Radiation therapy in breast cancer patients in south west Nigeria: an evaluation of protocols in a specialist cancer centre.

内容摘要

Breast cancer is the most common malignancy among women worldwide and carries disproportionate mortality in low- and middle-income countries (LMICs) where late presentation and constrained radiotherapy capacity are common. We report the initial institutional dosimetric experience of postoperative breast irradiation delivered with intensity-modulated radiotherapy (IMRT) at a new comprehensive cancer centre in South-West Nigeria. We retrospectively reviewed 67 consecutive patients (age 29-72 years; median 50.4 years) treated following definitive surgery with adjuvant locoregional irradiation (whole breast or chest wall ± regional nodes) using multi-field intensity-modulated radiotherapy (IMRT) on VitalBeam and Halcyon linear accelerators. Clinicopathologic, surgical, systemic therapy and treatment planning data were collected. Organs-at-risk metrics included ipsilateral lung V20Gy and V25Gy and mean dose; heart V5Gy and V25Gy and mean dose; mean thyroid dose; and contralateral breast mean dose. Biologically effective dose (BED) and EQD2 (α/β = 3.0) were used to harmonise heterogeneous prescriptions. Planning objectives were derived from QUANTEC/RTOG-based institutional protocols, and all plans underwent peer review prior to delivery. The cohort was predominantly composed of patients with locally advanced disease at presentation, with T2 tumours accounting for 23.9% and T3-T4 disease collectively accounting for 23.8%, while nodal involvement was frequent, with N1 and N2-N3 disease observed in 23.9% and 16.4% of patients, respectively. Metastatic disease (M1) was present in 19.4% of cases. Surgery was predominantly modified radical mastectomy (55/67, 82.1%), and axillary lymph node dissection was performed in 54/67 (80.6%). Regional nodal irradiation was delivered in 63/67 patients (94%). Systemic therapy exposure was common, with most patients receiving anthracycline- and/or taxane-based chemotherapy, and a minority receiving anti-HER2 therapy (7.5%). Prescriptions clustered around hypofractionated regimens (42.0 Gy/15 fractions, n = 28; 45.0 Gy/18 fractions, n = 28), with a median prescribed dose of 44.0 ± 2.0 Gy; hypofractionation was used in the majority (≈ 60/67). Cohort dosimetry demonstrated a mean heart dose of 9.2 Gy, with heart V5Gy 61.2 ± 30.1% and V25Gy 4.9 ± 6.0%; ipsilateral lung V20Gy 19.3 ± 10.8% and V25Gy 12.8 ± 7.5%; mean thyroid dose 19.9 ± 10.1 Gy; and contralateral breast mean dose approximately 2.4 ± 1.3 Gy. These findings provide an institutional baseline of postoperative breast radiotherapy dosimetry in a resource-constrained setting and identify practical targets for ongoing quality improvement. The observed dosimetric profile demonstrates acceptable target coverage alongside measurable cardiac, pulmonary and thyroid exposure, reflecting the extent of nodal irradiation in this population. This work provides a foundation for prospective evaluation of treatment-related toxicity and long-term oncologic outcomes, and supports continued refinement of radiotherapy planning and delivery practices within the region.