Abstract 163P
Background
Deleterious or likely deleterious gTP53m is a rare situation that increases the risk of many cancers, among which BC comes first for women. 12 years(y) ago, we published one of the first series that suggested an increased risk of 2ndM after RT among these women (Heymann, Rad Oncol 2010). The present study evaluated the long-term risk of any 2ndM among women with BC and gTP53m treated with RT.
Methods
We retrospectively reviewed the medical records of women with gTP53m who were treated for a stage I-III BC at our referral tertiary center between 01/1982 - 04/2020. Outcomes assessed included the time interval between first BC and the occurrence of a local in-BC (outcome 1), a contralateral (CL) new primary BC (outcome 2) or a non-BC primary tumor (outcome 3), whichever occurred first. Patients (pts) were censored at the time of metastatic relapse and death.
Results
Among the 65 women included, median age at primary diagnosis was 33y. Invasive ductal carcinoma (72.3%), ER+ (56.6%) and HER2+ (43.4%) were the main tumor characteristics. 24 pts (36.9%) received adjuvant RT, 69.2% received chemotherapy, 41.5% HER2-directed treatments and 44.6% endocrine therapy. 21 pts had prophylactic mastectomy. After a median follow-up of 8.6y, 11 local recurrences, 16 contralateral BC, 21 other primaries, 13 metastatic relapses were observed. The table reports time-to-event outcomes. In the multivariable analysis, history of a previous cancer before BC (HR 0.39, 95%CI 0.157-0.97) but not RT (HR 0.92, 95%CI 0.46-1.84) was associated with the occurrence of 2ndM. Table: 163P
Proportion (%) of pts without the outcome of interest at 5, 10, 15y
| Outcome 1 | Outcome 2 | Outcome 3 | |
| 5y | 86% | 80% | 87% |
| 10y | 81% | 73% | 73% |
| 15y | 76% | 73% | 42% |
Conclusions
Pts with BC and gTP53m have a high risk of new cancer events, mostly driven by BC events. The current recommendation of a CL/bilateral prophylactic mastectomy remains of major interest. In this cohort, RT was not an independent predictor of 2ndM, but this study’s power is limited. RT should not be formally contra-indicated among gTP53m carriers, but its benefit-risk ratio carefully assessed.
Legal entity responsible for the study
Gustave Roussy, Department of Cancer Medicine.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.