PSMA is a molecule; it is a receptor that is overexpressed in patients with prostate cancer. Practically all prostate cancer patients will express PSMA, and the PSMA receptor gets up-regulated as the tumor becomes more aggressive.
And this becomes a very potent target for us to treat with radioligand therapy. This means that we have radioisotopes, which target the PSMA receptors in prostate cancer.
And, they deliver a high payload of a radioactive substance to prostate cancer, thereby killing these prostate cells and improving progression-free survival in patients with metastatic prostate cancer.
The PSMA receptors can be targeted by various radioisotopes, which may be beta emitting radioisotopes like lutetium or novel alpha-emitting radioisotopes like bismuth or actinium.
Lutetium is used worldwide; there is a lot of data available on the use of lutetium PSMA for the treatment of metastatic prostate cancer. Which has become refractory to androgen deprivation therapy as well as to chemotherapy.
We started doing lutetium PSMA therapy way back in the year 2013 just a few months after the first lutetium PSMA therapy was performed in Germany. And since then we treat more than 300+ new patients every year. And these patients are not just from India or the surrounding countries, but from all over the world. Some of these countries include the USA, Canada, Australia, and some European countries.
Lutetium therapy is being done at a few select centers across the world. While the protocols are still being defined, we at our center not only do clinical work with patients but also try, and refine these therapies further. And we are probably one of the few centers in the world that believes in evidence-based and dosimetry-based treatment.
We do a very meticulous dosimetry on all patients who are undergoing lutetium PSMA therapy in our center. And that’s the reason why we have been able to escalate the dose over the years. Because by doing the dosimetry studies, we know that we are working within safe limits.
By escalating the dose, we can improve the efficacy and give a longer duration of response to patients. And this is possible because we work with a team of researchers who work with very refined and sophisticated algorithms of dosimetry.
We have patients with lutetium therapy almost every week. We source our radioisotopes every Monday, from international suppliers mainly ITG/ITM in Germany as well as the Indian lutetium from the Bhabha Atomic Research Center in Mumbai. We treat our patients on the first days of the week, i.e., Monday, Tuesday, and Wednesday, and go on to do the dosimetry at the end of the week.
A typical patient is here with us for about 5 days. On the first day, it is required we assess with a gallium PSMA scan. We discuss every patient on a multi-disciplinary tumor board. This board consists of not just nuclear medicine physicians but specialists from the field of medical oncology, radiation oncology, and urology.
If there is another need any patient has, which can be common problems like dysuria, or problems of obstruction of flow. All these factors are taken into account for deciding whether the patient is eligible before administering the radioisotope therapy.
Lutetium therapy not just extends survival in patients but also improves the quality of life. Improving the quality of life includes, not just reducing pain but increasing energy levels, and increasing the general sense of well-being.
Of most patients who undergo lutetium therapy, about 75-80% of these patients will show a good response to the therapy. There will be 15-20% of patients who might not show a good response to the therapy. And out of those patients who showed a response, there would be a small subset of patients who would recur early.
Typically, patients who undergo lutetium therapy, have a duration of response of about a year to a year and a half. This is the median duration of response; there would be a group of patients who would have a response and will continue to be in response for much longer than this. My longest surviving patient is almost 6 years and post-lutetium therapy has continued to be in complete response.
However, most patients will have a response of one to one and a half years from the start of the therapy. The more important aspects of lutetium therapy are the improvements in the quality of life, in terms of reduction in bone pain, reduction in the number of painkillers, and analgesics that the patient has to take, improvements in energy levels, and general well-being.
Lutetium therapy is fairly well tolerated, and there are no severe or adverse effects. The most common adverse effect is dry mouth. There would be about a 10-15% reduction in the salivary gland function, post-lutetium therapy. Some of it recovers with time, but there would always be a slight deficit in salivary gland function post-lutetium PSMA therapy.
Typically we give about four doses of lutetium and the lutetium PSMA is administered at intervals of about two months. During the interval, patients undergo routine blood tests which look at the complete blood counts and the liver and kidney function tests. And these tests are shared with me through email, by patients. I am constantly in direct contact with patients; my team and I hold hands with the patients throughout this entire journey of this therapy and even beyond that.
Many of my patients have stayed in touch with me over the years, and we have become part of not just their treatment protocols but an extended family itself.
So, if you have queries about lutetium PSMA therapy, please get in touch with my team or me. We would be happy to tell you more about these therapies and to take you on to our program if you need these therapies.