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Although 64% of cancer survivors are expected to live at least five years beyond diagnosis, the receipt of cancer screening by this population is unclear. The study objective is to assess the relation between a cancer diagnosis and future cancer screening, exploring provider, patient, and cancer-specific factors that explain observed relationships.
The Wisconsin Longitudinal Study (WLS) and Wisconsin Tumor Registry were used to identify two participant groups: 415 diagnosed with non-metastatic cancer between 1992-1993 (pre-cancer) and 2003-2004 (post-cancer) and 4,680 no-cancer controls. Adjusted average predicted probabilities of cancer screening were estimated with models that first did not include and then included, provider (provider relationship length), participant (depressive symptoms (CES-D)) and cancer-specific (time since diagnosis) factors. Participants with a history of the cancer associated with a given screening test were then excluded to assess whether relationships are explained by screening for recurrence versus second cancers.
Female cancer survivors were more likely than no-cancer controls to undergo pelvic/pap (70%, 95% confidence interval (CI)=63-76% and 61%,CI=59-63%) and mammography screening (86%,CI=78-90% and 76%,CI=74-77%), though male cancer survivors were not more likely to receive prostate exams (76%,CI=70-82% and 69%,CI=67-71%). After excluding people with a history of the cancer being screened for, there were few significant differences in cancer screening between short or long-term survivors (>5 years) and no-cancer controls. Relationships were not sensitive to adjustment for provider or participant factors.
The significant positive differences in cancer screening between people with and without cancer can be explained by screening for recurrence. Long-term cancer survivors are not more likely to receive follow-up screening for second cancers. This information should be used by providers to ensure patients receive recommended follow-up preventive care.
Cancer detection and treatment advances have produced declining cancer death rates,1 with 64% of cancer survivors expected to live >5 years from diagnosis.2 Despite improvements, cancer survivors remain at risk of recurrence and second cancers.3 In recognition of these risks, the Institute of Medicine outlined a critical need to improve the long-term follow-up of cancer survivors, including cancer screening, to optimize health outcomes.4
Given long-term health risks, there is reason to believe cancer survivors would be likely to undergo recommended cancer screening,5 but evidence on whether this occurs is mixed. Several studies show cancer survivors to be more likely to receive mammograms,6-11 Papanicolaou (Pap) smear/pelvic exams,6-8 and prostate-specific antigen tests6, 8 than adults without a personal history of cancer. Other studies found either no difference12 or underutilization of certain services once people with a history of the cancer being screened for were excluded.10, 12 These studies were largely analyses of administrative datasets (e.g., SEER-Medicare) and focused on recently diagnosed breast and colorectal cancer survivors over age 65. This limits the ability to control for a comprehensive set of patient-level factors or explore mechanisms through which a cancer diagnosis influences screening behavior.
The amount of time a person has lived with cancer may play influence cancer screening behavior. Surviving 5 years is considered a “milestone”13 that represents a reduction in health risks,13, 14 though many long-term survivors remain at risk of recurrence and second cancers. Studies using SEER-Medicare data suggest that mammography and cervical cancer screening decline following a diagnosis of breast and colorectal cancer.9, 15 Cancer screening however, has not been described in individuals surviving longer than 5 years or compared to trends in people without cancer. Studies addressing this gap have important clinical implications. As the number of cancer survivors continues to increase, providers will need to remain vigilant in screening for recurrent and new cancers.
Research exploring factors that affect cancer screening has primarily focused on provider type and patient mental health. After 5 years from diagnosis, nearly two-thirds of cancer survivors visit their PCP exclusively,15 making a shared care model for the systematic long-term care of cancer survivors less feasible. In primary care, continuity of care generally fosters patient adherence to physician recommendations for cancer-specific services,16, 17 though this has not been explored for cancer survivors. Depressive symptoms are commonly reported by cancer survivors18 and could be a modifiable mechanism by which a diagnosis impacts screening, though to our knowledge this has not been explored. Cross-sectional studies have yielded mixed results with some studies associating depressive symptoms with underutilization,19 and others with more primary care visits20, 21 or better guideline adherence.22
We address prior limitations with a unique dataset that combines a longitudinal study with a state tumor registry database. This linkage allowed for an investigation of the relation between a cancer diagnosis and cancer screening and provider and patient factors that explain screening behavior.
Participants were from the Wisconsin Longitudinal Study (WLS), a long-term cohort study of a one-third random sample of Wisconsin high school graduates in 1957 (n=10,317) and 8,778 of their randomly selected siblings. The WLS is representative of non-Hispanic white men and women with at least 12 years of education, an ethnic/educational subgroup that includes approximately two-thirds of the U.S. population in the relevant age bracket.23 Participants who responded to the 1992-1993 and 2003-2004 telephone and mail surveys were included (N=8,054). Among participants, 1992-1993 response rates for graduates and siblings were 93% and 87% for the telephone and 76% and 77% for mailed surveys, respectively. In order to capture incident cancer cases, the sample was restricted to Wisconsin residents (66% of participants, N=5,317).
The WLS was linked to the Wisconsin tumor registry,24 allowing for a medical records-based assessment of cancer diagnosis year, site, and SEER summary stage, defined as in situ, localized, regional (direct extension and lymph nodes alone or in combination, or not otherwise specified), and distant (metastatic).25, 26 Participants diagnosed before 1992-1993 (n=174) or at a “distant” stage (n=33) were excluded. The sample was further restricted to respondents at the USPSTF minimum recommended age for each of the cancer screening tests (age 40 for mammogram and 50 for prostate exam) in place at the time of survey administration27-29 resulting in the exclusion of 15 men. The final sample included 415 participants diagnosed with cancer between 1992-1993 (pre-cancer) and 2003-2004 (post-cancer) and 4,680 participants without a cancer diagnosis in the state tumor registry during this time period.
Our dependent variables included three cancer screening measures assessed in 2003-2004 (post-cancer diagnosis for the cancer group). These questions asked whether participants received a pelvic exam/Pap smear, mammogram, or prostate exam within the previous 12 months (yes/no). The first two services are recommended by the U.S. Preventive Services Task Force (A-B rating); prostate exams are not (“insufficient evidence” rating).30 At the time of the survey, the American Cancer Society recommended annual mammograms,31 pap/pelvic exams (unless 3 consecutive tests were negative),32 and prostate exams33 for people in the age range of this cohort.
The primary explanatory variable was a cancer diagnosis between 1992-1993 and 2003-2004 (yes/no). Provider, participant and cancer-specific factors included: 1) “provider relationship length” (no usual provider; <5; 5-9; 10-14; ≥15 years); 2) “depressive symptoms” (measured in 1992-1993 and 2003-2004 using the Center for Epidemiological Studies Depression survey34); and 3) “time since cancer diagnosis” (no cancer diagnosis; diagnosed <5 years; diagnosed ≥5 years before 2003-2004).
Analyses were adjusted for factors (measured in 1992-1993), associated with the likelihood of a cancer diagnosis and/or cancer screening. These factors were chosen based on a cancer stress process model35 that relates a cancer diagnosis to subsequent health behaviors and correspond to predisposing, enabling, and need factors included in the Andersen model of health services utilization.36
Sociodemographic measures included age, gender, marital status, number of children, education, household income, and employment status. Health measures included self-reported diagnosed chronic conditions with a prevalence over 10% in the sample (hypertension, heart disease (heart trouble, circulation problems), respiratory conditions (asthma/bronchitis/emphysema), and arthritis/rheumatism) with a summary indicator encompassing conditions with less than a 10% prevalence. Functional status was defined by a condition/illness/disability that limited activities now or was likely to in the future. Self-rated health was assessed as excellent, good, fair, poor, or very poor. A cancer family history variable indicated whether a participant’s biological mother, father, or siblings had been diagnosed with cancer. Health behavior measures included body mass index (underweight/normal (<24.9 kg/m2); overweight (25.0-29.9 kg/m2); obese (>30 kg/m2)37), physical activity (“sedentary”; “light”; “moderate”; “vigorous”),38 and cigarette smoking (never; former; current). Insurance status in 2003-2004 was categorized as public or private. Uninsured participants (2%) were included in the “public” category due to small sample size and because both groups have historically had reduced health care access and screening rates relative to the privately insured.39
Psychosocial measures included personality, stressful life events, and social support and participation. Personality (related to preferences for medical decision making40 and provider choice41) was assessed with a modified version of the five-factor model: extraversion, openness to experience, conscientiousness, neuroticism, and agreeableness.42, 43 Stressful life events were measured with a scale44, 45 that inventories 18 life events/problems (e.g., spousal physical abuse). Social support is a reinforcing factor for preventive care use,46 and along with life stress, influences health care use in older adults,47 and was measured as social participation (a count of participation in 16 social network types (e.g., church-connected groups)48 and social relationships (a count of social get-togethers with friends/relatives in the prior month).
Data were analyzed using Stata v10.0.49 Though the item non-response rate averaged across items was low (2.4%), multiple imputation by chained equations was employed at the item level. Five imputed datasets were created. Parameter estimates (mean, proportion, regression) and standard errors were obtained using Rubin’s combination rules.50-54 Adjusted multivariable logistic regression models were fit to assess the relation between a cancer diagnosis and cancer screening. Models were estimated separately for men and women and re-estimated including “time since diagnosis” group, post-cancer depressive symptoms, and provider relationship length variables to determine whether these factors accounted for between-cancer group screening differences. Participants with a history of the cancer being screened for were then excluded to assess whether the relation between a cancer diagnosis and screening can be explained by screening for recurrence versus second cancers. We accounted for the clustering of sibling and graduate respondents by calculating 95% confidence intervals using the Stata “robust” command. Statistical significance was defined as p<0.05.
To aid in interpretation, average predicted probabilities of cancer screening were estimated for the cancer and no cancer groups adjusted to the overall distribution of covariates. Covariate values for a given participant (e.g., female, employed) were used to estimate the probability of receiving a given screening test, having or not having cancer under actual and counterfactual scenarios. This was accomplished by first setting all participants’ cancer status to 1 (indicating that they had cancer), while maintaining each participant’s unique set of other characteristics (e.g., age, gender), and averaging individual probabilities across the sample. Next, cancer status was set to 0 for all participants (indicating that they did not have cancer), and the procedure was repeated. The difference in these two sets of mean predicted probabilities can be interpreted as the difference in the probability of the given screening between those with cancer and without, for a population with the mix of other characteristics present in the sample. A similar approach was followed to calculate average predicted probabilities for the 3 “time since diagnosis” groups. In order to obtain standard errors, individual predicted probability estimates were combined as previously described and averaged, with the process bootstrapped 200 times. The sample drawn during each replication represented a bootstrap sample of clusters.
Survey participants in 1992-1993 (pre-cancer) were 53 years old on average, with relatively high levels of income and education (Table 1). Eighty-nine percent reported good/excellent health. Participants who went on to receive a cancer diagnosis were significantly more likely than those who did not to be older, male, have a family history of cancer and a higher education level.
The most frequently diagnosed cancers were prostate, breast, and colorectal, which were commonly diagnosed at a local stage (Table 2). Fifty-six percent of cancers were diagnosed within five years of the 2003-2004 survey.
There was moderate variation in the proportion of participants who received cancer screening (Table 3). Proportions ranged from 62% for Pap smears/pelvic exams to 76% for mammograms.
Controlling for pre-cancer and insurance factors, women with cancer were more likely than those without to receive cancer screening (Table 4). Female cancer survivors were more likely to receive Pap smears/pelvic exams (70%, 95%CI=63-76%) and mammograms (86%, 95%CI=78-90%) than were women without cancer (61%, 95%CI=59-63% and 76%, 95% CI=74-77%, respectively). Once women with the cancer associated with a given screening test were excluded, the difference for pelvic exam/Pap smear remained (69%, 95%CI=63-76% and 61%, 95%CI=59-63%), though the difference for mammograms was no longer statistically significant (80%, 95%CI=69-86% and 76%, 95%CI=74-77%). Among men, cancer survivors were not significantly more likely than men without cancer to receive prostate exams (76%, 95%CI=70-82% and 69%, 95%CI=67-71%), nor were they more likely to receive them after prostate cancer survivors were excluded (69%, 95%CI=57-77% and 69%, 95%CI=67-71%).
The association between a cancer diagnosis and cancer screening differed by the amount of time a person had cancer. Within five years of diagnosis, cancer survivors were more likely than controls to have had cancer screening tests other than for prostate cancer. However, the only difference for longer-term survivors was for mammograms (86%, 95%CI=78-92% and 76%, 95%CI=74-77%) (Table 4). Once participants with a history of the cancer associated with the screening test were excluded, there were few significant differences for short-term survivors and no significant differences for longer-term cancer survivors compared to no-cancer controls. The magnitude of the differences described remained when post-cancer provider and patient factors were included in the models.
To our knowledge, this is the first study to prospectively assess the relation between a cancer diagnosis and cancer screening in short and longer-term survivors, while exploring a comprehensive set of provider, patient and cancer-specific factors that might explain observed relationships. Although the majority of cancer survivors received recommended cancer screening, there was important variation by screening type. Overall, cancer survivors were more likely than people without cancer to receive cancer screening, with proportions that changed little with adjustment. However, once participants who had the cancer associated with a given screening test were excluded, the only statistically significant difference was higher Pap smears/pelvic exams for short-term cancer survivors. There were no differences in cancer screening among long-term survivors relative to no-cancer controls. The magnitude of these relationships did not change when post-cancer depressive symptoms or provider-patient relationship length were included in the models.
It is encouraging and not surprising that cancer survivors were more likely than participants without cancer to receive the screening test associated with their cancerwithin five years of diagnosis, as this likely represents screening for recurrence. Twenty to thirty percent of cancer survivors did not undergo screenings for other cancer types however, despite evidence that many cancer survivors remain at risk of developing second primary cancers.5, 55 This gap between recommended care and actual practice has been demonstrated in other studies.8, 12 There were no significant differences from controls in the receipt of any of the cancer screening services ≥5 years from the time of diagnosis, again suggesting the influence on results of screening for recurrence within five years of diagnosis.
Given the health risks, one might expect cancer survivors to be more likely to follow screening guidelines than people without cancer. One explanation for lack of adherence may be access to care. However, our study cohort had few uninsured participants and even then, cancer screening rates were no better than national rates for breast cancer survivors.11 This suggests that better access to care and higher socioeconomic status do not necessarily translate into preventive service guideline adherence. A second explanation may be related to provider type. Ninety-one percent of cancer survivors identified a primary care provider as their usual provider. Rates of non-cancer-related preventive care utilization have been shown to be higher for cancer survivors who see PCPs, whereas survivors who see oncologists receive more cancer screening,7, 15, 56 which may account for some of the observed effects.
It is noteworthy that adjusting for a comprehensive set of factors did little to affect cancer screening probabilities in the study cohort. Instead, probabilities were most impacted by cancer-related factors (site and time since diagnosis). Depressive symptoms may not impact cancer screening behavior in this cohort because of the relatively high levels of access to care coupled with long-standing provider relationships in the cancer and no cancer groups (10.4 and 10.7 years, respectively).
Some study limitations that should be noted. First, though USPTF recommended age thresholds for cancer screening in place at the time of survey administration were used,27-29 thresholds for some of the screening services under investigation have changed. Prostate cancer screening is no longer recommended for men over 75, nor mammography for women after 75-85 or cervical cancer screening after 65 (unless otherwise at risk or had adequate prior screening). However, given the higher risks of second cancers faced by many cancer survivors, one would expect cancer survivors to be more likely than people without cancer to receive cancer screening. This was not found to be the case for longer-term cancer survivors once participants were excluded who had a history of the cancer being screened for. Second, this study relied on self-reported cancer screening. Correlations between self-reported and medical-record-based assessments of cancer screening however are moderate to high.57 Third, our study did not have information on recurrence or treatment. For participants undergoing cancer treatment, not undergoing screening for a cancer type other than their own may reflect energies rightly directed toward treatment. However, this is unlikely to explain all study findings, as significant differences in screening between the cancer and no-cancer control groups were primarily seen within the first five years of diagnosis, when the majority of survivors would likely be undergoing treatment and surveillance for cancer recurrence. Fourth, colon cancer screening was not available in the WLS. Therefore, the only follow up cancer screening assessed in men was prostate cancer screening. Last, the sample size of cancer survivors precluded the examination of interaction effects and may have contributed to the lack of differences observed for analyses that excluded cervical cancer survivors.
Despite these limitations, the current study found that while the majority of cancer survivors receive recommended care, there remains room for improvement. Survivorship care plans that detail recommended follow-up care have been suggested as a mechanism to facilitate provider-patient communication.4 Given that 5 years from diagnosis, nearly two-thirds of cancer survivors visit their PCP exclusively,15 a plan such as this could provide additional opportunities for clear communication between health care providers (e.g., oncologists and PCPs). Since only 28% of breast cancer survivors report good communication between their PCP and oncologist58 and more than half of PCPs rate the transfer of care between oncologists and PCPs as “poor”,59 a survivorship care plan has the potential to align provider and patient expectations and optimize care delivery and healthy outcomes for cancer survivors.
This work was supported by the Agency for Healthcare Research and Quality (AHRQ)/ National Research Service Award (NRSA) T-32 Institutional Training Program (grant number T32 HS00083); the National Cancer Institute (grant number R21 CA137288); the National Institute on Aging (grant number P01 AG021079); and the Community-Academic Partnerships core of the University of Wisconsin Institute for Clinical and Translational Research (UW ICTR), National Center for Research Resources, National Institutes of Health (grant number UL1 RR025011). In addition, Dr. Pandhi’s time on this project is supported by a National Institute on Aging Mentored Clinical Scientist Research Career Development Award, grant number l K08 AG029527. This project was further supported by the Health Innovation Program. This research uses data from the Wisconsin Longitudinal Study (WLS) of the University of Wisconsin-Madison. Since 1991, the WLS has been supported principally by the National Institute on Aging (grant numbers R01 AG09775, R01 AG033285), with additional support from the Vilas Estate Trust, the National Science Foundation, the Spencer Foundation, and the Graduate School of the University of Wisconsin-Madison. A public use file of data from the WLS is available at http://www.ssc.wisc.edu/wlsresearch/data/. Portions of these results were presented at a National Research Service Award Trainees Research Conference sponsored by the Agency for Healthcare Research and Quality (AHRQ).