Understanding the Long-term Implications of Treatment of Rare Brain Tumours on Health-related Quality of Life: A European Cross-sectional Study

The WHO classification of primary brain tumours has recently been updated and now also takes molecular parameters into account to provide clinicians with more accurate information on the expected disease course and to guide treatment decisions.1 Patients with oligodendrogliomas of WHO grades II or grade III (OII and OIII) defined by IDH mutation and 1p/19q co-deletion represent rare tumour groups (~10% of adult gliomas) with relatively favourable prognosis (median survival 11.9 years for OII and 8.5 years for OIII).2 However, this disease remains life-threatening as over time, all tumours are likely to progress with a more malignant phenotype.

Recent changes in the management of these patients followed after the publication of long-term follow-up data from two landmark studies on OIII carried out by EORTC and RTOG in the 1990s,3, 4 and a RTOG study on low-grade glioma including OII.5 These data suggest that standard treatment should comprise surgical resection of the tumour as feasible followed by radiotherapy and chemotherapy. These studies used radiotherapy doses of 54-60 Gy and PCV (procarbazine, CCNU, vincristine) polychemotherapy. Among high-risk WHO grade II glioma patients, including OII, postoperative temozolomide chemotherapy was not superior in terms of progression-free survival or health-related quality of life (HRQOL) compared to postoperative radiotherapy.6,7 The discussion on whether temozolomide or PCV would be the better chemotherapy in these two patient groups is still ongoing. With patients surviving longer whilst receiving more treatments that may have long-term toxic side-effects, additional questions are raised regarding the effects on HRQOL and cognitive functioning of patients. Indeed, investigating the long-term effects of treatment is listed as a top priority in neuro-oncology research. 8

Preliminary research

The investigational team has almost three decades of research experience in the area of HRQOL and cognitive deficits after glioma treatment. Previous research has found that patients with both low- and high-grade gliomas can experience compromised HRQOL and cognitive functioning, which was generally more pronounced in the high-grade glioma group. However in those with stable, low-grade glioma, HRQOL and cognitive deficits were highly correlated, supporting the notion that even subtle cognitive deficits can affect autonomy in long-term glioma survivors.

While short-term negative effects of chemotherapy on HRQOL are well-documented, longer-term effects of antineoplastic drugs (e.g., bevacizumab) are unknown. Moreover, even low fraction doses of radiotherapy have been shown to have negative consequences for patients' cognitive functioning. WHO grade I and II glioma survivors were assessed on average 12 years after diagnosis and while cognitive functioning had remained stable in patients who had not been treated with radiotherapy, even those who received presumed safe doses (</= 2 Gy) showed a progressive decline in cognitive functioning.9 Moreover, a considerable number of patients showed detectable decline on one or more aspects of HRQOL despite long-term stable disease.6 More recently there have also been investigation into long-term functioning of patients with anaplastic oligo- and oligoastrocytoma. In progression-free patients, HRQOL remained relatively stable whereas cognitive functioning was highly variable across patients, regardless of PCV treatment.7