Size-based analysis of cell-free tumor DNA for classifying level of cancer

Patent metadata

Field	Value
Publication number	US-10741270-B2
Application number	US-201715411695-A
Country	US
Kind code	B2
Filing date	Jan 20, 2017
Priority date	Mar 8, 2012
Publication date	Aug 11, 2020
Grant date	Aug 11, 2020

Abstract

A classification of a level of cancer in an organism is determined by analyzing a biological sample of the organism. The biological sample comprises clinically-relevant DNA and other DNA. At least some of the DNA is cell-free in the biological sample. An amount of a first set of DNA fragments from the biological sample corresponding to each of a plurality of sizes is measured. A first value of a first parameter is calculated based on the amounts of DNA fragments at the plurality of sizes. The first value is compared to a reference value. A classification of a level of cancer in the organism is determined based on the comparison.

First claim

What is claimed is:

1. A method of analyzing a biological sample of an organism, the biological sample comprising cell-free DNA, the method comprising:
for each size of a plurality of sizes, measuring an amount of DNA fragments from a first set of DNA fragments from the biological sample, the amount corresponding to one of the plurality of sizes, the amount including the cell-free DNA, thereby measuring amounts of DNA fragments at the plurality of sizes, the first set of DNA fragments corresponding to a plurality of regions of a genome of the organism;
calculating a first value of a parameter based on the amounts of DNA fragments at the plurality of sizes;
comparing the first value to a reference value; and
determining a classification of a level of cancer in the organism based on the comparison.

2. The method of claim 1 , wherein the first set of DNA fragments are chosen at random.

3. The method of claim 1 , further comprising selecting the first set of DNA fragments from the one or more regions of the genome by capturing DNA fragments from the one or more regions or by amplifying DNA fragments from the one or more regions.

4. The method of claim 1 , further comprising selecting the first set of DNA fragments from the one or more regions of the genome by aligning sequence reads of the first set of DNA fragments to the one or more regions in a reference genome.

5. The method of claim 1 , wherein the one or more regions of the genome of the organism comprise one or more predetermined regions of the genome of the organism.

6. The method of claim 5 , wherein the one or more predetermined regions are multiple regions of a same length.

7. The method of claim 6 , wherein the same length is 1 Mb or greater.

8. The method of claim 5 , wherein the predetermined regions are regions that are commonly altered in a cancer type of interest.

9. The method of claim 8 , wherein the cancer type of interest comprises at least one of colorectal, breast, lung, HCC, and ovarian cancer types.

10. The method of claim 8 , wherein the commonly altered regions include a gain or a loss, wherein the gain comprises an amplification of a chromosome or a portion thereof with one or more additional copies within a particular segment and the loss comprises a deletion of one or both homologous chromosomes within a particular segment.

11. The method of claim 5 , wherein the predetermined regions include regions not associated with cancer, the method further comprising determining the reference value based on the measured amounts of DNA fragments corresponding to such regions not associated with cancer.

12. The method of claim 1 , further comprising:
identifying additional sets of DNA fragments from the biological sample, wherein each of the additional sets of DNA fragments corresponds to different regions of the genome;
for each of the additional sets of DNA fragments:
measuring amounts of DNA fragments corresponding to the plurality of sizes;

calculating additional values of the parameter for the additional sets of DNA fragments;
comparing each of the additional values to a respective reference value; and
identifying regions where the corresponding additional value is statistically different than the respective reference value.

13. The method of claim 12 , further comprising using the identified regions to determine one or more possible types of cancer, wherein the possible types of cancer are associated with the identified regions.

14. The method of claim 12 , wherein determining the classification of the level of cancer in the organism based on the comparison includes:
determining a number of identified regions where the corresponding additional value is statistically different than the respective reference value; and
comparing the number to a threshold number of regions to determine the classification of the level of cancer in the organism.

15. The method of claim 12 , wherein at least two of the respective reference values are different.

16. The method of claim 1 , wherein the biological sample is obtained from the organism after treatment, and wherein the reference value corresponds to a value of the parameter determined from a sample obtained from the organism before treatment.

17. The method of claim 1 , wherein the reference value corresponds to a value of the parameter determined from a sample obtained from the organism at a time when the organism is presumed to have no cancer.

18. The method of claim 1 , wherein the reference value is determined from samples obtained from healthy organisms.

19. The method of claim 1 , wherein the classification is that the organism does not have cancer or that the organism does have cancer.

20. The method of claim 1 , wherein the classification is that the level of cancer has decreased or that the level of cancer has increased relative to a previously-determined level of cancer for the organism.

21. The method of claim 1 , wherein the level of cancer corresponds to at least one of: whether cancer exists, a stage of cancer, a size of tumor, an amount of deletions of a chromosomal region, an amount of amplifications of a chromosomal region, a severity of cancer, a premalignant condition, or a precancerous condition.

22. The method of claim 1 , wherein each size of the plurality of sizes is a mass or a length.

23. The method of claim 1 , wherein the parameter provides a statistical measure of a size profile of DNA fragments in the biological sample, the statistical measure representing an abundance of DNA fragments at a particular size or within a particular size range relative to an abundance of DNA fragments at another size or range.

24. The method of claim 1 , wherein the at least some of the cell-free DNA originates from a cancer cell.

25. The method of claim 1 , wherein the reference value is different for different regions.

26. The method of claim 1 , wherein the reference value comprises a normal value or a cutoff value derived from the normal value.

27. The method of claim 26 , wherein the normal value is different for different regions.

28. The method of claim 26 , wherein the cutoff value is a specified distance from the normal value.

29. The method of claim 1 , wherein the classification is numerical or textual.

30. The method of claim 1 , wherein the classification is a binary result of yes or no as to cancer.

31. The method of claim 1 , wherein the classification is a probability or other score.

32. The method of claim 1 , wherein the plurality of sizes comprises a first size and a second size greater than the first size.

33. The method of claim 32 , wherein the first size comprises a first size range and the second size comprises a second size range having sizes greater than any size in the first size range.

34. The method of claim 33 , wherein the first size range corresponds to short DNA fragments having lengths between 100 and 150 bp and the second size range corresponds to long DNA fragments having lengths greater than the first size range.

35. The method of claim 1 , wherein determining the classification comprises:
determining a number of regions statistically different than the reference value and
comparing the number to a threshold number, wherein the threshold number is deter

Assignees

• Univ Hong Kong Chinese

Inventors

• Lo Yuk Ming Dennis
• Chiu Wai Kwun Rossa
• Chan Kwan Chee
• Zheng Wenli
• Jiang Peiyong
• Liao Jiawei

Classifications

• C12Q1/6806 Primary

  Preparing nucleic acids for analysis, e.g. for polymerase chain reaction [PCR] assay (C12Q1/6804 takes precedence) · CPC title

• G16B30/10 Primary

  Sequence alignment; Homology search · CPC title

• G16B20/20

  Allele or variant detection, e.g. single nucleotide polymorphism [SNP] detection · CPC title

• G16B20/10

  Ploidy or copy number detection · CPC title

• G16B30/00 Primary

  ICT specially adapted for sequence analysis involving nucleotides or amino acids · CPC title