New Treatments for Anal Cancer. Part 3.
If you look at the etiology and how people might get anal cancer, certainly in males there is a very strong correlation with anal receptive intercourse. There doesn’t appear to be the correlation in females. This is from Cancer Medicine, Brenda Shank in 1994. There also is a strong correlation with HPV virus. Presumably the HPV virus is transmitted in male homosexual populations as a sexually transmitted disease. If you look at other associations, just like cervical cancer, there is a mild association with herpes virus type II. Immunosuppression is actually important. If you work in an institution where there is a lot of solid organ transplant – for example, liver and heart transplant – where patients are on cyclosporine for long periods of time – years – you’ll see an increased risk of anal cancer. And these are in patients who previously had HPV infection, and as I’ll show you, immunosuppression appears to facilitate or decrease the period of time for viral carcinogenesis in people with previous HPV infection. It’s interesting that what cyclosporine as an immunosuppressive does is that it doesn’t change CD-4 numbers but what it does is it freezes CD-4 cells so that they cannot divide, they cannot function. So in effect you are getting a very similar defect to what you get with HIV which of course decreases CD-4 numbers. Smoking has some increased relative risk. And HIV alone is not necessarily associated with anal cancer. It’s HIV in patients who have had a previous papilloma virus infection.
These are very interesting, very recent, data suggesting or giving you an insight in to what may be happening with concomitant HIV infection, or for that matter immunosuppression, and the presence of patients who have a history of anal cancers. This was presented at the Digestive Diseases Week a couple of months ago in Florida from a group in Paris. Essentially what they did is they took patients who were HIV positive and HIV negative, all of them had anal condylomata. Because genital warts are not terribly uncommon and people can get them without being immunosuppressed. They treated the genital warts as you would, resected them, froze them or did whatever was necessary to make them go away. Then they looked at recurrence and they found that within a year about 75% of the HIV positive patients recurred versus only 8% of the HIV negative patients. There was a ten-fold increase in dysplasia. So again suggesting that what happens here is that when you have HIV infection, what you are doing – because of the immune dis-modulation of HIV infection – you are accelerating the rate with which viral neoplasia, in this case benign viral neoplasias or perhaps pre-malignant viral neoplasia, can occur.
What about treatment and prognosis with anal cancer? There are a couple of things that are important. One is the size of the tumor and another is the differentiation of the tumor and obviously the metastatic dissemination of the tumor, if it has disseminated. Although the vast majority of the times, anal cancers – because of their location -are picked up fairly early. The patients have symptoms very early of bleeding and pain in the anal canal. These are older data from Bruce Bowman, who is now at Jefferson actually but was at the Mayo Clinic at the time, looking at the experience with anal cancer at the Mayo Clinic. And pointing out that if you looked at patients with very small, grade I to II, good risk, small primary tumors that could be locally resected – which is an unusual group – there was essentially a high cure rate with surgical resection. If you looked at the squamous-basaloid group that were at higher grade tumors, there was a recurrence rate that was very high with local resection. So you can’t treat these. Occasionally the small cell patients you can get small cell carcinoma much like a non-pulmonary small cell cancer, and those patients do very badly with local therapy.
Сontinued at Cancer treatment blog