How long does it take chemotherapy to shrink tumors?

Many cancer patients ask how long it might take for chemotherapy to shrink their tumors.

That’s a tough question because the answer depends on so many variables. We have to consider the type of cancer, as well as its stage, size and location. The type of chemotherapy drug(s) we’re giving the patient also plays a role, along with any other kinds of therapy they’re receiving.

The most important factor, though, is the biology of the cancer itself. That’s because no two cancers are alike, even if someone else has the same type, stage and location of disease as you do. Cancer itself is a product of mutation. Mutations are random by nature. So, there’s no one-size-fits-all answer.

Is your cancer slow-growing or fast-growing?

Chemotherapy works by inserting itself into newly created cancer cells and killing them. So, the chemotherapy’s effectiveness depends on the process of cellular division.

Ironically, that means patients with slow-growing or “lazy” tumors might not see as quick of a response to chemotherapy as those with aggressive or fast-growing cancers. That’s why we typically give someone at least two cycles of chemotherapy — or 6 to 9 weeks —before we reassess them to see if it’s working. 

Sometimes, we might stretch that period out to 12 weeks if a patient is doing well on their chemotherapy regimen. But if someone is having significant symptoms or is experiencing severe side effects, we might restage them sooner.

Watch for gradual symptom reversal

When the goal of chemotherapy is to shrink or kill a tumor, the hope is that patients will start seeing their symptoms gradually reverse as time goes on. If they have lung cancer, for instance, they might start noticing that they can breathe a bit more easily. If they have throat cancer, on the other hand, they might have less difficulty swallowing. 

When chemotherapy is effective, patients may also see:

• reduced pain levels
• higher energy levels and/or
• a general sense of feeling better.

Some patients experience symptom relief as soon as 2 to 3 weeks after starting chemotherapy. Others may not notice any changes for 2 to 3 months. And sometimes, side effects can make symptoms slightly worse before they get better. So, results can vary a lot between one patient and the next.

Scans don’t always tell the whole story about tumor growth

The most obvious way to measure a tumor’s growth or shrinkage is through scans. But infections and inflammation from other sources can occasionally make tumors appear larger than they are, a condition known as “fake progression.” 

Aside from a biopsy, time is normally the only thing that can reveal if a tumor’s enlargement was due to the disease advancing or just inflammation. And, a biopsy might be too invasive or impractical to perform. So, in many of these cases, we just have to wait and see.

Other times, chemotherapy might be working, but the patient is feeling much worse, simply because the treatment is so hard on the body. Then, we have to make a judgment call: do we reduce the dosage, skip a dose or two, or substitute one drug for another, to reduce the patient’s side effects? 

Generally speaking, though, when a patient starts feeling better, it’s because the chemotherapy is working and they’re actually getting better.

How I explain chemotherapy to my patients

I often tell patients to think of themselves as a flower garden and cancer as a weed. 

Surgical oncologists are the “weed-pullers,” because sometimes they can remove cancer completely, including any “roots,” or affected lymph nodes. Radiation oncologists are like people holding a magnifying glass on a very sunny day; they focus intense energy beams on an unwanted growth for a certain amount of time each day to destroy it. Medical oncologists like me, meanwhile, use chemotherapy as a weed killer, spraying it over the entire garden. 

Sometimes, we hope that the flowers will keep blooming, while the weeds shrivel up, making them easier to remove. But others, the goal is to keep the weeds from multiplying or growing past their current size. As long as the weeds are not getting any bigger or spreading, they can sometimes coexist alongside the flowers.

Still, every patient is different. So, talk to your care team if you have questions about the goals of chemotherapy for you, or how long it might take you to start seeing results.

Janet Tu, M.D., is a head and neck and thoracic medical oncologist who treats patients at MD Anderson in Sugar Land.

Request an appointment at MD Anderson online or call 1-877-632-6789.