[Cheryl G]

Re: Deletion 17P (TP53)

by Cheryl G on Sat May 23, 2015 6:05 pm

Hi heddleandhook,

TP53 deletion and del(17p) are not exactly the same thing, as far as I understand it. TP53 is a region of the p arm of chromosome 17. So it would be possible for you to have a deletion of the TP53 region without necessarily having a deletion of the entire p arm of the chromosome.

On the other hand, a del(17p) would be necessity mean that you have a deletion of the TP53 region, since it's on the p arm.

(Each human chromosomes is made up of two arms – a "p" arm and a "q" arm – and people typically have two pairs of each chromosome, other than chromosome 23, which determine's a person's gender).

I think that people user "TP53 deletion" and "del(17p)" interchangeably because its the removal of the TP53 region of the 17p arm that is believed to have the most impact on how aggressive a person's myeloma is. This was seen, for example, in this recent study that looked at the impact of the TP53 deletion on myeloma patients who underwent a stem cell transplant at MD Anderson:

S Gaballa et al, "Clinical Outcomes of Multiple Myeloma Patients with TP53 Gene Deletion after Autologous Stem Cell Transplantation: The MD Anderson Cancer Center Experience," BMT "Tandem" Meeting 2015, Abstract 79 (link to abstract)

There is a report from the Arkansas group, however, reporting that deletion of TP53 did not have an adverse effect on prognosis in patients who underwent treatment with the Total Therapy 3 protocol:

JD Shaughnessy et al, "TP53 Deletion is Not an Adverse Feature in Multiple Myeloma Treated with Total Therapy 3," British Journal of Haematology, Nov 2009, (full text of article)

It's also worth pointing out that there are studies suggesting that del(17p) has to be present in a lot of myeloma cells (more than 60 percent) for the deletion to have a negative effect on prognosis. This was mentioned in a forum thread last fall, which has some abstract related to the issue ("Percentages in FISH test results - significance?", started Oct 16, 2014)

I hope this helps a bit!

[heddleandhook]

Re: Deletion 17P (TP53)

by heddleandhook on Sun May 24, 2015 6:09 pm

Cheryl G,

Thank you. I read through the different articles, but must admit the details are a bit over my head. Certainly good questions have come up for me to discuss with the specialists, especially given the slow response I've had with induction using VRD.

I've finished 4th round, but will have to have a 5th before harvesting.