Peripheral neuropathy is common after chemo, but long-term studies are rare

Even years after completion of chemotherapy, patients with early-stage breast cancer can experience peripheral neuropathy, according to results from a systemic review and a study both published in the Journal of the National Cancer Institute. Few studies, however, have been done to confirm these effects in the long-term, leaving clinicians and patients with little on which to base informed decisions.

“Until recently, the really strong focus has been to identify treatments to reduce breast cancer recurrence and mortality,” said co-author Joy Melnikow, MD, MPH, director, Center for Healthcare Policy and Research, University of California, Davis. “I think we’ve reached the point now where we need to ask questions about the adverse effects that come along after curative treatments. We need to balance what are sometimes small therapeutic benefits with the risk of long-term adverse events.”

Dr. Melnikow and colleagues conducted a review to better determine the effects of neuropathy on breast cancer patients at 1 or more years after treatment. Unfortunately, they found only five studies that followed these patients for 1 year or more. Results from this handful of studies also varied widely.

“The most striking finding from the review was how little data were out there,” said Dr. Melnikow. “And these studies report a wide range of frequency for peripheral neuropathy, from as low as 11% to more than 80% of patients at 1 to 3 years after treatment.”

In the second study, researchers included 1,512 patients with early-stage breast cancer from the National Surgical Adjuvant Breast and Bowel Project Protocol B-30 (NSABP B039), which sought to determine the efficacy of various combinations of doxorubicin, cyclophosphamide, and docetaxel, and their effects on long-term peripheral neuropathy.

They found that 2 years after treatment initiation with any of the chemotherapeutic combinations, a full 42% of patients experienced symptoms of neuropathy, while 10% reported severe discomfort. Those who had more severe symptoms of neuropathy reported much worse quality of life.

Fewer patients treated with lower-dose docetaxel combinations experienced long-term neuropathy, and women with pre-existing neuropathy symptoms tended by be older, more obese, and fared worse.

Currently, adjuvant chemotherapy is believed, by many clinicians, to protect patients against recurrence. But the potential for side effects and the efficacy of other treatment options led these authors to conclude that the choice of foregoing adjuvant chemotherapy treatments or which to use should now include considerations of the long-term effects of such treatment.

“There is very little treatment for neuropathy, and there’s nothing that’s actually proven to work,” said senior author Patricia Ganz, MD, director, Center for Cancer Prevention & Control Research, UCLA’s Jonsson Comprehensive Cancer Center, Los Angeles, CA.

“Since we don’t have an effective treatment, ideally it would be best to prevent it from happening by not administering chemotherapy if it is likely to have minimal additional benefit. Alternatively, this class of drugs could be avoided in patients who are at higher risk for persistent neuropathy. At the minimum, patients need to be informed about the likelihood of persistent symptoms,” said Dr. Ganz.

Thus, both groups of researchers called for further studies of peripheral neuropathy and the other side effects of chemotherapy, to determine which treatments are effective without generating long-term side effects that reduce quality of life in these women.

“This is a call to action. We can’t definitively define the frequency of peripheral neuropathy or understand the differences between chemotherapy regimens with the data we have. This issue of adverse effects in survivors goes beyond peripheral neuropathy. There are other effects that need to be considered while women are making treatment decisions,” concluded Dr. Melnikow.