Q&A

Answer: If the samples of primary and metastatic cancer are mixed for testing, it will have a certain impact on the frequency of the detected genes, and it is impossible to compare the differences in genetic mutations between primary and metastatic cancer. The medication description part of the report will follow the prompts of the primary lesion, and it is recommended that clinicians treat the patient's condition in combination with the patient's actual situation.

Response: It is necessary to conduct a comparison of the crucial performance indicators of the two kits, including the detection gene range, detection method, and lower detection limit, in order to provide an explanation. 

Sample Collection and Transportation

After collecting blood using Streck blood collection tubes and other specialized blood collection tubes for cell - free nucleic acids, invert the tubes 10 times. Ensure that the mixing is not overly vigorous to fully blend the preservation solution with the blood, thereby preventing clotting or hemolysis. After collection, store the samples in a dry environment at a temperature ranging from 6 to 37 °C. Samples should be delivered to the laboratory within 72 hours.

 Low Mutation Abundance below the Detection Threshold

Blood samples may contain mutations where the circulating tumor DNA (ctDNA) content is below the lower detection limit, leading to undetected mutations. It is advisable to comprehensively assess the performance of the high - throughput sequencing experimental platform, the sequencing depth, and the proportion of tumor cells. Particularly for genes associated with targeted therapy, it is recommended to employ other detection methods, such as digital polymerase chain reaction (PCR), for further verification and confirmation.

Detection Limitations

Since the mutations carried by the subject may fall outside the detection scope, the test may yield false negative results.

Patient's Own Condition

If the patient is in the early stage of tumor development or is currently undergoing treatment with a certain degree of efficacy, the amount of tumor - derived ctDNA will be reduced, thus affecting the detection rate.

Recommendation

If the plasma test result is negative, other types of samples may still be required for verification when necessary. 

Answer:

1. For germline testing: When an adult receives less than 2000 ml of whole blood or concentrated red blood cells within a short period, it will not interfere with the genetic testing of the recipient. However, after receiving more than 2000 ml of whole blood or concentrated red blood cells, it will affect the genetic testing results of the recipient. It is advised to collect blood samples every three months after blood transfusion. For genetic testing, if genetic testing is necessary, other tissue cells, such as oral mucosa, can be utilized for testing.

2. For somatic testing: It is recommended to collect blood samples for genetic testing seven days after blood transfusion.

Reference:

【1】 JiangMingzhang, Li Changzheng, Gao Bo, Yi Aixiang, Wang Yongping, Sun Xianxue, Xu Weidong, Wang Jun. Effects of different blood transfusions on PCR-STR testing of blood samples of newly infected persons [J]. Journal of Forensic Medicine, 2003(04): 230-231.

Answer: The patient's ongoing drug therapy will influence the ctDNA content. Research has indicated that subsequent to the treatment of patients with non - small cell lung cancer using tyrosine kinase inhibitors, the ctDNA content reaches its peak at 24 hours and then declines rapidly, suggesting that the drug also has an impact on the ctDNA content.

Reference:

[1] RIEDIGER A L, DIETZ S, SCHIRMER U, etal. Mutation analysisof circulating plasma DNA to determine response to EGFR tyro⁃sine kinase inhibitor therapy of lung adenocarcinoma patients［J］. Sci Rep，2016，6：33505.

Response: Based on the detection rate, the order is as follows: fresh tissue > paraffin sections > supernatant of thoracic ascites > cells in thoracic ascites > peripheral blood.

During clinical sampling, the most crucial factor to consider is the convenience of clinical sampling. On the premise of tissue availability, tissue samples should be prioritized for examination.