Update: Stereotactic Body Radiation Therapy (SBRT)

In my prior post, I discussed a worsening cough and recommendation from my oncologist, Dr. David Pfister at Memorial Sloan-Kettering Cancer Center (MSKCC), to consider stereotactic body radiation therapy or SBRT. This treatment is designed to deliver extremely precise, very intense doses of radiation to cancer cells while minimizing damage to healthy tissue.

My radiation oncologist, Dr. Nancy Lee at MSKCC, developed a treatment plan using SBRT to target single tumor sites in each of my lungs and spleen. Starting with my left lung, the first treatment took place Monday, July 23, 2018, and continued on Wednesday and Friday of that same week. The same schedule was used the following week for my right lung. A single SBRT session was used to target the lesion on my spleen, which was completed last Wednesday, August 15, 2018.

The unit for radiation measurement of absorbed dose is “gray” (Gy). I received a total of about 27 Gy to each lung site (9 Gy per session / 3 sessions) and about 9 Gy to my spleen in a single session. In contrast, I received about 70 Gy to my head/neck over the course of 7 weeks back in early 2016 as part of my conventional chemoradiation treatment.

With SBRT, only a small area of your body is exposed to radiation. This means that SBRT usually causes fewer side effects than other types of radiation therapy. According to patient education materials provided by MSKCC, about half of the people who have SBRT don’t have any side effects from treatment.

So far, the SBRT “experience” has been exactly as billed. Other than post-traumatic stress from going through the radiation procedure again, along with some mild fatigue, I haven’t experienced any significant side effects from SBRT. Encouragingly, my cough has already diminished both in frequency and severity. So, the radiation is likely doing its job of shrinking tumors that may be obstructing my airway.

Towards the end of September, I’ll have another CT scan to see how the radiated (and non-radiated) tumors responded to the SBRT. Radiation can cause inflammation in the short-term, which hampers the interpretation of scan results. Accordingly, it is prudent to wait at least a month before imaging.

Until then, I’m continuing my human papillomavirus (HPV) awareness activities and encouraging vaccination of preteen boys and girls to help prevent six cancers linked to HPV. Sadly, there is still a lot of room for improvement in vaccination rates.

In 2017, nearly 49 percent of adolescents received all the recommended doses to complete the HPV vaccination series according to a new study. This is less than a 5% increase from 2016 when 43.4% of adolescents (49.5% of females; 37.5% of males) were up to date with the HPV vaccination series. Today, 51 percent of adolescents still have not completed the HPV vaccine series!

To be meaningful, HPV vaccination rates need to be closer to the Centers for Disease Control and Prevention’s (CDC) Healthy People 2020 target of 80 percent coverage. This isn’t unrealistic, as around 80 percent of adolescents receive two other recommended vaccines—a vaccine to prevent meningococcus, which causes bloodstream infections and meningitis, and the Tdap vaccine to prevent tetanus, diphtheria, and pertussis.

Parents, I beg you again—please vaccinate your children against HPV.

Radioactive

As I compose this post, I cannot get the 1985 song “Radioactive” by English rock band The Firm out of my mind. But perhaps this will make more sense in a moment.

At the end of June 2018, I announced my intent to remain off cancer treatment. A decision so complex that it couldn’t be adequately addressed in a blog post. Simply put, after going through three very difficult therapies from 2016-2018, I decided to emphasize the quality of life over quantity of life.

My last palliative systemic treatment consisted of nine cycles/months of combination chemotherapy (carboplatin and paclitaxel). For a while, it significantly reduced the size of tumors in my lungs and spleen. Most importantly, it prolonged my life—and for that, I am very grateful.

But most cancer treatments are associated with toxicities, which can range from mild to severe. For example, my initial treatment consisted of daily radiation to my head/neck in combination with chemotherapy and was brutal with regard to side effects. In exchange for these toxicities, however, chemoradiation offered the “potential” for a cure at the time. It seemed like a fair trade.

Once my disease spread (metastasized) to distant sites, including my lungs and spleen, the intent of treatment switched from curative to palliative—providing relief from disease symptoms and helping me live longer. Accordingly, I became less willing to endure the side effects of palliative systemic treatment (chemotherapy, cetuximab, etc.) with cure no longer a likely option. This largely resulted in my decision to discontinue treatment.

However, I discussed my worsening cough during a recent appointment at Memorial Sloan-Kettering Cancer Center (MSKCC) with my oncologist, Dr. David Pfister, and Nicole Leonhart, ANP, RN. Absent chemotherapy, the tumors in my lungs continue to grow and create additional problems—chronic coughing, wheezing, shortness of breath, etc. To address my cough, Dr. Pfister introduced the concept of stereotactic body radiation therapy, or SBRT, to deliver extremely precise, very intense doses of radiation to cancer cells while minimizing damage to healthy tissue.

For more than a century, radiotherapy has been an effective treatment for cancer patients. But the new millennium saw the affirmation of SBRT, especially for the treatment of metastatic tumors. In fact, select patients with limited metastases treated with SBRT are long-term survivors.

During a follow-up appointment with my radiation oncologist, Dr. Nancy Lee at MSKCC, she informed me that SBRT is associated with fewer side effects than the conventional radiation therapy I received as part of my initial treatment back in 2016. Conventionally fractionated radiation involves low-dose fractions given once a day (e.g., 10–30 fractions of 1.8–3 Gy each), while SBRT involves giving smaller numbers of higher-dose fractions (e.g., 1–5 fractions of 6–30 Gy each). Accordingly, SBRT can usually be given in five or fewer daily sessions within a week. Fast, safe, and effective—there was a lot to like about SBRT.

SBRT involves the use of sophisticated image guidance that pinpoints the exact three-dimensional location of a tumor so that the radiation can be more precisely delivered to cancer cells. Adverse events associated with SBRT can include pneumonitis, cough, pain, esophagitis, and dermatitis. However, severe toxicities (Grade 3 and 4) are fairly uncommon, occurring in 5% to 10% of patients after SBRT.

Possibly due to my background working with radiopharmaceuticals, I’ve long been interested in the role of radiation therapy beyond its cytotoxic effects. Radiation therapy interacts with cancer and immune system through a variety of mechanisms. It promotes the release of tumor neoantigens during cancer cell death in addition to stimulating immune adjuvant effects, engaging the two key arms of the immune system and functioning like an in situ vaccine, generating tumor-specific T cells.

In fact, localized radiation can infrequently trigger systemic antitumor effects, called the “abscopal effect.” Recent studies presented at ASCO 2018 have explored SBRT in combination with checkpoint inhibitors to potentially improve the abscopal effect with mixed results.

In one study, cancer patients were treated with SBRT and at least 1 cycle of pembrolizumab. Results of the study showed an abscopal response defined by 30% reduction in any single non-irradiated measurable lesion was present in 27% of patients, but only 13% of patients when defined by a 30% reduction in aggregate diameter of non-irradiated measurable lesions. It is difficult from these data to separate out whether the effects seen were because of the combination or from SBRT alone.

In another study, head/neck cancer patients with at least two measurable lesions were randomized to either nivolumab alone for 2 cycles or nivolumab with SBRT to a single lesion (9 Gy x 3) between the 1st and 2nd doses of nivolumab. While safe, the addition of SBRT to nivolumab failed to improve objective response rate (ORR), progression-free survival (PFS), or overall survival (OS).

For now, a treatment plan was developed using SBRT to target tumor sites in each of my lungs. Starting with my left lung, the treatment takes place Monday, Wednesday, and Friday of this week. The same schedule will be used next week for my right lung. For reasons still unclear, questions remain regarding the use of SBRT to also target the lesion on my spleen.

Yesterday was my first SBRT session. Lorie stopped me for a quick kiss before I disappeared into the men’s locker room at MSKCC to change clothes. It was traumatic to see the same rooms and equipment from my prior chemoradiation experience. And while my body needs to be kept in the same position for each treatment, thankfully this is accomplished through the use of a mold of my back instead of being pinned to the table by a face/shoulder mask like last time.

The SBRT session was quick and painless. I thought readers might enjoy seeing what the process is like, so embedded in this post is a brief time-lapse video of me holding still on the table in my shorts and shoes as the linear accelerator components twirl around me.

I’ll update the blog with any significant updates on my SBRT experience. For now, I’m simply hoping to get some relief from coughing.