Part VIII · Therapeutic foundations · Chapter 41

Principles of multidisciplinary treatment

Why the field spent forty years learning to give less, and what that argument requires.

1 · Curative intent and disease control as different goals

Curative intent and disease control are not two points on one scale. They are two different decision rules, and they price toxicity differently.

Under curative intent the benefit is a shift in the probability of an event that may never happen. Nothing observable in the individual patient confirms that the treatment worked. Toxicity is paid now and the return is collected over decades. That asymmetry is why adjuvant decisions are so sensitive to the absolute size of the benefit, and why the same relative risk reduction justifies very different treatment in a high-risk and a low-risk patient.

Under disease control the benefit is measurable in the patient in front of you. The currency is time, symptom burden and function. A treatment that shortens survival by a month and removes a symptom may be the right treatment, and under curative intent it never is.

The two goals are not fixed by stage. Limited metastatic disease is sometimes approached with ablative intent. One randomised trial added stereotactic ablative radiotherapy to standard care in 99 patients with one to five metastatic lesions, across several primary tumour types. Five-year overall survival was 42.3% with ablation and 17.7% without it1. That result is discussed further in Reirradiation and metastatic applications. It is a reason to randomise more patients rather than a reason to treat, and the design detail that makes it so is in Clinical trials and evidence interpretation.

Naming the goal out loud changes the conversation. A patient told that treatment is for control rather than cure understands a dose reduction differently. Early integration of palliative care in the disease-control setting improves outcomes rather than signalling retreat2.

2 · Neoadjuvant, adjuvant, and metastatic strategy compared

The three settings differ in what is being treated and in what can be measured. Those two differences drive almost every strategic choice in this book.

Neoadjuvant therapy treats disease that is still present and still measurable. The tumour is an assay. Response is read in tissue at surgery, and that reading is the most informative predictive test available in early breast cancer, because it integrates the tumour, the host and the actual drug. The scientific uses of this setting are developed in The neoadjuvant setting as a scientific platform.

Adjuvant therapy treats a probability. There is nothing to measure, so the decision rests entirely on pretreatment risk estimation and on trial-level effect sizes. The whole apparatus of genomic assays in Prognostic and predictive assays and somatic profiling exists to compensate for that blindness.

Metastatic therapy treats measurable disease with no expectation of cure in almost all cases. The decision is about sequence and about cumulative burden rather than about a single best regimen, which is why General principles of metastatic management is organised around ordering.

The choice between neoadjuvant and adjuvant delivery of the same chemotherapy is settled for survival. A meta-analysis of individual patient data for 4756 women in ten randomised trials found no difference in distant recurrence at 15 years, at 38.2% with neoadjuvant and 38.0% with adjuvant chemotherapy3. Breast cancer mortality was 34.4% against 33.7%. Breast-conserving therapy was more frequent after neoadjuvant treatment, in 65% against 49% of women. The earlier randomised evidence from NSABP B-18 and B-27 pointed the same way4.

Caution

The same meta-analysis found more local recurrence after neoadjuvant chemotherapy, at 21.4% against 15.9% at 15 years3. The obvious reading is that neoadjuvant chemotherapy is less effective locally. The authors' reading is different and better supported. Surgery was planned to the downsized tumour rather than to its original extent, so the operation removed less tissue. That is a consequence of how the response was used, not of the chemotherapy.

3 · Escalation, de-escalation, and treatment omission

This section names the movement that the rest of Part VIII instantiates. Three operations are routinely grouped together and they are not the same.

Escalation adds a component to a regimen for a population at higher risk. De-escalation substitutes something less burdensome for something more burdensome, and expects the same disease outcome. Omission removes a component entirely and accepts a defined loss in some outcome in exchange for avoided harm.

The evidence each one needs is different. Escalation is tested by superiority, and a null result means the addition is not worth making. De-escalation and omission are tested against a non-inferiority margin, and a null result means nothing on its own. The margin is a value judgement made before the trial about how much disease-outcome loss is acceptable for the harm avoided. Different margins applied to the same data give different verdicts, and Designing de-escalation trials and the non-inferiority margin problem works through how those margins are chosen.

The arc runs through the whole book. Radical mastectomy gave way to breast conservation Breast-conserving surgery and mastectomy. Axillary dissection gave way to sentinel node biopsy and then to no axillary surgery at all Axillary staging and the long retreat from dissection. Whole-breast radiation became shorter, smaller and in some populations optional Fractionation, hypofractionation, and acceleration, Omission in low-risk and older patients. Chemotherapy is now omitted on the basis of a genomic assay rather than anatomy Genomic assays and the decision to omit chemotherapy. Each of these is one instance of a single argument. The history of how the field learned to make it is in History of breast cancer.

Caution

The recurring error in reading this literature is treating "no statistically significant difference" as "proven equivalent". They are different claims and one does not imply the other.

De-escalation trials recruit low-risk populations, so they accrue few events, so their confidence intervals are wide. A wide interval around a hazard ratio near one is compatible with a real and clinically important loss. The trial has not excluded that loss. It has failed to detect it.

The only statement a non-inferiority trial licenses is that the data exclude a loss larger than the prespecified margin. Ask what the margin was before accepting the conclusion. Clinical trials and evidence interpretation is where this book makes that argument in full, and every de-escalation section that follows points back here and forward there.

4 · Response-adapted treatment

Response-adapted treatment uses the tumour's behaviour under therapy as the biomarker. No pretreatment assay can match it, because response integrates tumour biology, host pharmacology and adherence in a single readout.

Two post-neoadjuvant escalations are built on this logic. KATHERINE randomised patients with residual invasive HER2-positive disease after neoadjuvant therapy to trastuzumab emtansine or trastuzumab. Invasive disease or death occurred in 91 of 743 against 165 of 743 patients5. In CREATE-X, patients with HER2-negative disease and residual invasive disease after neoadjuvant chemotherapy received standard treatment after surgery with or without capecitabine6. In both, the selection rule was observed response rather than a molecular marker.

The strategy has three requirements and all three are real constraints. Response must be measurable, which restricts it to settings with tissue or reliable imaging. A different and effective treatment must exist for the non-responders, or the information changes nothing. And the response measure itself must mean something, which is why the continuous alternatives to a binary pathological complete response matter residual cancer burden and are developed in Residual cancer burden and continuous response measures.

The next version of this logic replaces tissue response with molecular residual disease after definitive therapy. That is attractive and it is not yet established. Whether acting earlier on a molecular signal improves outcome is the open question set out in Lead time and the unresolved question of whether acting early helps.

5 · Sequencing local and systemic therapy

Order is decided by three questions. Does local therapy need the tumour to be smaller. Does the systemic decision need information that only surgery provides. Does delaying either one cause harm.

Giving systemic therapy first buys downstaging and buys response information. Giving it second preserves an untreated surgical specimen and avoids any delay to definitive local therapy. The cost of the adjuvant route is rarely stated plainly. Once the tumour is removed, the opportunity to observe its response is gone permanently, and with it the decision rule in Response-adapted treatment.

Within local therapy the constraints are mostly practical rather than randomised. Radiation generally follows chemotherapy and follows surgery. Endocrine therapy is commonly given concurrently with radiation. Reconstruction changes the radiation target and the complication profile, so the reconstructive plan and the radiation plan have to be made together rather than in sequence7. The detail belongs to Integration with systemic therapy and reconstruction.

The honest summary is that much of the accepted ordering rests on single trials, on toxicity reasoning and on consensus. That is acceptable as long as it is not mistaken for randomised evidence when a patient asks why.

Interplay

Every strategic choice in this section is a choice about when to measure. A tumour sampled before treatment, at surgery, and at progression is three different populations of cells, not three looks at one thing. The framework in Part VI is what makes response-adapted treatment coherent, because it says that the composition of the disease changes under the pressure that treatment applies.

See A framework for heterogeneity

6 · Shared decision-making and preference-sensitive choices

A preference-sensitive choice is one where the options differ in the kind of burden rather than in expected survival. Breast conservation against mastectomy is the archetype Breast-conserving surgery and mastectomy. Radiation omission in an older patient is another Omission in low-risk and older patients. Extended endocrine therapy is a third Treatment duration and extended therapy.

These are not choices where the clinician holds the answer and the task is communication. The evidence establishes the trade. The patient supplies the exchange rate.

Decision aids change measurable things. One systematic review pooled 209 randomised trials involving 107,698 participants8. Knowledge improved by 11.90 points on a 0 to 100 scale across 107 studies. Accuracy of risk perception improved with a risk ratio of 1.94 across 25 studies. The proportion of people taking a passive role in the decision fell. Decision regret did not differ from usual care. Consultations using an aid during the visit ran about 1.5 minutes longer.

In practice

Say which kind of decision this is before discussing it. "These two options give the same survival and differ in what they ask of you" is a different opening from "here is what I recommend".

Give absolute numbers, not relative ones. A third fewer recurrences means nothing without the baseline risk, and the reasoning is set out in Absolute and relative benefit, and why the difference matters.

Name the outcome that actually differs. In most local-therapy de-escalation choices that outcome is local recurrence rather than survival, and patients weigh those two very differently.

Separate what is known from what is assumed. The margin argument in Escalation, de-escalation, and treatment omission is part of the honest version of this conversation, not a technicality to be spared.

7 · The multidisciplinary conference and how decisions actually get made

A multidisciplinary conference is good at some things and poor at others, and the difference is predictable.

It is good at catching errors of fact. In a review of 149 consecutive patients presented at one breast multidisciplinary board, re-reading the imaging changed the interpretation in 67 patients and re-reading the pathology changed it in 439. Surgical management recommendations changed in 77 of the 149 patients. Most of those changes did not follow from a reinterpretation at all. They followed from discussion among the surgeon, the medical oncologist and the radiation oncologist.

Whether this changes outcomes is harder to establish. One comparative cohort study covered 13,722 women in the west of Scotland10. Before multidisciplinary working was introduced, breast cancer mortality in the intervention region was 11% higher than in the comparison region. Afterwards it was 18% lower. That is a natural experiment rather than a randomised comparison, and it cannot separate the conference from everything else that changed alongside it.

What a board cannot do is make a preference-sensitive choice. A room without the patient in it can establish what the options are. It cannot supply the exchange rate from Shared decision-making and preference-sensitive choices, and a recommendation issued as though it could is a category error.

In practice

Bring the questions the board can answer. Is the imaging complete, is the pathology internally consistent, is this operable, does the sequence make sense.

Record what was uncertain rather than only what was agreed. A minuted recommendation with the disagreement stripped out is worse than no record, because the clinic conversation then presents a consensus that did not exist.

Present the patient's stated priorities when they are known. Board recommendations that ignore them are revised in clinic anyway, and the revision looks like indecision to the patient.

Variation from a guideline is not automatically a quality failure, and the distinction between justified and unjustified variation is developed in Guideline adherence and justified variation.

References

All 10 references
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  2. Temel JS, Greer JA, Muzikansky A, et al. Early palliative care for patients with metastatic non-small-cell lung cancer. N Engl J Med 2010 363:733-742. PMID 20818875
  3. Early Breast Cancer Trialists' Collaborative Group (EBCTCG). Long-term outcomes for neoadjuvant versus adjuvant chemotherapy in early breast cancer: meta-analysis of individual patient data from ten randomised trials. Lancet Oncol 2018 19:27-39. PMID 29242041
  4. Rastogi P, Anderson SJ, Bear HD, et al. Preoperative chemotherapy: updates of National Surgical Adjuvant Breast and Bowel Project Protocols B-18 and B-27. J Clin Oncol 2008 26:778-785. PMID 18258986
  5. von Minckwitz G, Huang CS, Mano MS, et al. Trastuzumab emtansine for residual invasive HER2-positive breast cancer. N Engl J Med 2019 380:617-628. PMID 30516102
  6. Masuda N, Lee SJ, Ohtani S, et al. Adjuvant capecitabine for breast cancer after preoperative chemotherapy. N Engl J Med 2017 376:2147-2159. PMID 28564564
  7. Jagsi R, Momoh AO, Qi J, et al. Impact of radiotherapy on complications and patient-reported outcomes after breast reconstruction. J Natl Cancer Inst 2018 110:157-165. PMID 28954300
  8. Stacey D, Lewis KB, Smith M, et al. Decision aids for people facing health treatment or screening decisions. Cochrane Database Syst Rev 2024 1:CD001431. PMID 38284415
  9. Newman EA, Guest AB, Helvie MA, et al. Changes in surgical management resulting from case review at a breast cancer multidisciplinary tumor board. Cancer 2006 107:2346-2351. PMID 16998942
  10. Kesson EM, Allardice GM, George WD, Burns HJG, Morrison DS. Effects of multidisciplinary team working on breast cancer survival: retrospective, comparative, interventional cohort study of 13 722 women. BMJ 2012 344:e2718. PMID 22539013