Combinations of drugs have effectively reduced the side effects of large drug dosages given to some cancer patients and have overcome the ability of cancer cells to resist chemotherapy, researchers say.
Up to 80% of patients with solid tumors such as breast, lung, testicular and ovarian cancer respond to standard chemotherapy, but far fewer of those are actually cured because many become resistant to anti-cancer drugs 18 months to two years after treatment starts, said Dr. Robert F. Ozols, head of the National Cancer Institute’s experimental therapeutics section.
Ozols said that combining chemotherapy and other drugs increased the survival of patients with ovary and testicle cancers and “provide optimism we will increase the effectiveness of chemotherapy and reduce toxicity.”
The techniques already are in use at some medical centers, he said during the American Cancer Society’s annual science writers’ seminar.
In ovarian cancer, resistance to adriamycin apparently occurs when the membrane around tumor cells changes and the cells expel the drug so it can’t kill them, Ozols said. But laboratory experiments have shown adriamycin can be trapped in cancer cells if combined with verapamil, normally used to treat abnormal heart rhythms.
So the NCI researchers are giving a combination of the two drugs to eight women whose ovarian cancer has been considered terminal because they are resistant to adriamycin.
Preliminary results show it is possible to give the women enough verapamil to overcome their resistance to adriamycin, but Ozols said it’s too early to tell whether the treatment will save their lives.
He said some cancers are resistant to low drug doses but can be halted with high doses. However, high doses can be toxic to normal cells.
Cisplatin is used against ovarian and testicular cancer but high doses damage the kidneys. Dr. Charles Litterst at NCI recently demonstrated that a dose of cisplatin which normally killed lab animals could be made completely safe if administered in a 4% salt solution.