Abstract 979P
Background
Immunotherapy has been one of the most important developments in cancer treatment of the past few decades. With the inclusion of immunotherapy in cancer treatment, overall survival rates have increased in some cancers. However, its usage comes with harmful side effects and research has shown that concomitant use of antibiotics has decreased its efficacy. Hence, our study aims to evaluate the risks and benefits of using pembrolizumab with or without concomitant use of antibiotics, in which such evidence can be used for the development of biomarkers for immunotherapy treatment in the future.
Methods
This is a retrospective chart review done in the Bons Secours Hospital, Cork (BSHC). Eligible participants had to be on pembrolizumab between 2014 – 2020. This includes all commercial, self-pay, compassionate access and deceased patients. Patients on clinical trial use are excluded. A total of 44 patients were selected. Concomitant use of antibiotics refers to any usage between 2 months before and 1 month after immunotherapy treatment.
Results
9 out of 44 patients (20%) received antibiotics in the therapeutic window and 35 did not. Antibiotic use was associated with a shorter progression-free survival (PFS) median (64 days vs 335 days). Overall survival (OS) median was almost similar in both groups – no antibiotic use (544 days) and antibiotic use (547 days). However, the Kaplan Meier curves of OS and PFS are not statistically significant (log-rank p=0.96 and log-rank p=0.64, respectively). 26 patients (59%) developed adverse events during their treatment. These events were also more prevalent in the antibiotics group (67% vs 57%). Table: 979P
Demographic table
| Characteristics | N=44 |
| Gender (%) Male, Female | 29 (66), 15 (34) |
| Age at Diagnosis (median) | 67 |
| Stage at Diagnosis (%) 1, 2, 3, 4 | 2 (4.5), 8 (18), 12 (27), 22 (50) |
| Cancer type (%) Urothelial cancer, Metastatic melanoma, NSCLC, Mesothelioma, Breast cancer, Endometrial cancer, Oesophageal cancer | 5 (11), 25 (57), 10 (23), 1 (2.3), 1 (2.3), 1 (2.3), 1 (2.3) |
| Metastasis (%) Brain, Lung, Bone, Liver, Other | 35 (80), 9 (26), 12 (34), 19 (54), 8 (23), 8 (23) |
| Antibiotic use (%) No antibiotic use, At time of initiation (-2+1 months), After 1 month of initiation | 35 (80), 9 (20), 12 (27) |
| Adverse events (%) Gastrointestinal, Endocrine, Respiratory, Renal, Liver, Other | 26 (59), 5 (19), 3 (12), 7 (27), 3 (12), 3 (12). 11 (42) |
Conclusions
The results shown in this study were comparable to the outcomes of previous studies. There were worse outcomes when treated with antibiotics, although it is not statistically significant. A larger sample size is needed and further research into other biomarkers of immunotherapy efficacy will be greatly needed to improve cancer therapy.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
University College Cork.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.