I have a dataset with TCGA patient ID as the column names. What I want to do is that removing the latter part of the names, but retaining forepart of them. My data:

```
GeneID        | TCGA-3L-AA1B-01A-11R-A37K-07   | TCGA-4N-A93T-01A-11R-A37K-07 | TCGA-4T-AA8H-01A-11R-A41B-07
------------- | -------------------------------| -----------------------------|------------------------------
100130426     | 0.5174                         | 0.0000                       |0.0000
100133144     | 18.0851                        | 4.4315                       |9.8995

```

The column names I want to retain as follows: 

```
GeneID        | TCGA-3L-AA1B-01A               | TCGA-4N-A93T-01A             | TCGA-4T-AA8H-01A
------------- | -------------------------------| -----------------------------|------------------------------
100130426     | 0.5174                         | 0.0000                       |0.0000
100133144     | 18.0851                        | 4.4315                       |9.8995

```

Thanks a lot!