As promised, here’s the first update from the San Antonio Breast Cancer Symposium.
The morning started with several studies that looked at whether adding bisphosphonates (osteoporosis drugs) to the treatment of women with metastatic breast cancer could decrease bone mets as well as improve breast cancer survival. The studies found that there is a small benefit which was most evident in women who had what the researchers called a low estrogen environment. (I think that means menopause whether naturally occurring or medically caused by drugs or surgery.)
A new report from the Institute of Medicine, “Breast Cancer and the Environment: A Life Course Approachâ€ was presented to an expectant audience. The report, pursued at the request of and funded by Komen, did not, however, have any new information or smoking gun. The IOM committee defined environment widely to include any factor other than inherited DNA. This meant that they included lifestyle changes, which ended up comprising the bulk of their recommendations.
The IOM committee did not conduct any new analysis or studies but rather reviewed the findings from previous studies. The strongest links with breast cancer included postmenopausal HRT, medical radiation, oral contraceptive pills, obesity, and alcohol consumption. Decreased risk of breast cancer was related to physical activity. The committee concluded that smoking had mixed results and that personal hair dyes and non ionizing radiation (cell phones) had no relationship to breast cancer. They categorized some factors as needing more research and better data, such as benzene, and night shift work. (Note to night shift workers we need you for our currently open Army of Women study. The IOM committee also noted that several potential risk factors had been identified in studies some studies done in cells and animals but not yet in women. They recommended more research that would help us to better understand how various exposures that occur at different points in the lifespan but might increase breast cancer risk. This is, of course, the work we are trying to do at the Foundation, and that we described in our recently published study that looked at whether chemicals that get into milk also get into the resting (non-lactating) breast. We need now to study this more extensively to be able to predict what exposures actually can affect the breast.
An interesting retrospective study (that means they just looked back at women who had had these treatments and did not conduct a prospective randomized trial) on partial radiation (brachytherapy) versus whole breast radiation in women over 75 suggested that the risk of subsequent mastectomy within 5 years was more common with the shorter course. This sounded worrisome, until they said that the risk of needing a subsequent mastectomy was 4% with partial breast radiation and 2% in women with 6-week radiation. We will need to wait for the randomized data to mature to answer this question. At this point I don’t see a significant difference.
The second radiation study looked to see if there was a subgroup of breast cancer patients who had a very low risk of recurrence in the breast without radiation. Indeed the Luminal A (ER + PR+ Her 2 â€“ Ki67 <14%) fit the bill, with less than 5% relapse rate without radiation but with tamoxifen after 10 years. This will need to be tested prospectively but may indicate that there are not only differences in systemic therapy dependent on the kind of cancer but also on the local treatment.