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Regularly visiting a primary care physician (PCP) before cancer diagnosis was associated with better disease outcomes among a cohort of patients from the Veterans Affairs health system.

Compared with no prior visits, annual PCP use among over 200,000 veterans with 12 different tumor types was linked with lower odds of being diagnosed with metastatic disease (OR 0.61, 95% CI 0.59-0.63, P<0.001) and reduced risk of cancer-specific mortality (subdistribution hazard ratio [SHR] 0.79, 95% CI 0.77-0.81, P<0.001), reported Brent S. Rose, MD, of the University of California San Diego, and colleagues.

Even "some" PCP use -- one to four visits over the 5 years prior to diagnosis -- was associated with reduced odds of metastatic disease at diagnosis (OR 0.74, 95% CI 0.71-0.76, P<0.001) and reduced risk of cancer-specific mortality (SHR 0.88, 95% CI 0.86-0.89, P<0.001), they noted in .

"While the association between consistent preventative healthcare with improved cancer outcomes is frequently discussed among clinicians, our study represents the first -- and largest -- to estimate the association of prediagnostic primary healthcare with cancer outcomes for a variety of tumor subtypes," Rose and team wrote. "These findings suggest that PCPs are vital for early cancer detection, and allocating additional resources toward primary care may reduce the nationwide cancer burden."

Of the 245,425 veterans included in the study, the largest proportion had prostate cancer (38.1%), followed by lung cancer (19.6%) and colorectal cancer (9.7%), while breast cancer (1.4%) and gastric cancer (1.4%) had the lowest representation. About one in six presented with metastatic disease.

"Some" PCP use was associated with a statistically significant reduction in the OR for metastatic disease at diagnosis for seven of the tumor types -- prostate, lung, colorectal, bladder, gastric, and kidney cancer, as well as melanoma. When looking at annual PCP use, there was an associated statistically significant reduction in the OR for metastatic disease at diagnosis for all tumor types but pancreatic cancer.

The largest effect size for prior PCP use was observed for prostate cancer (OR for annual use 0.32, 95% CI 0.30-0.35, P<0.001), and the lowest was observed for pancreatic cancer (OR 0.87, 95% CI 0.73-1.04, P=0.12).

Annual PCP use was also linked to a statistically significant reduction in cancer-specific mortality for all tumor subtypes, with the largest effect size observed for prostate cancer (SHR 0.51, 95% CI 0.48-0.55, P<0.001) and melanoma (SHR 0.51, 95% CI 0.44-0.59, P <0.001). The lowest effect size was again seen in pancreatic cancer (SHR 0.89, 95% CI 0.82-0.97, P=0.007).

Some PCP use was associated with a statistically significant reduction in the risk of cancer-specific mortality in melanoma, and prostate, kidney, bladder, esophagus, lung, and colorectal cancers.

"These cancer-specific risk estimates may help physicians provide more personalized guidance for patients at elevated risk of developing certain cancers," Rose and colleagues noted.

They pointed out that higher PCP use was associated with improved outcomes in cancer subtypes that may undergo frequent screening -- such as prostate, colorectal, and breast cancers -- while "less screenable tumors," such as pancreas tumors, had no such association.

However, "even in cancers without well-established screening paradigms, we observed improved outcomes for patients with higher PCP use," they wrote. "Consistent PCP use represents an obvious and advantageous preventative measure for these occult malignancies."

"Quantifying this complex patient-clinician relationship requires additional prospective studies," they noted. They also suggested that it is possible that patients who see a PCP more often may follow healthier lifestyles that could lower their cancer risk compared with patients who see a PCP less frequently.

The study population included veterans older than 39 years who had been diagnosed with a solid tumor cancer from 2004 to 2017, with a median follow-up of 68 months. Mean age was 65.8, most were men, and 76% were white. They had a median of four previous PCP visits; 43.8% saw a PCP annually, and 12.7% had no prediagnostic PCP visit.

Rose and colleagues acknowledged that a limitation to their study was that they were unable to determine if cancer screening or prevention was discussed at each PCP visit, "as time might be allocated toward chronic disease management instead."

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