What scientists know – and don’t know – about treating cancer with nutrients.
Hydroxyurea. Mercaptopurine. Cyclophosphamide. One thing all cancer drugs seem to have in common is their hard-to-spell names.
Or do they? How about A? D? E? These aren’t fancy new drugs – they’re plain old vitamins. Yet, when administered by scientists in large doses, some vitamins may act like drugs, or work with standard cancer-fighting drugs. It isn’t clear yet whether the research into this futuristic notion of vitamin chemo-therapy will ever pan out. But if the research is successful, chemotherapy could be much easier to take – and a lot easier to spell.
Here’s what scientists have learned so far:
BATTLING IN THE BLOODSTREAM
Synthetic versions of vitamins A and D seem to hold promise in the treatment of myeloid leukemia, a cancer of white blood cells.
The main problem in leukemia is that immature white blood cells proliferate in the bloodstream, crowding out normal red and white cells. This causes severe anemia and comprises the immune system. But through a hormonal interaction, vitamins A and D seem to make the immature cells grow up. Mature cells appear to stop their rapid reproduction and are able to carry out their immune-system functions.
Initially the active form of vitamin D was tested, but in high doses this has the unfortunate side-effect of causing the body to retain calcium. That could cause complications, including hardening of the vital organs and death. But the synthetic version of vitamin D has a more powerful maturing influence on leukemia cells – and a much-lowered calcium-loading mechanism. In studies on leukemia lab mice, this synthetic compound achieved much better results than pure vitamin D. “Some of the mice treated with synthetic D may actually be cured of their leukemia,” reports H. Phillip Koeffler, M.D., professor of medicine at UCLA and one of the leading researchers in this field.
Synthetic vitamin A has been tested in humans against leukemia, but not on a very widespread scale. A few years ago, American researchers at several different medical centers were involved in a double-blind, randomized trial of 13-cisretinoic acid (a retinoid compound) in patients with a pre-leukemia condition called myelodysplastic syndrome. Problems with the study – including many patients quitting the trial – cast suspicion on the results, according to Dr. Koeffler.
One of the researchers, however, continued the study on his own after the trial ended, and found a significant response. Was the original trial too short? It’s hard to say without attempts to duplicate those results. The study also showed physicians that the side-effects of retinoid therapy drying can be reduced with doses of vitamin E.
More reports have come from other countries. Researchers in China and France have reportedly achieved promising results using trans retinoic acid (ATRA) against acute promyelocytic leukemia (APL). Most of the patients in Chinese studies went to remission. A French researcher has reportedly duplicated their results.
Other research shows that of seven APL patients (from four different studies) treated with isotretinoin, four had what was termed “remarkable responses.” Clearly, there’s enough evidence to warrant further research on both synthetic A and D.
FIGHTING WITH FOLATE
Leucovorin is a synthetic form of the B vitamin folate. It’s being used in in combination with a cancer drug called fluorouracil, commonly referred to as 5-FU. 5-FU/leucovorin is being used against several types of cancer.
By itself, 5-FU has been used against colon cancer for more than 5 decades. It interferes with cancer growth by binding to an enzyme needed for cell reproduction. (Some cancer cells reproduce much faster than normal cells. That’s how some tumours grow in relation to surrounding tissue.)
Leucovorin, though, seems to strengthen the bond between 5-FU and the enzyme. The drug/vitamin combination hold onto the enzyme for a longer period than the drug alone. Fewer free enzymes means slowed or stopped tumour growth.
5-FU/leucovorin has determined its effectiveness against advanced, inoperable colon cancer. “That’s where we hope to have real impact on the survival rates,” says Susan G. Arbuck, a research clinician at Roswell Park Memorial Institute, in New York.
5-FU/leucovorin is currently also being tested against a variety of other melignancies, including cancers of the stomach, breast, pancreas, head and neck.
Colorectal polyps are easy to remove but may recur. That prompted researchers at the Ludwig Institute for Cancer Research in Canada to test the effect of vitamin C and E on polyp recurrence.
Two hundred people who were free of polyps after surgery were split into two groups. One was given daily supplements of 400 mg. of vitamin E. the other got blank look-alikes. After about two years, all the patients were checked for polyp recurrence. The researchers noted a slight reduction in polyp recurrence among the patients receiving vitamins C and E. they stressed that further studies should be performed to rule out the possibility that this was a chance finding.
VITAMINS VS. BLADDER CANCER
Bladder polyps, which can become cancerous, are fairly easy to treat by surgical removal. But there’s a 70 per cent risk of recurrence or that new polyps will form. To prevent that, researchers at West Virginia University tested mega-doses of four vitamins as an adjunct to conventional therapy after bladder surgery.
Patients are being divided into two groups: People in one group take multiple vitamins at the recommended daily allowance levels; those in the other group get the same, but with mega-doses of vitamins A, B6, C and E. vitamin B6 has been tested with good results in other preliminary blabber-cancer studies in humans. Vitamins A and C have been tried against blabber cancer in animal studies, with early encouraging results. Vitamin E hasn’t been tested specifically against bladder polyps before, but has shown promise in other cancer trials.
VITAMIN A FOR ORAL HEALTH
A few years ago, a report from the British Columbia Cancer research Center, in Vancouver, announced that Vitamin A could heal oral leukoplakias (pre-cancerous sores inside the mouth). The study involved 21 people who chew betel leaves with tobacco and betel nut mixture known to cause an abundance of leukoplakias. After six months of taking vitamin A supplements, 57 per cent of the people showed no detectable disease. And none of the tobacco/betel chewers developed new sores while on the vitamin A. experts estimate that normally only 5 per cent of such sores disappear on their own.
Now word comes from the University of California Clinical Cancer Center and the University of Arizona Cancer Center that a milder form of vitamin therapy has the same effect. Seventeen people with oral leukoplakias were given beta-carotene. Each person took 30 mg. of supplemental beta-carotene per day for three months. Those whose leukoplakias responded to the treatment were kept on it for an additional three months.
At the end of the study, two patients had complete remission of their leukoplakias, and 12 others had partial remission. Of the remaining three, one showed no change and the other two got worse. Overall, that’s an 82 per cent positive response rate.
The exciting aspect of this study is that beta-carotene, the safest source of vitamin A, was so effective. Pure vitamin A is toxic in high doses, and even the retinoids have unpleasant side-effects (primarily skin problems). But beta-carotene is virtually problem-free, even in high doses. That’s because the body converts only as much beta-carotene into vitamin A as is needed at the moment. The excess is excreted harmlessly.
RETINOIDS AGAINST SKIN CANCER
Several synthetic forms of vitamin A, collectively called retinoids, have been tested as treatments for skin cancers known as basal-cell and squamous-cell carcinoma. In several tests – just in the experimental stage – oral doses of retinoids have been effective against these carcinomas because retinoids accumulate primarily in the skin.
Most of the studies performed so far have been small, but the results are encouraging. These skin cancers, like all the others that retinoids have been used against, are unlikely to regress on their own. So researchers think that even though their tests are preliminary and have no control groups, the retinoids are probably responsible for the positive effects.
The retinoids etretinate and isotretinoin have been used to treat basal-cell carcinoma. In three separate studies on a total of 56 people, 23 showed a partial regression of cancer (the tumour shrank), and five showed complete regression (disappeared). This is an overall response rate of 50 per cent, meaning that half the people experienced some decrease in the number or size of tumours.
Retinoids have also been tested against malignant melanoma, a more serious form of skin cancer. Preliminary results from a small study of 20 people with advanced melanoma showed some shrinkage of tumours in three people. It’s far from a cure, but it’s a glimmer of hope against a type of cancer that has been resistant to drugs.
A rare skin cancer called mycosis fungoides had shown good response to retinoid therapy. In five preliminary studies, a total 78 people with the disease were put on oral isotretinoin. More than half showed at least a partial response.
Once treatment was completed, though, many of the cancers returned. This suggests that regular doses of retinoids may be required for a “cure”. Among other things, doctors are conducting studies to determine the best maintenance dose: one that minimizes skin and mucous-membrane drying, the main side-effect.
Researchers are having better luck using oral retinoids against squamous-cell carcinoma. In four small studies, a total 14 squamous-cell patients were treated with etretinate (4 patients), isotretinoin (9), or arotinoid (1). Six of the 14 had partial remission (tumour reduced in size) or temporary remission (tumours shrank or stopped growing for a short time); another 4 had complete, sustained remissions of the squamous-cell tumours. That adds up to a 71 per cent response om an admittedly small sample.
Both basal-cell and squamous-cell carcinomas are relatively easy to cure with surgical removal (used in 90 per cent of cases), radiation therapy or tissue destruction with extreme heat or cold. So, why all this fuss about retinoids?
Surgery and other tissue-destroying therapies leave scars. That’s not a big problem for a person with one tumour on the back of a hand. But a majority of people with carcinoma have several tumours on areas of body that are regularly exposed to the tumour-inducing ultraviolet rays of the sun: not only the hands, but the head and neck as well.
Retinoids don’t leave scars: Tumours shrink away and normal tissue fills in. That’s especially valuable in advanced disease. “One patient had severe, disfiguring tumours on his neck and nose. After six months on isotrtinoin, the neck tumour had shrunk to a small, flat lesion. And the nose tumour had shrunk by 70 per cent, with preliminary rebuilding of his all-but-eroded nose,” explained Scott M. Lippman, M.D., of the hematology/oncology department of M.D. Anderson Cancer Center at the University of Texas.
WHAT THE GOOD NEWS MEANS
Vitamin chemotherapy is a seductive idea: The ultimate goal is an effective natural cancer treatment with no pain and minimal expense. But it’s not quite that simple – yet.
Scientists are going full bore to see if any of these treatments will turn out to be effective. And even for the vitamins showing the greatest potential, questions of dosage and side-effects must be resolved.
Note, too, that several of the vitamin therapies don’t use pure vitamins. Leucovorin and isotrtinoin are synthetic chemical equivalent of folate and vitamin A, respectively. Slight alterations in their chemistry make them more efficient treatments and/or reduce dangerous side-effects seen in high doses of the original vitamin. These synthetic vitamins are different enough to be treated as drugs by the Food and Drug Administration in the U.S. where they’re available by prescription only.
Until scientists nail down the facts, the best course is to go with what we know. Opt for the proven medical treatments. Have suspected cancer checked by a physician. And try a good defense: There’s strong scientific evidence that a healthy diet can help prevent the start of certain types of cancer. To use this evidence to your fullest advantage, eat a well-balanced, nutrient-dense diet that is low in fat. This includes low-fat meats and poultry, fish, whole-grain products, and generous amounts of fresh fruits and vegetables. If you’re on a restricted diet – or need added assurance that you’re getting the requisite amount of vitamins and minerals – you may want to consider taking a multiple supplement.