Is Individualized Dose Intensification Appropriate for Inflammatory Breast Cancer?

Inflammatory breast cancer (IBC) is an uncommon but aggressive variant. The current treatment paradigm is trimodality therapy with neoadjuvant chemotherapy, modified radical mastectomy (MRM), and post-mastectomy radiation therapy (PMRT). As systemic therapy decreases rates of distant metastatic disease and improves survival, the need for long-term locoregional control has become more essential. We hypothesize select subgroups benefit relatively less from conventional PMRT. We report the benefit of RT on oncologic outcomes of IBC by subgroup to identify patients that may be suitable for individualized treatment intensification. We searched the Surveillance, Epidemiology, and End Results (SEER) database for women with breast cancer. This cohort was narrowed to women with non-metastatic [Adjusted AJCC 6th M (1988+) M0] IBC [Adjusted AJCC 6th T (1988+) T4d] with MRM [(1998+) Breast] with or without external beam PMRT. To be included, patients were treated with either ipsilateral MRM with or without reconstruction with the specified race, age, hormone receptor [ER/PR Status], grade, nodal stage [Adjusted AJCC 6th N (1988+)], and radiation data. Our primary endpoint was actuarial 5-year cause-specific survival (CSS). We identified a cohort of 4841 women treated between 1998 and 2007. The median age of diagnosis was 55. Black and white women comprised 13% and 81% of the cohort respectively. The actuarial 5-year CSS for the whole cohort was 56%. PMRT (n = 2903) was utilized in 67% of patients while 33% received no RT. There was a significant benefit of PMRT compared to no RT with 5-year CSS of 59% and 50% respectively (Table 1). The benefit was not statistically significant (SS) in black women, but was in white women. N0, N1, N2, and N3 patients comprised 12%, 33%, 27%, and 28% of the cohort respectively. Node negative women had no CSS benefit at 5 years, but node positive women had a significant benefit of RT regardless of nodal stage. Low, intermediate, and high-grade tumors made up 2%, 27%, and 71% of the group. PMRT provided a significant CSS benefit in high-grade tumors with a trend in benefit in the intermediate group. Women over 70 years of age had a significantly lower CSS compared to women between 50-69, but not when compared to ages 20-49. A SS benefit of PMRT was seen regardless of age, but the greatest benefit was seen in the 20-49 group (59% v 47%). Our study suggests select subgroups have worse survival and may benefit relatively less from conventional PMRT. As such, select patients may benefit from individualized treatment intensification including dose escalated PMRT and/or additional adjuvant systemic therapy. Further prospective data, if feasible, is needed to confirm our findings and conclusions.Tabled 1Abstract 2099; Table 1.PatientsSubgroupPMRTn=5-year CSS (95% CI)Whole Cohortn/aAll484156% (54.0-57.2)PMRT290359% (57.3-61.3)No143950% (46.7-52.4)RaceBlackPMRT36046% (39.4-51.3)No20235% (27.6-42.1)WhitePMRT236261% (59.0-63.5)No114352% (48.2-54.7) Open table in a new tab