Subtotal Resection With Radiation Therapy

The goal of limited surgery can be to establish a diagnosis, drain cystic components of the tumor, and decompress surrounding anatomical structures. In subtotal resections, removal of the tumor from the pituitary stalk or hypothalamus is typically avoided to minimize the late effects associated with complete resection.[20]

Surgery is often followed by radiation therapy, because radiation therapy can decrease the risk of recurrence after a subtotal resection.[21] With this approach, the 5-year PFS rates are approximately 70% to 90%,[5,22-25]; [26][Level of evidence C1] and the 10-year overall survival (OS) rates exceed 90%, which are similar to the rates in patients who undergo a gross-total resection.[27,28][Level of evidence C1]; [29][Level of evidence C2] Most often, radiation therapy is timed to immediately follow subtotal resection. However, in certain cases, such as in young patients or in patients without existing neuroendocrine or visual deficits, serial imaging may be used to delay or avoid radiation therapy for as long as feasible.[7,30] The standard approach to radiation therapy involves fractionated external-beam radiation, with a recommended dose of 50 to 54 Gy, in 1.8-Gy fractions, restricting the optic chiasm dose to 54 Gy.[31-34] Newer radiation technologies such as intensity-modulated photon therapy and proton-beam radiation therapy may reduce the radiation dose to uninvolved parts of the brain and spare normal tissue.[23,34-36] It is unknown whether such techniques reduce the late effects of radiation therapy.[26,34,36,37] Transient cyst enlargement may be noted during radiation therapy, and serial imaging may be required during radiation therapy to assess cyst changes and consider updates to radiation mapping.[38][Level of evidence C3]

Surgical complications with a subtotal resection can be similar to, but are less likely than, with a complete resection. If radiation therapy is used, additional complications must be considered, including the following:

A phase II single-arm study included 94 patients (aged 12 months to 21 years) with craniopharyngiomas who were treated with proton-beam radiation therapy after individualized surgical resection. These patients were compared with a historical cohort of patients who were treated with photon-beam radiation therapy.[41] The survival outcomes of patients who received proton therapy were similar to those of patients who received photon therapy. The cumulative incidence rates of necrosis, vasculopathy, changes in vision, and severe complications were also similar between the two groups of patients. However, patients treated with proton therapy in the more recent cohort had superior cognitive outcomes.

A long-term study of 101 children who were treated for craniopharyngiomas evaluated visual, neurocognitive, and endocrine outcomes after photon radiation therapy. Race and presence of a shunt affected baseline scores.[42] For children who presented with lower intelligence quotient (IQ) scores at diagnosis, the impact of treatment often resulted in an IQ score reduction to the borderline mental disability range of 70 to 84. The investigators demonstrated that age at treatment (younger children had worse outcomes), radiation dose to the temporal lobes and hippocampi, and visual impairment significantly impacted neurocognitive function after radiation therapy. This study demonstrates the importance of these factors in the treatment and late effects of craniopharyngioma.

A report from the prospective registry study KiProReg examined the use of proton-beam therapy in 84 children younger than 18 years with craniopharyngioma.[43] The estimated 3-year OS rate was 98.2%, and the PFS rate was 94.7%. With a median follow-up of 4.3 years, late toxicities appeared acceptable. Sixty-three of the patients were treated with pencil-beam scanning, which is considered an advancement in proton technology.