# Body surface area and weight-based dose calculation for anticancer drugs, including full doses in obesity

Source: https://onco.cc/protocols/body-size-based-dose-calculation/  
OnCo record `body-size-based-dose-calculation` (Protocol). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Most chemotherapy doses are worked out from your height and weight. Both are measured in metric units and checked by two people before a new treatment starts, and your weight is rechecked during treatment. If you are a larger person, the American guideline says you should get the full dose for your actual size, not a reduced or 'capped' one.

## Summary

Most cytotoxic doses are expressed per square metre of body surface area (BSA), calculated from height and weight (DuBois or Mosteller), or per kilogram. Errors start at the scales: ASCO-ONS (2024) cites a study of 10,000 records in which 20% held height or weight errors, and now requires height and weight in metric units, measured and documented and verified by two people, one licensed, before a new treatment plan is prepared. The order must state the calculation method, the variables, how often they are re-evaluated and what change prompts recalculation. BOPA (2025) requires an up-to-date height, weight and BSA on the first prescription and a local policy on when weight change triggers a new dose; it bands adult doses where national bands exist and asks that any BSA capping be documented.

For people with obesity, ASCO (2012, updated 2021) recommends full weight-based cytotoxic doses, especially when the aim is cure, and the 2021 update adds full approved doses of immunotherapy and targeted therapy; toxicity is handled the same way as in anyone else. The 2012 guideline found that up to 40% of obese patients received limited doses and that fears of toxicity were unfounded. Capping persists: in a German cohort of 730 women with early breast cancer capped at BSA 2.0 m2, those above 2.1 m2 had lower dose intensity and worse survival, with obesity a possible confounder. How often to re-weigh is unsettled; a 2,276-patient study found a 10% BSA change in at most 7.6% of patients and suggested three- to six-monthly weighing for most.

## Fields

- Kind: Protocol
- Last checked: 2026-11-11
- Also known as: BSA dose calculation; body surface area dosing; mg/m2 dosing; chemotherapy dose calculation; dosing in obesity; dose capping; BSA capping; actual body weight dosing; re-weighing during chemotherapy; chemotherapy dosing for obese patients

## Connected records

- technologies: [Body-surface-area dosing](https://onco.cc/technologies/body-surface-area-dosing/), [Full weight-based chemotherapy dosing for people with obesity](https://onco.cc/technologies/chemotherapy-dosing-in-obesity/)
- protocols: [Anticancer treatment prescribing and pharmacy verification before each cycle](https://onco.cc/protocols/sact-prescribing-and-pharmacy-verification/), [Carboplatin dose calculation by the Calvert formula and kidney function](https://onco.cc/protocols/carboplatin-dose-calculation/), [Dose banding of anticancer drugs](https://onco.cc/protocols/dose-banding-of-anticancer-drugs/)
- terms: [Pharmacokinetics (PK), half-life and exposure](https://onco.cc/terms/pharmacokinetics/)

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