Radiation therapy improves outcomes in metaplastic breast cancer
With a poor prognosis and high rates of distant metastasis (DM), metaplastic breast cancer (MBC) does not appear to have distinct histologic subtypes with significantly different clinical outcomes, and radiation therapy plays an important role in the treatment of MBC patients, a new study reveals.
“The majority of published studies on MBC have been relatively small with conflicting results. To the best of our knowledge, this is the largest single institutional study of histologically confirmed MBC cases in the literature to date,” investigators claimed.
Over a median follow-up period of 37.8 months, the 2-year local-regional recurrence (LRR) of the malignancy in 113 MBC patients (median age 61 years; 27 to 95) was 12 percent. On the other hand, rates of DM and overall survival (OS) were 25 and 69 percent, respectively. The corresponding values at 5 years were 21, 35 and 69 percent. [Breast Cancer Res Treat 2017;doi:10.1007/s10549-017-4367-5]
There was a significantly higher risk of LRR in patients who did not have radiation after resection (p=0.027), while T-stage was significantly associated with DM (p=0.008). Moreover, those who received adjuvant radiation after breast conserving surgery (BCS) had better LRR (p<0.001) and OS (p=0.009) than those who did not.
“Although [the effects of radiation therapy] did not remain significant in mastectomy patients who received treatment at the physician discretion, it underscores the role of [radiation therapy] in the treatment of patients with MBC,” investigators said.
“There may be a role for consideration of post-mastectomy [radiation therapy] in certain high-risk patients; however, it is not possible to make substantive conclusions given our limited sample size,” they added.
Interestingly, chemotherapy use was not significantly associated with OS, DM or LRR, while radiation did not significantly improve outcomes for mastectomy patients.
Of the 113 participants, 75 percent (n=85) received systemic chemotherapy; of this, 66 were given adjuvant chemotherapy following surgery while 23 had neoadjuvant chemotherapy.
A further 14 of the 23 patients given neoadjuvant chemotherapy had no pathologic complete response (pCR), seven of whom developed DM while 2 developed LRR.
“While it is difficult to draw conclusions from our evaluation given the diverse nature of both type and timing of chemotherapy, this is consistent with previous studies showing a more limited response to systemic therapy in MBC,” investigators said. [Asian Pac J Cancer Prev 2012;13:4645-4649; Breast Cancer Res Treat 2011;130:345-351]
The participants’ information were retrieved from the investigators’ pathology database and reviewed for relevant treatment, demographic, histological and clinical outcomes. Those who were male, were positive for metastasis at baseline and had incomplete information were excluded.
“At this time there does not appear to be a clear histologic subset of MBC which has significantly different clinical outcomes from the other subtypes,” investigators said.
“Although limited in its sample size, this study shows [radiation therapy] remains important in local–regional control,” they added.