GENEVA (FRONTLINE MEDICAL NEWS) – In patients with limited stage–small cell lung cancer (LS-SCLC) treated with concurrent chemotherapy and radiation, the use of antibiotics to prevent febrile neutropenia was associated with worse outcomes, but granulocyte-colony stimulating factor (G-CSF) prescribed for the same purposes appeared to be safe, reported investigators.
In a subanalysis of data on patients with early SCLC enrolled in the phase III CONVERT trial comparing chemotherapy with concurrent once-daily vs. twice-daily radiation, the use of antibiotic prophylaxis of neutropenia was associated with worse overall survival (OS) and progression-free survival, (PFS) compared with no antibiotics, reported Fabio Gomes, MD, from the Christie NHS Foundation Trust Hospital in Manchester, England.
However, “we found no evidence that use of G-CSF is detrimental on patient outcomes with modern radiotherapy. We may even wonder if the use of G-CSF maintains the treatment dose intensity on this subgroup of patients and thus improves their outcomes,” he said at the European Lung Cancer Conference here.
The use of G-CSF was, however, associated with higher rates of grade 3 or 4 thrombocytopenia and anemia, requiring supportive measures, he acknowledged.
The role of G-CSF with concurrent thoracic radiotherapy is controversial because of safety concerns, but data are scarce, Dr. Gomes said. He noted that the American Society of Clinical Oncology guidelines on the use of white blood cell growth factors recommend against their routine use.
However, some of those concerns arose in the mid-1990s when granulocyt macrophage–stimulating colony factor (GM-CSF) was used, rather than G-CSF, which acts on only a single blood lineage, namely neutrophils. Additionally, modern radiology techniques are more precise than they were 20 years ago, reducing the risk of toxicity, he noted.
In the CONVERT trial, 547 patients with LS-SCLC were randomly assigned to receive four to six cycles of cisplatin and etoposide chemotherapy concurrently with either once daily thoracic radiation for a total dose of 66 Gy divided into 33 fractions delivered over 45 days or to twice-daily radiation at a total dose of 45 Gy divided into 30 fractions delivered over 19 days.
There was no difference between the groups in the primary endpoint of overall survival.
In the subanalysis reported here, Gomes et al. looked at the use of G-CSF, delivered at the investigator’s discretion, in 487 patients. Approximately 40% of patients in the subanalysis received G-CSF during at least one treatment cycle.
Prophylactic antibiotics were recommended by the investigators for use in association with at least one chemotherapy cycle, and 49% of patients in the subanalysis received them during at least one cycle.
Hematological toxicities included grade 3 or 4 thrombocytopenia occurring in 29.9% of patients who received G-CSF, vs. 13.3% of those who did not (P less than .001). The rates were similar between the once-daily and twice-daily radiation groups.
Grade 3 or 4 anemia occurred in 16.9% of patients who received G-CSF, vs. 10.7% of those who didn’t (P = .027). The difference was significant only among patients in the twice-daily radiation arm (20.9% vs. 8.3%, respectively; P = .004).
Patients in the twice-daily radiation arms who received G-CSF also required more platelet transfusion, compared with the once-daily arm (P less than .001), and, in both arms, G-CSF was associated with more red-cell transfusions (P = .007 for once-daily and .001 for twice daily).
G-CSF was not associated with either pneumonitis or esophagitis, and there were no differences in treatment-related deaths with either G-CSF or antibiotics.
Median OS by G-CSF use was 29 months with and 27 months without, a difference that was not significant (P = .08). Median PFS also did not differ by G-CSF use or nonuse.
When it came to antibiotic prophylaxis, however, both median OS and PFS were significant worse with antibiotic use (OS, 24 months with vs. 33 months without; P = .016; PFS, P = .03).
The investigators speculated that the worse outcomes seen with prophylactic antibiotics could be related to selection bias or to chemotherapy dose reduction to suboptimal levels for those who received antibiotics.
“We are very reassured that there are no significant additional toxicities [with G-CSF] from radiation in the acute setting,” commented Sanjay Popat, FRCP, PhD , from the Royal Marsden Hospital in London, the invited discussant.
“However, we have no data as yet on the impact of G-CSF usage on febrile neutropenia, which is of course the fundamental that we’re aiming to improve in the hope that this will contribute to [lowering] costs,” he added.
The study was sponsored by the Christie Hospital National Health Service Foundation Trust, Cancer Research UK, EORTC, GECP, GFPC, and IFCT. Dr. Gomes reported no relevant disclosures. Dr. Popat reported consultation, honoraria, travel expenses, and institutional research from multiple entities.