Which of the following agents is known to cause tumor flare as a side effect?

Luteinizing hormone-releasing hormone (LHRH) agonists are known to induce a phenomenon called "tumor flare," which is particularly relevant in the treatment of hormone-sensitive cancers, such as prostate cancer. When LHRH agonists are initiated, they initially stimulate the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the pituitary gland. This leads to a temporary increase in testosterone levels in men, which can cause a short-term exacerbation of cancer symptoms, known as tumor flare, due to the surge in hormones stimulating the growth of androgen-sensitive tumors.

This response typically occurs within the first few weeks of treatment and is particularly impactful in patients with advanced disease where the flares can be symptomatic. The subsequent effect, however, is a significant decrease in testosterone production, leading to tumor shrinkage over longer periods; this is the intended effect of the therapy.

In contrast, the other agents listed do not typically induce a tumor flare response. Aromatase inhibitors work by reducing estrogen levels rather than causing a surge, vinca alkaloids target cancer cell division and do not promote an initial increase in tumor size, and nonsteroidal anti-inflammatory drugs primarily manage pain and inflammation