Malpractice Suits for Postcolonoscopy Cancer
The plaintiff must prove that the performance of the colonoscopy was below the standard of care and that this resulted in harm to the patient. The issue of harm is referred to as causation. The level of harm the plaintiff must establish can vary according to state laws and regulations. For example, in one state the plaintiff might be required to establish that the harm was such that the patient was more likely than not (51% probability) to die or another outcome as a result of the negligence. In another state the plaintiff might be required only to show that the negligence resulted in a reduction in the chance for survival. For example, if the cancer was alleged to have been stage I at the time of the colonoscopy and was stage III with 2 positive lymph nodes at the time of diagnosis then the patient still would have a greater than 50% chance of survival with surgery and adjuvant chemotherapy, but the colonoscopist could be found responsible for a reduction in the chance of survival as well for the cost and suffering associated with adjuvant chemotherapy.
The case can be won for the defense on causation alone. For example, the patient undergoes a negative colonoscopy and 12 months later presents with abdominal pain and weight loss and a CT scan showing large liver metastases throughout both lobes. The expert oncologist for the defense might argue successfully that metastases of this size had to have been present 12 months earlier, and would have resulted in the patient's death irrespective of the colonoscopy result.
The plaintiff seeks to establish negligence and maximize the damages. Important elements for discussion are the size of the colon lesion at diagnosis, the interval of time between the negative colonoscopy and the diagnosis, and the alleged size and stage of the lesion at the time of the colonoscopy. These size estimates often are made by oncologists and are based on limited science. Further, there is little evidence that the primary tumor and the liver metastases would be expected to grow at the same rate. In my experience, an estimation of the tumor passing through one stage in about a year is not uncommon. Estimations of growth rates of the primary are more variable. The paradox for the plaintiff is that to credibly establish negligence they must conclude that the lesion in the colon was of a sufficient size that it should have been detected by a well-trained colonoscopist performing a careful examination. However, a larger lesion that is closer in size to the cancer's size at diagnosis makes it more difficult to suggest a much earlier stage at the time of the negative colonoscopy. If multiple plaintiff experts give varying estimates of size and stage at the time of the negative colonoscopy, it can help to shed doubt on the entire process of determining the extent of harm.
The idea that plaintiffs' experts have special expertise in the area of colonoscopy is generally incorrect. They are typically gastroenterologists or surgeons in general practice who may perform a lot of colonoscopies but who do not necessarily know the medical literature on missing during colonoscopy in detail. The defendant doctor and the defense attorney should learn the details of this literature. The plaintiff's expert must opine that missing a lesion greater than some particular size during colonoscopy is below the standard of medical care. If the size suggested by the expert is inconsistent with the medical literature, it provides an opportunity to attack the expert's knowledge and credibility. I have seen experts say that missing a lesion as small as 5 mm in size is below the standard of care. Even to suggest that a lesion 1 to 2 cm in size can never be missed is inconsistent with the results of tandem colonoscopy and CTC studies with segmental unblinding. Obviously, the risk of missing a particular lesion is a function not only of its largest diameter but also its shape and whether the lesion is located in clear view or on the proximal side of a fold or flexure. Both very old barium enema studies and recent CTC studies establish that these locations in the colon are associated with increased missing during colonoscopy. Thus, the credible plaintiff's expert either must admit that a small lesion could be missed by careful technique or hypothesize that the lesion was sufficiently large at the time of the negative colonoscopy that the damages are diminished, because the hypothesized lesion size (and likely the stage) then would be closer to the lesion size at the ultimate diagnosis.
The defense initially should establish that colonoscopy is not perfect. First, colonoscopy has been studied for its miss rate in both tandem colonoscopy studies and in CTC studies using segmental unblinding. In these studies, in which well-trained gastroenterologists were aware that their miss rate was being studied, even polyps 1 cm and larger were missed 6% of the time in tandem colonoscopy studies, and polyps 6 to 9 cm in size were missed nearly 15% of the time. However, tandem colonoscopies are inherently flawed from the perspective of measuring the sensitivity of colonoscopy because a second colonoscopy is considered the gold standard, and the same technical issues that impaired the sensitivity of the first colonoscopy also affect the second colonoscopy. Therefore, CTC studies using segmental unblinding from centers of excellence are of greater relevance. These studies show that the miss rate of colonoscopy for polyps 1 cm or larger is 12% to 17%. These studies cannot be used to measure the sensitivity of colonoscopy for polyps less than 1 cm in size because the sensitivity of CTC is less than colonoscopy for polyps in that size range. Juries are very understanding of the concept that no medical test is perfect, and if a test misses 12% to 17% of polyps greater than 1 cm in size, they can understand that this is a sufficient frequency that missing a polyp could have come into play in the individual case, even in the face of a careful examination.
The literature is increasingly replete with evidence that colonoscopy is imperfect with regard to overall protection against colorectal cancer, with studies showing protection in the proximal colon ranging from none to 56%, and protection in the range of 80% to 85% in the left colon. Again, this evidence underscores for the jury that the event of postcolonoscopy cancer is not rare and is not per se evidence of negligence.
Consideration can be given to having the tumor tested for microsatellite instability or immunostaining of the tumor for a mismatch repair gene products. Both in the setting of Lynch syndrome and in the case of hypermethylated tumors with BRAF mutations, there is general acceptance that microsatellite instability is associated with more rapid transition through the polyp/cancer sequence. Poor tumor differentiation also generally is accepted as being associated with faster growth. These arguments will assist the defense only if the tumor has these characteristics.
Considerable attention will be placed on the specific facts of the case. To the extent that the examination generally presents a picture of high quality, that there is documentation of the digital rectal examination, notation of cecal landmarks and photography, description of adequate preparation, documentation of withdrawal time, and photography of retroflexion, it becomes much easier for the defense expert to argue that the colonoscopist was clearly aware of and attentive to recommendations regarding high-quality examinations. If the doctor participates in a colonoscopy quality program and is aware of their ADR and their ADR is adequate (the higher the better), the defense arguments begin to become overwhelming. Finally, the case is made easier for the defense with a colonoscopist who shows in their deposition that they are personable, know the relevant literature and quality recommendations, and are committed to careful colonoscopy.
The final element depends largely on the defense attorney. The defense attorney should become aware of the medical literature and the issues that surround these cases, through reading of the literature and direct consultation with defense experts. Although one approach to deposing the plaintiff's expert is to simply ask for their opinions, a more effective approach is to both get their opinions and thoroughly explore their understanding of the medical literature, so that errors that are made can be brought out later for the jury. There is no question that the case can be won or lost by the competence of the defense attorney and experts. The plaintiff oncologist and defense oncologist almost invariably will have differing opinions about growth rates and doubling times.
Defending an Allegation of Missed Cancer
The Plaintiff's Burden
The plaintiff must prove that the performance of the colonoscopy was below the standard of care and that this resulted in harm to the patient. The issue of harm is referred to as causation. The level of harm the plaintiff must establish can vary according to state laws and regulations. For example, in one state the plaintiff might be required to establish that the harm was such that the patient was more likely than not (51% probability) to die or another outcome as a result of the negligence. In another state the plaintiff might be required only to show that the negligence resulted in a reduction in the chance for survival. For example, if the cancer was alleged to have been stage I at the time of the colonoscopy and was stage III with 2 positive lymph nodes at the time of diagnosis then the patient still would have a greater than 50% chance of survival with surgery and adjuvant chemotherapy, but the colonoscopist could be found responsible for a reduction in the chance of survival as well for the cost and suffering associated with adjuvant chemotherapy.
The case can be won for the defense on causation alone. For example, the patient undergoes a negative colonoscopy and 12 months later presents with abdominal pain and weight loss and a CT scan showing large liver metastases throughout both lobes. The expert oncologist for the defense might argue successfully that metastases of this size had to have been present 12 months earlier, and would have resulted in the patient's death irrespective of the colonoscopy result.
The Plaintiff's Paradox
The plaintiff seeks to establish negligence and maximize the damages. Important elements for discussion are the size of the colon lesion at diagnosis, the interval of time between the negative colonoscopy and the diagnosis, and the alleged size and stage of the lesion at the time of the colonoscopy. These size estimates often are made by oncologists and are based on limited science. Further, there is little evidence that the primary tumor and the liver metastases would be expected to grow at the same rate. In my experience, an estimation of the tumor passing through one stage in about a year is not uncommon. Estimations of growth rates of the primary are more variable. The paradox for the plaintiff is that to credibly establish negligence they must conclude that the lesion in the colon was of a sufficient size that it should have been detected by a well-trained colonoscopist performing a careful examination. However, a larger lesion that is closer in size to the cancer's size at diagnosis makes it more difficult to suggest a much earlier stage at the time of the negative colonoscopy. If multiple plaintiff experts give varying estimates of size and stage at the time of the negative colonoscopy, it can help to shed doubt on the entire process of determining the extent of harm.
The Plaintiff's Experts
The idea that plaintiffs' experts have special expertise in the area of colonoscopy is generally incorrect. They are typically gastroenterologists or surgeons in general practice who may perform a lot of colonoscopies but who do not necessarily know the medical literature on missing during colonoscopy in detail. The defendant doctor and the defense attorney should learn the details of this literature. The plaintiff's expert must opine that missing a lesion greater than some particular size during colonoscopy is below the standard of medical care. If the size suggested by the expert is inconsistent with the medical literature, it provides an opportunity to attack the expert's knowledge and credibility. I have seen experts say that missing a lesion as small as 5 mm in size is below the standard of care. Even to suggest that a lesion 1 to 2 cm in size can never be missed is inconsistent with the results of tandem colonoscopy and CTC studies with segmental unblinding. Obviously, the risk of missing a particular lesion is a function not only of its largest diameter but also its shape and whether the lesion is located in clear view or on the proximal side of a fold or flexure. Both very old barium enema studies and recent CTC studies establish that these locations in the colon are associated with increased missing during colonoscopy. Thus, the credible plaintiff's expert either must admit that a small lesion could be missed by careful technique or hypothesize that the lesion was sufficiently large at the time of the negative colonoscopy that the damages are diminished, because the hypothesized lesion size (and likely the stage) then would be closer to the lesion size at the ultimate diagnosis.
General Basis of the Defense
The defense initially should establish that colonoscopy is not perfect. First, colonoscopy has been studied for its miss rate in both tandem colonoscopy studies and in CTC studies using segmental unblinding. In these studies, in which well-trained gastroenterologists were aware that their miss rate was being studied, even polyps 1 cm and larger were missed 6% of the time in tandem colonoscopy studies, and polyps 6 to 9 cm in size were missed nearly 15% of the time. However, tandem colonoscopies are inherently flawed from the perspective of measuring the sensitivity of colonoscopy because a second colonoscopy is considered the gold standard, and the same technical issues that impaired the sensitivity of the first colonoscopy also affect the second colonoscopy. Therefore, CTC studies using segmental unblinding from centers of excellence are of greater relevance. These studies show that the miss rate of colonoscopy for polyps 1 cm or larger is 12% to 17%. These studies cannot be used to measure the sensitivity of colonoscopy for polyps less than 1 cm in size because the sensitivity of CTC is less than colonoscopy for polyps in that size range. Juries are very understanding of the concept that no medical test is perfect, and if a test misses 12% to 17% of polyps greater than 1 cm in size, they can understand that this is a sufficient frequency that missing a polyp could have come into play in the individual case, even in the face of a careful examination.
The literature is increasingly replete with evidence that colonoscopy is imperfect with regard to overall protection against colorectal cancer, with studies showing protection in the proximal colon ranging from none to 56%, and protection in the range of 80% to 85% in the left colon. Again, this evidence underscores for the jury that the event of postcolonoscopy cancer is not rare and is not per se evidence of negligence.
Consideration can be given to having the tumor tested for microsatellite instability or immunostaining of the tumor for a mismatch repair gene products. Both in the setting of Lynch syndrome and in the case of hypermethylated tumors with BRAF mutations, there is general acceptance that microsatellite instability is associated with more rapid transition through the polyp/cancer sequence. Poor tumor differentiation also generally is accepted as being associated with faster growth. These arguments will assist the defense only if the tumor has these characteristics.
Considerable attention will be placed on the specific facts of the case. To the extent that the examination generally presents a picture of high quality, that there is documentation of the digital rectal examination, notation of cecal landmarks and photography, description of adequate preparation, documentation of withdrawal time, and photography of retroflexion, it becomes much easier for the defense expert to argue that the colonoscopist was clearly aware of and attentive to recommendations regarding high-quality examinations. If the doctor participates in a colonoscopy quality program and is aware of their ADR and their ADR is adequate (the higher the better), the defense arguments begin to become overwhelming. Finally, the case is made easier for the defense with a colonoscopist who shows in their deposition that they are personable, know the relevant literature and quality recommendations, and are committed to careful colonoscopy.
The final element depends largely on the defense attorney. The defense attorney should become aware of the medical literature and the issues that surround these cases, through reading of the literature and direct consultation with defense experts. Although one approach to deposing the plaintiff's expert is to simply ask for their opinions, a more effective approach is to both get their opinions and thoroughly explore their understanding of the medical literature, so that errors that are made can be brought out later for the jury. There is no question that the case can be won or lost by the competence of the defense attorney and experts. The plaintiff oncologist and defense oncologist almost invariably will have differing opinions about growth rates and doubling times.