Prostate-Specific Antigen Testing in the Evaluation of Chronic Low Back Pain

To the Editor:

I appreciated the review article from Dr. Maharty and colleagues on chronic low back pain in adults.¹ Evidence-based evaluation of this common condition has the potential to improve lives and avoid wasting resources. The authors suggest obtaining complete blood cell count, erythrocyte sedimentation rate, and C-reactive protein measurements in people older than 50 years with a history of cancer or multiple risk factors for neoplasia.

Central low back pain of insidious onset may be the only presenting symptom of prostate cancer metastatic to the spine. About 6% of prostate cancers are metastatic on presentation, and a delay in the diagnosis may result in decreased quality of life and prolonged, intractable pain.² Is there any evidence for or against including prostate-specific antigen (PSA) testing in the workup of eligible patients with chronic low back pain when physical examination suggests a localized bony source? A high PSA level may guide physicians to pursue appropriate workup; this provides an opportunity to alleviate considerable suffering.

In Reply:

We thank Dr. Rosenberg for bringing to light the question of the use and implications of a PSA test for the evaluation of chronic low back pain.

In the United States, 13% of adults will have chronic low back pain.¹ This means that a large population would potentially be subjected to PSA testing. Prostate cancer metastatic to the spine can be difficult to diagnose because lesions may not be apparent on plain radiography until 50% to 70% of the bony trabecular architecture has been obliterated.² There is also no clear correlation between pain chronicity and the size and severity of metastatic bone damage.³

PSA screening alone has been debated. It may provide a small benefit in reducing mortality, but there is a high risk of potential harms, including false-positive results and treatment complications, such as incontinence and erectile dysfunction.

Clinicians offering PSA testing opens the proverbial Pandora’s box considering the massive numbers of patients with chronic low back pain in the United States. Other more common diagnoses, such as spine osteoarthritis, are widespread, with 95% of male patients older than 60 years demonstrating evidence of osteoarthritis on spinal radiography. These patients would be unnecessarily subjected to the risks of PSA testing.⁴

Our recommendation is to offer magnetic resonance imaging (MRI) when a patient older than 50 years with chronic low back pain presents with localized midline tenderness, weight loss, or other history or symptoms suspicious for cancer (see Table 1 and Figure 1 in our article).⁵ Compared with plain radiography, MRI has superior sensitivity and specificity for the detection of metastasis.⁶

This route avoids the conundrum of managing an elevated PSA level that is more likely to harm than help a patient. Vigilance and a high degree of suspicion are essential. Periodic reassessment is recommended for symptoms that suggest cancer. We advocate a multidisciplinary management approach based on collaborations between the primary care physician and consultants aimed at improving patient outcomes through a “choose wisely” strategy.