Left atrial remodeling in patients with atrial septal defects

BACKGROUND

Information regarding left atrial (LA) substrate in conditions predisposing to atrial fibrillation (AF) is limited.

OBJECTIVE

This study sought to characterize the left atrial remodeling that results from chronic atrial stretch caused by atrial septal defect (ASD).

METHODS

Eleven patients with hemodynamically significant ASDs and 12 control subjects were studied. The following were evaluated using multipolar catheters: effective refractory period (ERP) at 7 sites, P-wave duration (PWD), conduction time, and inducibility of AF. LA electroanatomic maps were created to determine atrial activation, and regional conduction and voltage abnormalities.

RESULTS

Patients with ASDs showed significant LA enlargement (P <0.001), unchanged or prolonged atrial ERPs, increase in LA conduction times (P = 0.03), prolonged PWD (P <0.001), regional conduction slowing (P <0.001), greater number of double potentials or fractionated electrograms (P <0.0001), reduced atrial voltage (P <0.001), and more frequent electrical scar (P = 0.005) compared with control subjects. In addition, patients with ASDs showed a greater propensity for sustained AF with single extrastimuli (4 of 11 vs. 0 of 12, P = 0.04).

CONCLUSION

ASDs are associated with chronic left atrial stretch, which results in remodeling characterized by LA enlargement, loss of myocardium, and electrical scar that results in widespread conduction abnormalities but with no change or an increase in ERP. These abnormalities were associated with a greater propensity for sustained AF.

Defibrillator reset by radiotherapy

The number of patients with implantable cardioverter-defibrillator (ICD) is rapidly increasing due to their expanding indications. Amongst the various types of electromagnetic interferences, little is reported about the effects of radiotherapy. We report a case of electrical reset of a single chamber ICD by scattered irradiation from radiotherapy.

High-density mapping of atrial fibrillation in humans: relationship between high-frequency activation and electrogram fractionation

INTRODUCTION

Sites of complex fractionated atrial electrograms (CFAE) and dominant frequency (DF) have been implicated in maintaining atrial fibrillation (AF); however, their relationship is poorly understood.

METHODS AND RESULTS

Twenty patients underwent biatrial high-density contact mapping (507 +/- 150 points/patient) during AF. CFAE were characterized using software to quantify electrogram complexity (CFE-mean). Spectral analysis determined the frequency with greatest power and sites of high DF with a frequency gradient. CFE-mean was higher (less fractionated) for right compared with left atria (P < 0.001) and in paroxysmal compared with persistent AF (P < 0.001). DF was lower for right compared with left atria (P = 0.02) and in paroxysmal compared with persistent AF (P < 0.001). There was significant regional variation in DF in paroxysmal (P < 0.001) but not persistent AF. Highest DF points clustered together with 5.2 +/- 1.7 clusters/patient. Correlation between CFE-mean and DF was poor on a point-by-point basis (r =-0.17, P < 0.001), but moderate on an individual basis (r =-0.50, P = 0.03). Exploration of their spatial relationship demonstrated CFAE areas in close proximity (median 5 mm, IQR 2-10) to high DF sites; within 10 mm in 80% and 10-20 mm in 10%. Simultaneous activation mapping at these sites further supports this observation.

CONCLUSION

Greater fractionation and higher DF are seen in persistent AF and left atria during AF. Preferential areas of high DF are observed in paroxysmal but not persistent AF. CFAE and DF correlate within an individual but not point-by-point. Exploration of their spatial relationship demonstrates CFAE in areas adjacent to high DF, and this is supported by activation mapping at these sites.

Differential effects of intravenous magnesium on atrioventricular node conduction in supraventricular tachycardia

Evidence from noninvasive studies suggests magnesium has a differential effect on atrioventricular nodal (AVN) pathways. To further explore the electrophysiologic effects of intravenous magnesium sulfate (MgSO(4)) on supraventricular tachycardia, with particular reference to AVN conduction pathways, we studied 23 patients with supraventricular tachycardia at the time of electrophysiologic study. Tachycardia cycle length; AH, HV, and VA intervals; anterograde and retrograde Wenckebach thresholds; slow and fast pathway effective refractory periods (ERPs); accessory pathway ERP; right atrial and ventricular ERPs; blood pressure; and serum magnesium were evaluated before and after administration of MgSO(4) during sustained tachycardia. AVN reentry was induced in 14 patients and atrioventricular reentry was induced in 9; 1 of the latter had dual AVN physiology with tachycardia using the slow pathway. Serum magnesium level increased from 0.88 +/- 0.11 to 1.79 +/- 0.14 mmol/L (p <0.0001). Magnesium increased tachycardia cycle length to a greater extent in those with dual AVN physiology than those without: 340 +/- 54 to 370 +/- 57 ms versus 347 +/- 29 to 350 +/- 30 ms (p = 0.01). This was associated with greater increase in AH interval in those with dual AVN physiology than in those without: 241 +/- 59 to 270 +/- 60 ms versus 144 +/- 16 to 140 +/- 20 ms (p = 0.003). Presence of dual AVN physiology was more frequently associated with reversion to sinus rhythm: 5 of 15 versus 0 of 8 (p = 0.06). MgSO(4) did not alter other measured parameters. In conclusion, magnesium increases tachycardia cycle length and AH interval in patients with dual AVN physiology through a dominant effect on the slow AVN pathway.

Delayed termination of ventricular tachycardia after cardioversion

Both anti-tachycardia pacing and cardioversion via an implantable cardioverter defibrillator are effective therapies for ventricular tachycardia (VT). We report a case of VT where cardioversion resulted in delayed termination of tachycardia. Potential mechanisms for this observation are discussed.

Atrial fibrillation and anabolic steroid abuse

Atrial fibrillation (AF) is the most common sustained arrhythmia to occur in humans. Several predisposing substrates such as increasing age, heart failure, hypertension and valvular heart disease have been identified. The use of illicit drugs as the substrate for AF is not frequently recognized.

Integration of new chemotherapeutic agents into chemoradiotherapy for stage III non--small cell lung cancer: focus on docetaxel

Randomized clinical trials have shown that combinations of chemotherapy plus thoracic radiation improve survival compared with radiotherapy alone in stage III non--small cell lung cancer (NSCLC). Furthermore, two recent studies have concluded that concurrent chemoradiotherapy produces superior results to sequential administration. Dependent on the dose and schedule used, chemotherapy may contribute by eradicating distant micrometastases by improving local control as a radiosensitizer, or through both mechanisms. In general, sequential approaches in which full-dose platinum-based chemotherapy precedes thoracic radiation or surgery have improved outcome by impacting distant metastases. In contrast, concurrent chemoradiotherapy using low-dose cisplatin is reported to improve survival by reducing local recurrence without an impact on distant failure rates. In view of these observations, chemoradiotherapy strategies integrating both radiosensitizing agents and dose levels of chemotherapy effective against micrometastases may prove to be most efficacious. Because distant metastases remain the major site of failure, it also is likely that more effective chemotherapy will be required to further improve the current level of response and survival. Fortunately, several newly available chemotherapeutic agents are both highly active against NSCLC and are potent radiosensitizers. In this report we review recent data regarding integration of new chemotherapeutic agents into chemoradiotherapy programs in stage III NSCLC, focusing on trials investigating docetaxel. Encouraging results, including those of the Southwest Oncology Group trial 9504, suggest that docetaxel will play a major role in the future of combined-modality therapy for locally advanced NSCLC. Semin Oncol 28 (suppl 9):26-32.

Activity of high-dose toremifene plus cisplatin in platinum-treated non-small-cell lung cancer: a phase II California Cancer Consortium Trial

PURPOSE

Although cisplatin is an important agent in non-small-cell lung cancer (NSCLC), de novo resistance is common and acquired resistance emerges rapidly during therapy. Proposed mediators of platinum resistance include the protein kinase C (PKC) signal transduction pathway and associated c-FOS overexpression. While estrogen administration has been reported to upregulate PKC and c-FOS expression, the triphenylethylenes tamoxifen and toremifene potentiate platinum cytotoxicity by inhibition of PKC. Downregulation of c-FOS expression has been reported to result from PKC inhibition. In view of these findings, we hypothesized that toremifene would reverse platinum resistance and that this interaction would be influenced by tumor estrogen receptor (ER) status.

MATERIALS AND METHODS

A phase II trial of high-dose toremifene (600 mg orally daily on days 1-7) plus cisplatin (50 mg/m2 intravenously on days 4 and 11) every 28 days in NSCLC patients was conducted. A group of 30 patients with metastatic NSCLC who had been previously treated with platinum-based therapy were enrolled.

RESULTS

All of the 30 patients were assessable for toxicity and 28 for tumor response. Therapy was well tolerated with minimal hematologic and non-hematologic toxicity. Common toxicity criteria grade 3 hematologic toxicity was seen in only three patients. Five patients achieved a partial response for an overall response rate of 18% (95% CI 6-37). Median overall survival was 8.1 months (95% CI 5.4-17). To assess PKC, ER, and c-Fos expression by immunohistochemistry, 12 informative pretreatment patient tumor specimens were obtained. Four patient tumor specimens were positive for one or both PKC isoforms (alpha and epsilon) while c-Fos was overexpressed in three. None of the responding patient tumors exhibited c-FOS or PKC-epsilon overexpression. ER expression was found to be infrequent (8%), contrasting with previous reports in this tumor type.

CONCLUSION

While this phase II study indicates that high-dose toremifene plus cisplatin is feasible, active, and well tolerated in NSCLC patients previously treated with platinum compounds, the mechanism of action remains unclear. Further study of this regimen is warranted.

Sequential combination chemotherapy in patients with advanced nonsmall cell lung carcinoma: carboplatin and gemcitabine followed by paclitaxel

BACKGROUND

The objective of this Phase II study was to evaluate the concept of sequential chemotherapy in the treatment of patients with advanced nonsmall cell lung carcinoma (NSCLC) by the administration of carboplatin plus gemcitabine followed by of paclitaxel.

METHODS

Patients with Stage IIIB (pleural effusion) or Stage IV NSCLC and a Southwest Oncology Group (SWOG) performance status (PS) of 0--2 were eligible. Therapy consisted of three cycles of carboplatin (area under the concentration-time curve = 5.5 mg/mL per minute) on Day 1 and gemcitabine 1000 mg/m(2) on Days 1 and 8 every 21 days followed by three cycles of paclitaxel 225 mg/m(2) every 21 days.

RESULTS

Of the 37 eligible patients, 81% had Stage IV disease, and 27% had a PS of 2; all were assessable for survival and toxicity; 32 patients were assessable for response. After treatment with carboplatin plus gemcitabine, there were no complete responses (CRs) and eight partial responses (PRs) (response rate [RR], 25%; 95% confidence interval [95% CI], 11--43%). The best overall response was two CRs and eight PRs (RR, 31%; 95% CI, 16--50%). The median survival time was 9.5 months, the 1-year survival rate was 36% (95% CI, 26--44%), the 2-year survival rate was 11% (95% CI, 3--25%), and the median time to disease progression was 4.9 months. The median survivals were 11.2 months for patients with a PS of 0--1 and 6.4 months for patients with a PS of 2. Noncumulative, reversible thrombocytopenia was the principal toxicity with carboplatin/gemcitabine therapy. Paclitaxel therapy was well tolerated, and moderate (Grade 3) neutropenia was the primary toxic effect. One cardiac death occurred, possibly related to paclitaxel.

CONCLUSIONS

This study is the first to evaluate planned sequential chemotherapy in patients with NSCLC. Carboplatin plus gemcitabine followed by paclitaxel was well tolerated and resulted in promising survival in this patient population. This pilot experience forms the basis for an ongoing SWOG trial. Cancer 2001;92:146-52. Published 2001 American Cancer Society.

KT3.2 and KT3.3, two novel human two-pore K(+) channels closely related to TASK-1

We report the cloning of human KT3.2 and KT3.3 new members of the two-pore K(+) channel (KT) family. Based on amino acid sequence and phylogenetic analysis, KT3.2, KT3.3, and TASK-1 constitute a subfamily within the KT channel mammalian family. When Xenopus oocytes were injected with KT3.2 cRNA, the resting membrane potential was brought close to the potassium equilibrium potential. At low extracellular K(+) concentrations, two-electrode voltage-clamp recordings revealed the expression of predominantly outward currents. With high extracellular K(+) (98 mM), the current-voltage relationship exhibited weak outward rectification. Measurement of reversal potentials at different [K(+)](o) revealed a slope of 48 mV per 10-fold change in K(+) concentration as expected for a K(+)-selective channel. Unlike TASK-1, which is highly sensitive to changes of pH in the physiological range, KT3.2 currents were relatively insensitive to changes in intracellular or extracellular pH within this range due to a shift in the pH dependency of KT3.2 of 1 pH unit in the acidic direction. On the other hand, the phorbol ester phorbol 12-myristate 13-acetate (PMA), which does not affect TASK-1, produces strong inhibition of KT3.2 currents. Human KT3.2 mRNA expression was most prevalent in the cerebellum. In rat, KT3.2 is exclusively expressed in the brain, but it has a wide distribution within this organ. High levels of expression were found in the cerebellum, medulla, and thalamic nuclei. The hippocampus has a nonhomogeneous distribution, expressing at highest levels in the lateral posterior and inferior portions. Medium expression levels were found in neocortex. The KT3.2 gene is located at chromosome 8q24 1-3, and the KT3.3 gene maps to chromosome 20q13.1.

Integration of new chemotherapeutic agents into chemoradiotherapy for stage III non--small cell lung cancer: focus on docetaxel

Randomized clinical trials have shown that combinations of chemotherapy plus thoracic radiation improve survival compared with radiotherapy alone in stage III non--small cell lung cancer (NSCLC). Furthermore, two recent studies have concluded that concurrent chemoradiotherapy produces superior results to sequential administration. Dependent on the dose and schedule used, chemotherapy may contribute by eradicating distant micrometastases by improving local control as a radiosensitizer, or through both mechanisms. In general, sequential approaches in which full-dose platinum-based chemotherapy precedes thoracic radiation or surgery have improved outcome by impacting distant metastases. In contrast, concurrent chemoradiotherapy using low-dose cisplatin is reported to improve survival by reducing local recurrence without an impact on distant failure rates. In view of these observations, chemoradiotherapy strategies integrating both radiosensitizing agents and dose levels of chemotherapy effective against micrometastases may prove to be most efficacious. Because distant metastases remain the major site of failure, it also is likely that more effective chemotherapy will be required to further improve the current level of response and survival. Fortunately, several newly available chemotherapeutic agents are both highly active against NSCLC and are potent radiosensitizers. In this report we review recent data regarding integration of new chemotherapeutic agents into chemoradiotherapy programs in stage III NSCLC, focusing on trials investigating docetaxel. Encouraging results, including those of the Southwest Oncology Group trial 9504, suggest that docetaxel will play a major role in the future of combined-modality therapy for locally advanced NSCLC. Semin Oncol 28 (suppl 9):26-32.

Prospective evaluation of cancer clinical trial accrual patterns: identifying potential barriers to enrollment

PURPOSE

Well-conducted cancer clinical trials are essential for improving patient outcomes. Unfortunately, only 3% of new cancer patients participate in clinical trials. Barriers to patient accrual in cancer clinical trials must be identified and overcome to increase patient participation.

MATERIALS AND METHODS

We prospectively tracked factors that potentially affected patient accrual into cancer clinical trials at the University of California Davis Cancer Center. Oncologists seeing new outpatients were asked to complete questionnaires regarding patient characteristics and the physician's decision-making on patient eligibility, protocol availability, and patient opinions on participation. Statistical analysis was performed to correlate these parameters with subsequent protocol accrual.

RESULTS

There were 276 assessable patients. At the initial visits, physicians did not consider clinical trials in 38% (105/276) of patients principally because of a perception of protocol unavailability and poor performance status. Physicians considered 62% (171/276) of patients for participation in clinical trials. Of these, only 53% (91/171) had an appropriate protocol available for site and stage of disease. Seventy-six of 90 patients (84%) with available protocols met eligibility criteria for a particular study. Only 39 of 76 patients (51%) agreed to participate in cancer clinical trials, for an overall accrual rate of 14% (39/276). The remainder (37/76, 49%) declined trial participation despite meeting eligibility criteria. The most common reasons were a desire for other treatment (34%), distance from the cancer center (13%), patient refusal to disclose reason (11%), and insurance denial (8%). Patients with private insurance were less likely to enroll in clinical trials compared to those with government-funded insurance (OR, 0.34; P =.03; 95% CI, 0.13 to 0.9).

CONCLUSION

Barriers to cancer clinical trial accrual can be prospectively identified and addressed in the development and conduct of future studies, which may potentially lead to more robust clinical trials enrollment. Investigation of patient perceptions regarding the clinical trials process and the role of third party-payers is warranted.

Gemcitabine in combination with new platinum compounds: an update

Combinations of gemcitabine (Gemzar) with cisplatin (Platinol) are among the most active new chemotherapy regimens developed for advanced non-small-cell lung cancer. Carboplatin (Paraplatin) is a platinum analog devoid of many of the nonhematologic toxicities associated with cisplatin. Although few direct comparisons have been made, when administered by area under the concentration-time curve (AUC) dosing, carboplatin is probably equivalent to cisplatin in advanced non-small-cell lung cancer and provides an improved therapeutic index. Based on its favorable toxicity profile, carboplatin has supplanted cisplatin for use in combination with paclitaxel in several different tumor types. Initial trials combining gemcitabine and carboplatin using standard days 1, 8, and 15 dosing of gemcitabine suggested that thrombocytopenia was problematic. More recently, 21-day schedules in which gemcitabine is administered only on days 1 and 8 have demonstrated both efficacy and improved toxicity profiles. Here we review recent studies investigating gemcitabine plus carboplatin and preliminary data regarding combinations of gemcitabine with the new platinum analog oxaliplatin.

Neoadjuvant therapy for non-small cell lung cancer

Clinical trials evaluating neoadjuvant or preoperative therapy for locally advanced non-small cell lung cancer (NSCLC) have demonstrated the feasibility, tolerability and activity of this approach. Three randomized trials have reported improved survival in patients with stage III NSCLC treated with preoperative chemotherapy followed by surgical resection compared to surgery alone. Combinations of neoadjuvant chemotherapy plus thoracic radiotherapy have also been investigated, generally resulting in higher rates of pathologic response, but higher toxicity rates as well. The best approach to neoadjuvant therapy remains to be determined and may well be substage dependent. In bulky stage III NSCLC, the role of surgery itself remains unclear and is the subject of an ongoing intergroup trial in the US. Regardless, neoadjuvant therapy has emerged as an important paradigm for clinical research since it serves as an in vivo test of chemosensitivity in patients, and represents a 'window of opportunity' for testing new chemotherapeutic agents and novel strategies. Among the new chemotherapeutic agents being investigated in this setting is docetaxel, one of the most active agents in first- and second-line chemotherapy of NSCLC, and a potent radiosensitizer. Preliminary studies have confirmed the feasibility of integrating docetaxel into neoadjuvant treatment strategies and encouraging results have been reported.

Gemcitabine/carboplatin combination regimens: importance of dose schedule

Platinum compounds, either cisplatin (Platinol) or carboplatin (Paraplatin), in combination with a number of new chemotherapeutic agents, have demonstrated improved response or survival compared to cisplatin alone or older platinum-based regimens. Gemcitabine (Gemzar)-platinum combinations are of particular interest because of their interactive mechanisms of action, demonstrated preclinical synergism, and the single-agent activity of gemcitabine. Indeed, gemcitabine and cisplatin regimens have proven to be among the most efficacious in the palliative treatment of advanced non-small-cell lung cancer. In view of the reduced nonhematologic toxicities associated with the platinum analogue, carboplatin, several combinations of new agents and carboplatin have been developed and incorporated into clinical practice. This article describes recent clinical trials evaluating gemcitabine plus carboplatin, and the impact of the dosing schedule on the feasibility and tolerability of this combination.

Treatment of poor-prognosis extensive disease small-cell lung cancer with an all-oral regimen of etoposide and cyclophosphamide - a Southwest Oncology Group clinical and pharmacokinetic study

PURPOSE

An all-oral regimen of etoposide and cyclophosphamide was developed for use in poor-prognosis extensive disease small-cell lung cancer. Limited pharmacokinetic sampling was used to derive a pharmacodynamic model predictive of myelosuppression early in the course of therapy.

PATIENTS AND METHODS

Eligible patients were chemotherapy-naive and had extensive disease small-cell lung cancer with either SWOG performance status 2 or serum albumin <3.5 g/dl. The first cohort (n = 18) received etoposide orally at 50 mg daily and cyclophosphamide orally at 50 mg daily days 1-14 every 28 days. Due to good hematologic tolerance, the second cohort (n = 39) received both agents orally at 50 mg twice daily days 1-14 every 28 days. Plasma etoposide levels were determined in samples drawn at baseline, and at 1 h, 2 h, and 23.5 h (trough) after the first dose. Linear regression analysis was used to determine pharmacokinetic and demographic parameters predictive of myelosuppression.

RESULTS

A total of 173 treatment cycles were delivered. Patients on the daily regimen had a 22% response rate (complete and partial), a 22% unconfirmed response rate, and a 5-month median survival, while patients on the twice-daily regimen had a 28% response rate (complete and partial), a 13% unconfirmed response rate, and a 7-month median survival. Granulocytopenia and alopecia were the most common toxicities seen. Significant granulocytopenia could be predicted for the twice-daily regimen according to the formula ln(AGC nadir)=7.80 - 1.88(trough), with an increased incidence of granulocytopenia if the etoposide trough value was >/=1.49 microg/ml.

CONCLUSION

Oral etoposide and oral cyclophosphamide given days 1-14 every 28 days is well tolerated and results in an acceptable response rate and median survival in poor-prognosis (poor performance status or low serum albumin) extensive disease small-cell lung cancer. A trough etoposide level obtained within 24 h of starting therapy can predict severe granulocytopenia.

Paclitaxel (Taxol): an inhibitor of angiogenesis in a highly vascularized transgenic breast cancer

Paclitaxel (Taxol), a promoter of microtubule polymerization and a radiosensitizing agent, is one of the more active anticancer drugs in the current treatment of solid tumors. In this study, we show that paclitaxel possesses an antiangiogenic property associated with a down-regulation of vascular endothelial growth factor (VEGF) in a highly-vascularized transgenic murine breast cancer (Met-1). Paclitaxel, at non-cytotoxic doses of 0, 3 and 6 mg/kg/day, was administered intraperitoneally for 5 days to nude mice bearing the Met-1 breast tumor. Extent of intratumoral angiogenesis, as indicated by microvessel tortuosity and microvessel density, was significantly reduced by paclitaxel in a dose-dependent manner. Paclitaxel also suppressed expression of VEGF in the Met-1 cells transplanted in nude mice or maintained in cell culture. These results indicate that antiangiogenesis associated with a down-regulation of VEGF is an additional mode of action of paclitaxel.

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.

Southwest Oncology Group phase II trial of concurrent carboplatin, etoposide, and radiation for poor-risk stage III non-small-cell lung cancer

PURPOSE

A phase II study was conducted by the Southwest Oncology Group (SWOG) to assess the efficacy and toxicity of concurrent carboplatin, etoposide, and thoracic radiation (XRT) in a defined population of poor-risk patients with stage III non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients with stage III NSCLC were eligible if they were excluded from cisplatin-based protocols because of poor pulmonary or renal function, history of congestive heart failure, hearing loss, peripheral neuropathy, or weight loss. Carboplatin 200 mg/m2 daily intravenously days 1, 3, 29, and 31 and etoposide 50 mg/m2 daily intravenously days 1 through 4 and 29 through 32 were administered. Beginning day 1, XRT was delivered at 1.8 to 2.0 Gy daily to a total dose of 61 Gy.

RESULTS

Within a period of 1 year, 63 patients were registered and 60 were eligible. Patient characteristics were age 47 to 79 years, performance status 0 to 1 (82%) and 2 (18%), and stages IIIA (60%) and IIIB (40%) NSCLC. The most common grades 3 and 4 toxicities included leukopenia (50%), thrombocytopenia (23%), and esophagitis (15%). There were no treatment-related deaths. The overall confirmed response rate was 29%, and median overall survival was 13 months (95% confidence interval, 11 to 14 months). The 2-year survival rate was 21%.

CONCLUSION

This chemoradiotherapy regimen is well tolerated in poor-risk patients and yields a median survival similar to that of good-risk patients who received cisplatin-based chemoradiotherapy. This chemoradiotherapy regimen will be compared with XRT alone in poor-risk patients with stage III NSCLC in a randomized phase III trial.

Phase II trial of edatrexate plus carboplatin in metastatic non-small-cell lung cancer: a Southwest Oncology Group study

BACKGROUND

Edatrexate and carboplatin are each active single agents in the treatment of non-small-cell lung cancer (NSCLC). Preclinical studies in NSCLC lines have demonstrated schedule-dependent synergy of edatrexate followed by carboplatin. In a phase I trial, we demonstrated the tolerability of this combination, the ability of ice-chip cryotherapy to ameliorate dose-limiting mucositis, and promising activity in NSCLC. This phase II trial (SWOG 9207) was undertaken to investigate the efficacy of this regimen in stage IV NSCLC.

METHODS

A total of 24 patients with stage IV disease were accrued to this Southwest Oncology Group (SWOG) multicenter study. Treatment consisted of edatrexate 80 mg/m2 (50% dose on day 8) intravenously weekly for 5 weeks, then every other week, and carboplatin 350 mg/m2 every 28 days.

RESULTS

Of the 24 patients, 23 were assessable for toxicity and response; one was ineligible for study entry. Myelosuppression was the most significant toxicity; grade 3-4 neutropenia was seen in 8/23 patients. Two patients died of neutropenic sepsis during the first cycle of therapy, in both instances associated with the presence of pleural effusions. Although mild mucositis was common, it was dose-limiting (grade 3) in only three patients. Objective response was observed in 3/23 patients (13%). The median survival time was 7 months, and 30% of patients remained alive at one year.

CONCLUSIONS

This study suggests that ice-chip cryotherapy is effective in reducing the severity of mucositis typically associated with this edatrexate schedule of administration. However, unexpectedly severe myelosuppression resulted in death from neutropenic sepsis in two patients with third space fluid collections, leading to a protocol amendment to exclude such patients from study entry. Furthermore, response and median survival with this dose schedule of edatrexate and carboplatin do not appear to be improved compared to other chemotherapeutic regimens tested by SWOG in this patient population.

Twice-weekly paclitaxel and radiation for stage III non-small cell lung cancer

A phase I study was conducted to investigate the safety and efficacy of twice-weekly paclitaxel (Taxol; Bristol-Myers Squibb Company, Princeton, NJ) and concurrent thoracic irradiation in patients with stage III non-small cell lung cancer. Radiation therapy beginning on day 1 was delivered in 1.8- to 2.0-Gy daily fractions, to a total dose of 61 Gy. Paclitaxel at a starting dose of 25 mg/m2/d was administered intravenously over 1 hour before daily radiation on days 1, 4, 8, 11, 15, 18, 22, 25, 29, 32, 36, and 39, for a total of 12 doses over 6 weeks. The paclitaxel dose was escalated by 5 mg/m2/d in each cohort of patients to determine the maximum tolerated dose. The highest paclitaxel dose reached was 40 mg/m2/d, as defined by dose-limiting toxicities of esophagitis and desquamation within the radiation fields. For each dose group, the median total number of paclitaxel doses administered was 12 and the median total radiation dose was 61 Gy. Response rates ranging from 50% to 100% were observed (three of six patients at paclitaxel 25 mg/m2, four of six at 30 mg/m2, seven of seven at 35 mg/m2, six of six at 40 mg/m2), for an overall response rate of 80%. We conclude that the maximum tolerated dose of paclitaxel is 35 mg/m2 given twice weekly in a 1-hour infusion for 6 weeks concurrently with thoracic irradiation. This study provides the basis for an ongoing trial combining twice-weekly paclitaxel and carboplatin with concurrent thoracic irradiation for patients with stage III non-small cell lung cancer.

Clonal origin of multiple lung cancers: K-ras and p53 mutations determined by nonradioisotopic single-strand conformation polymorphism analysis

Disease stage is the most important factor in determining prognosis and treatment of lung cancer. Staging of lung cancer is complicated by presentation of multiple pulmonary malignant lesions with a similar histology. It is a dilemma to decide if these lesions are synchronous primaries arising from different malignant clones or metastases from a single clone. Lung cancer is associated with multiple genetic abnormalities including mutations of K-ras and p53, which are believed to occur prior to onset of metastasis. To determine the clonal origin of multiple pulmonary malginant nodules, we analyzed point-mutations of K-ras and p53 by microdissection, polymerase chain reactions (PCR), nonradioisotopic single-strand conformation polymorphism (SSCP) analysis, and DNA sequencing. Each pulmonary lesion was microdissected from paraffin slides. Genomic DNA was amplified by two sequential PCRs followed by electrophoresis in a minigel and silver staining. Deoxyribonucleic acid sequencing was performed if necessary to confirm a mutation found upon SSCP analysis. Applying this molecular approach, we were able to differentiate the clonal origins of multiple malignant nodules of the lung as exemplified by the two cases presented.

Chemoradiotherapy for poor-risk stage III non-small cell lung cancer

Cisplatin-based chemoradiotherapy is becoming a standard treatment for patients with stage III non-small cell lung cancer (NSCLC). However, a significant proportion of patients with lung cancer also present with co-morbid conditions that indicate a poor prognosis and poor tolerance of treatment. We have completed a phase I/II study to evaluate the tolerability and efficacy of carboplatin-based chemoradiotherapy for patients with poor-risk stage III NSCLC. Twenty-four patients with stage IIIA/B NSCLC and concurrent medical conditions rendering them ineligible for cisplatin-based chemoradiotherapy protocols were treated with thoracic irradiation, 1.8 to 2 Gy daily to the primary tumor and regional lymph nodes, for a total dose of 61 Gy. Concurrently, patients received carboplatin 200 mg/m2/d intravenously on days 1, 3, 29, and 31, and etoposide 50 mg/m2/d intravenously on days 1 through 4 and 29 through 32. Among 23 assessable patients, 96% completed the two planned courses of chemotherapy and 87% completed the planned chest irradiation. Grade 3/4 toxicities included neutropenia in nine patients (39%), thrombocytopenia in five (22%), esophagitis in seven (30%), and nausea in two (9%). Four patients (17%) achieved a complete response and 16 (70%) a partial response, yielding an overall response rate of 87%. The median survival was 12 months, and the 2- and 3-year survival rates were 30% and 20%, respectively. In conclusion, this treatment regimen was relatively well tolerated, with promising response and survival in patients with poor-risk stage III NSCLC. This pilot study provides a basis for further investigation of this treatment regimen.

Concurrent carboplatin, etoposide and thoracic radiation for poor-risk stage III non-small-cell lung carcinoma: a pilot study

PURPOSE

A pilot study was conducted to assess the tolerance and efficacy of concurrent carboplatin, etoposide, and thoracic radiation in poor-risk patients with Stage III non-small-cell lung carcinoma (NSCLC).

METHODS AND MATERIALS

Patients had Stages IIIA/IIIB NSCLC and were ineligible for available clinical trials employing cisplatin-based chemoradiation due to one or more protocol-defined poor-risk factors or concomitant medical conditions. Treatment consisted of thoracic radiation, 1.8 to 2 Gy daily, to the primary tumor and regional lymph nodes to a total dose of 61 Gy. Concurrently, patients received carboplatin 200 mg/m2/day intravenously on days 1, 3, 29, and 31, and etoposide 50 mg/m2/day intravenously on days 1-4 and 29-32. Response was assessed by chest computed tomography (CT) 4 weeks after treatment was completed.

RESULTS

A total of 26 patients were enrolled and 23 of these patients, including 11 with Stage IIIA and 12 Stage IIIB NSCLC, were eligible and assessable. Ninety-six percent (96%) of the patients completed the two planned courses of chemotherapy, and 87% completed the planned chest radiation. Grade III/IV toxicities included neutropenia in nine patients (39%), thrombocytopenia in five (22%), esophagitis in seven (30%), and nausea in two (9%). One patient died of a pulmonary embolism during treatment, and another died of complications due to a tracheoesophageal fistula. Four patients (17%) achieved a complete response and 16 (70%) a partial response, yielding an overall response rate of 87%. The median survival was 12 months, and the 2-year actuarial survival was 40%.

CONCLUSION

This treatment regimen was well tolerated, with promising response and survival in poor-risk patients with Stage III NSCLC. These results are being validated in a Phase II trial conducted by the Southwest Oncology Group.

Differential single- versus double-strand DNA breakage produced by doxorubicin and its morpholinyl analogues

The morpholinyl analogues of doxorubicin (DOX) have previously been reported to be non-cross-resistant in multidrug resistant (MDR) cells due to a lower affinity for P-glycoprotein relative to the parent compound. In order to further investigate the mechanisms of action of these morpholinyl anthracyclines, we examined their ability to cause DNA single- and double-strand breaks (SSB, DSB) and their interactions with topoisomerases. Alkaline elution curves were determined after 2-h drug treatment at 0.5, 2 and 5 microM, while neutral elution was conducted at 5, 10 and 25 microM in a human ovarian cell line, ES-2. A pulse-field gel electrophoresis assay was used to confirm the neutral elution data under the same conditions. Further, K-SDS precipitation and topoisomerase drug inhibition assays were used to determine the effects of DOX and the morpholinyl analogues on topoisomerase (Topo) I and II. Under deproteinated elution conditions (pH 12.1), DOX, morpholinyl DOX (MRA), methoxy-morpholinyl DOX (MMDX) and morpholinyl oxaunomycin (MX2) were equipotent at causing SSB in the human ovarian carcinoma cell line, ES-2. However, neutral elution (pH 9.6) under deproteinated conditions revealed marked differences in the degree of DNA DSB. After 2-h drug exposures at 10 microM, DSBs were 3300 rad equivalents for MX2, 1500 for DOX and 400 for both MRA and MMDX in the ES-2 cell line. Pulse-field data substantiated these differences in DSBs, with breaks easily detected after MX2 and DOX treatment, but not with MRA and MMDX. DOX and MX2 thus cause DNA strand breaks selectively through interaction with Topo II, but not Topo I. In contrast, MRA and MMDX cause DNA breaks through interactions with both topoisomerases with a predominant inhibition of Topo I.

Loss of nm23 and Alu DNA in human lung cancer propagated in nude mice

Freshly resected human non-small cell lung cancer (NSCLC) has been successfully transplanted and propagated subcutaneously in nude mice (Cancer Letters 61 (1991) 53-60). We used this model to study the changes of the human metastasis suppressor genes, nm23-H1 and nm23-H2, through the process of propagation and metastasis of human NSCLC. Using a non-radioisotopic Southern analysis, the nm23-H1 and nm23-H2 genes were detected without evidence of deletion in the early generations of the tumor grafts. These genes, however, were absent from the tumor grafts sampled past 4 generations of propagation and from all the propagated metastases originated from the subcutaneous grafts. Further restriction analysis revealed that only mouse DNA, but no human Alu DNA, was present in the tumor specimens which lacked the human nm23 genes. Thus, there is a loss of human DNA but a gain of mouse DNA in the propagated tumors originated from the transplanted human NSCLC. The mechanisms of loss of human DNA in these propagated tumors in nude mice have yet to be delineated.

Metabolic conversion of methoxymorpholinyl doxorubicin: from a DNA strand breaker to a DNA cross-linker

Methoxymorpholinyl doxorubicin (MMDX) is a novel anti-cancer anthracycline that differs from doxorubicin in its mechanisms of action, pattern of resistance and metabolism. Whereas doxorubicin is primarily an inhibitor of topoisomerase II, MMDX inhibits both topoisomerases I and II, resulting in predominantly single-strand DNA cleavage and, to a lesser extent, double-strand DNA breakage. MMDX is equally cytotoxic in vitro against the doxorubicin-sensitive and -resistant uterine sarcoma cell lines, MES-SA and Dx5. Using fluorescent laser cytometry, MMDX was retained intracellularly to a similar extent in MES-SA and Dx5; the intracellular retention of MMDX was 7.5-fold higher than that of doxorubicin in Dx5. The cytotoxicity of MMDX on an ovarian carcinoma cell line, ES-2, was potentiated 50-fold by preincubating the drug with human liver microsomes and NADPH. This cytotoxic potentiation was associated with the appearance of DNA interstrand cross-links. The in vitro potentiation of MMDX was inhibited by cyclosporin A, which is a substrate for human cytochrome P450 IIIA.

Characterization of covalent DNA binding of morpholino and cyanomorpholino derivatives of doxorubicin

BACKGROUND

The doxorubicin analogues cyanomorpholino doxorubicin (MRA-CN) and morpholino doxorubicin (MRA) were synthesized in an attempt to avoid the cardiotoxicity and drug resistance of doxorubicin therapy. MRA-CN forms interstrand DNA cross-links without requiring microsomal metabolic activation in the presence of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) to form a product that alkylates DNA, but MRA requires metabolic activation. Alkylation produces DNA cross-links, which are associated with potentiation of the cytotoxicity of some drugs.

PURPOSE

Our purpose was to study the DNA binding of MRA-CN and MRA with and without metabolic activation in order to better understand the mechanisms for cross-linking DNA.

METHODS

We used [3H]MRA and [3H]MRA-CN, with the 3H labeled at C-2 and C-6 of the morpholino ring. MRA (10 nM) was incubated with human liver microsomes with or without NADPH to measure DNA binding. In addition, a filter elution assay was used to determine the nature and extent of drug binding to DNA in the human ovarian carcinoma cell line ES-2. We studied the appearance of interstrand cross-links versus total DNA adducts in pBR322 plasmid DNA incubated with 100 nM MRA-CN in cell-free medium and then subjected to denaturation and agarose gel electrophoresis.

RESULTS

Regardless of the extracellular concentration of the drug (1-100 nM), 85% of intracellular MRA-CN was covalently bound to DNA, and the total amount of drug bound to DNA was proportional to extracellular drug concentration. No covalent binding of MRA to DNA was found in cells exposed to 10 nM MRA alone for 2 hours. In contrast, 10% of the intracellular drug was bound to DNA if the cells were exposed to MRA preincubated with human liver microsomes and NADPH. The percentage of plasmids containing at least one interstrand cross-link rose from 35% at 15 minutes to 92% at 2 hours. We estimate that eight molecules of MRA-CN were adducted per molecule of pBR322 DNA (or one drug adduct per 545 base pairs), with a minimum of 12% of the adducts forming interstrand cross-links.

CONCLUSIONS

These results suggest that the carbons at positions 2 and 6 of the morpholino ring of both MRA-CN and the activated metabolite of MRA are retained in the drug-DNA adduct. They also indicate that the formation of interstrand DNA cross-links by MRA-CN is preceded by formation of drug adducts to a single strand of DNA.

Role of cytochrome P-450 from the human CYP3A gene family in the potentiation of morpholino doxorubicin by human liver microsomes

The cytotoxicity of the morpholino derivative of doxorubicin (MRA) can be potentiated 50- to 100-fold by human liver microsomes and NADPH (J. Natl. Cancer Inst., 81: 1034, 1989). This metabolic potentiation is inhibited by carbon monoxide or hypoxia, indicating that it is cytochrome P-450-dependent. The potentiation is also inhibited by the cytochrome P-450 inhibitors, SKF-525A and cimetidine. The metabolism by the microsomes is substrate-specific, varying markedly with alterations of either the morpholino or anthracycline ring substituents. No potentiation occurred with doxorubicin itself, or the cyanomorpholinyl, methoxypiperidinyl, N-hydroxyethyl or the O-bridged cyanomorpholinyl analogues of doxorubicin. We utilized a panel of human liver microsomes and cytochrome P-450 type-specific antibodies to further identify the isoform(s) of cytochrome P-450 that potentiated the cytotoxicity of MRA. The potentiation correlates well with the benzyloxyresorufin assay (r2 = 0.98) and aflatoxin B1 metabolism (r2 = 0.98), both assays that are relatively specific for CYP3A proteins. Correlations were also observed for the expression of protein(s) cross-reacting with an antibody against rat cytochrome P-450 CYP3A1 (r2 = 0.97) and MRA metabolism. This antibody against the rat cytochrome P-450 CYP3A isoform(s) inhibited more than 90% of the potentiation of the cytotoxicity by human liver microsomes. Antibodies against the CYP1A2, CYP2C6, and CYP2B2 isoforms produced no inhibition, nor did their expression by Western blotting correlate with MRA potentiation. Complete inhibition of the potentiation of MRA by human liver microsomes was found when the CYP3A substrates cyclosporin A and erythromycin were used in the reaction system. These data indicate that the CYP3A isoform(s) of cytochrome P-450 play a major role in the metabolism of MRA in vitro to a more active species.

Sensitization of drug resistant human ovarian cancer cells to cyanomorpholino doxorubicin (MRA-CN) by modulation of glutathione metabolism

MRA-CN, the alkylating cyanomorpholino derivative of doxorubicin (DOX), is extremely potent (100 to 1000 fold increase in cytotoxicity in vitro and in vivo), more lipophilic, non-cardiotoxic, and non-cross-resistant in multidrug resistant cells compared to DOX. We have developed an ovarian carcinoma cell line ES-2R that is 4-fold resistant to MRA-CN, compared to the parental ES-2 cells. This resistant cell line exhibits cross-resistance to alkylators and ionizing radiation. Glutathione (GSH) and GSH-dependent enzymes were found to be altered in the resistant cells with 1.5-fold increase in GSH, and 2- to 3-fold increase in the pi-class glutathione-s-transferase (GST) protein. Both D,L buthionine-S,R-sulfoximine (BSO) and ethacrynic acid (EA), inhibitors of GSH biosynthesis and pi-class GST activity, respectively, could sensitize the ES-2R cells to MRA-CN. These findings implicate a role for GSH metabolism in resistance of ES-2R cells to MRA-CN. The data also indicates the potential utility of EA to modulate GST activity and sensitize tumor cells toward alkylators.

Multifactorial mechanisms associated with broad cross-resistance of ovarian carcinoma cells selected by cyanomorpholino doxorubicin

The cyanomorpholino derivative of doxorubicin (MRA-CN) is a DNA intercalator and alkylator that is a highly potent cytotoxin, non-cross-resistant in multidrug-resistant cells, and noncardiotoxic in comparison with doxorubicin. To further examine mechanisms of action and resistance to MRA-CN, a cell line resistant to MRA-CN, ES-2R, was established by growing a human ovarian carcinoma cell line, ES-2, in increasing concentrations of the drug. The resistant subline was 4-fold resistant to MRA-CN and cross-resistant to other DNA cross-linking agents, cisplatin (7-fold) and carmustine (3-fold), as well as to the DNA strand-breaking agents etoposide (6-fold), doxorubicin (2-fold), bleomycin (5-fold), and ionizing radiation (2-fold). In contrast, ES-2R cells were not cross-resistant to vinblastine. Several months of additional growth of ES-2R cells in MRA-CN did not yield higher, stable levels of drug resistance. A low level of P-glycoprotein was detectable in the ES-2R cells. However, the extent of intracellular accumulation of [3H]MRA-CN by this resistant cell line was identical to that of the sensitive line. The number of DNA cross-links formed by cisplatin in ES-2R was only 50% of that of the ES-2 cells and was associated with a 50% increase in the rate of repair of these cross-links in the resistant cells. Ionizing radiation induced similar amounts of single- and double-strand breaks in the ES-2 line as well as in the ES-2R cells. There was no apparent difference between the two cell lines in the rate and extent of repair of these DNA breaks. Thus, enhanced DNA repair cannot explain the phenomenon of cross-resistance to radiation. Comparisons of glutathione (GSH) content and the enzymes involved in GSH homeostasis showed significant differences. Resistant cells contained 1.5-fold more GSH, a 2.2-fold increase in gamma-glutamyltranspeptidase activity, and a 2.4-fold increase in GSH reductase compared with ES-2 cells (all P less than 0.05). Total glutathione-S-transferase (GST) activity was 2.6-fold higher (P less than 0.01) in the ES-2R line. The pi-class GST subunit by Western blotting and GST activity toward ethacrynic acid were increased 2-fold in the resistant cells. Depletion of GSH levels in ES-2R cells by buthionine sulfoximine restored the sensitivity of ES-2R to MRA-CN. These findings implicate a role for GSH metabolism in the resistance phenotype of ES-2R cells. We have previously reported that these cells have an increased generation time and decreased topoisomerase II content. Thus, the ES-2R cell line exhibits a complex phenotype of broad cross-resistance, which is likely to involve multiple mechanisms, and includes enhanced DNA repair and increased GSH content and GST activity.

Paradoxical increase in DNA cross-linking in a human ovarian carcinoma cell line resistant to cyanomorpholino doxorubicin

The cyanomorpholino analog of doxorubicin (MRA-CN) is a potent cytotoxic agent which is known to cross-link DNA. A human ovarian carcinoma cell line, ES-2, was grown in increasing concentrations of MRA-CN from 0.1 to 0.5 nM. The resultant resistant subline, ES-2R, was 4-fold resistant to MRA-CN. DNA damage and repair in response to MRA-CN were compared in the parental and resistant cell lines using alkaline elution. DNA cross-links were detectable after 3-h incubation of the cells at 37 degrees C in MRA-CN at concentrations greater than or equal to 1.0 nM. Paradoxically, 2-fold more cross-links were detected in the ES-2R cells as compared with the ES-2 cells. This paradoxical difference in cross-links between the 2 cell lines was observed to increase with time of exposure to 2.5 nM of MRA-CN. Non-protein-associated DNA strand breaks were also detected in the 2 cell lines after exposure to 2.5 nM of the drug. The ES-2 cells consistently showed twice as many breaks as the ES-2R cells, which could explain the paradoxical higher apparent DNA cross-linking observed with the ES-2R cells after exposure to MRA-CN. Studies of the time course of cross-link repair after exposure to MRA-CN revealed that 75% of the DNA cross-links disappeared in the ES-2R cells by the end of 8 h in drug-free medium. In contrast, cross-links in the ES-2 cells were undetectable after 4 h, which coincided with a progressive increase in DNA strand breaks. The topoisomerase II level in the ES-2 cells was 2- to 4-fold higher than that in the ES-2R cells. However, proteinase K treatment of the lysed cells did not increase the number of apparent strand breaks produced by MRA-CN, suggesting that topoisomerase II may not be involved. These findings indicate that, in addition to DNA cross-linking, MRA-CN causes DNA strand breakage. Resistance to MRA-CN in the ES-2R cells is associated with more apparent DNA cross-linking and less DNA strand breakage, which may be a consequence of differences in DNA repair and/or nonspecific DNA degradation between the resistant and the sensitive cell lines.