Читать книгу Surgical Management of Advanced Pelvic Cancer - Группа авторов - Страница 36

T2‐weighted MRI is the reference standard for assessment of tumor anatomy and resectability. There are two main radiological approaches for interpretation and reporting.

The first is tumor categorization according to the pelvic compartments affected, which can help determine patient prognosis. Various tumor categorization systems have been proposed and are summarized in Table 3.1. The Mayo Clinic classification is based on the presence of symptoms and the number of sites of fixation of the tumor to surrounding pelvic structures [33]; the Yamada classification describes broad categories of localized, sacral, and lateral fixation [34]; and the Wanebo classification is based on the UICC TNM system distinguishing bony or ligamentous pelvic involvement from non‐bony fixation [35]. The Memorial Sloan Kettering classification distinguishes four pelvic compartments [36], while the Royal Marsden Hospital classification distinguishes seven compartments [37]. Some of these systems have attempted to prognosticate as well, although any associations with survival outcomes must be interpreted with caution, as the different institutions had different patient populations and markedly variable R0 resection rates. Moreover, prognostication based on a compartment‐based classification is inherently subject to institutional views of which cancers are resectable according to availability of expertise at that time and not necessarily considering newer surgical techniques [6, 9, 11]. The emergence and implementation of these new techniques has changed opinion on which cancers are resectable and shifted the emphasis away from relying on compartment‐based radiological assessment alone. Indeed, most compartment‐based approaches were designed and validated retrospectively, i.e. after exenterative surgery had already been performed [37].

Table 3.1 Existing classification systems for pelvic compartments.

Group	Criteria for classification	Definitions
Mayo Clinic	Symptoms	S0	Asymptomatic
S1	Symptomatic without pain
S2	Symptomatic with pain
Tumor fixation	F0	No fixation
F1	Fixation to one point
F2	Fixation to two points
F3	Fixation to more than two points
Yamada	Pattern of pelvic fixation	Localized	Invasion to adjacent pelvic organs/tissues
Sacral invasive	Invasion to lower sacrum (≥ S3), coccyx, periosteum
Lateral invasive	Invasion to sciatic nerve, greater sciatic notch, pelvic sidewall, upper sacrum (S1/2)
Wanebo	Stages	TR1	Limited invasion of muscularis
TR2	Full thickness invasion of muscularis propria
TR3	Anastomotic recurrence penetrating beyond bowel wall into perirectal soft tissue
TR4	Invasion into adjacent organs without fixation
TR5	Invasion of bony/ligamentous pelvis
Memorial Sloan Kettering	Anatomic region	Axial	Anastomotic, mesorectal, perirectal soft tissue, perineum
Anterior	Genitourinary tract
Posterior	Sacrum and presacral fascia
Lateral	Soft tissues of the pelvic sidewall and lateral bony pelvis
Royal Marsden Hospital	Planes of dissection on MRI	Central	(Neo)rectum Intraluminal recurrence Perirectal fat or mesorectal, extraluminal recurrence
PR	Rectovesical pouch or recto‐uterine pouch of Douglas
AA PR	Ureters and iliac vessels above peritoneal reflection Sigmoid colon Small bowel Lateral sidewall fascia
AB PR	Genito‐urinary tract
Lateral	Ureters Iliac vessels distal to iliac bifurcation Lateral pelvic lymph nodes Sciatic nerve Sciatic notch S1/2 nerve roots Piriformis or obturator internus muscles
Posterior	Coccyx Presacral fascia Sacrum Retrosacral space
Inferior	Levator ani muscles External sphincter complex Perineal scar Ischio‐anal fossa

The second radiological reporting approach utilized by the authors of this chapter provides a roadmap for surgical excision, whereby a highly experienced radiologist reports a detailed and unambiguous roadmap for en‐bloc excision of the locally advanced cancer. Such a roadmap will be complemented by accurate exclusion of extrapelvic metastases and incorporate surgically relevant information such as significant coexisting pathology or findings which may challenge the surgical approach. In the authors’ experience, radiologists who personally review and examine patients and then communicate scan findings in the outpatient clinic, alongside their surgical and nursing colleagues, develop much greater insight into patient management and surgical approaches.

The following principles may help guide radiologists to provide roadmaps for advanced pelvic cancer:

 The radiologically derived roadmap for R0 excision is generally tailored to the maximum disease extent identified on sequential MRI, even in the context of downstaging from neoadjuvant treatment. This principle is based on the knowledge that radiologically occult microscopic foci of viable tumor cells may persist beyond the downstaged tumor margins, (e.g. peritumoral scar tissue) which could lead to R1 resection if resection were based on post‐treatment imaging alone [38–43]. Consequently, fibrosis in direct contact with the tumor on post‐treatment imaging should be regarded as potential tumor extension and therefore incorporated in the planned surgical resection [38, 42,44–55].

 Each radiological roadmap is created by the radiology team in close co‐operation with the surgical team. The roadmap is tailored to the individual patient based on their anatomy, tumor extent, and comorbidity. The detailed description of excision planes and margins should be based on (distance to) intraoperatively assessable and fixed anatomical landmarks, including sacral promontory, ischial tuberosity, ischial spine, piriformis muscle, sacral foramina and nerve roots, sacral ligaments (sacrotuberous, sacrospinous, and ischiococcygeal), gluteal muscles, bifurcation of aorta/common iliac vessels, and origin of the superior gluteal artery (SGA). In practice, the authors of this chapter use the term SLAM (“sacral ligaments and muscle”) to describe the intimately related sacrotuberous, sacrospinous, and ischiococcygeus complex.

 “BONVUE” or “a good view” is a helpful acronym which can be used to remind the team to include a description of bones, organs, nerves, vessels, ureters, and extra (tumor sites).

The key feature of the roadmap approach is that, in contrast to traditional compartment‐based reporting, this system addresses the extent of involvement and resection of individual structures potentially at risk and/or which need to be resected in order to obtain an adequate margin. The structures that are systematically assessed to build the roadmap, with the corresponding surgical considerations, are listed in Table 3.2. For any given patient, a roadmap is constructed based on assessment of the relevant elements in Table 3.2 and their surgical counterparts, which, when combined together, form the definitive surgical strategy.