Dear Dr. Roach: We’re all amazed at the substantial advances in treating cancer in recent years. But are there certain cancers that science and medicine haven’t had much success with? — A.M.H.

Answer: I’m afraid so. Many cancers remain difficult or almost impossible to cure, due to a combination of factors. One is that certain cancers usually don’t cause symptoms until they’re large in size and likely to have spread. Another is that there are no curative chemotherapy or radiation options. Some cancers also spread very early; breast cancers can be metastatic (spread to distant organs) when they are much smaller than 1 centimeter.

Breast cancer in particular is highly varied in its aggressiveness and can come back after an apparent cure, even after decades. (One breast cancer expert, Dr. Dan Hayes at the University of Michigan, told me that he has seen the same breast cancer return after 35 years.)

Other cancers that are frequently incurable include pancreatic cancer, a particular type of brain cancer called glioblastoma multiforme, liver cancer and esophageal cancer. As I write this list out, I remember with sadness patients, colleagues, students and family members who’ve passed with these conditions, despite the very best care we could give them.

Fortunately, we do seem to be on the edge of dramatic improvements in the treatment of some of these cancers, such as pancreatic cancer. A few years ago, I’d have put metastatic melanoma on the list of almost incurable cancers, and now 30% to 50% of people with this condition live more than five years. Even if their cancer doesn’t get cured, people can live many years with a good quality of life. The same is true for many people with ovarian cancer.

Continued research on these cancers is absolutely essential to make advances that turn these heartbreaking diagnoses into treatable conditions. This requires large investments in basic science.

Dr. Roach regrets that he is unable to answer individual letters, but will incorporate them in the column whenever possible. Readers may email questions to ToYourGoodHealth@med.cornell.edu.