What is a Biochemical Relapse in Multiple Myeloma?

When your doctor mentions a “biochemical relapse,” it means that the lab tests used to track your multiple myeloma (like your M-spike or free light chains) have started to go up, but you do not have any physical symptoms or new organ damage ^[1]. It is completely normal to feel perfectly fine during this stage, because the cancer has only relapsed “on paper” or in your blood chemistry, not in a way that affects how your body functions ^[2].

The Difference Between Biochemical and Clinical Relapse

To understand biochemical relapse, it helps to know how doctors define a full “clinical relapse.”

A clinical relapse happens when the cancer causes physical problems. Doctors look for the CRAB criteria (along with other specific findings called SLiM criteria) ^[3]:

• Calcium elevation: High calcium levels in the blood, which can cause confusion or thirst.
• Renal (kidney) issues: Kidneys not filtering waste properly.
• Anemia: Low red blood cells, leading to fatigue.
• Bone lesions: Weak spots or holes in the bones that can cause pain or fractures ^[4][5].

A biochemical relapse, on the other hand, means your blood or urine markers have increased by a specific amount from their lowest point (your “nadir”), but none of these physical CRAB symptoms are happening ^[6]. For example, your M-spike might go up by at least 0.5 g/dL, or your free light chains might rise significantly, signaling that myeloma cells are becoming active again ^[6].

Why Catching It Early is a Good Thing

Hearing the word “relapse” is scary, especially if you feel healthy. But a biochemical relapse is actually an early warning system. It gives you and your doctor a head start.

When a relapse is caught at the biochemical stage, your medical team has the luxury of time ^[7]. You do not need to rush into an emergency treatment to save a kidney or fix a bone fracture ^[3]. Instead, your doctor can thoughtfully plan your next steps and evaluate the “velocity” of your relapse—meaning they look at how quickly the numbers are rising or doubling over a few months ^[7].

What Happens Next?

Experiencing a biochemical relapse means your routine monitoring is working exactly as it should. There is no single “right” way to handle it, but your care team will generally guide you through the following steps ^[1]:

1. Verification and Restaging

Before making any treatment decisions, your doctor needs to be absolutely certain the relapse is strictly biochemical. Even if you feel fine, myeloma can sometimes cause “silent” bone damage ^[3]. Your doctor will likely order advanced imaging (like a PET/CT scan or whole-body MRI) and possibly a bone marrow biopsy to confirm there are no hidden physical issues ^[3].

2. Choosing a Path: Watchful Waiting vs. Early Treatment

Once your doctor confirms there is no physical damage, they will look at your unique situation—including how fast your numbers are rising and what treatments you have had in the past—to recommend one of two paths:

• Watchful Waiting: If your numbers are rising very slowly, your doctor might choose to safely delay starting a new therapy ^[1]. You will simply get your blood tested more frequently (often every month rather than every few months) to see if the slow trend continues ^[1].
• Early Treatment: Many doctors are shifting toward starting a new therapy during a biochemical relapse to catch the myeloma before it can cause end-organ damage (like bone holes or kidney issues) ^[3][8]. Research suggests that early treatment in this phase may delay the onset of physical symptoms and improve overall outcomes ^[2][9].

Whether you wait or treat, catching a relapse at the biochemical stage ensures you can stay ahead of the disease and make treatment decisions on your own terms.