Sometimes, I find that I have all these ideas in my head, and no logical place to go with them. So, I figure, as a prelude to articles that I will later develop, I can use this blog as a place to gather these thoughts.

I've been looking through old papers on tumors and cancer in rats, and decided that I would start compiling some of the things I wanted to research deeper. So, here goes a very mini article to keep me on track...

For me, the deepest interest regarding tumors and cancer in rats is why it occurs, as in the predisposition for it, and what we can do to help prevent it. As far as prevention goes, one of the leading medicines today is Tamoxifen, a drug used in humans to treat breast cancer. The drug has different effects depending on the animal it is used on, but it so happens that in rats, it has great promise in the prevention and reduction of mammary cancer (adenocarcinoma), as well as pituitary, adrenal, pancreatic, uterine, and testicular cancers. Because this is a drug, though, side effects cannot be overlooked. Liver cancer is a possible side effect, however, studies have shown that this is only an increased risk if the drug is given in large doses for prolonged periods of time. More realistic side effects are slight hair loss, abnormal or absent heat cycles, and poor blood clotting. To me, there is only one here that is a real issue, which is the clotting. So, if surgery is going to be performed on a rat that has been on Tamoxifen, the dosing must stop for at least 1-2 weeks prior to surgery, and be sure your vet knows the rat is on the medication. The other thing that I understand is that this drug is primarily used in female rats because it will increase the risk of mammary and pituitary cancers in males. To get Tamoxifen, your vet will have to call in a perscription to a human pharmacy. The current accepted dose is 1.5mg per pound of body weight, given 5-6 days a week. Spaying will also decrease the risk and/or growth rates of tumors and cancer, but remember to stop treatment with Tamoxifen long enough prior to surgery. There are plenty of stories out there of rats losing their lives on the operating table from blood loss because the Tamoxifen had decreased the blood's clotting ability so much.

As a side note, some other preventions for tumors that I have heard are to follow. Hey, nothing hurts to try, right?
400-800mg/kg of diet of DHEA
10% of diet consisting of miso
3-10% of diet consisting of flax

References:
"Tamoxifen can prevent and treat tumors" D. Ducommun, 1999, Rat Fan Club, http://www.ratfanclub.org/tamox.html.
"Results of three life span experimental carcinogenicity & anticarcinogenicity studies on Tamoxifen in rats", C. Maltoni, et al, 1997, Ann. NY Acad Sci, 837, 469-512.

Another bit on tumors in general to add to this topic...

Benign mammary tumors are one of the most common issues to strike rats. A benign tumor is easy to spot, as it is encapsulated in a membrane that separates it from neighboring tissues. The result is a distinctly palpatable lump that moves freely under the surface of the skin. The most common of these types of tumors is a fibroadenoma, and because it is stimulated by estrogen, they typically occur in rats around 18 months old. This is usually when a female rat stops ovulating. The most common locations for the tumors are in the armpits and groin, but since the mammary tissue spreads nearly the entire body, they can occur anywhere.
The nice thing about mammary tumors, if you can think of something nice, is that they are easily removed by a qualified vet. Obviously, the earlier you find a tumor and have it removed, the easier the surgery. So, one should make a point of checking their rats regularly for lumps. Not treating or removing a benign tumor is a death sentence. The tumor WILL continue to grow, often suprisingly rapidly, to the point where quality of life is effected. So, the bottom line is that ignoring it will not make it go away. Of course, there are other non-surgical options to try, but since the surgery is so minimally invasive and tumors may grow quickly, sometimes the surgery is the best option.
Tamoxifen, as discussed in the previous blog, is effective against some tumors..namely those that are stimulated by estrogen. So, it may help with some mammary tumors, but be prepared for the surgical alternative if there is not results withing 3 weeks. There is some information out there about natural ways to slow the growth of tumors as well, so there is no harm in trying those as well. And, since tumors may reappear, it's not a bad practice in general to add some prevention therapy to all female rats. CLA (conjugated linoleic acid) is one of the suggested supplements and the dose is 75mg a day. I have also heard of using shark cartilage (~1/4 tsp a day) to slow tumor growth. In any event, there are supplemental elements that can be added to your rat's diet in a preventative therapy. Of couse, when you talk about prevention, there is one thing that must be discussed and considered...spaying! This is the most effective prevention for mammary tumors, and can even reduce the risk of tumors from up to 70% down to 4%! These odds are hugely different, obviously. Spaying withing the first 3-6 months shows the most effectiveness, but spaying at any age still will result in reduced risk. Spaying also reduces the risk of pituitary tumors, which are unoperable, and it increases life span. So, there is great benefit to having a rat spayed in the long run.