Kramer Maria, Spohn Simon K B, Kiefer Selina, Ceci Lara, Sigle August, Oerther Benedict, Schultze-Seemann Wolfgang, Gratzke Christian, Bock Michael, Bamberg Fabian, Grosu Anca L, Benndorf Matthias, Zamboglou Constantinos
Department of Radiation Oncology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Institute of Surgical Pathology, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Front Oncol. 2020 Nov 23;10:596756. doi: 10.3389/fonc.2020.596756. eCollection 2020.
An accurate delineation of the intraprostatic gross tumor volume (GTV) is of importance for focal treatment in patients with primary prostate cancer (PCa). Multiparametric MRI (mpMRI) is the standard of care for lesion detection but has been shown to underestimate GTV. This study investigated how far the GTV has to be expanded in MRI in order to reach concordance with the histopathological reference and whether this strategy is practicable in clinical routine.
Twenty-two patients with planned prostatectomy and preceded 3 Tesla mpMRI were prospectively examined. After surgery, PCa contours delineated on histopathological slides (GTV-Histo) were superimposed on MRI using imaging as support for co-registration. According to the PI-RADSv2 classification, GTV was manually delineated in MRI (GTV-MRI) by two experts in consensus. For volumetric analysis, we compared GTV-MRI and GTV-Histo. Subsequently, we isotropically enlarged GTV-MRI in 1 mm increments within the prostate and also compared those with GTV-Histo regarding the absolute volumes. For evaluating the spatial accuracy, we considered the coverage ratio of GTV-Histo, the Sørensen-Dice coefficient (DSC), as well as the contact with the urethra.
In 19 of 22 patients MRI underestimated the intraprostatic tumor volume compared to histopathological reference: median GTV-Histo (4.7 cm, IQR: 2.5-18.8) was significantly (p<0.001) lager than median GTV-MRI (2.6 cm, IQR: 1.2-6.9). A median expansion of 1 mm (range: 0-4 mm) adjusted the initial GTV-MRI to at least the volume of GTV-Histo (GTV-MRI). Original GTV-MRI and expansion with 1, 2, 3, and 4 mm covered in median 39% (IQR: 2%-78%), 62% (10%-91%), 70% (15%-95%), 80% (21-100), 87% (25%-100%) of GTV-Histo, respectively. Best DSC (median: 0.54) between GTV-Histo and GTV-MRI was achieved by median expansion of 2 mm. The urethra was covered by initial GTVs-MRI in eight patients (36%). After applying an expansion with 2 mm the urethra was covered in one more patient by GTV-MRI.
Using histopathology as reference, we demonstrated that MRI underestimates intraprostatic tumor volume. A 2 mm-expansion may improve accurate GTV-delineation while respecting the balance between histological tumor coverage and overtreatment.
准确描绘前列腺内大体肿瘤体积（GTV）对于原发性前列腺癌（PCa）患者的局部治疗至关重要。多参数MRI（mpMRI）是病变检测的标准护理方法，但已被证明会低估GTV。本研究调查了在MRI中GTV需要扩大多少才能与组织病理学参考值一致，以及这种策略在临床常规中是否可行。
前瞻性检查了22例计划进行前列腺切除术且术前行3特斯拉mpMRI检查的患者。手术后，将组织病理学切片上勾勒出的PCa轮廓（GTV-Histo）叠加在MRI上，并使用成像作为共配准的支持。根据PI-RADSv2分类，由两位专家达成共识，在MRI中手动勾勒出GTV（GTV-MRI）。对于体积分析，我们比较了GTV-MRI和GTV-Histo。随后，我们在前列腺内以1毫米的增量各向同性地扩大GTV-MRI，并将其与GTV-Histo的绝对体积进行比较。为了评估空间准确性，我们考虑了GTV-Histo的覆盖率、Sørensen-Dice系数（DSC）以及与尿道的接触情况。
与组织病理学参考值相比，22例患者中有19例MRI低估了前列腺内肿瘤体积：GTV-Histo的中位数（4.7厘米，四分位间距：2.5-18.8）显著大于（p<0.001）GTV-MRI的中位数（2.6厘米，四分位间距：1.2-6.9）。中位数扩大1毫米（范围：0-4毫米）可将初始GTV-MRI至少调整到GTV-Histo（GTV-MRI）的体积。原始GTV-MRI以及扩大1、2、3和4毫米后的GTV分别在中位数上覆盖了GTV-Histo的39%（四分位间距：2%-78%）、62%（10%-91%）、70%（15%-95%）、80%（21%-100%）、87%（25%-100%）。GTV-Histo与GTV-MRI之间最佳的DSC（中位数：0.54）是通过中位数扩大2毫米实现的。8例患者（36%）的初始GTV-MRI覆盖了尿道。在应用2毫米的扩大后，GTV-MRI又多覆盖了1例患者的尿道。
以组织病理学为参考，我们证明了MRI低估了前列腺内肿瘤体积。2毫米的扩大可能会在尊重组织学肿瘤覆盖和过度治疗之间的平衡的同时，改善GTV的准确勾勒。
