Reader mail: Can viruses cause tumor shrinkage?

I just have time for a short take today. (If you need more, fortunately, Bora has posted the 33rd Meeting of the Skeptics’ Circle for your edification. Yes, my preamble was just an excuse to plug the Skeptics’ Circle one more time.)

In the comments of yesterday’s post about a medical student who is a young earth creationist, Karl asked a most interesting question:

I hope that you saw “House” last night (on FOX, of all places). A 15 year old faith healer shows up in the hospital. At one point he touches a patient who has been dignosed with terminal (Liver?) cancer. The cancer shrinks. House spends 45 minutes trying to figure it out, all the while arguing with everyone else that there has to be a rational explanation. At the end, he figures it out (amazing, considering that this show is on FOX).

I don’t know whether this show is in reruns or whether you will ever be able to see it, but there is a synopsis at http://www.tv.com/house/house-vs.-god/episode/633814/recap.html.

The explanation is that the boy has Herpes and that that particular version attacks cancer cells – when he touched her he passed the virus to her. So, the questions are 1) Is that valid? and 2) If it is, why isn’t that knowledge being used as a tool in combatting cancer?

Fortunately for you (and for me, because I’ve only managed to catch House a few times this year and missed all but the last 20 minutes or so of last night’s episode, but, more importantly, because it means I don’t have to write nearly as much), Scott has already taken this question on at Polite Dissent. (Of note, each week Scott reviews new episodes of House for medical content. It’s well worth checking out.) I’ll add my two cents below the fold.

Herpes virus can indeed be oncolytic (capable of lysing tumor cells). Indeed, weakened versions of the herpes simplex have been widely tested in preclinical tumor models (animal models) as cancer therapy because of its ability to preferentially infect and lyse certain kinds of tumor cells. The bottom line as I see it is that it’s theoretically possible for a herpes infection to cause temporary tumor shrinkage. However, in the brief time I took to look for them, thus far I’ve been unable to locate any case reports of this ever actually happening outside the context of clinical trials using herpes virus as an experimental treatment for cancer. (If anyone is aware of any studies or case reports showing tumor shrinkage due to herpes infections acquired outside the auspices of a clinical trial designed to test the activity of herpes against tumors, please chime in in the comments.)

So what cancers have oncolytic herpes viruses been tested in? Well, they’ve been tested in a variety of preclinical animal models in many different tumor types, for one thing, and have shown promise in these models since 1991. Here’s a report of a study describing the use of a weakened herpes simplex virus to treat pediatric neuroblastoma in mouse models, in which the virus nearly completely dissappeared.

But what about humans? Last summer at the European Society for Medical Oncology, there was a report of a phase I trial done at Memorial Sloan-Kettering Cancer Center using herpes simplex to treat colorectal cancer metastatic to the liver, although apparently it hasn’t yet been published in a medical journal. Other altered herpes viruses are being used in clinical trials as treatments for glioma, melanoma, head and neck cancers, astrocytomas, and glioblastomas. Herpes viruses modified to express immunomodutors such as GM-CSF are being tested against breast cancer, head and neck cancer, and melanoma. There are also a number of different kinds of oncolytic viruses other than herpes in preclinical development for cancer therapy.

It would not surprise me if one of these oncolytic herpes viruses is approved by the FDA for treatment of specific cancers sometime in the next five years or so, maybe even sooner.