Table 2. The main clinical evidence for CTC detection in various types of cancer.
| Type of cancer | Tumor stage | Clinical results | References |
|---|---|---|---|
| Breast cancer (BC) | Metastatic | CTCs ≥5/7.5 mL associated with reduced PFS and OS | (9,92) |
| CTCs C 5/7.5 mL at any time point during chemotherapy associated with adverse clinical outcome | (90) | ||
| CTCs C 5/7.5 mL after the initiation of a new systemic therapy were associated with shorter median PFS and higher incidence of radiographic disease progression | (95,96) | ||
| Lack of prediction in HER2-positive disease treated with targeted therapy | (99) | ||
| Change in CTC level during the course of chemotherapy was a surrogate marker monitoring therapeutic efficacy and was correlated with OS | (147) | ||
| Stages I-III | A low cutoff of 1 CTC was feasible. CTC detection was not associated with primary tumor response but was an independent prognostic factor for early relapse and OS after neoadjuvant therapy | (17,70,148,149) | |
| CTC detection incidence in early-stage disease paralleled with cancer stage. Each of CTC biomarker significantly correlated with ALN metastasis | (150) | ||
| CTC detection before adjuvant chemotherapy was independent predictor of DFS and OS. The persistence of CTCs after adjuvant treatment significantly correlates with a decreased DFS | (66,68,103) | ||
| Prostate cancer | Metastatic | CTCs ≥5/7.5 mL was associated with poor OS | (108,151) |
| Patients with unfavorable pre- or post-treatment CTC count had shorter OS and its predictive ability was superior to PSA level at all-time points | (152) | ||
| CTC count predicted OS and was a sensitive marker in monitoring disease status during treatment, especially in early-stage disease | (114) | ||
| CTC number as a continuous variable was prognostic for survival of patients with CRPC starting first-line chemotherapy | (115) | ||
| CTCs ≥4/7.5 mL was associated with poor OS, and their presence correlates with radiographic findings and classic markers | (110) | ||
| CTCs ≥2/7.5 mL was associated with disease status and clinical indicators of PSA and PSM | (111) | ||
| CTCs ≥1.8/mL was associated with shorter OS | (112) | ||
| Localized disease | No correlation between the number of CTC and known prognostic factor in localized prostate cancer patients | (121) | |
| Colorectal cancer | Metastatic | The CTCs level at baseline and follow-up was an independent predictor of PFS and OS, which correlate well with radiographic findings | (123) |
| The presence of at least 1 CTC at baseline count was found to be predictive for poor prognosis | (124) | ||
| Unfavorable baseline CTC was associated with worse PFS in patients receiving first- or second-line therapy, irinotecan, having liver involvement, ≥65 years, and ECOG PS of zero | (126) | ||
| CTC count was a reliable surrogate biomarker of predicting clinical outcome and assessing Japanese patients responsive to oxaliplatin-based chemotherapy | (127) | ||
| CTC count during treatment could become a new predictor of therapy response | (128,130,153,154) | ||
| Stage I-III | Patients with persistent presence of CTC even postoperatively exhibited higher incidence of postoperative relapse and poor relapse-free survival rate | (131) | |
| Molecular assessment for micrometastasis in sentinel lymph node along with CTC count may help to identify patients at high risk for recurrence and thus who could benefit from adjuvant therapy | (129,130) | ||
| Lung cancer | Localized and metastatic | The number of CTC was a robust surrogate prognostic indicator to predict the presence of distant metastasis. CTC status correlated with clinical and pathological stage | (134) |
| CTC enumeration well correlated with radiographic response at the end of two cycles of chemotherapy | (135) | ||
| CTCs decreased in all patients after on cycle of chemotherapy supporting CTC as a pharmacodynamic biomarker for small cell lung cancer (SCLC) | (137) | ||
| Stages III-IV | CTC detection at baseline and change in CTC number after one cycle of chemotherapy was a prognostic factor for tumor response, PFS and OS | (136,138,140-144) | |
| Stages I-IV | CTC level ≥5 was associated with worse survival of patients with resectable NSCLC | (145) |
CTCs, circulating tumor cells; PFS, progression-free; OS, overall survival; DFS, disease-free survival; CRPC, castration-resistant prostate cancer; NSCLC, non-small cell lung cancer.