How Does Sunitinib — Block Tumour Growth?

No. Chemotherapy works by damaging or killing cells that divide quickly, which means it affects normal fast-dividing cells — in hair follicles and the gut lining — as well as cancer cells. Sunitinib works differently: it blocks specific proteins that tumour blood vessels and certain cancer cells need to grow. The side effects reflect this difference. Hair loss is uncommon on sunitinib, whereas hand-foot syndrome and high blood pressure are not typical of chemotherapy. Your oncologist may use the term 'targeted therapy' or 'TKI' to distinguish it.

Both side effects happen because VEGF — the signal sunitinib blocks — is not only used by tumours. The same growth signal maintains tiny blood vessels in the palms and soles, and helps regulate blood vessel tone throughout the body. Blocking it affects those normal vessels too. Redness, soreness, and peeling on the palms and soles is hand-foot syndrome, and it is the most common reason for dose adjustments. Blood pressure tends to rise early in treatment and is monitored closely. Neither side effect means the drug is not working — both are a consequence of the same mechanism that makes sunitinib active against tumours.

Response is assessed after the first full treatment cycle, which is typically several weeks. You will not feel the drug working day-to-day. The way your oncologist checks whether it is effective is through imaging — usually a CT scan — comparing tumour size before and after the first cycles. Do not interpret a lack of obvious change in how you feel as a sign the drug is not working. Tumour stability, where the cancer is neither growing nor shrinking noticeably, is also a meaningful response with sunitinib.

Primarily it deprives the tumour of its blood supply, which starves cancer cells indirectly. In some cancer types — particularly gastrointestinal stromal tumour — sunitinib also directly blocks kinases on the cancer cells themselves. For kidney cancer, the anti-angiogenic effect is considered the main mechanism. The distinction matters less to most patients than the outcome, but it helps explain why sunitinib's side effects differ from those of medicines that attack dividing cells directly.

Sunitinib is a small molecule — small enough to be absorbed through the gut wall and enter the bloodstream after swallowing. Many older cancer drugs are large protein molecules that cannot survive the digestive system and must be given by infusion. Taking sunitinib at home is more convenient, but it also means that consistency of timing and food intake matters. Your oncologist or pharmacist will advise you on when to take it relative to meals and what to avoid.

Yes, and this is a known pattern with most targeted therapies. Tumours can develop or select for cells that find ways around the blocked signalling pathway — a process called acquired resistance. NCCN and ESMO guidance addresses this and includes second-line treatment options for when sunitinib is no longer controlling the disease. The goal of monitoring and follow-up imaging is to detect this change early, so that a switch in treatment can be made before there is significant progression. If your disease has been stable on sunitinib and then changes, ask your oncologist specifically what the next option is.