This is a observational, multicenter study, monitoring the circulating tumor DNA (ctDNA) in people who is at risk of cancers，assessing the sensitivity and specificity of ctDNA detection in early screening of pan-carcinoma.

2000 patients with positive tumor protein markers or cancer screening were recruited. All patients were tested for ctDNA at enrollment and followed up at 6 months and 1 year. The study was completed at the time of cancer diagnosis or the longest follow-up time (1 year).

Inclusion Criteria:

1. Patients aged at or over 45 years old.

2. Patients who with one or more of the following situations:

   1. In AFP (>20UG/L), CA125 (>70U/ml), CEA (>7ng/ml) and CA199 (>60U/ml), more than one item was abnormal for two consecutive times within one month.
   2. Patients with viral hepatitis (Hepatitis B / C surface antigen positive with liver function damage.
   3. Patients with liver nodules detected by ultrasound and hemangioma excluded.
   4. Patients with compensated cirrhosis.
   5. CA125>35U/ml and HE4 was abnormal (the reference value of HE4 in premenopausal and postmenopausal women was 68.96 pmol/L and 114.90 pmol/L respectively).
   6. Patients with ovarian masses found by ultrasonography (premenopausal > 5cm, postmenopausal > 3.5cm).
   7. Patients with pancreatic space-occupying found by ultrasonography.
   8. Patients with BI-RADS grade 4 or above by ultrasound or mammography.
   9. CA125>35U/ml and BI-RADS above grade 3 by ultrasound or mammography.
   10. CA153>25U/ml and BI-RADS above grade 3 by ultrasound or mammography.
   11. Family genetic history of breast cancer and ovarian cancer, and BI-RADS above grade 3 by ultrasound or mammography.
   12. Patients with a positive fecal occult blood test and haemorrhoids excluded
   13. Patients with a positive fecal occult blood test and positive CEA
   14. More than 2 items were abnormal in PGI, PGR and G-17 (criteria: PGI≤70 UG/L, PGR≤7.0, G-17≤1 pmol/L or G-17≥15 pmol/L).

3. Ability to collect specimens from each time point and provide corresponding clinical information.

4. Understand the research plan and voluntarily participate in the study, sign the informed consent form.

Exclusion Criteria:

1. Patients with previous or present cancer.
2. Patients with serious diseases, especially those with a survival period of less than 3 years.
3. Patients with factors that affect the diagnosis of the disease (such as MRI related cardiac pacemakers, ferromagnetic implants, etc.).
4. Patients with a known history of allogeneic organ transplantation or allogeneic hematopoietic stem cell transplantation.
5. Women who are pregnant or preparing for pregnancy.
6. Patients who voluntarily withdraw for any reason.
7. Patients who cannot complete the research plan

People with positive tumor protein marker or cancer screening.