Preview of Three Studies From The 2013 ASCO Breast Cancer Symposium

Results of three studies were unveiled at a Presscast in advance of the upcoming 2013 ASCO Breast Cancer Symposium to be held September 7-8, 2013, in San Francisco, CA. Two studies focused on management of ductal carcinoma in situ (DCIS), and a separate study focused on womens’ perception of their personal breast cancer risk.

The main findings of the studies were:

  • Radiation therapy for DCIS is safe and does not appear to increase the risk of cardiovascular disease (CVD) or CVD-associated death.
  • Routine MRI at the time of surgery for DCIS does not affect recurrence rates and is probably unnecessary in the majority of patients undergoing surgery.
  • A large survey of women undergoing screening mammography showed that only 10% of women had an accurate idea of their personal risk of developing breast cancer; the other 90% either over- or under-estimated their risk.

Radiation in DCIS

DCIS is a precancerous lesion that could progress to breast cancer – if untreated – in an unknown percentage of women.  Therefore, most women with DCIS undergo surgery, often followed by radiation therapy, to reduce the risk of recurrence. Concern has been raised that radiation to the general region of the heart can increase the risk of cardiovascular disease (CVD), even though modern protocols have been adjusted to reduce exposure of the heart to radiation.

A large population-based study in the Netherlands suggests that radiation does not increase the risk of CVD in women with DCIS compared to the general population and to DCIS patients treated with surgery alone. These results should be reassuring to women and their physicians who include radiotherapy in treatment plans.

The authors state that this is the first large study to evaluate long-term effects of radiotherapy for DCIS on both the incidence of CVD and associated deaths.

Although these results are encouraging, longer follow-up, perhaps 5 to 10 years or more, is needed before definitive statements can be made about the CV safety of radiation in patients with DCIS, said lead author Naomi B. Boekel, MSc, a PhD student at the Netherlands Cancer Institute in Amsterdam, Netherlands.

The retrospective study was based on data from 10,468 women diagnosed with DCIS under the age of 75 years between 1989 and 2004. Surgery alone was performed in about 71% (43% had mastectomy and the remaining women had lumpectomy), and 28% underwent both surgery and radiotherapy. At a median follow-up of 10 years, survivors of DCIS had a similar risk of dying from any cause and a 30% lower risk of dying of CVD compared with the general population in their county. Patients treated with surgery alone had a similar risk of developing CVD as those treated with both surgery and radiotherapy (9% versus 8%, respectively); no difference in risk of CVD was observed between patients who received left-sided radiotherapy (which includes a portion of the heart in the radiation field) or right-sided radiotherapy (which does not include the heart in the radiation field; in these subgroups, the incidence of CVD was 7 % versus 8%, respectively.

DCIS survivors may be more motivated to adopt a healthy lifestyle than the general population, which may explain the slightly lower risk of CVD compared with the general population, noted Dr. Boekel.

MRI in DCIS

A second study featured at the presscast suggests that perioperative MRI may not be necessary in patients undergoing surgery for DCIS. MRI was not associated with reduced risk of locoregional recurrence (LRR) or contralateral breast cancer (CBC) after surgery.

There are no official guidelines for perioperative use of MRI, but some centers order it routinely to detect additional cancers and to confirm or expand on data attained from mammograms or ultrasounds. This study indicates that MRI is not necessary for every patient with DCIS, stated first author Melissa L. Pilewskie, MD, Memorial Sloan-Kettering Cancer Center (MSKCC) in New York City and Commack, NY. These results are important because MRI is expensive and has a high false-positive rate, resulting in additional tests, while it does not appear to improve long-term outcomes for most women with DCIS, she added.

Dr. Pilewskie said that perioperative MRI may be useful in specific patients with DCIS, such as those with a palpable mass and nipple discharge, which are not detected by mammogram screening.

The study analyzed rates of LRR and CBC in 2321 women who underwent a lumpectomy between 1997 and 2010 at MSKCC. Of that group of women, 596 had an MRI before or immediately following lumpectomy, and 1725 did not. Follow-up was a median of 59 months. No significant difference in the 5-year LRR rates was found: 8.5% in those who had an MRI versus 7.2% for those who did not.

In an analysis adjusted for patient characteristics and risk factors associated with recurrence, MRI was not associated with lower rates of LRR. Additionally, no significant differences were seen in the 5-year rates of CBC (3.5 years in both groups).

In a group of patients followed for 8 years, LRR were 14.6% for those who had an MRI versus 10.2% for those who did not. The rate of CBC at 8 years was 3.5% and 5.1%, respectively.

In general, doctors ordered an MRI for women in the study who were at increased risk of developing breast cancer because of age and/or family history, which may explain the higher recurrence rates in that group, said Dr. Pilewskie. She believes that future studies should focus on settings where use of MRI may improves outcomes, such as monitoring response to therapy.

Perceptions of Breast Cancer Risk

In a large survey of almost 10,000 women undergoing mammography screening, more than 90% inaccurately estimated their lifetime risk of developing breast cancer. Results were evenly split between women who over-estimated and those who under-estimated their personal risk. Alarmingly, 40% of survey respondents said they had never discussed their personal risk of breast cancer with a doctor.

“These findings suggest that despite the pink ribbons, marches, and large public health awareness campaigns about breast cancer, educational messages are missing the mark. We should change the way breast cancer awareness is approached,” stated lead author Jonathan Herman, MD, Hofstra North Shore-LIJ Medical School in New Hyde Park, NY. The study is important, because appropriate decision-making rests on an accurate perception of breast cancer risk. Patients can either underutilize available chemoprevention strategies or overuse them depending on perception of personal risk.

The survey included 9873 women aged 35 to 70 years who had a mammogram at 1 of 21 centers on Long Island, NY. Twenty-five survey questions covered demographics, breast cancer risk factors, including personal and family history of breast cancer, and any prior breast cancer risk assessments and discussions. Survey questions were adapted from the NCI Breast Cancer Risk Assessment Tool used to estimate the risk of developing invasive breast cancer.

The actual lifetime risk of developing breast cancer was calculated for each respondent and then compared with that woman’s personal estimate; if the difference from the calculated value was greater than 10%, it was labeled as inaccurate.

Only 707 women (9.4%) correctly estimated their risk; 3359 women (44.7%) underestimated their risk and 3454 (45.9%) overestimated it.  In general, Caucasian women were more likely to overestimate their risk, while women in minority groups were more likely to underestimate it.

The level of overall understanding about breast cancer risk was low in this study, and this is especially concerning, since these women were already participating in mammography screening. Dr. Herman said that the level of understanding could be even lower in the general population not concerned enough about breast cancer risk to participate in mammography screening.

by Alice Goodman

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