Abstract PS6-43: The prognostic impact of breast cancer subtype based on hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) statuses for end-stage disease
Background: Most patients with metastatic cancer request information regarding their prognosis, most notably when death is clearly approaching. Several clinical indices are used to predict the prognosis of end-stage cancer based on performance status and clinical factors. For example, the Palliative Prognostic Index (PPI) includes a range of scores from 0-15 based on factors that include performance status, oral intake, presence of edema, dyspnea at rest, and delirium. For scores greater than six, survival for an additional three weeks was predicted with a sensitivity of 80% and a specificity of 85%. However, the predictive power of these indices is currently insufficient; the quality of life of end-stage breast cancer patients would be markedly improved with a more accurate prediction model. Breast cancer subtypes based on the hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) statuses are important prognostic factors with respect to the outcome of initial breast cancer therapy; the subtype defined by these parameters was also identified as an independent prognostic factor for outcomes in cases of metastatic breast cancer. However, the prognostic impact of breast cancer subtype with respect to end-stage disease remains unclear. In this retrospective observational study, we evaluated the relationship between survival time and associated clinicopathological factors, including breast cancer subtype, in order to develop a more accurate prognostic model for end-stage breast cancer patients. Methods: Seventy-three patients with end-stage breast cancer who were admitted to our hospice care unit from January 2014 to December 2018 were enrolled in the study. Patients in this unit were not provided with anticancer therapy but did receive highest-quality supportive care. The primary endpoint was survival time from the admission. Patient information, including age, PPI, disease-free interval (DFI), the number of treatments for the metastatic disease, metastatic site, and breast cancer subtypes were collected from medical records. Breast cancer subtypes included Luminal (Lum), Lum-HER2, HER2, and triple negative (TN) with respect to those that were HR+HER2−, HR+HER2−, HR−HER2+, and HR−HER2−, respectively. The study was approved by the ethical committee of the Oikawa Hospital (OHCT022). Results: The median survival time was 23 days (1-359 days). From the univariate analysis, PPI scores of less than six were associated with significantly shorter survival (14 days vs. 36.5 days, P = 0.001). Patients diagnosed with Lum-HER2 subtype, those who were older and were without liver metastasis, those with a shorter DFI, and those who underwent fewer treatments for metastatic disease showed a tendency toward a favorable prognosis, although these findings did not reach statistical significance. Multivariate logistic regression analysis revealed that a PPI score less than six (P = 0.001), Lum-HER2 subtype (P = 0.003), absence of liver metastasis (P = 0.001), and DFI lower than the median (33 months; P = 0.028) all contributed to longer survival time. Discussion & Conclusion: In addition to the PPI, breast cancer subtype can be used to provide more precise prognoses for end-stage breast cancer patients. Survival of patients diagnosed with the Lum-HER2 subtype was longer than that observed among those with any of the other subtypes who had not undergone any anticancer treatment for metastatic disease; these results suggest that anti-HER2 therapy may be associated with critical immunological modifications. Taken together, our results indicate that breast cancer subtype should be included to provide a more accurate prognostic model for end-stage breast cancer patients. Citation Format: Masahiro Oikawa, Yumika Setoguchi, Yasuko Enomoto, Kazuhumi Hisamatsu, Tetsuaki Inamitsu, Tatsuji Oikawa. The prognostic impact of breast cancer subtype based on hormone receptor (HR) and human epidermal growth factor receptor 2 (HER2) statuses for end-stage disease [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS6-43.