In October 2023, Paul Cahill settled a medical malpractice claim arising from a delayed diagnosis of breast cancer. The patient was 39 years old, married, and the mother of two young children. She did not survive. The settlement was made on behalf of her surviving husband, her children, and her estate.
A case of this kind sits at the intersection of two recurring challenges in Ontario medical malpractice litigation. The first is the recognition of breast cancer in younger women, a clinical task that is harder than it should be because of how the diagnostic system in this country is structured. The second is the causation analysis in a delayed-cancer-diagnosis case where the patient ultimately died, a question that turns on what would more likely than not have happened if the diagnosis had been made at an earlier stage. The case settled before trial. The terms are confidential.
The clinical context
Breast cancer is the most commonly diagnosed cancer in Canadian women and one of the leading causes of cancer death in women under 50. The disease has a substantially better prognosis when diagnosed at an early stage. Published five-year survival data from the Canadian Cancer Society distinguishes sharply between stages: in the high 90s for Stage I, in the low 90s for Stage II, in the 70s for Stage III, and dramatically lower for Stage IV (metastatic) disease. The survival data are consensus oncological figures and are well-established at the population level, though they should not be applied without qualification to any specific patient.
A particular concern in younger women is that the diagnostic system in Ontario is not primarily oriented toward catching breast cancer in this age group. The Ontario Breast Screening Program at the time of the events giving rise to this claim (October 2023) invited only average-risk women aged 50 and over to routine screening mammograms, with earlier entry available through the High Risk Ontario Breast Screening Program for women aged 30 to 69 who met specified high-risk criteria (such as a known BRCA mutation, a strong family history of breast or ovarian cancer, or prior chest-wall radiation). Effective October 8, 2024, Ontario Health lowered the starting age for average-risk screening to 40. The program now offers self-referred screening mammograms every two years to people aged 40 to 74 at average risk, in addition to the existing High Risk OBSP for ages 30 to 69. The expansion was estimated to add approximately 130,000 screening mammograms annually in Ontario.
The result, both at the time of these events and now, is that breast cancer in a woman in her late thirties is more likely to be detected because the patient noticed a lump, a skin change, nipple discharge, or another symptom and presented to her family physician, than because of a screening program designed to find the cancer before symptoms appeared. A 39-year-old woman without identified risk factors fell outside the screening pool at the time of these events, and even under the current expanded program would still fall outside the average-risk window by a year. Symptomatic presentation, and the clinical workup that follows, remains the primary diagnostic pathway for breast cancer in women under 40.
The clinical workup of a symptomatic breast finding in a younger woman is described in the published guidance (including the Canadian Association of Radiologists practice guidelines and the various provincial breast disease guidelines) as a “triple assessment” approach. The triple assessment has three components: a clinical examination, imaging (typically ultrasound as the first-line imaging modality in women under 40, with mammography added as appropriate), and tissue sampling (a core needle biopsy of any suspicious finding). Each component is necessary because each has limitations. Clinical examination can miss small or deep lesions. Imaging in women under 40 is complicated by denser breast tissue that can obscure cancers on mammography and that can make ultrasound interpretation challenging. Biopsy is the only modality that establishes the diagnosis definitively.
The standard of care that flows from this approach, in general terms, is that a younger woman presenting with a symptomatic breast finding should be evaluated with all three components of the triple assessment, and any suspicious finding on imaging or clinical examination should be biopsied. The standard of care in any particular case requires expert evidence and the description here is background only.
A further complication, particularly relevant in young-women cases, is that breast cancer in this age group tends to be biologically more aggressive than in older women. The published oncology literature reports a higher proportion of triple-negative, HER2-positive, and high-grade tumours in pre-menopausal women, and a higher proportion of advanced-stage disease at diagnosis. The combination of more aggressive biology and a diagnostic system not oriented toward early detection in this age group is one of the structural reasons why young women diagnosed with breast cancer experience disproportionately poor outcomes.
The patient
The patient was 39 years old at the time of the events giving rise to the claim. She was married. She had two young children. The terms of the settlement and the convention applied to confidential settlement reporting do not permit description of the clinical specifics of how the delay occurred, the duration of the delay, or the names of the defendant clinicians. What can be said is that the diagnosis was made later than the standard of care would have permitted, that by the time of diagnosis the disease had progressed beyond the stage at which it would have been treatable with curative intent, and that the patient ultimately died of the disease.
The family she left behind included her husband and her two children. The claim was brought on their behalf and on behalf of her estate.
The legal framework
A medical malpractice claim arising from a delayed cancer diagnosis in Ontario is analyzed under the four elements of the standard negligence framework: duty of care, breach of the standard of care, damages, and causation.
Duty of care. The duty of care owed to a patient by her family physician, by any specialists involved in the workup of a breast symptom, and by any imaging or pathology providers, extends to the diagnostic decisions that are made in the course of the workup. This element is not typically contested in cases of this type.
Standard of care. The standard of care in delayed-breast-cancer-diagnosis litigation is generally established through expert evidence from physicians of the same specialty and standing as the defendant. Where the defendant is a family physician, the expert is generally a Canadian family physician with experience in primary-care breast disease management. Where the defendant is a radiologist, the expert is generally a breast imaging radiologist. Where the defendant is a surgeon or oncologist, the expert is generally of the same specialty. The standard is set by reference to what a reasonably prudent specialist of the same training and experience would have done in the same clinical circumstances, drawing on the published guidelines and practice patterns that prevailed at the time. The Supreme Court of Canada’s formulation of the standard for specialists in ter Neuzen v Korn, [1995] 3 SCR 674, is the controlling authority.
Damages. The damages in a wrongful-death case arising from delayed breast cancer diagnosis are typically substantial. They include the past costs of medical treatment that the patient endured (chemotherapy, radiation, surgery, and palliative care), the loss of income that the patient would have earned over the balance of her working life, the loss of services that the patient provided to her family (housekeeping, child care, and other unpaid labour), funeral expenses, and the Family Law Act claims of the husband and children for loss of guidance, care, and companionship. In a case involving young children, the loss-of-guidance claim is particularly significant because the loss is measured over the period to age 18 or beyond, and the published case law on quantifying these losses for young children has produced substantial awards in recent years.
Causation. The causation analysis in a delayed-diagnosis case is the doctrinally most difficult element. The plaintiff must establish that, on a balance of probabilities, the earlier diagnosis that the standard of care would have produced would have changed the outcome. The analysis is the “but for” framework from Clements v Clements, 2012 SCC 32, applied to the counterfactual scenario where the delay had not occurred.
The counterfactual analysis typically proceeds in three steps. First, expert oncological evidence establishes the likely stage of the cancer at the time of the missed opportunity for diagnosis. Second, expert evidence establishes the treatment that would have been applied at that earlier stage, drawing on the published treatment guidelines for that stage. Third, expert evidence establishes the likely outcome of that earlier treatment, drawing on the survival data for the relevant stage and tumour biology. If the expert evidence supports a conclusion that the patient more likely than not would have survived (or, depending on the case, would have lived substantially longer or with substantially less suffering) with earlier diagnosis, the causation element is met.
Two doctrinal points are worth noting. The first is the guidance from the Supreme Court of Canada in Laferrière v Lawson, [1991] 1 SCR 541, that a court is not paralyzed by statistical abstraction and that scientific findings (such as published survival percentages) are not identical to legal findings (such as the balance-of-probabilities determination of whether this particular patient would have survived). The judge or jury is entitled to consider statistical evidence alongside the patient’s specific clinical context to reach a conclusion on causation. The second is the principle from Cottrell v Gerrard, 2003 CarswellOnt 4154 (leave to appeal to the Supreme Court of Canada refused), that loss of chance is not compensable in Canadian medical malpractice law. A plaintiff cannot recover damages on the basis that the patient lost a chance of survival; the plaintiff must establish, on the balance of probabilities, that the patient would have survived but for the breach. The Ontario Court of Appeal recently revisited and reaffirmed these principles in the cancer-misdiagnosis context in Hacopian-Armen Estate v Mahmoud, 2021 ONCA 545, a delayed-uterine-cancer-diagnosis case in which the Court of Appeal upheld the trial verdict and clarified the foreseeability analysis in delayed-cancer-diagnosis litigation.
The resolution
The matter resolved by settlement in October 2023. The settlement was reached before trial. The terms are confidential. The settlement reflects the assessment of both sides of the strength of the standard-of-care and causation evidence, the magnitude of the damages, and the risks and costs of trial.
Why this matters
For young women, the lesson of cases like this is that a symptomatic breast finding in a woman under 50 requires investigation, regardless of age. The argument that “you are too young for breast cancer” is not consistent with the epidemiology. Approximately one in six new breast cancer diagnoses in Canada in recent years has occurred in women aged 40 to 50, and a smaller but not negligible share in women under 40 (per Statistics Canada and Canadian Cancer Society reporting). A persistent lump, a skin change, nipple discharge, persistent or unilateral breast pain, or any other concerning finding should be evaluated with the triple-assessment approach. A patient whose findings have not been adequately investigated is entitled to seek a second opinion, request imaging, or ask directly whether a biopsy is indicated. The published guidance from the Canadian Cancer Society and from provincial cancer programs supports the proposition that no woman should be reassured out of an investigation that the standard of care would require.
For family physicians and specialists involved in the early workup of breast symptoms, the lesson is the cost of premature reassurance. A finding that is initially attributed to a benign cause (fibrocystic changes, fibroadenoma, mastitis, or a duct papilloma) requires confirmation through the appropriate imaging and, where indicated, tissue sampling. The diagnostic system in Ontario for breast disease is built on the premise that the clinician will refer for imaging and biopsy when the clinical assessment is suspicious. Where the clinician does not make that referral, the system does not function. The cost of the system not functioning, in a case like this, is the life of a 39-year-old woman.
For the broader practice of medical malpractice litigation in Ontario, this case joins the cancer-misdiagnosis sub-cluster in the notable-cases library. Other entries in this sub-cluster include the trial victory in Hacopian-Armen v Mahmoud (uterine cancer, where the breach was a failure to perform an endometrial biopsy), the appeal in the same matter (where the Court of Appeal clarified the foreseeability analysis), and the hepatitis B liver cancer surveillance settlement (where the breach was a long-term surveillance failure). For a more general overview of the common diagnostic patterns in cancer misdiagnosis cases, the firm’s blog post on common causes of cancer misdiagnosis is a useful starting point.
For prospective clients who have lost a family member to a delayed cancer diagnosis, the threshold question is whether the diagnostic system functioned as it should have. The records of the primary-care visits, the imaging reports, the pathology reports, and the timing of referrals are the starting points for the analysis. The two-year limitation period in Ontario runs from the date the surviving family knew or ought to have known that the death was caused by an act or omission of the defendant. In a delayed-diagnosis case, the relevant date is generally the date that the family understood that an earlier diagnosis would have made a difference, which often does not coincide with the date of death.
Settlement Date: October 2023
Settlement Type: Confidential settlement before trial
Counsel for the plaintiffs: Paul J. Cahill
