乳腺癌改良根治术后不同放疗计划方式下内乳区非计划性受照剂量的比较研究

Comparation study of incidental irradiation dose to the internal mammary chain during postmastectomy radiotherapy for patients treated with different irradiation techniques

目的探讨乳腺癌改良根治术后放疗患者不同放疗计划方式间内乳区非计划性照射的剂量学参数差异。方法 138例乳腺癌改良根治术后接受胸壁±锁骨上放疗的患者均未接受内乳区放疗，依据放射治疗肿瘤协作组（RTOG）标准勾画患侧内乳区，按照计划方式不同分为三维适形放疗（3D-CRT）组、野中野正向调强放疗（F-IMRT）组和逆向调强放疗（I-IMRT）组。比较3组间内乳区受照剂量、不同肋间内乳区相关剂量体积参数的差异，分析内乳区受照剂量与心肺受照剂量的相关性。结果 3D-CRT组、F-IMRT组和I-IMRT组内乳区中位受照剂量分别为33.80、29.65和32.95 Gy，差异无统计学意义（H=2.412，P=0.299）。3组间同一肋间内乳区受照剂量差异均无统计学意义（均P〉0.05）。3D-CRT组、F-IMRT组和I-IMRT组内乳区受照剂量≥45 Gy的患者分别占10.42%、2.04%、9.76%，3组内乳区受照剂量在不同剂量区段的比例差异均无统计学（均P〉0.05）。同一计划方式下，第2、3肋间内乳区的Dmean、V20、V30、V40、V50均明显高于第1肋间（均P〈0.05）。3D-CRT计划方式下，内乳区Dmean与心脏Dmean呈正相关（r=0.338，P=0.019），与肺Dmean无相关性。F-IMRT和I-IMRT方式下，内乳区Dmean与心脏受照剂量均无相关性，而与患侧肺Dmean及V20均呈正相关（F-IMRT方式：r=0.366，P=0.010；r=0.318，P=0.026；I-IMRT方式：r=0.427，P=0.005；r=0.411，P=0.008）。 结论 3D-CRT、F-IMRT和I-IMRT计划方式下，均有部分患者内乳区受照剂量可达到治疗量。相较于3D-CRT，F-IMRT和I-IMRT进一步降低了危及器官受照剂量，但内乳区为非计划靶区时，3种计划方式对内乳区的剂量覆盖没有差异。

Objective To evaluated the unplanned coverage dose to the internal mammary chain （IMC） in patient treated with postmastectomy radiotherapy （PMRT）.Methods One hundred and thirty eight patients with breast cancer receiving radiotherapy （RT） in our hospital were retrospectively analyzed. Patients were divided into three groups： three-dimensional conformal radiotherapy （3D-CRT） group, forward intensity-modulated radiotherapy （F-IMRT） group and inverse IMRT （I-IMRT） group. The IMC were contoured according to Radiation Therapy Oncology Group （RTOG） consensus, and were not include into the planning target volume （PTV）. The incidental irradiation dose to IMC among the three groups and the first three intercostal spaces IMC （ICS-IMC 1-3） were all compared, and explored the relationship between the mean doses （Dmean） of IMC and the OARs （ipsilateral lung and heart）.Results The dose delivered to IMC showed no difference in CRT, F-IMRT and I-IMRT（33.80 Gy, 29.65 Gy and 32.95 Gy）. And 10.42%, 2.04%, and 9.76% patients achieved ≥45 Gy when treated with CRT, F-IMRT and I-IMRT. For the IMC dose in the first three intercostal spaces （ICS1-3）, there was no difference to the three treatment plannings. The Dmean, V20, V30, V40 and V50 of the ICS-IMC2 and ICS-IMC3 were all obviously superior than ICS-IMC1 for all these three plannings. Moderate positive correlation was founded between Dmean for IMC and Dmean for heart for left breast cancer patients underwent CRT （r=0.338, P=0.01）. Whereas for F-IMRT and I-IMRT groups, positive correlation were founded between Dmean for IMC and Dmean and V20 for ipsilateral lung for all patients （F-IMRT： r=0.366, P=0.010; r=0.318, P=0.026; I-IMRT： r=0.427, P=0.005; r=0.411, P=0.008）.Conclusions In 3D-CRT, F-IMRT and I-IMRT planning methods, partial patients get IMC irradiated doses that could achieve therapeutic doses. Compared with 3D-CRT, F-IMRT and I-IMRT further reduced the dose of irradiated organs. However, there is no difference in the dose coverage of IMC for the three planned approaches when the IMC made an unplanned target.