Osteoporosis is a growing concern among breast cancer survivors and their
doctors, because certain cancer drugs can cause bone loss.
But a new study has found that cancer drugs aren't the only culprits. Among 64
breast cancer patients referred to a bone health clinic, 78 percent had at least
one other cause of bone loss, including vitamin D deficiency, excessive calcium
excretion in urine and an overactive parathyroid gland.
"Doctors evaluating breast cancer patients for possible bone loss should look
further than cancer drugs," said Dr. Pauline Camacho, lead author of the study
in the Journal of Clinical Oncology. Camacho is an associate professor in the
department of medicine, division of endocrinology and metabolism, Loyola
University Chicago Stritch School of Medicine.
A co-author of the study, Dr. Kathy Albain, said breast cancer survivors "are
just like the normal population as they age in that bone loss can be due to many
treatable causes." Albain is a professor in the Department of Medicine, division
of hematology/oncology at Stritch.
Previous studies have found that chemotherapy drugs can cause bone loss. Studies
also have found that a class of breast cancer drugs called aromatase inhibitors
can decrease bone mineral density and increase the risk of fractures in
postmenopausal women. Aromatase inhibitors decrease the body's production of
estrogen. While estrogen feeds cancer, it also protects against osteoporosis.
Aromatase inhibitors include letrozole (trade name, Femara), anastrazole (Arimidex)
and exemestane (Aromasin).
Researchers reviewed charts of 238 consecutive postmenopausal patients who had
osteoporosis or osteopenia and were referred to the Loyola's Osteoporosis and
Metabolic Bone Disease Center from 2000 to 2006. (Osteopenia is lower than
normal bone mineral density, but not low enough to be classified as
osteoporosis.) The patients included 64 women with breast cancer referred from
Loyola's Cardinal Bernardin Cancer Center and 174 patients without breast cancer
referred from primary care physicians.
Thirty eight percent of the breast cancer patients had vitamin D deficiency,
compared with 51 percent of the non breast cancer patients. Another cause of
osteoporosis, excessive calcium excretion in urine, was found in 16 percent of
cancer patients and 8 percent of noncancer patients. And in 5 percent of
patients, the parathyroid gland was overactive, producing a hormone that causes
bone to lose calcium.
Vitamin D deficiency can be treated with prescription doses of vitamin D
supplements. Excessive calcium excretion can be treated with a "water pill"
that's also used to treat high blood pressure, Camacho said. There are various
treatments for parathyroid gland disorder, depending on its cause.
In certain breast cancer patients, bone loss from cancer drugs can be treated
with osteoporosis drugs such as alendronate sodium (Fosamax) and ibandronate
sodium (Boniva), Camacho said.
Albain refers all her breast cancer patients for a comprehensive bone health
evaluation when osteopenia or osteoporosis is discovered. "Just prescribing a
medication for osteoporosis may not be enough for many of our patients," Albain
said. "They deserve a thorough workup."
Patient Rosaleen O'Connor, 71, of Elmhurst, Il., learned she had osteoporosis
while being treated by Albain for breast cancer. Albain referred O'Connor to
Camacho, who prescribed calcium supplements, prescription vitamin D and the
osteoporosis drug Boniva. Three years after O'Connor was diagnosed, her Stage 3
cancer is in remission, and she has suffered no bone fractures.
Other authors of the study, all from Loyola, are Dr. Amit Dayal, Dr. Josefina
Diaz, Dr. Fadi Nabhan, Dr. Monica Agarwal, Dr. John Norton and Dr. Patricia
Robinson.
The study was presented as a poster in the 2007 meeting of the American Society
of Bone and Mineral Research in Honolulu. It was supported by an
investigator-initiated grant from Procter and Gamble.
