Abstract 1385: Clinical outcomes between obese and non-obese breast and gynecological cancer patients with alterations in the PI3K/AKT/mTOR pathway
Authors: Kim Diana , Xu Bing , Elsey Rachel , Meissner Tobias , Williams Casey 
Published: July 2021

Purpose Obesity has been shown to be strongly associated with the development of breast and gynecologic cancers. PIK3CA is one of the most commonly altered genes in solid tumors, and patients who have alterations are routinely initiated on therapies that target this pathway. However, response can vary greatly between patients, and the reason for differences in response has yet to be completely understood. Obesity has been shown to alter cancer metabolism and further dysregulate the PI3K/AKT/mTOR pathway which may affect response to target therapy. L. Cantley and colleagues suggest that the state of consistent hyperinsulinemia, which is common in obesity, can compromise the clinical benefit of PI3K-pathway targeted therapy, as insulin is a known potent stimulator of this pathway. Therefore, the purpose of this study was to compare clinical outcomes between obese and non-obese patients on pathway-directed therapy.

Methods A retrospective analysis was performed on 140 patients with breast, ovarian, cervical, or endometrial malignancies at Avera Cancer Institute. Female patients with a documented oncogenic PIK3CA alteration were included in the study. Overall survival (OS) and progression free survival (PFS) were the primary endpoints. BMI groups were determined by using existing clinical categories of obesity as defined by the CDC. Patients were stratified into 2 BMI groups: Group A 25 kg/m2 and Group B 25 kg/m2. The Kaplan-Meier method was used to derive time-to-event estimates and test for significance. A cox proportional-hazard model was utilized to determine the association between survival time for patients with BMI being the predictor variable.

Results Of the 140 patients, 106 patients had breast cancer, 21 patients had endometrial cancer, 9 patients had ovarian cancer, 3 patients had cervical cancer, and 1 patient had vaginal melanoma. There were 52 patients in Group A and 88 patients in Group B. 25 of the 140 patients had documented PIK3CA alterations but were never initiated on targeted therapy. Group B was found to reduce the hazard by a factor of 0.63 (p=0.09). The subset of Group B with PI3K/mTOR targeted therapy was found to reduce the hazard by a factor of 0.43 (p=0.008). Among the 43 patients who were included in PFS analysis, it was found that there was no statistically significant (p=0.6) improved PFS between the two groups.

Conclusion In this analysis, patients with a PIK3CA mutation and who had a higher BMI had an improved response rate from targeted therapy and overall survival than compared to patients with a lower BMI. Treatment lines prior to initiation of targeted therapy varied greatly, and differences in the multiple types of malignancies studied in this analysis was a limitation. More prospective studies that are statistically powered are warranted in order to assess the true impact of obesity on improved OS compared to patients with a BMI 25.

Citation Format: Diana Kim, Bing Xu, Rachel Elsey, Tobias Meissner, Casey Williams. Clinical outcomes between obese and non-obese breast and gynecological cancer patients with alterations in the PI3K/AKT/mTOR pathway [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1385.