 0.01). On univariate analysis, age younger than 50 years (P = 0.01), treatment with C + P/RT (P = 0.005), and treatment break of 5 days or fewer (P < 0.05) were also predictive of improved overall survival. On multivariate analysis, only complete response (P < 0.0001) and treatment with C + P/RT (P = 0.02) remained statistically significant.

CONCLUSIONS

Chemoradiation provides patients with locally advanced SCCHN the opportunity for long term survival. Among the three chemoradiation regimens studied, C + P/RT was associated with the best complete response and survival rates. Complete response to therapy was the single most important predictor of overall survival. These three consecutive concurrent chemotherapy and radiation trials achieved a 5-year survival of greater than 30% for the entire population. These results support the use of this nonoperative approach for this group of patients with a historically poor prognosis.

A phase II study of paclitaxel, carboplatin, and hyperfractionated radiation therapy for locally advanced inoperable non-small-cell lung cancer (a Vanderbilt Cancer Center Affiliate Network Study)

PURPOSE

We conducted a prospective phase II study to determine the response rate, toxicity, and survival rate of concurrent weekly paclitaxel, carboplatin, and hyperfractionated radiation therapy (paclitaxel/carboplatin/HFX RT) followed by 2 cycles of paclitaxel and carboplatin for locally advanced unresectable non-small cell lung cancer (NSCLC). The weekly paclitaxel and carboplatin regimen was designed to optimize the radiosensitizing properties of paclitaxel during the concurrent phase of treatment.

METHODS AND MATERIALS

Forty-three patients with unresectable stage IIIA and IIIB NSCLC from the Vanderbilt Cancer Center and Affiliate Network (VCCAN) institutions were entered onto the study from June 1996 until May 1997. Weekly intravenous (IV) paclitaxel (50 mg/m(2)/l-hour) and weekly carboplatin (AUC 2) plus concurrent hyperfractionated chest RT (1.2 Gy/BID/69.6 Gy) were delivered for 6 weeks followed by 2 cycles of paclitaxel (200 mg/m(2)) and carboplatin (AUC 6).

RESULTS

Forty-two patients were evaluable for response and toxicities. Three patients achieved a complete response (7.2%) and 30 patients achieved a partial response (71.4%), for an overall response rate of 78.6% [95% C.I. (66.2%-91.0%)]. The 1- and 2-year overall and progression-free survival rates of all 43 patients were 61.6% and 35% respectively, with a median survival time of 14.3 months. The median follow-up time was 14 months. Esophagitis was the principal toxicity. Grade 3 or 4 esophagitis occurred in 11 patients (26%). There was an incidence of 7% grade 3 and 9.5% grade 4 pulmonary toxicities.

CONCLUSIONS

Weekly paclitaxel, carboplatin, plus concurrent hyperfractionated RT is a well-tolerated outpatient regimen. The response rate from this regimen is encouraging and appears to be at least equivalent to the more toxic chemoradiation trials. These findings warrant further clinical evaluation of weekly paclitaxel/carboplatin/HFX RT in a phase III study.

Paclitaxel exposure time determines the nature of the interaction with radiation in HeLa cells. the role of apoptosis

The purpose of the present study was to investigate further the mechanisms underlying subadditive and superadditive interactions of radiation and paclitaxel treatments in vitro. The protocol studied was a fixed radiation treatment (7 Gy) followed either immediately or after a 10 h delay by paclitaxel treatment. Paclitaxel treatment was exposure to either a fixed dose of paclitaxel (10 nM) for varying time intervals up to 25 h, or varying doses of paclitaxel up to 20 nM for a fixed exposure time of 24 h. The cells used were HeLa. Cell survival was assessed by colony forming ability and apoptosis was measured by flow cytometry. The results show that when the paclitaxel exposure time was 24 h superadditive interactions were observed at all paclitaxel doses. A reasonable correlation between surviving fraction as measured by colony forming ability and apoptosis in the attached cells at the end of paclitaxel treatment was observed. The nature of the interaction of radiation and subsequent paclitaxel treatment is critically dependent on the duration of the paclitaxel treatment.

The use of carboplatin and paclitaxel with daily radiotherapy in patients with locally advanced squamous cell carcinomas of the head and neck

PURPOSE

Unresectable squamous cell carcinomas of the head and neck (SCCHN) continue to pose a significant therapeutic challenge. This report defines the toxicities, efficacy, and prognostic factors associated with the combination of carboplatin (CBDCA), paclitaxel, and once-daily radiation for patients with locally advanced disease. Additionally, the pharmacokinetics of paclitaxel were investigated.

METHODS AND MATERIALS

From 1993-1998, 62 patients with Stage III-IV SCCHN were treated with 70.2 Gy of RT at 1.8 Gy/fraction/day to the primary site. Weekly chemotherapy was given during RT consisting of paclitaxel (45 mg/m(2)/wk) and CBDCA (100 mg/m(2)/wk). All patients presented with locally advanced disease; 77% had T4 disease and 21% had T3 disease. Fifty-eight percent had N2b-N3 disease.

RESULTS

Sixty patients were evaluable for response and survival with a median follow-up of 30 months (range 7-70). Ninety-eight percent of patients completed prescribed therapy. One patient died after refusing medical management for pseudomembranous colitis and is scored as a Grade 5 toxicity. Two patients suffered Grade 4 leukopenia. Median number of break days was two. A clinical complete response (CR) at the primary site was obtained in 82%, with a total (primary site and neck) CR rate of 75%. The median survival for the entire cohort is 33 months. Response to therapy and status of the neck at presentation were the only prognostic factors found to influence survival. The median survival for patients who attained a CR is 49 months versus 9 months in those who did not attain a CR (p < 0.0001). The 2- and 3-year overall survival for complete responders are 79% and 61%. Plasma paclitaxel concentrations in the range shown to be radiosensitizing were achieved.

CONCLUSIONS

Weekly carboplatin and paclitaxel given concurrently with definitive once-daily external beam radiation therapy is well tolerated with over 90% of patients completing prescribed therapy. An ultimate CR rate of greater than 70% was obtained, which translated directly into improved survival. With 48% 3-year overall survival for the entire group, this regimen is an excellent option for this group of patients with a historically poor prognosis.

Combination of paclitaxel and radiation: genotoxicity in vitro in four mammalian cell lines

Paclitaxel is an antimicrotubular agent that blocks the cells in the G2/M phase of the cell cycle. Due to this action, it is presumed that this drug could function as a radiation sensitizer. We studied the genotoxic effects of a combination of paclitaxel and radiation in four mammalian cell lines in the micronucleus assay. The results do not show a clear radiation-sensitizing effect. In the three cell lines, L5178Y, V79 and HeLa, the micronucleus frequencies varied around a theoretical additive effect of the single treatments (paclitaxel or radiation alone). Only the human breast cancer cell line MCF-7 showed consistently lower than additive micronucleus frequencies, although the deviation was not significant. Overall, it remains inconclusive whether paclitaxel exerts a radiosensitizing effect and, if so, whether this effect depends on the cell type or other characteristics of tumor biology.

Paclitaxel sensitivity correlates with p53 status and DNA fragmentation, but not G2/M accumulation

PURPOSE

The antitumor agent paclitaxel (Taxol) has been shown to arrest cells in mitosis through microtubule stabilization and to induce apoptosis. The tumor suppressor gene p53 is implicated in the regulation of cell cycle checkpoints and can mediate apoptotic cell death. Although initial studies demonstrated that various DNA-damaging agents can induce p53, more recent studies have also shown p53 induction following nonDNA-damaging agents, including paclitaxel. We investigated the influence of p53 abrogation on paclitaxel-induced cell kill and correlated the extent of mitotic arrest and DNA fragmentation by paclitaxel with the drug's cytotoxic effect.

MATERIALS AND METHODS

The parental human colorectal carcinoma cell line (RKO) with wild-type p53 alleles, and two transfected RKO cell lines with inactivated p53 (RKO.p53.13 with transfected mutant p53 and RC 10.3 with HPV-16-derived E6 gene) were exposed to graded doses of paclitaxel (1-100 nM) for 24-h intervals. The functional status of p53 in cells was assessed by thymidine and BrdU incorporation following exposure to ionizing radiation (4 Gy). Reproductive integrity following paclitaxel treatment was assessed by clonogenic assay. Immunolabeling and microscopic evaluation were used to assess mitotic accumulation and micronucleation. Apoptosis was assayed using DNA fragmentation analyses.

RESULTS

A 4-fold increase in paclitaxel sensitivity was observed among RKO cells deficient in p53 function compared with wild-type RKO cells (IC 50: 4 nM, 1 nM, 1nM for RKO, RKO.p53.13, RC 10.3, respectively). The increased cytotoxic effect in RKO cells with inactive p53 correlated with an increased propensity towards micronucleation and DNA fragmentation following paclitaxel treatment. However, no significant difference in peak mitotic accumulation was observed among RKO cells with functional or abrogated p53.

CONCLUSIONS

RKO cells lacking functional p53 demonstrate significantly enhanced sensitivity to paclitaxel compared with that of wild-type RKO cells. This response corresponded with increased micronucleation and DNA fragmentation in cells deficient in p53 function. Although previous published reports of enhanced paclitaxel sensitivity in p53-deficient cells correlated this finding with increased G2/M arrest, we did not observe any significant correlation between paclitaxel-induced cell kill and the degree of mitotic arrest. Our data suggest that apoptosis is the predominant mechanism of paclitaxel cytotoxicity in RKO cells and is likely mediated by a p53-independent process.

Hyperthermia enhances the response of paclitaxel and radiation in a mouse adenocarcinoma

PURPOSE

The aim of our study was to investigate if the efficacy of paclitaxel and paclitaxel-radiation treatments in vivo could be enhanced by hyperthermia.

MATERIALS AND METHODS

Paclitaxel was administered i.p. in doses from 30 to 60 mg/kg b.w. to (C3D2F1) mice bearing spontaneous mammary carcinoma. Local hyperthermia (41 degrees, 42 degrees, 43 degrees C) was carried out by immersing tumor-bearing legs in a water bath for 1 h. Single X-ray treatments from 10 to 90 Gy were performed. Tumor growth delay (TGD) or tumor control dose (TCD(50), radiation dose needed to induce local tumor control in 50% of irradiated animals) were the endpoints.

RESULTS

A significant increase of dose-dependent growth delay was observed in paclitaxel and 43 degrees C hyperthermia combined treatments, and a superadditive effect was seen with paclitaxel 45 mg/kg. Combined treatments with hyperthermia at 41 degrees and 42 degrees C were less effective. Administration of paclitaxel 24 h, 4 h, and 15 min before or 15 min and 4 h after hyperthermic treatments produced similar results (TGDs varying from 22.1 to 17 days), and administering paclitaxel 48 h before or 24 h after hyperthermic treatments decreased TGDs (about 10 days). Trimodality treatment (paclitaxel 45 mg/kg, hyperthermia, and X-ray), with a TCD(50) of 14. 1 Gy, in respect to the TCD(50) of 53.1 obtained with X-ray alone, was the most effective.

CONCLUSIONS

Hyperthermia enhanced the effectiveness of paclitaxel in all the tested protocols. Our results show a superadditive effect of paclitaxel 45 mg/kg combined with a hyperthermic treatment of 1 h at 43 degrees C. Trimodality treatment, evaluated in terms of percentage of cures, shows a very high enhancement ratio.

[In vitro study of a paclitaxel-radiotherapy combination on a human epidermoid tumor cell line]

PURPOSE

Paclitaxel is an agent which stabilizes microtubules, and has been shown to block different cells in the G2/M phase of the cell cycle and thus to modulate their radioresponsiveness. We investigated the radiosensitizing potential of paclitaxel in human head and neck cancer cells.

MATERIALS AND METHODS

ZMK-1 cells were incubated with paclitaxel for 3, 9, or 24 h before or during 24 h after irradiation. Paclitaxel concentrations of 70 nM, 7 nM, and 0.7 nM were chosen to obtain equivalent toxicity at the different incubation times: 3 h, 9 h, and 24 h, respectively. Radiation doses ranged from 0 to 8 Gy using 60Co source. Cell survival was measured by a standard clonogenic assay after a 9-day incubation. Flow cytometry was used to measure the capacity of paclitaxel to accumulate cells in the G2/M phase.

RESULTS

Paclitaxel alone possessed cytotoxicity dependent on time and concentration. There was a total of 40% of cells accumulated in G2/M after 24-36 h. When combined with radiation, the 9 h preincubation resulted in a radiosensitization. The 3 h pre-incubation as well as the 24 h post-incubation resulted in an infra-additive effect.

CONCLUSION

In our cells a radiosensitizing effect of paclitaxel could not be demonstrated unambiguously. The blockage of the cells in the G2/M phase is not the only mechanism to explain the potential radiosensitization of paclitaxel.

Paclitaxel is preferentially cytotoxic to human cervical tumor cells with low Raf-1 kinase activity: implications for paclitaxel-based chemoradiation regimens

BACKGROUND AND PURPOSE

Low Raf- kinase activity has been reported to be associated with radioresistance in epithelial tumor cell lines and with paclitaxel sensitivity in cervical tumor cells. Paclitaxel might thus be effective in eliminating radioresistant clones from cervical tumors, even in the absence of synergistic interaction between these therapeutic modalities. We thus established the relationship between Raf-1 kinase activity and radiosensitivity in human cervical tumor cells and determined if paclitaxel is preferentially cytotoxic to radio-resistant tumor clones.

MATERIALS AND METHODS

We established and contrasted the radiation and paclitaxel sensitivity of 12 human cervical tumor clones that exhibited a wide range of Raf-1 kinase activity.

RESULTS

Raf-1 kinase activity was inversely correlated (P = 0.001) with SF2 values in the 12 cervical tumor clones studied. Paclitaxel was preferentially cytotoxic to radioresistant tumor clones, with the level of paclitaxel-induced cytotoxicity being significantly (P = 0.0016) influenced by Raf-1 kinase activity levels.

CONCLUSIONS

Our in vitro data indicate that there are marked, but completely opposite, Raf-1 kinase dependencies of radiation and paclitaxel cytotoxicity in cervical tumor cells. The use of combined paclitaxel and radiotherapy treatment may thus lead to higher local control rates for squamous cell carcinoma of the cervix. Circumstantially, our data suggest that the greatest therapeutic gains might accrue if paclitaxel was administered when there is the greatest proportion of tumor clones with low Raf-1 kinase activity. It may thus be desirable to use paclitaxel towards the end of radiotherapy treatment or post-radiotherapy as consolidation therapy.

Cytotoxic and genotoxic effects of paclitaxel (Taxol) and radiation in a squamous cell carcinoma cell line of the larynx

Paclitaxel (Taxol) is an antimicrotubular agent which blocks the cells in the G2/M phase of the cell cycle. Because of this mechanism it is presumed that this drug could function as a radiation sensitizer. The cytotoxic and genotoxic effects of paclitaxel and a combination of paclitaxel and radiation were studied in the human laryngeal carcinoma cell line HLac 79. The growth of the cells was significantly reduced at concentrations of paclitaxel as low as 10 nM. Flow cytometry data showed a G2/M block after exposure to paclitaxel. Radiation at 12 and 24 h after drug treatment exerted an additive but no radiation sensitizing effect. As genotoxic effect paclitaxel induced multinucleated cells, possibly in a synergistic manner, at low concentrations (10 nM) and radiation doses up to 3 Gy.

Enhancement of radiation response by paclitaxel in mice according to different treatment schedules

PURPOSE

The aim of our study was to determine if paclitaxel could be used as a radiosensitizer in vivo.

MATERIALS AND METHODS

Paclitaxel was tested as a single agent and combined with an X-ray treatment. Paclitaxel was administered i.p. in doses from 30 to 120 mg/kg b.w. to (C3D2F1) mice bearing spontaneous mammary carcinoma. Tumor growth delay (TGD) or tumor control dose (TCD50, radiation dose needed to induce local tumor control in 50% of irradiated animals) and moist desquamation dose (MDD50, radiation dose needed to induce serious moist desquamation in 50% of the non-tumor-bearing feet) were the endpoints. DNA flow cytometric analysis was performed.

RESULTS

DNA analysis demonstrated a G2/M block of tumor cells and a depletion of cells in S phase, with a maximum at 24 h from paclitaxel administration. Administering paclitaxel, in graded doses, 15 min before a 10-Gy X-ray treatment resulted in a linear regression line, almost parallel to that with paclitaxel alone, with a growth delay of about 6 days. In contrast, varying the X-ray dose with a constant paclitaxel injection (45 mg/kg b.w.) treatment showed some degree of synergism as the linear regression curves diverged. Interval time and sequence between paclitaxel administration and a 10 Gy X-ray treatment did not influence TGD. Protocols with paclitaxel at 30, 45, or 60 mg/kg were combined with radiation treatments at various doses (from 10 to 65 Gy). Values of TCD50 varied from 50.8 Gy for X-ray alone to 31.8 Gy for paclitaxel 60 mg/kg + X-ray. No differences were observed among MDD of different protocols.

CONCLUSIONS

These results suggest that, under some conditions, paclitaxel combined with radiation can show superadditive effects and this result combined with the lack of severe normal tissue damage indicate that a favorable therapeutic gain can be obtained.

Phase I trial of taxol as a radiation sensitizer with cisplatin in advanced cervical cancer

OBJECTIVE

The aim of this study was to determine tolerable doses and potential toxicities of taxol, administered weekly, with concomitant cisplatin and radiation therapy in advanced cervical cancer.

METHODS

Patients with cervical cancer, either with evidence of distant metastatic disease at presentation or otherwise at high risk for recurrent disease, were eligible for this phase I study. Taxol was administered weekly as a 3-hr intravenous infusion in addition to the prescribed radiation therapy. The starting dose was 10 mg/m2/week and escalated at 10 mg/m2/week increments if tolerated by successive cohorts of three new patients. Cisplatin was given every 3 weeks at 50 mg/m2. Chemotherapy was continued until radiation was completed. For each patient quality of life was assessed weekly during therapy.

RESULTS

Sixteen patients, undergoing a total of 102 cycles, have been enrolled. Dose escalation of taxol from 10 mg/m2/week to 50 mg/m2/week was well tolerated, with no significant change in quality of life during therapy. Two radiation fractions (0.5%) were delayed due to toxicity from this chemotherapy regimen. Of 102 cycles, 6 resulted in grade 2 and 1 in grade 3 neutropenia, and no patient developed >grade 2 anemia or thrombocytopenia. Three patients developed GI-related toxicities and 1 patient presented with urosepsis during treatment. There was a 93% response rate to this regimen, with 10 patients (63%) presently having no evidence of disease.

CONCLUSIONS

This study has demonstrated that up to 50 mg/m2/week of taxol is well tolerated in patients undergoing radiation therapy for advanced cervical cancer. A phase II trial will assist in determining the efficacy of taxol as a radiation sensitizer in these patients.

Radiotherapy and concomitant weekly 1-hour infusion of paclitaxel in the treatment of head and neck cancer--results from a Phase I trial

PURPOSE

To define the maximum tolerated dose (MTD) by describing the dose-limiting toxicity (DLT) of weekly paclitaxel (PAC) given as a 1-h I.V. infusion in patients with head and neck cancer concomitant to irradiation.

METHODS AND MATERIALS

Patients with unresectable or incompletely resected head and neck cancer were enrolled into a prospective, dose-escalating Phase I study. Toxicity was graded according to the WHO toxicity score. MTD dose was defined when two out of six patients developed DLT. The starting dose of PAC was 20 mg/m2 once weekly I.V. over 60 min, with a subsequent dose escalation of 10 mg/m2 in cohorts of three new patients. Radiation therapy was administered in three field technique over 6-7 weeks in 2.0 Gy/daily fractions for 5 consecutive days/week up to total doses of 60-70 Gy.

RESULTS

From 1994-1996, 18 patients completing three dose levels were included into the study. Altogether, 101 courses of chemotherapy were evaluable for toxicity. On the second dose level (30 mg/m2) one of three patients experienced DLT with Grade IV mucositis. On the next dose level with 40 mg/m2 PAC weekly one patient experienced DLT being prolonged Grade III mucositis. From the following three patients required, two patients showed no DLT. The third patient showed mucositis of WHO Grade 4 and died from hemorrhage caused by a rupture of the a pharyngeal wall. Dose level 2 (30 mg/m2) was repeated and one of the three newly treated patients again suffered from mucositis WHO Grade 4.

CONCLUSION

When PAC is given weekly as a 1-h infusion concomitant to radiotherapy, MTD is 30 mg/m2 with mucositis being DLT; hematological and further nonhematological toxicity is mild.

The effect of paclitaxel on the radiosensitivity of gynecological tumor cells

BACKGROUND

Paclitaxel, a natural product from Taxus brevifolia, is a microtubule stabilizing agent, which has been shown to block different cells in the G2/M phase of the cell cycle and consequently, to modulate their radioresponsiveness. Our aim was to test the cytotoxic and radiosensitizing potential of paclitaxel, with respect to different gynecological tumors with varying radiosensitivities.

MATERIAL AND METHOD

We performed clonogenic assays and flow cytometry on 2 cell lines, MCF-7 (breast) and CaSki (cervix) cells, and on 2 primary ovarian tumor samples (OC-I and OC-II). The cells were irradiated with 200 kV X-rays, radiation doses of up to 8 Gy were applied either as single doses or in 2 Gy fractions. Paclitaxel concentrations varied from 0.07 to 700 nM, incubation times varied from 3 to 120 h.

RESULTS

Paclitaxel alone changed the cell cycle distribution of the cells tested and was cytotoxic in a time and concentration dependent manner. When combined with radiation, most schedules resulted in additive effects of the combined treatments. However, for MCF-7 cells, when 7 nM paclitaxel, applied 24 h before irradiation, were combined with fractionated irradiation a supra-additive effect with a SER of 1.2 was found. For CaSki cells, under comparable conditions the SER was 1.13 but the effects were not statistically significant.

CONCLUSION

Under specific conditions, paclitaxel exerted a weak radiosensitizing effect on breast and cervical carcinoma cells. A therapeutic gain may be possible on the basis of an optimal paclitaxel/radiation scheduling.

Subadditive interaction of radiation and Taxol in vitro

PURPOSE

To examine the dependency of Taxol-radiation interactions on the scheduling of the two agents.

METHODS AND MATERIALS

The human laryngeal squamous cell carcinoma line SCC20 was used for this study. Cells were irradiated as subconfluent cultures using Cs-137 gamma rays at a dose rate of 1.75 Gy/min. Cultures were pretreated with Taxol (7.5 nM for 12 h, S.F. = 0.4) and then irradiated with graded doses followed by either immediate plating or holding for 6 h either in the absence or presence of 7.5 nM Taxol prior to plating for colony-forming ability. Experiments in which cells were irradiated and then exposed to 7.5 nM Taxol for both 12 and 18 h were also performed. Parallel-flow cytometric analyses of cell-cycle distribution of the various treated populations were carried out.

RESULTS

The results indicate that pretreatment with Taxol induced a G2 block which was maintained during 6 h postirradiation holding either in the presence or absence of Taxol. No modification of radiosensitivity in the low-dose region was seen for cells treated with Taxol, irradiated, and plated immediately, with the resulting survival being compatible with an additive effect. However, for Taxol-pretreated cells held for 6 h postirradiation, either in the absence or presence of Taxol, the resulting survival reproducibly demonstrated a marked less than additive effect. This was particularly prominent for cells held in the presence of Taxol. Subsequent experiments in which Taxol was added to cells immediately postirradiation again demonstrated a less than additive effect of the two modalities.

CONCLUSION

The results of this study are consistent with a dual mechanism of action involving Taxol-induced radiation resistance, possibly as a consequence of postirradiation holding in G2, and radiation-induced Taxol resistance through an as-yet-undefined mechanism.

Cytotoxicity and cell-cycle effects of paclitaxel when used as a single agent and in combination with ionizing radiation

PURPOSE

This study aimed to determine the extent of paclitaxel-induced cytotoxicity and cell-cycle perturbations when used alone and in combination with radiation in human glioma cells.

METHODS AND MATERIALS

The effect of paclitaxel alone on three human glioma cells lines--SF-126, U-87 MG, and U-251 MG--was assessed after 24, 48, 72, or 96 h treatment. For experiments in combination with radiation, cells were exposed to either a long (48-h) or short (8-h) duration of paclitaxel treatment prior to irradiation. Cell survival was determined by clonogenic assay. Cell cycle perturbations were assessed by using flow cytometry to measure the proportion of cells in G1, S, and G2/M phases.

RESULTS

When cells were treated with paclitaxel alone for > or = 24 h, cytotoxicity increased up to a threshold dose, after which it plateaued. When treatment duration was < or = 24 h, cytotoxicity was appreciably greater in U-251 MG cells than in SF-126 and U-87 MG cells. After 24 h of paclitaxel treatment, cells in plateau phase growth had increased survival compared to cells in log phase growth. In contrast, after 8 h paclitaxel treatment, mitotic cells had reduced survival compared to cells from an asynchronous population. Cell-cycle perturbations were consistent with the presence of a mitotic block after paclitaxel treatment, although changes in other cell-cycle phase fractions varied among cell lines. For experiments in combination with radiation, cytotoxicity was increased when cells were irradiated after 48 h of paclitaxel treatment but not after 8 h of treatment.

CONCLUSION

The duration of paclitaxel treatment and the location of cells in the cell cycle modify the degree of radiation cytotoxicity. The mechanisms of paclitaxel cytotoxicity are likely to be multifactorial because varying effects are seen in different cell lines. Furthermore, it is clear that simply increasing the number of cells in G2/M is insufficient in itself to increase the response of cells to radiation.

In vitro evaluation of Taxol combined with radiations in human squamous cell carcinoma spheroids

The effect of Taxol on the radiation sensitivity of human squamous carcinoma of the head and neck region was determined in vitro, using clonogenic assays and multicellular tumor spheroids (MTS). Radiosensitivity parameters were determined by alpha and beta for clonogenic assays, and by the residual/control volume ratios at 2 Gy (RSV2) and the dose inducing 50% decrease in MTS number (SCD50) for spheroids. In HTB43 and CAL27 colonies, the combination was antagonist. In spheroids, Taxol induced a decrease of RSV2 and SCD50 in HTB43 and CAL27 MTS and their combinations with radiation were synergistic and additive, respectively. Therefore, the different results obtained by clonogenic assays and MTS may suggest higher drug incorporation through the multiple cell layers of the spheroids than in monolayers.

Concurrent Paclitaxel and Radiation Therapy for Solid Tumors

BACKGROUND: Combination radiation and chemotherapy has an intuitive appeal for improving cancer treatment. Experimental results suggest that paclitaxel plus radiation might produce additive or synergistic effects. METHODS: A series of phase I and II trials to test tolerance and begin to evaluate effectiveness were performed on patients with non-small cell lung cancer, high-grade astrocytic brain tumors, and pancreatic and gastric cancers. RESULTS: Tolerance of the combined drug and radiation programs was generally good. Esophagitis was dose-limiting for the intrathoracic tumors. Hematologic toxicity was mild, but peripheral neuritis and cutaneous reactions were common. CONCLUSIONS: These trials show that paclitaxel plus concurrent radiation is feasible at the dose levels and schedules tested. Antitumor responses have been observed.

In vitro concurrent paclitaxel and radiation of four vulvar squamous cell carcinoma cell lines

BACKGROUND

The antitubule agent paclitaxel causes a cell cycle blockage in the most radiosensitive part of the cell cycle, the G2/M phase. The possible radiosensitizing effect of paclitaxel was tested in four vulvar (UM-SCV-1A, UM-SCV-1B, UM-SCV-2, and UM-SCV-4) squamous cell carcinoma (SCC) cell lines.

METHODS

A 96-well plate clonogenic assay was performed with paclitaxel and radiation, both separately and concomitantly. Survival data were fitted to the linear quadratic model. The area under the curve, equivalent to the mean inactivation dose (D), was obtained by numerical integration. The effect of paclitaxel on radiosensitivity was measured as the AUC ratio (paclitaxel plus radiation: radiation alone). This ratio was compared with the surviving fraction (SFP) after paclitaxel alone.

RESULTS

Paclitaxel concentrations of 0.4 to 2.0 nanomolar (nM) caused 1 to 70% inhibition of clonogenic survival. The AUC values of the cell lines were 1.9 to 2.9 gray. A full additive effect was observed when paclitaxel and radiation were administered concurrently; however, a supra-additive effect never occurred. The type of paclitaxel radiation interaction was not affected by the concentration of the drug nor did the type of interaction vary between cell lines studied.

CONCLUSIONS

Paclitaxel and radiation used concomitantly produced a clear additive effect at all concentrations and in all vulvar carcinoma cell lines tested. Although no supra-additive effect was observed, the additive effect already in nM concentrations could be beneficial in clinical use and, therefore, requires further investigation.

Treatment of mice with a novel antineoplastic agent taxol before irradiation increases the frequency of micronuclei in the bone marrow

The frequency of micronucleated polychromatic erythrocytes (MPCE) and the normochromatic erythrocytes (MNCE) and polychromatic and normochromatic erythrocyte ratio (P/N ratio) was studied at 12, 24 and 36 h postirradiation in the bone marrow of male mice treated or not with taxol before exposure to 0-4 Gy of 60Co gamma radiation. The frequency of MPCE increased with the increase in radiation dose in a dose-related manner in the irradiated control group. A peak frequency of MPCE was observed at 24 h postirradiation in irradiated control group. The pattern of increase in MNCE was similar to that of MPCE except that a highest number of MNCE was scored at 36 h postirradiation. Taxol administration to animals before irradiation resulted in a significant elevation in the frequency of MPCE and MNCE at all the postirradiation time periods studied. This increase was dose related as observed in the irradiated control group. Irradiation resulted in a dose-dependent decline in the P/N ratio at all the postirradiation time periods studied. The P/N ratio was significantly lower in the taxol + irradiated group compared to the irradiated control group at all postirradiation time periods. A maximum decline in P/N ratio was observed at 36 h postirradiation for both irradiated control and taxol + irradiated groups. The dose response for MPCE, MNCE and P/N ratio was linear quadratic for both the irradiated and taxol + irradiated groups.

Proliferation and clonal survival of human lung cancer cells treated with fractionated irradiation in combination with paclitaxel

PURPOSE

This study was performed to determine the effects of a continuous exposure to paclitaxel (taxol) in combination with fractionated irradiation on cell proliferation and survival.

METHODS AND MATERIALS

Human lung carcinoma cells (SW1573) were given a daily treatment with 3 Gy of x-rays during 5 days in the continuous presence of 5 nM taxol. The surviving fraction and the total number of cells were determined every 24 h before and immediately after irradiation.

RESULTS

Irradiation with 5 x 3 Gy and 5 nM taxol cause approximately the same inhibition of cell proliferation. In combination these treatments have an additional effect and the cell population increases no further after the first 24 h. Whereas the cells become more resistant to taxol after the first 24 h with a minimum survival of 42%, taxol progressively reduces the population of surviving cells in combination with x-rays when the number of fractions increases, up to 25-fold relative to irradiation alone. The enhancement effect of 5 nM taxol is likely to be attributed to an inhibition of the repopulation during fractionated irradiation and not to an increased radiosensitivity. Only after treatment with 10 or 100 nM taxol for 24 h, which is attended with a high cytotoxicity, is moderate radiosensitization observed.

CONCLUSION

Taxol, continuously present at a low concentration with little cytotoxicity, causes a progressive reduction of the surviving cell population in combination with fractionated irradiation, mainly by an inhibition of the repopulation of surviving cells between the dose fractions.

Radiation recall dermatitis and pneumonitis in a patient treated with paclitaxel

BACKGROUND

Radiation recall refers to a tissue reaction produced by a chemotherapeutic agent in a previously irradiated field that would not occur in a nonirradiated field. A number of agents have been reported to cause radiation recall. Recently, there have been case reports of recall dermatitis from paclitaxel treatment.

METHODS

A patient with metastatic lung cancer received palliative radiation to her mediastinum and ribs. Because of disease progression, she subsequently received paclitaxel.

RESULTS

After paclitaxel administration, the patient became acutely dyspneic. A subsequent chest X-ray revealed a parenchymal opacity in a region that corresponded with the patient's radiation portal. She also developed a severe skin reaction in the previously treated electron field.

CONCLUSIONS

This is one of few reported cases of recall dermatitis from paclitaxel and is also suggestive of recall pneumonitis, a phenomenon previously unreported to the authors' knowledge. Given paclitaxel's ability to function as a radiosensitizer, this response is not unexpected. As the frequency of paclitaxel administration increases, its potential as a radiation sensitizer and radiation recall should be considered.

S-phase specificity of cell killing by docetaxel (Taxotere) in synchronised HeLa cells

Cell viability following short (1 h) contact with paclitaxel or docetaxel was assayed using synchronised HeLa cells. Docetaxel proved almost totally lethal against S-phase cells. Its toxicity was only partial against cells in mitosis, and declined to a minimum with progression to G1. For paclitaxel, cytotoxicity increased with progression through S and G2, peaked at the time of mitosis, and decreased thereafter. Maximum resistance to paclitaxel was in early S. Although lethal, brief exposure to docetaxel in S-phase did not delay progression through S and G2. Gross damage was detectable immediately after mitosis, with dysfunction in cytokinesis and accumulation of multinucleated, non-viable cells. Arrest of cells at prometaphase required continuous contact with lethal amounts of docetaxel or reintroduction of drug shortly before mitosis following pulse-chase treatment in mid-S-phase. Paclitaxel at moderate doses presumably acts mostly via damage to the mitotic spindle. In contrast, the available data suggest that docetaxel primarily targets centrosome organisation, leading to abortive mitosis and cell death.