Oligometastatic Prostate Cancer Part II

Doctor talking to patient in hospital room
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In Part One, I reviewed some of the background theories on how treating metastatic disease, when only a limited number of metastatic sites exist, might be beneficial, and in some cases, even curative. At the meeting of the American Society of Clinical Oncology in 2015, Dr. Daniel Henderson from Royal Marsden Hospital in London reported on his experience treating 21 oligometastatic prostate cancer patients with radiation.

 He defined oligometastatic prostate cancer as 1-3 sites of metastasis, typically occurring some years after radical treatment for primary disease with surgery or radiation directed at the prostate gland.  Dr. Henderson pointed out in his presentation that standard treatment is long-term androgen deprivation therapy  (ADT), which is effective at controlling cancer but has a negative impact on quality of life, as it causes fatigue, weight gain, osteoporosis, muscle loss, hot flashes and loss of libido.

In the study, Dr. Henderson’s group evaluated how long they could delay starting ADT by treating the metastatic site with stereotactic beam radiation therapy (SBRT), in the hopes that the SBRT would delay disease progression and forestall the need for using ADT.

The patients who had rising PSA levels after previous surgery or radiation underwent scanning with F-choline PET/CT.  None of the patients received previous hormone therapy.

 When the SBRT was administered, a dose of 30 Gy in 3 fractions was given with a Cyberknife system. The time delay before there was a need to start ADT was calculated starting from the time of the SBRT. PSA was checked every three months and additional scanning with F-choline PET/CT was performed as needed.

Palliative ADT was initiated for metastatic disease not amenable to further SBRT.

Out of the 21 patients, 6 were given 3-6 months of ADT along with the SBRT. Most of the men had only one oligometastatic site, and the majority of the metastatic sites were in the lymph nodes rather than the bones.  Overall, there were a total of 8 bone lesions and 20 treated lymph node sites.  At a median follow up of 16.7 months, 81% (17 patients) have not required any therapy with ADT.  Median ADT-free survival is 28 months for the whole group.  Twenty of the patients had a decline in PSA after treatment.  The median percent reduction in PSA was 84%. No serious radiation toxicity above grade 2 was noted.  The incidence of grade 1 and 2 CTCAE toxicity (see below*) was 29% (6 patients) and 5% (1 patient), respectively.  No toxicity of grade 3 or above was observed. Overall, Dr. Henderson and his group felt that the SBRT was well-tolerated and advantageous in delaying initiation of hormone therapy. 

This study illustrates how brand new treatment opportunities are resulting from the advent of two new types of improved technology:  First, better scanning technology that can detect small metastases at an early stage, before the disease spreads to multiple areas in the body.

  And secondly, how more powerful radiation that is capable of “sterilizing” the cancer, while also being accurate enough to spare the closely surrounding healthy organs from any damage from the radiation therapy.   This aggressive approach of detecting metastatic disease at the earliest possible stage and then initiating an aggressive treatment protocol by administering curative doses of radiation is likely to become more popular as people become aware that this treatment option exists.

*Grade I Radiation Toxicity: Mild side effects that do not require medical intervention. If there are any lab abnormalities the patient is asymptomatic; the same can be said for radiographic findings.

Basically, grade I means that the changes are of marginal clinical relevance.

Grade II Radiation Toxicity: Moderate side effects that require minimal corrective intervention.

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