A total of 103 subjects were accrued to this protocol between August 2004 and July 2008. Seven patients who did not receive temozolomide were excluded from analysis. Data from the remaining 96 subjects who received standard radiation and temozolomide are the focus of this report. Fifty percent of the subjects were female, 95% were Caucasian, and 80% had a debulking surgical procedure (). The histologic diagnosis was glioblastoma in 85%, anaplastic astrocytoma in 12%, anaplastic oligodendroglioma in 2%, and an otherwise unspecified malignant glioma in 1%. The median age of the subjects was 57 years (range 28–85) and the median KPS was 90. Eighty-one percent of the subjects were prescribed anticonvulsants and 82% were taking glucocorticoids when they began radiation and temozolomide. The average elapsed time between surgery and the initiation of radiation and temozolomide was 3.9 weeks (range 2–12.6). In addition to the standard radiation and temozolomide, 24% of patients received experimental agents. These were non-cytotoxic agents unlikely to affect lymphocyte counts. They included talampanel, an oral glutamate receptor blocker (14 subjects); cilengitide, an integrin antagonist (5 subjects); poly-ICLC, an immunostimulant (3 subjects); and BSI, a PARP inhibitor, (1 subject). Talampanel and cilengitide were initiated on the first day of radiation and temozolomide and continued until tumor progression or toxicity while BSI and poly-ICLC were added in the tenth week of therapy. As this study was designed before the overall importance of MGMT was appreciated, the MGMT status of patients accrued to this multi-institutional study was not evaluated.
Baseline Patient Characteristics
This protocol was a non-interventional study to follow CD4 counts and outcomes with standard radiation and temozolomide. As a result, it did not specify the duration of post-radiation temozolomide which is commonly prescribed for six months or longer. The median time that patients on this multi-institutional study received temozolomide was 5.8 months (STD = ± 3 months). Only four patients (4%) continued on temozolomide for 11 months or more. Eighty-five of the 96 patients (89%) did not have second line chemotherapy during the 12 months they were followed on this study. Of the 11 patients who received salvage chemotherapy during the follow-up period, only two were treated with bevacizumab. Others received BCNU, CCNU, Gliadel wafers, imatinib, IL-13, bortezomib, tamoxifen, and/or a dendritic cell vaccine.
CD4 COUNTS OVER TIME
CD4 counts were reliably obtained from patients on this study. No deaths occurred during the first two months of therapy and all patients had a baseline CD4 count and one or more follow-up CD4 counts during the first three months after beginning radiation and temozolomide.
Serial CD4 count results are provided in . The median CD4 count in these patients prior to initiating radiation and temozolomide was 664 cells/mm3 (range: 90 to 2010 cells/mm3). Two months after initiating radiation and temozolomide the median CD4 count was 255 cells/mm3 (range: 8–1580 cells/mm3) and subsequent CD4 counts remained persistently low during the 12 months of observation ( and ). The lowest CD4 counts were observed two months after beginning antineoplastic therapy when 70 patients (73% [95% CI: 63–82%]) had CD4 counts below 300 cells/mm3, and 38 (40% [95% CI: 30–50%]) had CD4 counts below 200 cells/mm3. Although there was a wide range of CD4 counts noted at baseline this variability was greatly reduced at two months ().
Percent Decline in Hematologic Values over Time
Age, sex, KPS, extent of surgery, and time from surgery to treatment were not associated with a low post-treatment CD4 count (). Subjects who developed grade III–IV CD4 count depression had significantly lower CD4 counts (458 vs 887 cells/mm3, p = 0.0001) and total lymphocyte counts (1044 vs 1645 cells/mm3, p =0.001) prior to beginning radiation and temozolomide than those who did not. In addition, they were more likely to be on glucocorticoids (92% vs 76%, p = 0.04) prior to beginning radiation and temozolomide, have a diagnosis of glioblastoma (92% vs 79%, p=0.09), and have had a biopsy rather than resection (26% vs 16% p=0.19).
Two months after initiating radiation and temozolomide, the average absolute reduction in CD4 counts was 476 cells/mm3. The median percent reduction in CD4 counts at two months was 69% in all patients. Patients with baseline CD4 counts of >500 cells/mm3 fell by 72% while those with baseline CD4 counts of <500 cells/mm3 fell by 49%. The reduction in CD4 counts paralleled changes in total lymphocyte counts but was not related to changes in the white blood cell counts, neutrophil counts, platelet counts, or hematocrit (). The percent of subjects who developed CD4 counts <200 cells/mm3 was similar in those receiving radiation and temozolomide alone or with the addition of talampanel, cilengitide, BSI, or poly ICLC (42% versus 31%, P=0.4).
A total of 40 subjects (41%) had a documented infection during the12 month study period. Infections were seen in 17 individuals (46%) with CD4 counts that fell below 200 cells/mm3 and in 23 (40%) with CD4 counts that remained above 200 cells/mm3 (p=0.54). Seven subjects developed pneumonia and one of these was diagnosed as PJP despite recommended PJP prophylaxis. Only two of the 81 deaths (2.5%) that occurred in the study population were due to infection, and these occurred in subjects who survived for 11 and 25 months. The median survival time of individuals with infection was 16.8 months (95% CI: 15.2 – 20.7 months) and of those without infection was 17.8 months (95% CI: 13.2 – 23.5 months). Also, time-to-first-infection was assessed as a time dependent covariate in a univariate and a multivariate proportional hazards model. After adjusting for baseline age, surgical procedure, histology, KPS, and CD4 counts (greater than or less than 200 cells/mm3), the adjusted hazard ratio for death attributed to infection was 1.16 (95% CI: 0.73–1.83; p=0.5, ).
Associations between Patient Characteristics and Survival:
Fifty-three of the 96 subjects (55%) were hospitalized during the year of observation. Hospitalizations were more frequent in subjects with CD4 counts <200 cells/mm3 at two months than in those with higher CD4 counts (73% versus 43%, p=0.003). Among those who required hospitalization, the median number of hospitalizations was two (range 1–6) for all CD4 counts, two for those with CD4 counts <200 at 2 months and one for those with higher CD4 counts (p=0.8). The reasons for hospitalization were highly variable and over 50 different admission diagnoses were recorded. Examples included additional surgery, thromboembolic disease, change in mental status or seizures, nausea/vomiting, peripheral edema, fatigue, weakness, pain management, glucose control, constipation, drug allergy, GI bleed, hematoma, meningitis, pneumonia, and spontaneous pneumothorax.
At the time of analysis, 81 of the 96 subjects had died. The overall median survival time was 17.3 months (95% CI: 14.6–19.7 months). The unadjusted and adjusted hazard ratios with respect to the factors associated with overall survival are listed in . As shown in , an analysis of the unadjusted hazard ratio for death identified previously known prognostic factors for patients with high grade gliomas: histology (GBM vs other high grade gliomas, p = 0.003), extent of surgery (biopsy vs craniotomy, p = 0.003), and age (≥55 vs <55, p = 0.02). Baseline CD4 counts (<500 vs ≥500, p=0.002) and CD4 counts at 2 months (<200 vs ≥200, p=0.003) were identified as related to survival. The median survival time in patients with CD4 counts <200 cells/mm3 at two months was 13.1 months (95% CI: 9.1–16.4) compared to 19.7 months (95% CI: 15.9–24.0) in subjects with higher CD4 counts (p=0.002, log-rank test). The relevant Kaplan Meier survival curves are presented in (hazard rate = 1.99, 95% CI: 1.27–3.1).
Overall Survival by CD4 Count at 2 Months
A proportional hazards model was constructed to estimate the risk of death attributed to low CD4 count at two months while accounting for known baseline clinical prognostic factors (). Covariates entered into this model included those identified in the univariate analysis (histology, surgical procedure, age and baseline and two month CD4 counts) as well as KPS and infection. The adjusted hazard ratio for death for three known prognostic factors were confirmed in this model: histology (GBM vs other) = 3.39 (p = 0.006), surgical procedure (biopsy vs craniotomy) = 2.3 (p=0.004), and KPS (60–70 vs 80–100) = 3.18 (p=0.02). The adjusted hazard ratio for death attributable to baseline CD4 count (dichotomized at 500) was 1.29 (p=0.38). The corresponding hazard ratio attributable to CD4 count at 2 months (dichotomized at 200) was 1.66 (p=0.03) after two months of therapy. Further analysis revealed that survival was related to the CTC toxicity grades for CD4 counts at two months. The median survival of patients who developed Grade I (n=9), Grade II (n=49) and Grade III–IV (n=38) reductions in CD4 counts at two months were 23.8 months, 19.7 months, and 13.1 months respectively (p=0.009). A common hazard ratio for death with respect to the severity of the toxicity grade (per unit increase) was 1.7 (95% CI: 1.13 to 2.54, p=0.01) after adjusting for age, surgical procedure, histology, and KPS.