摘要目的:探讨无均整器（FFF）模式在左侧乳腺癌术后深吸气屏气（DIBH）调强放疗中的价值。方法:回顾性病例系列研究。回顾性分析2021年1月年2022年12月于梅州市人民医院改良根治术后行DIBH调强放疗的21例左侧乳腺癌患者临床资料。分别用6 MV FFF模式下制订的计划（FFF组）和6 MV有均整器（FF）模式下制订的计划（FF组）在每例患者的DIBH模式CT上设计7野调强计划。比较两种计划下各靶区和危及器官剂量学参数和生物学参数以及剂量验证结果。结果:21例患者均为女性，年龄[ M（ Q1， Q3）]47岁（32岁，61岁）。FF组和FFF组靶区接受95%处方剂量的靶区占比（V 95%）分别为（95.9±0.8）%和（95.7 ±1.9）%（ t＝2.98， P＝0.089），最大剂量分别为（5 401±251）cGy、（5 424±201）cGy （ t＝2.85， P＝0.181），适形指数分别为0.88±0.05、0.87±0.06（ t＝0.32， P＝0.562），均匀指数分别为1.06±0.01、1.07±0.02（ t＝2.91， P＝0.009），等效均匀剂量（EUD）分别为（51.81±0.21）Gy、（51.97±0.20）Gy （ t＝0.51， P＝0.309），肿瘤控制率（TCP）分别为（99.68±0.01）%、（99.61±0.02）%（ t＝0.81， P＝0.560）。FFF组和FF组计划均符合要求，所有危及器官受照剂量均在临床可接受范围内，FFF组在左肺[5 Gy照射体积（V 5 Gy）、平均剂量（D mean）、EUD、正常组织并发症发生率（NTCP）]、右肺（V 5 Gy、D mean）、心脏（V 10 Gy、D mean、EUD、NTCP）和右侧乳腺（V 5 Gy、D mean、EUD）的辐射剂量均不同程度低于FF组，差异均有统计学意义（均 P<0.05）。FFF组和FF组机器跳数分别为（984±132）MU、（751±145）MU（ t＝-1.25， P<0.001），总出束时间分别为（1.4±0.3）min和（2.2±0.4）min（ t＝0.68， P<0.001）；单个射野出束时间分别为（12±7）s、（16±10）s（ t＝2.68， P＝0.001），FFF组患者每个射野出束时间均25 s以下；γ通过率分别为（97.1±2.8）%、（97.6±2.1）%（ t＝0.59， P＝0.484）。 结论:在左侧乳腺癌调强放疗中，FFF模式对危及器官的辐射剂量较低，并具有更高的剂量率和更短的治疗时间。FFF联合DIBH技术在乳腺癌调强放疗中具有积极的临床意义。

abstractsObjective:To investigate the value of flattening filter-free (FFF) mode in postoperative deep inspiration breath-hold (DIBH) intensigy-modulated radiotherapy for left breast cancer.Methods:A retrospective case series study was conducted. Clinical data of 21 patients with left breast cancer who underwent DIBH intensity-modulated radiotherapy after modified radical surgery in Meizhou People's Hospital from January 2021 to December 2022 were retrospectively analyzed. On the DIBH-mode CT of each patient, the 7-field intensity-modulation plan was designed using the plan developed in the 6 MV FFF-mode (FFF group) or the plan developed in the 6 MV flattening filter (FF)-mode (FF group). The target areas and organs at risk, dosimetric and biological parameters, and dose validation results were compared between the two plans.Results:Twenty-one patients were female with the age [ M ( Q1, Q3)] of 47 years old (32 years old, 61 years old). The percentage of target areas receiving 95% of the prescribed dose (V 95%) was (95.9±0.8)% and (95.7±1.9)% in the FF and FFF groups ( t = 2.98, P = 0.089), and the maximum dose was (5 401±251) cGy and (5 424±201) cGy ( t = 2.85, P = 0.181), the fitness indices were 0.88±0.05 and 0.87±0.06 ( t = 0.32, P = 0.562), the homogeneity indices were 1.06±0.01 and 1.07±0.02 ( t = 2.91, P = 0.009), the equivalent uniform doses (EUD) were (51.81±0.21) Gy and (51.97±0.20) Gy ( t = 0.51, P = 0.309), and the tumor control probability (TCP) was (99.68±0.01)% and (99.61±0.02)% ( t = 0.81, P = 0.560). The plans of the FFF group and the FF group were compliant, and the doses of all organs at risk to be irradiated were within the clinically acceptable range, and the radiation doses in the FFF group in the left lung [5 Gy irradiated volume (V 5 Gy), mean dose (D mean), EUD and normal tissue complication rate (NTCP)], right lung (V 5 Gy and D mean), heart (V 10 Gy, D mean, EUD and NTCP), and right breast (V 5 Gy, D mean and EUD) were differently lower than those in the FF group, and the differences were statistically significant (all P < 0.05). The monitor units in the FFF and FF groups were (984±132) MU and (751±145) MU ( t = -1.25, P < 0.001), and the total beam-on time was (1.4±0.3) min and (2.2±0.4) min ( t = 0.68, P < 0.001); individual field beam-on time was (12±7) s and (16±10) s ( t = 2.68, P = 0.001), and the beam-on time for each field in patients of the FFF group was less than 25 s; γ pass rates were (97.1±2.8)% and (97.6±2.1)% ( t = 0.59, P = 0.484). Conclusions:In the intensity-modulated radiotherapy of left breast cancer, the radiation dose of the energy to the critical organs in FFF mode is lower and has higher dose rate and shorter treatment time. FFF combined with DIBH technique has positive clinical significance in the intensity-modulated radiotherapy of breast cancer.