Few children with cancer in low- and middle-income countries (LMICs) have access to proton therapy. Evidence exists to support replacing photon therapy with proton therapy to reduce the incidence of secondary malignant neoplasms (SMNs) in childhood cancer survivors. The purpose of this study was to estimate the potential reduction in SMN incidence and in SMN mortality for pediatric medulloblastoma patients in LMICs if proton therapy were made available to them. For nine children of ages 2 to 14 years, we calculated the equivalent dose in organs or tissues at risk for radiogenic SMNs from therapeutic and stray radiation for photon craniospinal irradiation (CSI) in a LMIC and proton CSI in a high-income country. We projected the lifetime risks of SMN incidence and SMN mortality for every SMN site with a widely-used model from the literature. We found that the average total lifetime attributable risks of incidence and mortality were very high for both photon CSI (168% and 41%, respectively) and proton CSI (88% and 26%, respectively). SMNs having the highest risk of mortality were lung cancer (16%), non-site-specific solid tumors (16%), colon cancer (5.9%), leukemia (5.4%), and for girls breast cancer (5.0%) after photon CSI and non-site-specific solid tumors (12%), lung cancer (11%), and leukemia (4.8%) after proton CSI. The risks were higher for younger children than for older children and higher for girls than for boys. The ratios of proton CSI to photon CSI of total risks of SMN incidence and mortality were 0.56 (95% CI, 0.37 to 0.75) and 0.64 (95% CI, 0.45 to 0.82), respectively, averaged over this sample group. In conclusion, proton therapy has the potential to lessen markedly subsequent SMNs and SMN fatalities in survivors of childhood medulloblastoma in LMICs, for example, through regional centralized care. Additional methods should be explored urgently to reduce therapeutic-field doses in organs and tissues at risk for SMN, especially in the lungs, colon, and breast tissues.

中文翻译：

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低收入和中等收入国家可以通过将儿科颅脊髓病例转诊到集中质子治疗中心来降低后续肿瘤的风险

在低收入和中等收入国家 (LMIC) 中，很少有癌症儿童能够获得质子治疗。有证据支持用质子治疗取代光子治疗，以降低儿童癌症幸存者继发性恶性肿瘤 (SMN) 的发生率。本研究的目的是评估 LMIC 儿童髓母细胞瘤患者的 SMN 发病率和 SMN 死亡率的潜在降低，如果他们可以获得质子治疗。对于 9 名 2 至 14 岁的儿童，我们计算了 LMIC 中光子颅脊髓照射 (CSI) 和高收入国家质子 CSI 的治疗性辐射和杂散辐射在有放射性 SMN 风险的器官或组织中的等效剂量。我们使用文献中广泛使用的模型预测了每个 SMN 站点的 SMN 发病率和 SMN 死亡率的终生风险。我们发现，光子 CSI（分别为 168% 和 41%）和质子 CSI（分别为 88% 和 26%）的发病率和死亡率的平均总终生归因风险都非常高。死亡风险最高的 SMN 是肺癌 (16%)、非部位特异性实体瘤 (16%)、结肠癌 (5.9%)、白血病 (5.4%) 和女孩乳腺癌 (5.0%)质子 CSI 后的光子 CSI 和非位点特异性实体瘤 (12%)、肺癌 (11%) 和白血病 (4.8%)。年幼儿童的风险高于年龄较大的儿童，女孩的风险高于男孩。在该样本组中，SMN 发病率和死亡率总风险的质子 CSI 与光子 CSI 的比率分别为 0.56（95% CI，0.37 至 0.75）和 ​​0.64（95% CI，0.45 至 0.82）。综上所述，例如，通过区域集中护理，质子治疗有可能显着减少 LMIC 儿童髓母细胞瘤幸存者的后续 SMN 和 SMN 死亡。应紧急探索其他方法，以减少有 SMN 风险的器官和组织的治疗野剂量，尤其是肺、结肠和乳腺组织。