Abstract 318P
Background
Various adverse events and underlying co-morbidities often delay or make physicians reduce the dose of chemotherapy, both of which can lead to inferior oncology outcomes. As data are sparse on this subject we did a retrospective multi-institutional study to evaluate the impact of the dosing vs. timing of chemotherapy on the oncology outcomes in patients taking first-line chemotherapy for metastatic breast cancer.
Methods
This was a retrospective analysis of 538 case records from 4 institutes during the periods of 2013-2019. All the patients received chemotherapy as per NCCN guidelines based on receptor status. The baseline characteristics were similar in all the groups assessed. They were startifed into those who took >90% of planned dose within 3 days of schedule (on time & right dose) vs those who had more than 4 days of delay (delayed dose) vs those who had received less than 85% of planned dose besides other supportive therapies like growth factors. The outcomes were compared between the groups.
Results
The charecters and outcomes of the pateints were as below: Table: 318P
| No. | Demographic profile | Distribution | Took chemo on-time and right dose (N=272) | Took reduced dose of chemo but on time (N=184) | Took right dose but with longer interval (N=82) |
| 1 | Age (years) | ≤ 65 | 221 (82%) | 136 (74%) | 47 (58%) |
| >65 | 51 (18%) | 48 (26%) | 35 (42%) | ||
| 2 | Co-morbidities (any) | Yes | 142 (52%) | 92 (50%) | 42 (51%) |
| No | 130 (48%) | 92 (50%) | 40 (49%) | ||
| 3 | Grade III/IV AE | Yes | 196 (72%) | 178 (97%) | 75 (91%) |
| No | 76 (28%) | 6 (3%) | 7 (9%) | ||
| 4 | Performance status | 0-1 | 209 (76%) | 160 (87%) | 70 (83%) |
| 2-3 | 63 (24%) | 24 (13%) | 12 (17%) | ||
| 5 | Response | PR/CR | 186 (68%) | 105 (57%) | 25 (31%) |
| SD | 41 (15%) | 39 (21%) | 32 (38%) | ||
| PD | 45 (17%) | 40 (22%) | 25 (31%) | ||
| 6 | Median PFS | In months | 18.3 (11.3-23.8) | 12.6 (8.6-18.3) | 10.4 (5.3-14.6) |
Conclusions
Dose delays ≥ 7 days, dose reductions ≥ 15%, and reduced dose intensity are quite common (almost 50% of subjects) for various reasons. There was a significant negative impact of the delay in dose or reduction in the dose of chemotherapy. The adverse impact on the outcome is more pronounced in the delay in timing rather than reduced dose of chemotherpay. Though it is a retrospective analysis (as we could not conduct a prospective study with such design in view of ethical issue), it gives an important insight that it’s better to give chemotherapy on time with reduced dose rather than increaing the interval between the doses. Our results indicate the problem is much deeper than the ones reported from the west, which have 15-32% incidence of dose miss/reductions.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
The authors.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.