P4-07-02: Detection, Enrichment, Characterization and Propagation of Circulating Tumour Cells from Patients with Advanced Metastatic Breast Cancer

Background: Circulating tumour cells (CTCs) have attracted much attention lately due to their potential utility in diagnostic, therapeutic and prognostic applications. Characterization of these cells may indeed permit more targeted and individualized therapeutic approaches, as well as provide a means to monitor treatment response. Although detection of CTCs in peripheral blood (PB) is relatively easy using current methodologies, characterization of the CTC pool has proven more challenging due to their low abundance. Furthermore, in-vitro expansion of this elusive cell pool in mammosphere cultures has not yet been reported. In order to achieve a more complete characterization of CTCs and attempt to obtain live cells in sufficient quantity for in vitro expansion, we have used aphaeresis as a means to collect a large initial cell fraction from which to enrich CTCs from peripheral blood.

Methods: A cohort (n=17) of late stage breast cancer patients were first screened using 10ml PB. Peripheral blood mononuclear cells (PBMCs) were isolated using a Ficoll gradient and then enriched for CTCs by anti-CD45 negative selection using an automated system (RoboSep) based on magnetic bead separation. CTCs were detected by immunocytochemistry (ICC) for cytokeratin expression and patients classified as CTC-positive were selected for the aphaeresis procedure. Following collection of aphaeresis material (APM), PBMCs were isolated using a Ficoll gradient, enriched by automated anti-CD45 negative selection and characterized for a variety of markers by ICC, immunofluorescence and flow cytometry. CTCs were then cultured in serum-free medium as monolayers and suspensions. Recovery at the various steps of the isolation process was determined using PB from healthy subjects spiked with MCF-7 breast cancer cells and processed using the same approach.

Results: Recovery of spiked MCF-7 cells was about 40% after Ficoll and magnetic bead separation. Using this negative selection procedure 17/17 (100%) of subjects tested were positive at screening. Most patients (14/17) underwent aphaeresis and a large number (9,600 to 108,000) of enriched CTCs was recovered from APM in all patients tested, either as individual cells or as CTC clusters. Using dual immunofluorescence labelling, co-localization of the epithelial cell marker CK8 and the chemokine receptor CXCR4 was observed within CTCs. Furthermore, over 20% of CTCs were positive for both CK8 and ALDH1, indicative of a stem-like phenotype. APM-derived CTCs from all patients (14/14) could be propagated, both as attached cells and in suspension culture. They formed colonies in monolayer culture, and clusters in mammosphere culture, indicating stem cell-like properties. They replicated for at least three passages in mammosphere culture.

Conclusion: Our CTC detection and enrichment method using negative selection offers a distinct advantage over current methodologies, including collection of clusters, and the ability to grow and expand CTCs in serum-free culture conditions. Furthermore, these cells demonstrate breast cancer stem cell-like characteristics, the ability to replicate for multiple passages as mammospheres in suspensions and a metastatic signature.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-07-02.

Is tamoxifen prevention in younger women underutilized? Analysis of competing causes of mortality

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Background: Our past work on Tamoxifen impacting overall mortality outcome among survivors of the 1st breast cancer (JCO, 1998, 16:2018–24) introduced methodology permitting analyses of competing cause mortality, adjustable as new data emerge. This analysis estimates Tamoxifen impact on four conditions among BrCa survivors known to be affected by Tamoxifen, i.e. contralateral breast cancer; uterine cancer, cardiovascular (CVS) mortality, and thromboembolism (TE). Updated RR rates of Tamoxifen impacting the four conditions were obtained from recent literature (Lancet, 2005, 365:1687–1717; JNCI,2005, 97:1652–62; 97:1609–10). Methods: The effect of Tamoxifen was calculated by applying Relative Risk Rates (RR) to the respective underlying Canadian age-specific mortality figures, separately for each condition. The final mortality impact was the “net mortality”, defined as differences of deaths, from each condition, between 1,000 Tamoxifen users vs 1,000 non-users (Dif N/1,000), expressed for ages <50 and >50. (i.e sum of avoidances [-] vs hazards[+]) Results: see Table below. Conclusion: Our results show a favorable Tamoxifen impact on overall mortality, particularly evident for women age <50, in whom the breast cancer mortality reduction significantly outweighs the hazards. These data are applicable to Tamoxifen prevention in population-women who are at high risk for BrCa. Their outcome profiles affected by Tamoxifen mirror those of the survivors of the 1st BrCa. While for women >50, other chemoprevention alternatives exist (i.e. trials of Aromatase Inhibitors), for younger women no chemoprevention trials are presently in existence. Our data indicate that in those, routine use of Tamoxifen may save substantial numbers of lives.

[Table: see text]

No significant financial relationships to disclose.

Phase II study of concurrent temozolomide and whole brain radiation therapy in patients with brain metastasis

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Background: 30% of patients (pts) with lung cancer develop brain metastases, with XRT representing the conventional treatment of multiple BM. Methods: Pts with lung cancer, Brain metastases (BM) and performance status of 0–2 were enrolled. TMZ (75mg/m2 day 1–14) given on cycle 1 with XRT (3000cGy in 10 fractions) followed by cycles 2–4 TMZ (200mg/m2 day 1–5, q 4 weeks). Pts with active systemic disease received also chemotherapy (cisplatin or docetaxel or paclitaxel) during TMZ cycles 2–4. Primary end points: 1. Radiological response of BM assessed after 4–6 weeks from the end of XRT, 2. Treatment related toxicity, 3.Functional Scale score(FSS)(1 best, 3 worst, based on interaction of WHO performance status, score 0–4, with the neurological status score 1–3). FSS was assessed at baseline, and during the follow up visits. Secondary end points: time to progression and overall survival. Results: 22 patients enrolled, 8 pts received TMZ alone and 14 pts had additional chemotherapy. CR was documented in 2 pts, PR in 6 pts, SD in 5 pts, 4 pts progressed on treatment; 5 pts were not evaluable (death from other causes within 2 months from diagnoses). FSS at baseline was available on 19/22 patients. Of those, thirteen, four and two pts had a FSS of 1, 2 and 3, respectively. Fifteen of the 19 pts maintained their FSS at the end of Tx, with 3 pts exhibiting deterioration, and one patient improved. Post treatment FSS remained stable in 16 patients up to one month prior to death. The median survival (22 pts) from the time of diagnosis of BM was 9 months with average TTP of 3.5 months. Except for moderate nausea and vomiting there was no significant toxicity by combining TMZ with XRT. The addition of single agent chemotherapy to TMZ was well tolerated but two patients who required GCSF support. Conclusion: Adding TMZ to XRT for the treatment of BM from in lung cancer patients showed a response in 13 out of 17 assessable patients with a median survival of 9 months which is above the mean 3 to 6 months survival reported in the literature with XRT alone. More importantly, the majority of patients maintained a stable FSS up to one month prior to death suggesting a quality of life benefit during most of their life span. TMZ can be safely administered concomitantly with either XRT or with other single agent chemotherapy.

No significant financial relationships to disclose.

A phase I study of gemcitabine/cisplatin/etoposide in the treatment of small-cell lung cancer

PURPOSE

To define the maximum tolerated dose and toxicity of combined cisplatin, etoposide, and gemcitabine in patients with small-cell lung cancer.

METHODS

We undertook a phase I study in patients with either extensive small-cell lung cancer with or without prior chemotherapy, or limited disease who had progressed or recurred despite prior treatment. Patients received cisplatin 75 mg/m2 i.v. day 1, etoposide 50-100 mg/m2 i.v. day 1 followed by oral administration of 50-100 mg/m2 days 2 5, and gemcitabine at either 800 or 1000 mg/m2 i.v. days 1 and 8, on a 3 weekly cycle.

RESULTS

We treated 20 patients, 14 at the 800 mg/m2 gemcitabine dose level, and six at the 1000 mg/m2 dose level. The protocol initially used an etoposide dose of 100 mg/m2 etoposide daily (i.v. day 1 and orally days 2-5), but the first two patients died of septic complications. With reduction of the etoposide dose to 50 mg/m2 daily x 5, the regimen was well tolerated. At this etoposide dose, neutropenia, mucositis, and gastrointestinal toxicity occurred in one patient at each of the two gemcitabine dose levels. In addition, one patient receiving gemcitabine at the 1000 mg/m2 level experienced a possible allergic reaction. The overall response rate was 54%. Patients on gemcitabine at the 800 mg/m2 level who had not received prior chemotherapy had the highest response rate, at 75%.

CONCLUSION

The recommended phase II doses for this regimen are cisplatin 75 mg/m2 i.v. day 1, etoposide 50 mg/m2 i.v. day 1 and orally days 2-5, and gemcitabine 800 mg/m2 i.v. days 1 and 8. Future trials should further examine the optimal relative doses and schedule of gemcitabine and etoposide.