The Significance of Circulating Tumour Cells in the Clinic

BACKGROUND

Despite the hype about circulating tumour cells (CTCs) in the early 2000s and their potential in the diagnosis of metastasis, in recent years, the hope for personalised cancer management relies more on circulating tumour (ct)DNA that has entered the clinic in a much more efficient way. So far, approved methods for CTCs in the clinic only provide the counting of CTCs, which enables monitoring of the progression of metastatic breast, prostate, and colorectal cancer patients with therapy. Approved methods for ctDNA facilitate the analysis of specific mutations in lung cancer, thereby providing indications for potentially successful treatments. This situation inclined the balance towards molecular analysis in liquid biopsy, leveraged by new technologies and companies providing broader mutation and gene expression analysis towards the early diagnosis of cancer.

STUDY DESIGN

We conducted a search for the studies published to date that provide details about the significance of CTCs in the clinic.

RESULTS

Many studies and clinical trials have demonstrated the potential of CTCs in patient screening, early diagnosis, therapy resistance, and patient prognosis.

CONCLUSIONS

Large multi-centre studies are still needed to formally validate the clinical relevance of CTCs. Meticulous design of the clinical trials is a crucial point to achieve this long-sought objective.

Detection of circulating tumor cells in patients with locally advanced rectal cancer undergoing neoadjuvant therapy followed by curative surgery

PURPOSE

Circulating tumor cells (CTCs) represent an independent prognostic factor in metastatic colorectal cancer, while their significance in early stages is still an open issue. The aim of the study is to investigate the role of CTCs in rectal cancer patients undergoing neoadjuvant chemoradiotherapy (CT-RT).

METHODS

In this prospective single institutional study, cT3-4 and/or N+ rectal cancer was treated with neoadjuvant CT-RT. The primary endpoints were as follows: evaluation of CTCs at baseline (t0), after CT-RT (t1), within 7 days after surgery (t2), and at 6 months from surgery (t3) and correlation with main patient/tumor characteristics, CEA, response to neoadjuvant therapy, and disease-free survival (DFS). CTCs were enumerated with the CellSearch System in 22.5 ml peripheral blood. A repeated measure analysis for binary outcome was used to evaluate over time changes in the percentage of CTCs detectable in blood samples.

RESULTS

Of the 90 patients enrolled in this study, 85 were eligible consisting of 52 males and 33 females. Median age was 63 years and median follow-up was 38 months. CTCs were available for all patients at t0, for 67 at t1, for 68 at t2, and for 62 at t3. CTCs >0 were reported on 16 (19%) at t0, on 5 (7.5%) at t1, on 6 (9%) at t2, and on 3 (5%) at t3 (P value for trend 0.039). Only for CT-RT responders, CTCs reduced from t0 to t1. No statistically significant association was found between CTCs and main patient/tumor characteristics and DFS.

CONCLUSIONS

Sixteen patients (19%) had CTCs ≥1 at t0 with reduction in CTC number in case of objective remissions. The proportion of patients with CTCs ≥1 decreased over the time as the therapeutic course proceeded. Much effort should be oriented toward increasing CTC detection rate by enhancing technical tests and achieving better patient characterization.

Differential effect of adjuvant taxane-based and taxane-free chemotherapy regimens on the CK-19 mRNA-positive circulating tumour cells in patients with early breast cancer

Background:

To determine the effect of adjuvant taxane-free and taxane-based chemotherapy regimens on the elimination of circulating tumour cells (CTCs) in patients with early breast cancer.

Methods:

The presence of CK-19 mRNA-positive CTCs in the peripheral blood was evaluated before and after chemotherapy, using a real-time RT–PCR assay, in a historical comparison of two cohorts of women with stage I–III breast cancer treated with adjuvant taxane-free (N=211; FE₇₅C or E₇₅C) and taxane-based (N=334; T/E₇₅C or T/E₇₅) chemotherapy.

Results:

Taxane-based chemotherapy resulted in a higher incidence of CTCs' elimination than taxane-free regimens since 49.7% (74 of 149) and 33.0% (29 of 88) of patients with detectable CTCs before chemotherapy, respectively, turned negative post-chemotherapy (P=0.015). Patients treated with taxane-free regimens had a significantly lower disease-free survival (DFS) (P=0.035) than patients treated with taxane-based regimens; this difference was observed in patients with but not without detectable CTCs before chemotherapy (P=0.018 and P=0.481, respectively). The incidence of deaths was significantly higher in the taxane-free cohort of patients with but not without detectable CTCs before chemotherapy compared with that of the taxane-based cohort (P=0.002). Multivariate analysis revealed that the chemotherapy regimen was significantly associated with prolonged DFS (HR: 2.00; 95% CI=1.20–3.34).

Conclusion:

Elimination of CK-19 mRNA-positive CTCs during adjuvant chemotherapy seems to be an efficacy indicator of treatment and is associated with a favourable clinical outcome of patients with detectable CTCs before chemotherapy.

HER2-positive DTCs/CTCs in breast cancer

The presence of circulating tumor cells (CTCs) in the blood as well as disseminated tumor cells (DTCs) in the bone marrow of breast cancer patients is associated with a worsened prognosis in the primary as well as in the metastatic situation. Next to their detection, evaluation of human epidermal growth factor receptor (HER2) expression is a valuable feature of CTCs/DTCs. As the HER2 status may change during disease progression CTCs/DTCs might (1) characterize the phenotype of minimal residual disease in the adjuvant setting and (2) serve as a "real time biopsy" of metastatic breast cancer. Phenotyping of CTCs/DTCs will thus help to understand mechanism of resistance to HER2-directed therapy. Moreover, patients that are likely to benefit from HER2-directed therapy despite a HER2-negative primary tumor might be identified. 

CTCs in primary breast cancer (I)

The prognostic and predictive value of circulating tumor cells (CTCs) in primary breast cancer patients is subject of several recent publications. In the context of neoadjuvant chemotherapy CTCs were detected in 22-23% of patients before and in 10-17% after systemic treatment. These findings did not correlate with primary tumor characteristics or tumor response rates. One major trial evaluated the prognostic value of CTCs in 2.026 primary breast cancer patients after tumor resection but before adjuvant chemotherapy. The prevalence of CTCs was 22%. In multivariate analysis, the presence of CTCs before treatment was shown to be an independent predictor for both disease-free (hazard ratio; HR 1.88) and overall survival (HR 1.91). Results demonstrate that not only the mere presence but also the quantity of CTCs is associated with worse outcome. The risk for recurrence or tumor-related death increased with higher numbers of CTCs detected (≥5 CTCs: HR 4.04 for DFS and 3.05 for OAS; p < 0.05). In subsequent analyses of smaller subgroups within this trial, using a cutoff for positivity of >1 CTC, 10% of patients with the detection of CTCs before chemotherapy remained CTC-positive after completion of chemotherapy. Eight percentage of initially negative patients showed CTCs immediately after chemotherapy. Early data demonstrate that persisting CTCs after cytostatic treatment correlate with a decreased disease-free survival (p = 0.0623). Increasing evidence confirms the prognostic relevance of CTCs in primary breast cancer. CTC detection could help to identify patients with increased risk for relapse. Present trials will show whether CTCs can also be used as a valid tool for treatment monitoring or direct treatment target.

Circulating tumour cells in cancer patients: challenges and perspectives

Ultrasensitive methods have been recently developed to detect circulating tumour cells (CTCs) in the peripheral blood and disseminated tumour cells (DTCs) in the bone marrow (BM) of cancer patients. Studies with these new methods indicate that BM is a common homing organ and a reservoir for DTCs derived from various organ sites including breast, prostate, lung and colon. Peripheral blood analyses, however, are more convenient for patients than invasive BM sampling and many research groups are currently assessing the clinical utility of CTCs for prognosis and monitoring response to systemic therapies. Moreover, molecular analyses of CTCs/DTCs have provided new insights into the biology of metastasis with important implications for the clinical management of cancer patients.

Significance of micrometastases: circulating tumor cells and disseminated tumor cells in early breast cancer

Adjuvant systemic therapy targets minimal residual disease. Our current clinical approach in the adjuvant setting is to presume, rather than confirm, the presence of minimal residual disease. Based on assessment of the primary tumor, we estimate an individual's recurrence risk. Subsequent treatment decisions are based on characteristics of the primary tumor, with the presumption of consistent biology and treatment sensitivity between micrometastases and the primary lesion. An alternative approach is to identify micrometastatic disease. Detection of disseminated tumor cells (DTC) in the bone marrow and circulating tumor cells (CTC) from peripheral blood collection may offer quantification and biocharacterization of residual disease. This paper will review the prognostic and predictive potential of micrometastatic disease in early breast cancer.

Detection and HER2 expression of circulating tumor cells: prospective monitoring in breast cancer patients treated in the neoadjuvant GeparQuattro trial

PURPOSE

This study was aimed at detecting and characterizing circulating tumor cells (CTC) before and after neoadjuvant therapy (NT) in the peripheral blood of patients with breast cancer.

EXPERIMENTAL DESIGN

The clinical trial GeparQuattro incorporated NT approaches (epirubicin/cyclophosphamide prior to randomization to docetaxel alone, docetaxel in combination with capecitabine, or docetaxel followed by capecitabine) and additional trastuzumab treatment for patients with HER2-positive tumors. We used the Food and Drug Administration-approved CellSearch system for CTC detection and evaluation of HER2 expression and developed HER2 immunoscoring for CTC.

RESULTS

We detected > or =1 CTC/7.5 mL in 46 of 213 patients (21.6%) before NT and in 22 of 207 patients (10.6%) after NT (P = 0.002). Twenty (15.0%) initially CTC-positive cases were CTC-negative after NT, whereas 11 (8.3%) cases were CTC-positive after NT, although no CTC could be found before NT. CTC detection did not correlate with primary tumor characteristics. Furthermore, there was no association between tumor response to NT and CTC detection. HER2-overexpressing CTC were observed in 14 of 58 CTC-positive patients (24.1%), including 8 patients with HER2-negative primary tumors and 3 patients after trastuzumab treatment. CTC scored HER2-negative or weakly HER2-positive before or after NT were present in 11 of 21 patients with HER2-positive primary tumors. HER2 overexpression on CTC was restricted to ductal carcinomas and associated with high tumor stage (P = 0.002).

CONCLUSION

CTC number was low in patients with primary breast cancer. The decrease in CTC incidence during treatment was not correlated with standard clinical characteristics and primary tumor response. Information on the HER2 status of CTC might be helpful for stratification and monitoring of HER2-directed therapies.

Clinical utility of circulating tumor cell measurement in the diagnosis of indeterminate lesions of the pancreas

The quantification of circulating tumor cells has been historically problematic due to the different methods applied to their measurement. Following the development of standardized technology, they are now becoming well-established prognostic and predictive markers in patients with breast, colon and prostate cancer. While they represent a real-time noninvasive test, their use in diagnostics has seldom been reported. We report their use to help diagnose an indeterminate pancreatic mass. The use of an automated circulating tumor cell platform as described is likely to have utility as an aid to differential diagnosis, although larger studies will be required to ascertain its positive or negative predictive value.

Changes in circulating tumor cell detection in patients with localized breast cancer before and after surgery

BACKGROUND

Few data exist on the potential role of circulating tumor cells (CTCs) in patients with operable breast cancer. If the presence of CTCs in early breast cancer could predict an increased risk for relapse, it might be an early marker for treatment efficacy and could help in deciding treatment continuation.

METHODS

Thirty milliliters of peripheral blood was taken from 56 breast cancer patients before surgery and again 5 days after surgery, and the presence of CTCs was evaluated. In case of positivity of one of the perioperative samples, another sample was taken after 30 days. The presence of CTCs was assessed with the CellSearch System (Veridex, Warren, NJ).

RESULTS

One to three CTCs were found in 16 (29%) of 56 patients before surgery, in 14 (30%) of 47 patients at day 5, and in 8 (30%) of 27 at day 30. No association with pathological characteristics was found, apart a borderline significant association between presence of CTCs at baseline and vascular invasion (P = 0.07). When we looked at concordance between CTCs at baseline and after day 5 (47 patients), we found 40% discordant samples (10 negative at baseline and positive at day 5, and 9 vice versa).

CONCLUSIONS

This study provides evidence of the presence of CTCs in approximately 30% of patients with localized breast cancer both before and after surgery, with change from positive to negative and vice versa in 40% of cases. No association with the pathological variables was found, except for vascular invasion and presence of preoperative CTCs. Long-term follow-up will be required to understand the significance of these data.

Let me do more than count the ways: what circulating tumor cells can tell us about the biology of cancer

Tumor cells in the circulation of patients with advanced cancers have been described for over a century, but only recently have methods become available to reproducibly and robustly detect these cells in patients with cancer. A variety of methods have been developed to study this phenomenon, reflecting a broad interest in the field. The presence of circulating tumor cells (CTCs) in the peripheral blood of patients with metastatic cancer has been found to be of prognostic significance, and changes in CTC numbers over time appear to reflect treatment outcome. The ability to detect and study CTCs suggests that CTC concentration in blood may be able to be used as an intermediate biomarker in therapeutic trials of novel therapies in cancer patients and that molecular changes in patients' tumors may be able to be detected and addressed with appropriate therapeutic interventions. Studies in patients with early, nonmetastatic cancers are beginning, and some studies indicate that circulating tumor cells can predict outcome in this setting. While the ability to count and characterize circulating tumor cells holds much potential for the future, improvements in and standardization of assay methods need to be made before the potential of this technology is fully realized.

Unique localization of circulating tumor cells in patients with hepatic metastases

PURPOSE

There are few data on the impact of immediate and differing surgical interventions on circulating tumor cells (CTCs), nor their compartmentalization or localization in different anatomic vascular sites.

PATIENTS AND METHODS

CTCs from consecutive patients with colorectal liver metastases were quantified before and immediately after open surgery, laparoscopic resection, open radiofrequency ablation (RFA), or percutaneous RFA. For individuals undergoing open surgery, either hepatic resections or open RFA, CTCs were examined in both systemic and portal circulation by measuring CTCs in samples derived from the peripheral vein, an artery, the hepatic portal vein, and the hepatic vein.

RESULTS

A total of 29 consecutive patients with colorectal liver metastases with a median age of 55 years (range, 30 to 88 years) were included. CTCs were localized to the hepatic portosystemic macrocirculation with significantly greater numbers than in the systemic vasculature. Surgical procedures led to a statistically significant fall in CTCs at multiple sites measured. Conversely, RFA, either open or percutaneous, was associated with a significant increase in CTCs.

CONCLUSION

Surgical resection of metastases, but not RFA, immediately decreases CTC levels. In patients with colorectal liver metastases, CTCs appear localized to the hepatic (and pulmonary) macrocirculations. This may explain why metastases in sites other than the liver and lungs are infrequently observed in cancer.

Detection of cytokeratin-19 mRNA-positive cells in the peripheral blood and bone marrow of patients with operable breast cancer

Background:

To compare detection rates and evaluate the clinical relevance of cytokeratin-19 (CK-19) mRNA-positive cells in the peripheral blood (circulating tumour cells, CTCs) and bone marrow (disseminated tumour cells; DTCs) of patients with early breast cancer.

Methods:

Paired samples of peripheral blood and bone marrow were obtained from 165 patients with stage I–II breast cancer before the initiation of adjuvant chemotherapy. In 84 patients, paired blood and bone marrow samples were also available after chemotherapy. The detection of CK-19 mRNA-positive CTCs and DTCs was assessed by real-time PCR.

Results:

CK-19 mRNA-positive CTCs and DTCs were detected in 55.2 and 57.6% of patients before chemotherapy, respectively. After chemotherapy, CTCs and DTCs were identified in 44 (52.4%) and 43 (51.2%) of the 84 patients, respectively. There was a 93.9% (McNemar; P=0.344) and 72.6% (McNemar; P=0.999) concordance between blood and bone marrow samples before and after chemotherapy, respectively. The detection of CK-19 mRNA-positive CTCs or DTCs before chemotherapy was associated with decreased overall survival (P=0.024 and P=0.015, respectively). In addition, their simultaneous detection was also associated with an increased incidence of disease-related death and decreased overall survival (P=0.016).

Conclusions:

The detection of CK-19 mRNA-positive CTCs using reverse transcription-PCR (RT–PCR) both before and after chemotherapy is correlated with the detection of CK-19 mRNA-positive DTCs in patients with early-stage breast cancer. The determination of the CTC status by RT–PCR conveys clinically relevant information that is not inferior to DTC status and, owing to the ease of sampling, warrants further evaluation as a tool for monitoring minimal residual disease.