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GATK Workflow for Cancer

gaiusjaugustusgaiusjaugustus Arizona, USAMember
edited July 2015 in Ask the GATK team

I am new to Bioinformatics, and would like some advice on changes to the GATK workflow for cancer. I was told that the cancer workflow is different, and see that several different tools are available.

I have Exome data from tumor and normal. I have aligned them, and have BAM files for each sample. I am interested in identifying somatic variants.

The current workflow as I understand it is:
-(Non-GATK) Picard Mark Duplicates or Samtools roundup
-Indel Realignment (Realigner TargetCreator + Indel Realigner)
-Base Quality Score Reacalibration (Base Recalibrator + PrintReads)
-UnifiedGenotyper
-Annotation using Oncotator (?)
-MuTect (identify somatic mutations)

My questions are:
1. Is the above workflow reasonable/correct for what I'm trying to do?
2. Is there any difference running samples one pair at a time, or running them all together? (I have 57 pairs. Should I do 57 runs of normal-tumor pairs, or 1 run of all 57 pairs?)

Thank you,
Gaius

Answers

  • gaiusjaugustusgaiusjaugustus Arizona, USAMember

    I've gotten this answer before (just now found it):

    "We (GATK docs team) are working on some docs for the somatic variant calling use case. In a nutshell, you'll need to do an additional pre-processing step called co-cleaning where you perform indel realignment on the tumor and normal in a pair together, use ContEst to estimate cross-sample contamination, use MuTect to call variants (not HC, which is not able to call low-AF variants like MuTect), do some manual filtering and processing to eliminate artifacts (VQSR is not appropriate for somatic calls) and finally annotate with Oncotator. " -vdauwera

    But unsure of what I can use to do the co-cleaning. And unsure where the other steps go in my workflow. Does this mean I don't need to use Picard/Samtools, Indel Realignment, etc? Do I ONLY need to use the workflow here?

    -Co-cleaning
    -ContEst (estimate cross-sample contamination)
    -MuTect (Call variants)
    -Eliminate artifacts (How?)
    -Oncotator (Annotate)

    And my #2 question above still stands.

  • Geraldine_VdAuweraGeraldine_VdAuwera Cambridge, MAMember, Administrator, Broadie admin

    As an update (since it was pointed out to us that this post comes up when searching for GATK + cancer), we have some new workflows coming out with GATK4 enabling somatic analysis of SNPs and indels (Mutect2) and CNVs (GATK4-CNV). We'll post more details in the Best Practices section in the near future.

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