Surgical Decision Making in Chordomas

Chordomas are difficult pathologies to treat. Despite the benign histopathology and slow growth, chordomas create special challenges related to the biology of the disease. ¹ The insidious but locally aggressive, osteoinvasive growth pattern, the deep central anatomical location, and the large tumor burden at the time of diagnosis make chordomas exceptionally challenging surgical targets, and their relative resistance to radiation therapy complicates the management of chordomas. ² A wide surgical excision with negative margins yields very rewarding results in chordomas, whether they are located in the skull base, sacrum, or the mobile spine. However, this goal is exceptionally difficult to reach. The anatomical location and extent of the disease necessitate the use of advanced equipment and complicated skull base approaches and require experience. Standard surgical approaches fall short of providing the necessary exposure for extensive tumor resections. Skull base techniques have made it possible to increase the extent of resection but at the cost of increased risk for mortality and morbidity. This is especially true in the elderly, who make up one-fifth of the patient population. ³ Although treatment of chordomas requires complex approaches, surgery remains the most effective form of treatment. Chordomas do not respond to current chemotherapy, and very high radiation doses are needed to control the disease, which adds to the mortality and morbidity risk, given the close proximity of the usual tumor to surrounding neurovascular structures, including cranial nerves, brain stem, and cerebral vessels. Because of these factors, decision making in chordomas is complicated. Treatment decisions become even more complicated at the event of recurrences. Recurrences are seen in almost all chordomas, and although surgical excision is still the most effective form of treatment, it is not possible in all patients.

12.2 Current Consensus

Chordoma is a rare disease and therefore quality evidence to guide the treatment is also very limited. ⁴ Therefore, current treatment decisions in chordomas rest mostly on level III or level IV evidence. Since the description of the disease in 1856, there were only 13 studies reported in PubMed, presenting a patient cohort of more than 30 patients. ⁵^,⁶^,⁷^,⁸^,⁹^,¹⁰^,¹¹^,¹²^,¹³^,¹⁴^,¹⁵^,¹⁶^,¹⁷ Nevertheless, some standards have been established.

12.2.1 Surgery is the most effective treatment option.

Surgery is the treatment of choice for chordomas when it can be performed with an acceptable risk. Today, there is worldwide consensus that surgery should be the initial form of treatment in skull base chordomas. As a reflection of this consensus, the National Comprehensive Cancer Network guidelines recommend maximal safe resection of skull base chordomas as the initial treatment option and also as the first treatment option for treatment of local recurrences. ¹⁸

12.2.2 The volume of residual disease has a major effect on the disease course.

Current literature also supports that patients do benefit from the extent of resection and that the volume of the residual disease has a strong impact on the course of the disease. Until the 2000s, the role of aggressive surgical removal was debated. However, analyses involving larger cohorts have indicated that recurrence rates were much higher in patients with gross residual disease ¹⁹^,²⁰^,²¹. Also, it was shown that the effect of radiation therapy, which is currently the only form of adjuvant therapy, diminished with increasing residual tumor volume. Therefore, today, it is an established fact that the initial surgical attempt should aim for at least gross total resection. Many authors even support additional resections at the margin to decrease peritumoral bony invasion, when it is can be safely performed. ⁵ Aggressive surgical removal is not synonymous with risky surgery. It is well known that unintended tumor residuals may be discovered in postoperative imaging in a large proportion of cases. Therefore, centers specializing in chordoma treatment make use of all available assistive technologies such as neuronavigation, endoscope assistance, and intraoperative magnetic resonance imaging (MRI). Skull base surgical techniques, which have made extensive resections in chordomas possible, have also evolved and have been refined over the last three decades. Many approaches that are detailed in other chapters in this book have been standardized, the risks have been identified, and techniques have modified to make them safer and less morbid for the patient, while preserving their efficiency.

Surgery is the most effective form of treatment also in recurrences. Recurrences are the rule in chordomas, and management becomes even more complicated at the event of a recurrence. At the event of a recurrence, surgery is again the most effective form of treatment, when it can be safely performed. Due to the invasive nature of the disease, recurrences are very commonly associated with further invasion outside the tumor resection cavity and frequently are associated with novel neurologic deficits such as cranial nerve findings. Routine, periodic follow-up imaging does aid in early diagnosis of recurrences before they result in new neurologic deficits. Identification of recurrences on follow-up scan is challenging, as recurrences require differential diagnosis from postoperative changes, but a positive finding is very rewarding, as focal recurrences can best be treated when they are still small in size. The decision making at the event of a recurrence involves a decision to treat and also a decision of how to treat. The treatment decision will be affected by the patient’s age, medical condition, and comorbidities, the recurrent tumor’s anatomical localization and extent, the tumor’s histopathologic diagnosis, any known previous treatment complications, and whether the patient had received previous radiation therapy. Patients with localized recurrences fare best from repeat surgical excisions, regardless of the size of recurrence. Extensive resections carry the potential of significantly altering the course of the disease even in recurrences. ²²^,²³^,²⁴^,²⁵ Most chordomas are slow-growing tumors and resection of a focal recurrent tumor will provide a long symptom-free period, even when the lesion is large. It has been demonstrated that the time to recurrence is dependent on achieving tumor-negative margins rather than how many times the patient had been operated on. ²⁶ As a reflection of this fact, a large proportion of cases in large surgical series are for recurrences. ¹⁵^,²⁰^,²⁵^,²⁷^,²⁸ Aside from surgery, repeat radiosurgical treatments are becoming increasingly more popular for focal lesions of limited tumor volume. It must be kept in mind, however, that repeated radiation treatments increase the chance of radiation-related complications and that the repeat dose will be limited to decreasing the risk of complications. Therefore, the radiosurgery option is offered to patients with small tumor volumes. However, chances of definitive surgery or definitive radiosurgical treatments diminish with repeated recurrences and the risk of complication rises considerably. At such repeated recurrences, most treatment efforts will be palliative, aiming to preserve the quality of life.

12.2.3 The initial treatment attempt has the highest chance of success.

Therefore, an effective surgical removal at the initial attempt is of crucial importance. With recurrences after successive surgeries and radiation treatments, the expectancy from any further treatment attempt falls abruptly. ¹⁵^,²⁹^,³⁰^,³¹^,³²^,³³^,³⁴^,³⁵^,³⁶^,³⁷^,³⁸ The basic strategy is to achieve as much as we can at the initial treatment attempt.

12.2.4 Chordoma surgery should be performed at centers of excellence.

Potential limitations and challenges to an effective surgical resection of chordoma are severalfold. Surgery for chordomas is complex and requires advanced surgical techniques, advanced technology, skills, and expertise. Therefore, it is widely accepted that surgery should be performed at centers with expertise in the management of chordomas, where multidisciplinary teams as well as assistive intraoperative technologies and modern radiation therapy/radiosurgery tools are available.