Younger breast cancer survivors are at increased risk for osteoporosis -- weak, brittle bones -- due to breast cancer treatments, new study finds. The study included 211 women who had been diagnosed with breast cancer within the past nearly three years and 567 women with no history of cancer. Over about six years of follow-up, women diagnosed with breast cancer at age 50 or younger had twice the risk of developing either osteoporosis or a severe bone-loss condition called osteopenia than those without cancer.

The risk was up to four times higher among breast cancer survivors who had undergone treatments that block estrogen production, according to the study. "These findings show that even younger women have a relatively high risk of bone loss with standard breast cancer treatments, and in many cases we saw this bone loss occurring in just a few years," said senior study author Dr. Kala Visvanathan. She's a professor in the department of epidemiology at Johns Hopkins Bloomberg School of Public Health in Baltimore.

"These results suggest that we should monitor even young breast cancer patients for bone loss during and after therapy," Visvanathan said in a Hopkins news release.

Previous research has shown that older breast cancer survivors are at increased risk of bone loss.

Breast cancer treatments can trigger premature menopause by damaging the ovaries or otherwise interrupting estrogen production, making women more vulnerable to bone loss.

This study found that the risk of bone loss was particularly high after certain types of breast cancer treatment. Women receiving the standard combination of chemotherapy plus hormonal therapy had a 2.7 times increased risk of osteopenia and osteoporosis compared to those without cancer.

Chemotherapy plus tamoxifen was associated with a 2.5 times higher risk, but not tamoxifen alone. Aromatase inhibitors, which reduce estrogen production, were associated with a 2.7 times higher risk for bone loss alone, and a 3.8 times higher risk when combined with chemotherapy, the study found.

The increased risk of bone loss in breast cancer survivors was evident even when women with premature menopause were not included in the analysis.

"There seems to be an effect of cancer treatment on bone health that works independently of menopause -- perhaps by directly inhibiting bone formation," Visvanathan said.

The poorest prognosis is for metastatic breast cancer (stage IV), when the cancer has spread beyond the lymph nodes to other parts of the body.  An overall survival rate shows the percentage of people who are alive after a certain period of time after diagnosis of a disease (such as breast cancer). For example, say the 5-year overall survival for women with stage I breast cancer was 90 per cent.

This would mean 90 per cent of women diagnosed with stage I breast cancer survive at least 5 years beyond diagnosis. (Most of these women would live much longer than 5 years past their diagnoses.) Overall survival varies by breast cancer stage. People diagnosed with stage 0, I or II breast cancers tend to have higher overall survival rates than people diagnosed with stage III or IV breast cancers.

However, overall survival rates are averages and vary depending on a person’s diagnosis and treatment. Relative survival compares survival rates for people with breast cancer to survival rates for people in the general population.

 HealthDay