番茄社区

"Medical Journeys" is a set of clinical resources reviewed by physicians, meant for the medical team as well as the patients they serve. Each episode of this journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.

Radiation therapy for prostate cancer has advanced substantially in recent years to become more precise. Highly effective radiation therapies for many cases now lead to fewer side effects than were seen in the past. Radiation therapy is considered a good option for many prostate cancer patients. Those with a very large prostate or with significant urinary symptoms may do better with other types of therapy, such as surgery.

Options for radiation therapy for prostate cancer include:

• External-beam radiation therapy (EBRT)

• Intensity-modulated radiation therapy (IMRT)

• Stereotactic body radiation therapy (SBRT)

• Brachytherapy

Radiation therapy uses high-energy rays or particles to kill cancer cells. Depending on the stage of the prostate cancer and other factors, radiation therapy might be used as the first treatment for prostate cancer contained within the gland; along with hormone therapy for cancer outside the prostate gland; if cancer recurs, after prostatectomy; and for advanced cancer, to help palliate symptoms.

Multiple factors need to be considered in determining the most appropriate radiation approach for each patient. These include the patient's age, comorbidities, history of urinary or gastrointestinal symptoms or risk factors, prostate volume and anatomy, as well as the stage and grade of the prostate cancer. Prostate cancer specialists take into account the patient's prostate-specific antigen (PSA) level, Gleason score of the biopsy, and findings from the prostate MRI scan.

"There are now many viable radiation approaches, and the decision-making has become very personalized," noted Jonathan E. Leeman, MD, of Dana-Farber Cancer Institute in Boston.

EBRT

EBRT is an important option to consider for most men who are diagnosed with localized prostate cancer. It directs radiation beams specifically designed for the tumor located within the prostate. This type of radiation can be used with curative intent for earlier-stage cancers, or to help relieve symptoms such as bone pain if the cancer has spread to a specific area of bone. Patients usually have treatment 5 days a week in an outpatient center for several weeks.

Conventional radiotherapy has been replaced with hypofractionated EBRT, which delivers more doses of radiation per treatment. "We have moved away from conventional radiation in most cases, since equivalent results and toxicity have been noted with ," explained Peter A.S. Johnstone, MD, of Moffitt Cancer Center in Tampa, Florida. Hypofractionated regimens allow therapy to be delivered in 4-5 weeks instead of 8-9 weeks.

The shortened treatment time of hypofractionated EBRT allows patients to complete their treatment more quickly. "This can be quite important for patients so that they can return to their lives sooner, and it results in higher rates of treatment compliance," Leeman said. "The preponderance of evidence has shown that clinical outcomes in terms of efficacy and side effects are similar between conventionally fractionated and moderately hypofractionated EBRT, and this is likely the case for the majority of patients."

IMRT

IMRT is the most common type of EBRT for prostate cancer and has been routinely used for prostate cancer since the early 2000s. This type involves more precise delivery of radiation compared with previous radiotherapy methods, using a computer-driven machine that moves around the patient as it delivers radiation. Some newer radiation machines have imaging scanners that deliver image-guided radiation therapy.

The result is a reduction in urinary and bowel side effects associated with treatment and the ability to give higher radiation doses, which are more effective, in a safe manner.

SBRT

SBRT uses advanced image-guided techniques to deliver large doses of radiation to a precise area in the prostate. Because there are large doses of radiation in each dose, the entire course of treatment is much shorter. This allows selected prostate cancer patients to receive full therapy in a total of five treatments over 10 days.

This very short, convenient treatment carries some additional potential advantages in terms of further reducing side effects. However, because the radiation treatment is condensed into just five sessions and generally involves a higher dosage of radiation, advanced technology and expertise are typically needed to ensure that the treatment is conducted appropriately and safely, said Leeman.

Brachytherapy

Also known as seed implantation or interstitial radiation therapy, brachytherapy uses small radioactive pellets placed directly into the prostate. Imaging tests, such as transrectal ultrasound, CT scans, or MRI, are used to help guide the placement of the radioactive pellets. Special computer programs calculate the exact dose of radiation needed.

Brachytherapy is a good option if the prostate cancer is localized and meets certain requirements. Typically, brachytherapy is used for men with early-stage prostate cancer that is relatively low-grade, or combined with EBRT for men who have a higher risk of the cancer growing outside the prostate.

"Brachytherapy is a wonderful option for prostate cancer patients who have not had prior urethral resections, if they have glands smaller than about 60 cc, and if they have low urinary symptoms scores," Johnstone said.

If a patient is high-risk, clinicians may add on a brachytherapy boost. As IMRT treats the prostate, a simultaneous targets a cancer nodule seen in MRI or positron emission tomography to provide a specific extra dose.

In general, when choosing radiation therapy, a patient's staging and risk factors need to be taken into consideration. Low-risk and intermediate-risk patients do well with radiation therapy, and may require only active surveillance or brachytherapy, said Savita Dandapani, MD, PhD, of City of Hope in Duarte, California.

Intermediate-risk patients can be divided into favorable or unfavorable groups. Favorable risk patients may receive SBRT or brachytherapy. "For unfavorable-risk patients, I offer hypofractionated EBRT," said Dandapani.

Radiation Therapy After Prostatectomy

A patient with a rising PSA level after prostate cancer surgery may also require radiation therapy. The goal of adjuvant is to reduce the risk or eliminate a recurrence of cancer in the prostate. This treatment is given 5 days a week for approximately 7 weeks. The planning process is similar to that for patients receiving IMRT to their prostate.

The decision to consider using radiation therapy after prostatectomy is based on pathologic findings identified from the surgical specimen, as well as postoperative PSA measurements. Leeman said that if the PSA level becomes detectable and begins rising at any point following prostatectomy, radiation therapy should be considered and discussed with a radiation oncologist.

"If a patient has positive lymph nodes after prostatectomy, then I consider radiation therapy," said Dandapani. "Depending how many lymph nodes are positive and the stage of the disease, administering earlier radiation therapy may be of benefit."

Choosing the Most Appropriate Radiation Therapy

When choosing appropriate therapy for prostate cancer, the initial discussion with the patient typically involves active surveillance versus surgery versus radiotherapy -- ideally as part of a multidisciplinary consultation. "The effectiveness is very similar whether patients choose to have radiation or surgery," Leeman said. "The decision-making process typically comes down to side effects and impacts on quality of life."

The key to choosing the best radiation therapy for an individual patient is shared decision-making. In general, it is paramount to consider the impact of treatment on urinary, gastrointestinal, and sexual quality of life and how this may weigh against the efficacy of the treatment. A multidisciplinary approach provides patients with information and input on both radiation therapy and surgical options.

"I talk about staging, whether the patient's disease is low, intermediate, or high risk, and ask about overall goals and quality of life," said Dandapani. "We discuss the options, whether it's brachytherapy, SBRT, or IMRT, and go through the risks and benefits of each."

A discussion of gastrointestinal and genitourinary toxicity, both short-term and long-term, is important. Brachytherapy tends to lead to less gastrointestinal toxicity, and SBRT may be preferred over IMRT to lessen gastrointestinal issues.

"There are now multiple available options and modalities for delivering prostate radiotherapy effectively, which are supported by evidence," Leeman said. "Arriving at the right approach for each individual requires thorough discussion. I suggest that any man who is diagnosed with prostate cancer be given the opportunity to consult with a radiation oncologist to learn about radiotherapy options."

Read previous installments in this series:

Part 1: Prostate Cancer: Epidemiology, Diagnosis, and Treatment

Part 2: The Latest on Prostate Cancer Diagnosis

Part 3: The Real-Life Consequences of Controversies About PSA Testing

Part 4: Case Study: What Is Causing This Painful Abdominal Mass and Systemic Symptoms?

Part 5: Choosing Among the Many Treatment Options for Prostate Cancer