Previous studies found that in the United States, uninsured and Medicaid insured patients with breast, cervical, colorectal, head and neck, lung, prostate or uterine cancer have higher mortality or lower survival than do patients with private insurance or Medicare, even after adjustment for other factors [1–13]. Authors of studies comparing cancer survival among Canadian residents with U.S. residents concluded that low-income Canadians have a survival advantage over low-income U.S. residents, probably due to Canada's universal health care system which provides equal access to medically necessary care [14, 15]. These and other studies also found that age, sex, race, ethnicity, socioeconomic status (SES), marital status, stage at diagnosis, comorbidities, behavioral risk factors, and treatment significantly impact survival from cancer [1–25]. As substantial proportions of the U.S. population are uninsured or enrolled in Medicaid – 48.6 million (15.7%) and 50.8 million (16.5%), respectively, in 2011 [26], it is important to determine differential effects of health insurance on health status.

We examined the association between health insurance status and cause-specific survival from seven common cancers diagnosed in New Jersey (NJ) residents aged 18–64 using a high-quality population-based cancer registry and adjusting for other significant factors. We excluded patients aged 65 or older because nearly all are insured through Medicare. We also compared cancer survival by insurance status between two time periods. The cancers we examined, female breast (breast), cervical, colorectal, lung and bronchus (lung), non-Hodgkin lymphoma (NHL), prostate and urinary bladder (bladder), accounted for 61% of the incident cancers and 56% of cancer deaths among NJ residents during 2005–2009 [27]. To our knowledge, this is the first study of survival disparities by insurance status to include NHL and urinary bladder cancer, as well as changes in the relationship between health insurance status and cancer survival over time.

The New Jersey State Cancer Registry (NJSCR) is the population-based cancer incidence registry that serves the state of NJ, with a diverse population of over 8.7 million people. The NJSCR has participated in the Centers for Disease Control and Prevention's National Program of Cancer Registries since it began and is a National Cancer Institute (NCI) Surveillance, Epidemiology and End Results (SEER) expansion registry. The NJSCR includes patient demographics and clinical information (e.g., date of diagnosis, stage at diagnosis, primary payer at diagnosis, or first course of treatment) on each cancer case. The primary site and histology of each case are coded to the International Classification of Diseases for Oncology (ICD-O), 3rd edition [28] and the stage at diagnosis is coded according to SEER summary stage [29, 30]. The North American Association of Central Cancer Registries awarded the Gold Standard to the NJSCR for quality and completeness of 1995 through 2009 data. Additional details of NJSCR operations are in the most recent annual report [27].

All first primary invasive breast, cervical, colorectal, lung, prostate, and bladder (also in situ) cancers and NHLs in the NJSCR diagnosed during 1999–2004 in persons aged 18–64 years were included. The ICD-O-3 codes for the seven cancers are those in the SEER site recode definition [31]. Cases were excluded if: ascertained by death certificate or autopsy report only; health insurance status other than private, Medicaid or uninsured, for example, Medicare, military, Indian Health Service; race other than white, black, or Asian/Pacific Islander (API); unknown race or insurance status or no survival time.

Vital status in the NJSCR is updated annually through linkages with state and national death files, state taxation files, hospital discharge files, Medicare and Medicaid files, Social Security Administration Services for Epidemiologic Researchers and motor vehicle registration files. Additionally, hospitals are required to submit annual vital status updates on all cases they have reported. Completeness of vital status follow-up in December 2011 (when the study data file was prepared) for the 54,002 study cases was 97%, ranging from 92% for cervical cancer to 99% for lung cancer. Cause of death codes were obtained from the state and national death file in the NJSCR.

After linkage with NJ hospital discharge data using Link Plus (CDC software), 6.1% of the eligible cases (4.3% to 9.4% depending on cancer type) had unknown primary payer compared with 8.3% before the linkage. About 6% of the cases had been uninsured as the primary payer after the linkage versus 7% before the linkage.

After exclusions, 54,002 cases remained of the 63,429 eligible cases; among the cases excluded were 217 cases ascertained by death certificate or autopsy report only and 8363 cases with Medicare, military, or unknown health insurance status. For each nonsex-specific cancer type, males represented 53% to 75% of the cases and the distribution of cases by age, race, ethnicity, marital status, and SES varied greatly (Table 1). The proportion of cases diagnosed at the distant stage was between 2% (prostate, bladder) and 54% (lung). The percentage of uninsured cases ranged from 5% (breast, prostate, bladder) to 18% (cervical) and the percentage with Medicaid ranged from 2% (prostate) to 9% (cervical). Women with cervical cancer also were more likely to be young (32%), Hispanic (20%), in the lowest SES quartile (33%), and not married (53%) than patients with other types of cancer.

Significant sex differences in insurance status occurred only for lung cancer, with higher proportions of men than women uninsured or Medicaid insured (P < 0.0001). Age differences in insurance status were statistically significant for breast, colorectal and lung cancer and NHL (P ≤ 0.0002), with the youngest age group most likely uninsured or Medicaid insured. Within each cancer type, Hispanics were most likely uninsured and non-Hispanic blacks most likely had Medicaid compared with the other race/ethnic groups, except Hispanic colorectal and bladder cancer cases most likely had Medicaid (P < 0.0001). Unmarried cases with each type of cancer were far more likely uninsured or Medicaid insured than married cases (P < 0.0001). Across all cancer types, much higher percentages of the lowest SES quartile cases were uninsured or had Medicaid, with higher percentages of uninsured or Medicaid cases in each successively lower SES quartile (P < 0.0001). Cases diagnosed at the distant or unknown stage were more likely uninsured or Medicaid insured than cases diagnosed at the local or regional stage (P ≤ 0.0015).

Among NJ patients 18–64 years old with breast, colorectal, lung, prostate, bladder cancer, or NHL, those without insurance had a significantly higher risk of death within 5 years of diagnosis (41%–97%) than those with private insurance even after adjustment for important prognostic factors such as gender, age, race/ethnicity, marital status, SES, and stage. Medicaid insured patients with these same cancers (except bladder cancer) also had significantly higher risks of dying within 5 years of diagnosis than those with private insurance – 21% to 198%. Our results for breast, colorectal, lung, and prostate cancer are comparable to previous studies' results, although the populations and years studied and analytic methods were different [2, 4, 5, 7, 9–13]. The previous study of NJ breast cancer patients diagnosed in 1985–1987 found 1.49 and 1.40 adjusted relative risks of death among uninsured and Medicaid insured women, respectively, compared with privately insured women [13], similar to our adjusted HRs of 1.44 and 1.56 for breast cancer patients diagnosed in 1999–2004. Thus, among NJ women with breast cancer, survival disparities by insurance status appear not to have changed in the past several decades.

Possible reasons for uninsured and Medicaid insured cancer patients' poorer survival compared with privately insured cancer patients, even after adjustment for other factors, may include: poorer health with more comorbidity and unhealthy behaviors; no or inadequate preventive health care and management of chronic conditions prior to cancer diagnosis; barriers to receiving treatment and adhering to a treatment regimen such as high cost, inability to navigate the health care system, misinformation about and mistrust of the health care system, lack of a usual source of health care, lack of transportation, lack of time off from work; no treatment or delay in receiving treatment; not all providers accept uninsured or Medicaid insured patients; and lower quality treatment by providers primarily serving the uninsured and Medicaid insured [3, 4, 8, 9, 12].

A recent study found that patients insured through Medicaid after cancer diagnosis had higher disease-specific mortality than patients insured through Medicaid before cancer diagnosis and that both Medicaid insured groups had significantly higher mortality than the non-Medicaid insured group [35]. The authors noted that in other studies cancer patients enrolled in Medicaid before diagnosis compared to cancer patients enrolled after diagnosis were more likely to receive screening mammography and be diagnosed at earlier stages [35].

For cervical cancer, we found no significant difference in survival between uninsured or Medicaid insured versus privately insured patients when other factors were taken into account, similar to results from a previous study of cervical cancer survival in Florida [6]. Authors of the Florida study concluded that racial, ethnic, and SES disparities in cervical cancer survival were explained by late-stage presentation and undertreatment [6]. NJ cervical cancer patients appear to be particularly vulnerable with relatively high proportions in demographic groups with poorer survival generally, that is, non-Hispanic black, Hispanic, low SES, unmarried, without insurance or Medicaid insured, than patients with other types of cancer (Table 1). As cervical cancer is mostly preventable with human papillomavirus vaccination (HPV) and Pap tests (which detect precancerous lesions), emphasis needs to remain on reaching all women with these measures.

The results from the comparison of two time periods showed that while 5-year survival significantly improved or remained the same for privately insured patients (except those with cervical cancer), survival did not improve for uninsured or Medicaid insured patients (except Medicaid insured patients with NHL). Thus, the survival disparities between privately insured and uninsured or Medicaid insured patients widened over time. The much greater improvement in survival over time for Medicaid insured NHL patients was unexpected and cannot be explained by this study.

We found no other studies with which to compare our study results relating to NHL and bladder cancer survival, or changes over time in the relationship between insurance status and cancer survival.

Survival from cancer appears to be related to a complex set of interrelated demographic and clinical factors of which insurance status is a part. The finding that Medicaid insured cancer patients also have worse survival than privately insured cancer patients suggests that while ensuring that everyone has adequate health insurance is an important step, additional measures are needed to address cancer survival disparities. These include: building capacity in the U.S. public health and health care systems, especially in underserved communities; education about cancer prevention, detection, and treatment; preventive and chronic health care before a diagnosis of cancer; assistance to cancer patients in accessing and navigating the health care system; and workplace policies that encourage patients' attention to their health.