Post-mastectomy radiation in node-positive breast cancer in Ontario

Utilization and predictors of postmastectomy radiation receipt in an Oncology Center in Zimbabwe

PURPOSE

Few sub-Saharan African studies have ascertained utilization for postmastectomy radiation (PMRT) for breast cancer, the second most common cancer among African women. We estimated PMRT utilization and identified predictors of PMRT receipt in Zimbabwe.

METHODS

Retrospective patient cohort included non-metastatic breast cancer patients treated from 2014 to 2019. PMRT eligibility was assigned per NCCN guidelines. Patients receiving chemotherapy for non-metastatic disease were also included. The primary endpoint was receipt of PMRT, defined as chest wall with/without regional nodal radiation. Predictors of receiving PMRT were identified using logistic regression. Model performance was evaluated using the c statistic and Hosmer-Lemeshow test for goodness-of-fit.

RESULTS

201 women with localized disease and median follow-up of 11.4 months (IQR 3.3-17.9) were analyzed. PMRT was indicated in 177 women and utilized in 59(33.3%). Insurance coverage, clinical nodal involvement, higher grade, positive margins, and hormone therapy receipt were associated with higher odds of PMRT receipt. In adjusted models, no hormone therapy (aOR 0.12, 95% CI 0.043, 0.35) and missing grade (aOR 0.07, 95% CI 0.01, 0.38) were associated with lower odds of PMRT receipt. The resulting c statistic was 0.84, with Hosmer-Lemeshow p-value of 0.93 indicating good model fit.

CONCLUSION

PMRT was utilized in 33% of those meeting NCCN criteria. Missing grade and no endocrine therapy receipt were associated with reduced likelihood of PMRT utilization. In addition to practice adjustments such as increasing hypofractionation and increasing patient access to standard oncologic testing at diagnosis could increase postmastectomy utilization.