Influenza season is here again, and with it comes unique concerns and questions for cancer patients and their caregivers. During a circulating influenza epidemic, between 21% and 33% of cancer patients who are admitted to a hospital with respiratory symptoms might test positive for influenza. Further, the influenza mortality rate is very high, with reports of between 11% and 33% for patients with cancer.1 Another concern for cancer patients is that influenza can delay cancer treatments, thus indirectly causing suboptimal oncological outcomes.2 Health care providers should also keep in mind that all live vaccines are contraindicated in patients receiving cancer therapy and within 6 months of its end, and the killed influenza vaccine should be administered as an alternative.3
Many questions arise in response to these concerns. Should all cancer patients receive the influenza vaccine? Since so many cancer treatments are immunosuppressive, how well does the vaccine really protect cancer patients from getting the flu? How do the new targeted cancer treatments react with the vaccine? Lastly, how do pediatric oncology patients respond to the influenza vaccine?
VACANCE Study: Immunogenicity of A/H1N1v
These questions became particularly urgent during the widespread outbreak of the 2009 H1N1 influenza, which was especially a concern for immunocompromised patients. The immunogenicity and safety of the A/H1N1v vaccine was examined in the VACANCE study, which was a prospective, open-label study.4 The study vaccinated 65 cancer patients with two doses. The first dose was given on Day 7 of chemotherapy for those receiving chemotherapy every 2 or 3 weeks, and the second dose was given 3 weeks later. When baseline antibody titers against A/H1N1v were measured on Day 1, 5% of the patients had antibody titers ≥1:40. At Day 21, 44% of patients had an immune response to the vaccine, while 72.7% of the patients did at Day 42. Side effects and reactions to the vaccine were all mild to moderate. The authors concluded that two doses of influenza vaccine are needed for most cancer patients, though those receiving targeted therapies had satisfying results after one dose.
Tyrosine Kinase Inhibitors and the Influenza Vaccine
The tyrosine kinase inhibitors sunitinib and sorafenib affect innate and adaptive immune responses. A recent prospective, open-label, single-center study examined antibody response to influenza vaccination in 26 patients with metastatic renal cell carcinoma (mRCC), three with gastrointestinal stromal tumors (GIST), seven nontreated mRCC controls, and 11 healthy controls.5 A total of 16 of these patients were treated with sunitinib and six with sorafenib. A single shot of influenza vaccine was enough for the cancer patients who were treated with either sunitinib or sorafenib to mount an antibody response that was comparable to that of the healthy controls and nontreated mRCC controls.