James J. Kilpatrick's call to "Legalize Heroin for Patients in Pain" {op-ed, June 14} is based on unfortunate misconceptions -- unfortunate for the cancer patient who would be given the heroin and unfortunate for society as a whole.

The simple fact is that there is no scientific evidence demonstrating that heroin offers any advantages in pain relief over the many other currently available, approved medications. Absent such evidence, the risks of making this popular street drug legally available for any purpose are not worth taking.

Kilpatrick suggests that injectable heroin would be more effective than morphine in certain patients. The one advantage often claimed for heroin is that it is more soluble than morphine and can be injected in smaller doses, which makes it easier to administer to patients who have lost a great deal of weight and muscle mass.

In most cancer patients, however, pain can be controlled effectively with oral medications. For those who need injectable narcotics, there is available Dilaudid-HP, approved by the Food and Drug Administration in 1983, which is highly soluble and is more potent, faster-acting and longer lasting than heroin.

New techniques for administering pain killers, such as constant infusion, also provide proven, effective alternatives for controlling pain in patients, making frequent injections unnecessary.

Kilpatrick minimizes the threat of heroin diversion by citing the claim that the entire amount needed to treat cancer pain would only be 2 percent to 4 percent of illicit street supplies of the drug. But why should we take the chance that any heroin will be diverted to illicit channels, and why should we subject hospitals, hospices and pharmacies to the danger of robberies and other violent crimes for a drug that offers no therapeutic benefits over existing medications?

Nearly every organization of concerned medical and health-care professionals opposes legalizing heroin to treat cancer pain. The American Medical Association, the National Hospice Organization, whose members often care for dying cancer patients, the American Society of Hospital Pharmacists, the American Society of Internal Medicine, the American Society of Anesthesiologists, and many others all urged the House to reject this legislation in 1984, which it did by a vote of 355 to 55.

Prominent British physicians have also changed their minds about heroin and have cautioned their American counterparts against legislation to legalize heroin.

In addition, after considering the use of heroin for intractable pain, the U.N. Commission on Narcotic Drugs passed a resolution in February urging all governments to prohibit the manufacture and importation of heroin and using it on humans.

These individuals and organizations do not lack compassion for the victims of cancer and their families. Rather, they recognize that existing medications, when properly administered, are adequate to relieve pain in the vast majority of cases and that heroin will not improve our ability to control cancer pain.

Heroin is not a panacea for the problem of cancer pain. We must not hold out false hope for cancer victims and their families. What is needed is more education of physicians and other health-care professionals in the proper use of available medications and other techniques to control intractable pain.

-- Charles B. Rangel The writer, a Democratic representative from New York, is chairman of the Committee on Narcotics Abuse and Control.